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Offer to Purchase – Acquisition of Micromet, Inc. by Amgen Inc.

Offer to Purchase for Cash

All Outstanding Shares of Common Stock

(Including the Associated Preferred Share Purchase
Rights)

of

MICROMET, INC.

at

$11.00 Net Per Share

by

ARMSTRONG ACQUISITION CORP.,

a wholly owned subsidiary of

AMGEN INC.

THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00
MIDNIGHT, NEW YORK CITY TIME, AT THE END OF THURSDAY, MARCH 1, 2012, UNLESS THE
OFFER IS EXTENDED.

The Offer (as defined herein) is being made pursuant to the Agreement and
Plan of Merger, dated as of January 25, 2012 (as it may be amended, modified or
supplemented from time to time in accordance with its terms, the “Merger
Agreement”), by and among Amgen Inc., a Delaware corporation (“Amgen”),
Armstrong Acquisition Corp., a Delaware corporation (“Purchaser”) and a
wholly-owned subsidiary of Amgen, and Micromet, Inc., a Delaware corporation
(“Micromet”). Purchaser is offering to purchase all of the shares of common
stock, par value $0.00004 per share (together with the associated preferred
share purchase rights, the “Shares”), of Micromet that are issued and
outstanding at a price of $11.00 per Share, net to the seller in cash (the
“Offer Price”), without interest, less any applicable withholding taxes, upon
the terms and subject to the conditions set forth in this offer to purchase
(this “Offer to Purchase”) and the related letter of transmittal (the “Letter of
Transmittal”), which, together with any amendments or supplements hereto and
thereto, collectively constitute the “Offer.”

Pursuant to the Merger Agreement, following the consummation of the Offer and
the satisfaction or waiver of the remaining conditions set forth in the Merger
Agreement, Purchaser will merge with and into Micromet (the “Merger”), with
Micromet continuing as the surviving corporation in the Merger and as a
wholly-owned subsidiary of Amgen. At the effective time of the Merger (the
“Effective Time”), each Share then outstanding (other than Shares that are held
by any stockholders who properly demand appraisal in connection with the Merger
as described in Section 17 : “Certain Legal Matters; Regulatory Approvals :
Appraisal Rights”) will be converted into the right to receive the Offer Price,
without interest, less any applicable withholding taxes, except for Shares then
owned by Amgen, Micromet or any of their respective wholly-owned subsidiaries,
which Shares will be cancelled and retired and will cease to exist, and no
consideration will be delivered in exchange therefor. Under no circumstances
will interest be paid with respect to the purchase of Shares pursuant to the
Offer, regardless of any extension of the Offer or any delay in making payment
for Shares.

THE BOARD OF DIRECTORS OF MICROMET UNANIMOUSLY
RECOMMENDS THAT YOU TENDER ALL OF YOUR SHARES INTO THE OFFER.

After careful consideration, the board of directors of Micromet (the
“Micromet Board”) has unanimously (1) determined that the Merger Agreement and
the transactions contemplated by the Merger Agreement are advisable, fair to and
in the best interests of Micromet and its stockholders, (2) approved, and
declared advisable, the Merger Agreement, the Offer, the Merger and the
transactions contemplated by the Merger Agreement in accordance with the
requirements of Delaware law and (3) resolved to recommend that Micromet’s
stockholders accept the Offer and tender their Shares to Purchaser pursuant to
the Offer, and, to the extent required by applicable law, adopt the Merger
Agreement.

The Offer is not subject to any financing condition. The
Offer is conditioned upon: (i) there being validly tendered in accordance with
the terms of the Offer and not validly withdrawn prior to 12:00 midnight, New
York City time, at the end of Thursday, March 1, 2012 (the “Expiration Date,”
unless the Offer is extended pursuant to and in accordance with the terms of the
Merger Agreement, in which event “Expiration Date” will mean the latest time and
date at which the Offer, as so extended, will expire) that number of Shares that
when added to the Shares then beneficially owned by Amgen and its subsidiaries
would represent one Share more than one-half (1/2) of the total number of then
outstanding Shares on a fully diluted basis (which total number is the number of
Shares issued and outstanding plus the number of Shares which Micromet would be
required to issue pursuant to any then outstanding options, warrants or other
rights to acquire Shares (other than the Top-Up Option (as defined below))
regardless of whether or not then vested) and (ii) the termination or expiration
of any applicable waiting period under the Hart-Scott-Rodino Antitrust
Improvements Act of 1976, as amended, and the regulations thereunder (the “HSR
Act”), as well as other customary conditions. See Section 15 : “Conditions to
the Offer.”

A summary of the principal terms of the Offer appears on pages i through ix.
You should read this entire Offer to Purchase and the Letter of Transmittal
carefully before deciding whether to tender your Shares into the Offer.

The Dealer-Manager for the Offer is:

February 2, 2012


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of Contents

IMPORTANT

If you desire to tender all or any portion of your Shares to Purchaser
pursuant to the Offer, you should, prior to the Expiration Date, (i) complete
and execute the Letter of Transmittal that is enclosed with this Offer to
Purchase in accordance with the instructions contained therein, and mail or
deliver the Letter of Transmittal together with the certificates representing
your Shares and any other required documents, to American Stock Transfer & Trust Company, LLC, in its capacity as depositary for the Offer (the
“Depositary”), (ii) tender your Shares by book-entry transfer by following the
procedures described in Section 3 : “Procedures for Accepting the Offer and
Tendering Shares : Book-Entry Transfer” or (iii) if applicable, request that
your broker, dealer, commercial bank, trust company or other nominee effect the
transaction for you. If you hold Shares registered in the name of a broker,
dealer, commercial bank, trust company or other nominee, you must contact such
nominee in order to tender your Shares to Purchaser pursuant to the Offer. The
associated preferred share purchase rights are currently evidenced by the
certificates representing shares of Micromet common stock, and by tendering
shares of Micromet common stock, a stockholder will also tender the associated
preferred share purchase rights. If the preferred share purchase rights are
separated from the shares of Micromet common stock under the terms of the Rights
Agreement (as defined below), stockholders will be required to tender one
associated preferred share purchase right for each shares of Micromet common
stock tendered in order to effect a valid tender of such shares of Micromet
common stock.

If you desire to tender your Shares pursuant to the Offer and the
certificates representing your Shares (and/or, if applicable, associated
preferred share purchase rights) are not immediately available, or you cannot
comply in a timely manner with the procedures for tendering your Shares by
book-entry transfer or you cannot deliver all required documents to the
Depositary prior to the Expiration Date, you may tender your Shares to Purchaser
pursuant to the Offer by following the procedures for guaranteed delivery
described in Section 3 : “Procedures for Accepting the Offer and Tendering
Shares : Guaranteed Delivery.”

*****

Georgeson Inc., the information agent for the Offer, may be contacted at the
address and telephone numbers set forth on the back cover of this Offer to
Purchase for questions and/or requests for additional copies of this Offer to
Purchase, the Letter of Transmittal, the notice of guaranteed delivery and other
tender offer materials. You may also contact your broker, dealer, commercial
bank, trust company or other nominee for assistance.

This Offer to Purchase and the Letter of Transmittal contain
important information, and you should read both carefully and in their entirety
before making a decision with respect to the Offer.


Table
of Contents

TABLE OF CONTENTS

SUMMARY
TERM SHEET

i

INTRODUCTION

1

THE
TENDER OFFER

4

1.

Terms
of the Offer.

4

2.

Acceptance
for Payment and Payment for Shares.

5

3.

Procedures
for Accepting the Offer and Tendering Shares.

7

4.

Withdrawal
Rights.

10

5.

Certain
Material U.S. Federal Income Tax Consequences of the Offer and the Merger.

11

6.

Price
Range of Shares; Dividends.

12

7.

Certain
Information Concerning Micromet.

13

8.

Certain
Information Concerning Purchaser and Amgen.

14

9.

Source
and Amount of Funds.

15

10.

Background
of the Offer; Past Contacts, Transactions, Negotiations and Agreements with
Micromet.

16

11.

The
Merger Agreement; Other Agreements.

20

12.

Purpose
of the Offer; Plans for Micromet.

41

13.

Certain
Effects of the Offer.

43

14.

Dividends
and Distributions.

44

15.

Conditions
to the Offer.

44

16.

Adjustments
to Prevent Dilution
.

45

17.

Certain
Legal Matters; Regulatory Approvals.

46

18.

Fees
and Expenses.

49

19.

Miscellaneous.

50

Annex
A Certain Information Regarding the Directors and Executive Officers of Amgen
Inc.

A-1

Annex
B Certain Information Regarding the Directors and Executive Officers of
Purchaser

B-1


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of Contents

SUMMARY TERM SHEET

Securities Sought:

All of the shares of common stock, par value $0.00004 per share (together
with the associated preferred share purchase rights, the “Shares”), of Micromet,
Inc., a Delaware corporation (“Micromet”), that are issued and outstanding.

Price Offered Per Share:

$11.00 per Share, net to the seller in cash (the “Offer Price”), without
interest, less any applicable withholding taxes.

Scheduled Expiration Date:

12:00 midnight, New York City time, at the end of Thursday, March 1, 2012,
unless the Offer (as defined below) is extended.

Purchaser:

Armstrong Acquisition Corp., a Delaware corporation (“Purchaser”) and a
wholly-owned subsidiary of Amgen Inc., a Delaware corporation (“Amgen”).

Micromet Board Recommendation:

The board of directors of Micromet (the “Micromet Board”) has unanimously (1)
determined that the Merger Agreement (as defined below) and the transactions
contemplated by the Merger Agreement are advisable, fair to and in the best
interests of Micromet and its stockholders, (2) approved, and declared
advisable, the Merger Agreement, the Offer, the Merger (as defined below) and
the transactions contemplated by the Merger Agreement in accordance with the
requirements of Delaware law and (3) resolved to recommend that Micromet’s
stockholders accept the Offer and tender their Shares to Purchaser pursuant to
the Offer, and, to the extent required by applicable law, adopt the Merger
Agreement.

The following are some questions that you, as a stockholder of Micromet,
may have and answers to those questions. This summary term sheet highlights
selected information from this offer to purchase (this “Offer to Purchase”) and
may not contain all of the information that is important to you and is qualified
in its entirety by the more detailed descriptions and explanations contained in
this Offer to Purchase and the related letter of transmittal (the “Letter of
Transmittal”), which, together with any amendments or supplements hereto and
thereto, collectively constitute the “Offer.” To better understand the Offer and
for a complete description of the terms of the Offer, you should read this Offer
to Purchase, the Letter of Transmittal and the other documents to which we refer
you carefully and in their entirety. Questions or requests for assistance may be
directed to Georgeson Inc., our information agent (the “Information Agent”), at
the address and telephone numbers set forth for the Information Agent on the
back cover of this Offer to Purchase. Unless otherwise indicated in this Offer
to Purchase or the context otherwise requires, all references in this Offer to
Purchase to “we,” “our” or “us” refer to Purchaser.

Who is offering to buy my Shares?

We are a wholly-owned subsidiary of Amgen incorporated under the laws of the
State of Delaware and were formed for the purpose of making the Offer and
thereafter consummating the merger (the “Merger”) with and into Micromet, with
Micromet continuing as the surviving corporation in the Merger (the “Surviving
Corporation”) and as a wholly-owned subsidiary of Amgen. To date, we have not
carried on any activities other than those related to our formation, the Merger
Agreement, the Offer and the Merger. Amgen is a corporation incorporated under
the laws of the State of Delaware. See the “Introduction” and Section 8 :
“Certain Information Concerning Purchaser and Amgen.”

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How many Shares are you offering to purchase in the Offer?

We are making the Offer to purchase all issued and outstanding Shares on the
terms and subject to the conditions set forth in this Offer to Purchase and the
Letter of Transmittal. See the “Introduction” and Section 1 : “Terms of the
Offer.”

Why are you making the Offer?

We are making the Offer pursuant to the Agreement and Plan of Merger, dated
as of January 25, 2012, by and among Amgen, Micromet and us (as it may be
amended, modified or supplemented from time to time in accordance with its
terms, the “Merger Agreement”), in order to acquire control of, and ultimately
following the Merger, the entire equity interest in, Micromet, while allowing
Micromet’s stockholders an opportunity to receive the Offer Price promptly (and
in any event within three business days after our acceptance of such Shares) by
tendering their Shares into the Offer. If the Offer is consummated, we, Amgen
and Micromet expect to consummate the Merger as promptly as practicable
thereafter in accordance with the General Corporation Law of the State of
Delaware (the “DGCL”). At the effective time of the Merger (the “Effective
Time”), Micromet will become a wholly-owned subsidiary of Amgen. See Section 12
: “Purpose of the Offer; Plans for Micromet.”

How much are you offering to pay and what is the form of payment?
Will I have to pay any fees or commissions?

We are offering to pay $11.00 per Share, net to the seller in cash, without
interest, less any applicable withholding taxes. If you are the record owner of
your Shares and you tender your Shares to us in the Offer, you will not have to
pay brokerage fees, commissions or similar expenses. If you own your Shares
through a broker, dealer, commercial bank, trust company or other nominee and
such nominee tenders your Shares on your behalf, such nominee may charge you a
fee for doing so. You should consult with your broker, dealer, commercial bank,
trust company or other nominee to determine whether any charges will apply. See
the “Introduction,” Section 1 : “Terms of the Offer” and Section 2 : “Acceptance
for Payment and Payment for Shares.”

What does the Micromet Board recommend?

After careful consideration, the Micromet Board has unanimously (1)
determined that the Merger Agreement and the transactions contemplated by the
Merger Agreement are advisable, fair to and in the best interests of Micromet
and its stockholders, (2) approved, and declared advisable, the Merger
Agreement, the Offer, the Merger and the transactions contemplated by the Merger
Agreement in accordance with the requirements of Delaware law and (3) resolved
to recommend that Micromet’s stockholders accept the Offer and tender their
Shares to us pursuant to the Offer, and, to the extent required by applicable
law, adopt the Merger Agreement.

See the “Introduction” and Section 12 : “Purpose of the Offer; Plans for
Micromet” and Micromet’s Solicitation/Recommendation Statement on Schedule 14D-9
(the “Schedule 14D-9”) that is being filed with the Securities Exchange
Commission (the “SEC”) and, together with this Offer to Purchase, the Letter of
Transmittal and other related materials, mailed to Micromet’s stockholders in
connection with the Offer.

What are the most significant conditions to the Offer?

The Offer is conditioned upon, among other things:

(a) there being validly tendered and not withdrawn prior to the Expiration
Date (as defined below) that number of Shares that when added to the Shares then
beneficially owned by Amgen and its subsidiaries would represent one Share more
than one-half (1/2) of the total number of then outstanding Shares on a fully
diluted basis (which total number is the number of Shares issued and outstanding
plus the number of Shares which Micromet would be required to issue pursuant to
any then outstanding options, warrants or other rights to acquire Shares (other
than the Top-Up Option (as defined below)) regardless of whether or not then
vested) (the “Minimum Condition”); and

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(b) the applicable waiting period under the Hart-Scott-Rodino Antitrust
Improvements Act of 1976, as amended, and the regulations thereunder (the “HSR
Act”) having expired or been terminated (the “HSR Condition”), as well as other
customary conditions.

We may waive any condition, in whole or in part, other than the Minimum
Condition, at any time and from time to time, without Micromet’s consent. See
Section 15 : “Conditions to the Offer.”

Is the Offer subject to any financing condition?

No. The Offer is not subject to any financing condition.

What percentage of Shares do you or your affiliates currently own?

Neither we nor Amgen nor any of our respective affiliates currently own any
Shares.

Do you have the financial resources to pay for all Shares?

Yes. The total amount of funds required by us to consummate the Offer and
purchase all outstanding Shares in the Offer and to provide funding in
connection with the Merger is approximately $1.16 billion, plus related fees and
expenses. Amgen, our parent company, will provide us with sufficient funds to
purchase all Shares validly tendered in the Offer and will provide funding for
our acquisition of the remaining Shares in the Merger. Amgen expects to fund
such cash requirements from its available cash. The Offer is not subject to any
financing condition. See Section 9 : “Source and Amount of Funds.”

Is your financial condition relevant to my decision to tender into
the Offer?

No. We do not think that our financial condition is relevant to your decision
whether to tender Shares and accept the Offer because:

the consummation of the Offer is not subject to any financing condition;

the Offer is being made for all Shares solely for cash;

if the Offer is consummated, we will acquire all remaining Shares in the
Merger for the same cash price as was paid in the Offer (i.e., the Offer Price);
and

we, through Amgen, have sufficient funds available to us to purchase all
Shares validly tendered and not properly withdrawn pursuant to the Offer and to
provide funding for the Merger in light of Amgen’s financial capacity in
relation to the amount of consideration payable.

See Section 9 : “Source and Amount of Funds” and Section 11 : “The Merger
Agreement; Other Agreements.”

How long do I have to decide whether to tender into the Offer?

You will be able to tender your Shares into the Offer until 12:00 midnight,
New York City time, at the end of Thursday, March 1, 2012 (the “Expiration
Date,” unless we extend the Offer pursuant to and in accordance with the terms
of the Merger Agreement, in which event “Expiration Date” will mean the latest
time and date at which the Offer, as so extended by us, will expire). Further,
if you cannot deliver everything that is required in order to make a valid
tender in accordance with the terms of the Offer by the Expiration Date, you may
be able to use a guaranteed delivery procedure by which a broker, a bank or any
other fiduciary that is an eligible institution may guarantee that the missing
items will be received by American Stock Transfer & Trust Company, LLC, our
depositary for the Offer (the “Depositary”), within three NASDAQ Stock Market
(“NASDAQ”) trading days. Please give your broker, dealer, commercial bank, trust
company or other nominee instructions in sufficient time to permit such nominee
to tender your Shares by the Expiration Date. See Section 1 : “Terms of the
Offer” and Section 3 : “Procedures for Accepting the Offer and Tendering
Shares.”

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Can the Offer be extended and, if so, under what circumstances can or
will the Offer be extended?

Yes, the Offer can be extended. In some cases, we are required to extend the
Offer beyond the initial Expiration Date, but in no event will we be required to
extend the Offer beyond the End Date (as defined below).

Pursuant to the Merger Agreement, we are required to extend the Offer:

for periods of not more than five business days each, or such other number of
business days as we, Amgen and Micromet may agree, but not beyond June 25, 2012
(the “End Date”), in order to permit the satisfaction of all remaining
conditions (subject to our right to waive any condition to the Offer (other than
the Minimum Condition) in accordance with the Merger Agreement), if at any
scheduled Expiration Date any condition to the Offer has not been satisfied or
waived (other than the Minimum Condition, which we may not waive); and

for any period or periods required by applicable law or any interpretation or
position of the SEC or its staff or NASDAQ or its staff, provided that (1) we
will extend the then current Expiration Date until the first business day on
which the Offer can be accepted under applicable law and (2) we are not
obligated to extend the Offer beyond the End Date.

If we extend the Offer, such extension will extend the time that you will
have to tender your Shares. See Section 1 : “Terms of the Offer”.

How will I be notified if the time period during which I can tender
my Shares into the Offer is extended?

If we extend the Offer, we will inform the Depositary of that fact and will
make a public announcement of the extension no later than 9:00 a.m., New York
City time, on the next business day after the previously scheduled Expiration
Date.

If we elect to provide a subsequent offering period, a public announcement of
such election will be made no later than 9:00 a.m., New York City time, on the
next business day following the Expiration Date.

Will there be a subsequent offering period?

We may elect to provide a subsequent offering period of neither less than
three business days nor more than 20 business days, during which time Micromet’s
stockholders whose Shares have not been tendered prior to the Expiration Date
(or whose Shares were tendered and later withdrawn prior to the Expiration Date)
may tender, but not withdraw, their Shares and receive the Offer Price. See
Section 1 : “Terms of the Offer” and Section 4 : “Withdrawal Rights”.

What is the difference between an extension of the Offer and a
subsequent offering period?

If the Offer is extended, no Shares will be accepted or paid for until
following the Expiration Date (as so extended), and you will be able to withdraw
your Shares until the Expiration Date.

A subsequent offering period, if one is provided, would occur after the time
we accept for payment Shares tendered in the Offer (the “Acceptance Time”) and
after we have become obligated to pay for all Shares that were validly tendered
and not properly withdrawn prior to the Expiration Date. Shares that are validly
tendered during a subsequent offering period will be accepted and paid for
promptly after they are received and cannot be withdrawn. See Section 1 : “Terms
of the Offer” and Section 4 : “Withdrawal Rights.”

How do I tender my Shares into the Offer?

To tender your Shares into the Offer, you must deliver the certificates
representing your Shares, together with a properly completed and duly executed
Letter of Transmittal, together with any required signature guarantees (or, in
the case of book-entry transfer of Shares, either such Letter of Transmittal or
an Agent’s

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Message (as defined in Section 3 : “Procedures for Accepting the Offer and
Tendering Shares : Valid Tender of Shares”) in lieu of such Letter of
Transmittal), and any other documents required by the Letter of Transmittal, to
the Depositary prior to the Expiration Date. If your Shares are held in street
name (i.e., through a broker, dealer, commercial bank, trust company or other
nominee), your Shares can be tendered by such nominee through The Depository
Trust Company. If you are unable to deliver any required document or instrument
to the Depositary prior to the Expiration Date, you may gain some extra time by
having a broker, a bank or any other fiduciary that is an eligible guarantor
institution guarantee that the missing items will be received by the Depositary
by using the enclosed notice of guaranteed delivery (the “Notice of Guaranteed
Delivery”). For the tender to be valid, however, the Depositary must receive the
Notice of Guaranteed Delivery prior to the Expiration Date and must then receive
the missing items within three NASDAQ trading days after the date of execution
of such Notice of Guaranteed Delivery. See Section 3 : “Procedures for Accepting
the Offer and Tendering Shares.”

If the associated preferred share purchase rights separate from Micromet’s
common stock under the terms of the Rights Agreement, dated as of November 3,
2004, between Micromet (as successor to CancerVax Corporation) and American
Stock Transfer & Trust Company, LLC (as successor to Mellon Investor
Services LLC), as rights agent (as amended, the “Rights Agreement”), you also
must tender one associated preferred share purchase right for each share of
common stock tendered in order to validly tender such shares in the Offer.

Until what time may I withdraw previously tendered Shares?

Shares tendered into the Offer may be withdrawn at any time prior to the
Expiration Date. Thereafter, tenders of Shares are irrevocable, except that they
may also be withdrawn after April 2, 2012 which is the 60th day from the
commencement of the Offer, unless such Shares have already been accepted for
payment by us pursuant to the Offer. If you tendered your Shares by giving
instructions to a broker, dealer, commercial bank, trust company or other
nominee, you must instruct such nominee to arrange for the withdrawal of your
Shares. See Section 4 : “Withdrawal Rights.”

You may not withdraw Shares tendered during any subsequent offering period
that we may elect to provide. See Section 4 : “Withdrawal Rights.”

How do I properly withdraw previously tendered Shares?

To properly withdraw any of your previously tendered Shares, you must deliver
a written notice of withdrawal with the required information (as specified in
this Offer to Purchase and in the Letter of Transmittal) to the Depositary while
you still have the right to withdraw Shares. If you tendered your Shares by
giving instructions to a broker, dealer, commercial bank, trust company or other
nominee, you must instruct such nominee to arrange for the proper withdrawal of
your Shares. You may not withdraw Shares tendered during any subsequent offering
period that we may elect to provide. See Section 4 : “Withdrawal Rights.”

Upon the successful consummation of the Offer, will Shares continue
to be publicly traded?

Following the consummation of the Offer, we, Amgen and Micromet expect to
consummate the Merger as promptly as practicable thereafter. If the Merger takes
place, no Shares will be publicly owned. If all of the conditions to the Offer
are satisfied or waived (see Section 15 : “Conditions to the Offer”) and we
purchase all tendered Shares, prior to the Merger becoming effective, there may
then be so few remaining stockholders and publicly held Shares that such Shares
will no longer be eligible to be traded on the NASDAQ or any other securities
exchange and there may not be a public trading market for such Shares. See
Section 13 : “Certain Effects of the Offer.”

If you do not consummate the Offer, will you nevertheless consummate
the Merger?

No. None of us, Amgen and Micromet are under any obligation to pursue or
consummate the Merger if the Offer has not been earlier consummated.

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If I object to the price being offered, will I have appraisal rights?

Appraisal rights are not available to the holders of Shares in connection
with the Offer. However, if the Merger is consummated, each holder of Shares
(that did not tender such Shares into the Offer) at the Effective Time who has
neither voted in favor of the Merger nor consented to the Merger in writing, and
who otherwise complies with the applicable statutory procedures under Section
262 of the DGCL, will be entitled to receive a judicial determination of the
fair value of such holder’s Shares (exclusive of any element of value arising
from the accomplishment or expectation of the Merger) and to receive payment of
such judicially determined amount in cash, together with such rate of interest,
if any, as the Delaware court may determine for Shares held by such holder. This
value may be more or less than, or the same as, the Offer Price. See Section 17
: “Certain Legal Matters; Regulatory Approvals : Appraisal Rights.”

If I decide not to tender my Shares into the Offer, how will the
Offer affect my Shares?

Following the consummation of the Offer, we, Amgen and Micromet expect to
consummate the Merger as promptly as practicable. If the Merger is consummated,
then stockholders who did not tender their Shares into the Offer will receive
the same amount of cash per Share that they would have received had they
tendered their Shares into the Offer (i.e., the Offer Price), subject to any
appraisal rights properly exercised by such stockholders in accordance with
Delaware law. Therefore, if the Merger takes place, the only difference to you
between tendering your Shares into the Offer and not tendering your Shares into
the Offer would be that, if you tender your Shares, you may be paid earlier and
no appraisal rights will be available. No interest will be paid for Shares
acquired in the Merger.

Furthermore, following the consummation of the Offer until the Effective
Time, there may then be so few remaining stockholders and publicly held Shares
that such Shares will no longer be eligible to be traded on the NASDAQ or any
other securities exchange and there may not be a public trading market for such
Shares. See the “Introduction” and Section 13 : “Certain Effects of the Offer.”

There is no assurance that we will acquire enough Shares to exercise the
Top-Up Option (as defined below) or that a subsequent offering period will
result in our owning in excess of 90% of the outstanding Shares. As a result, we
may not be able to effect the Merger under the “short-form” merger provisions of
Section 253 of the DGCL. If we do not own at least 90% of the outstanding
Shares, the Merger Agreement must be adopted by Micromet’s stockholders.
Adoption of the Merger Agreement requires the affirmative vote of holders of a
majority of the outstanding Shares. Thus, if the Minimum Condition and the other
conditions to the Offer are satisfied and the Offer is completed, we would have
sufficient voting power to adopt the Merger Agreement without the affirmative
vote of any other stockholder of Micromet. See Section 11 : “The Merger
Agreement; Other Agreements” and Section 12 : “Purpose of the Offer; Plans for
Micromet : Purpose of the Offer.”

What is the market value of my Shares as of a recent date and the
“premium” I am receiving?

The Offer Price of $11.00 per Share represents an approximate:

33% premium to the closing price per Share reported on the NASDAQ on January
25, 2012, the last day before we announced the execution of the Merger Agreement
and the Offer;

52% premium to the closing price per Share reported on the NASDAQ on December
23, 2011, the last closing price 30 days before the day we announced the
execution of the Merger Agreement and the Offer;

24% premium over the 52-week-high intraday price per Share reported on the
NASDAQ for the period ended January 25, 2012, the last day before we announced
the execution of the Merger Agreement and the Offer; and

34%, 58%, 86% and 87% over the volume-weighted average trading prices for the
Shares for the one-month, three-month, six-month and twelve-month periods ending
on the last day before we announced the execution of the Merger Agreement and
the Offer.

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On February 1, 2012, the last trading day before we commenced the Offer, the
closing price of Shares reported on the NASDAQ was $10.94 per Share. We
encourage you to obtain a recent quotation for Shares in deciding whether to
tender your Shares. See Section 6 : “Price Range of Shares; Dividends.”

Have any stockholders of Micromet already agreed to tender their
Shares into the Offer or to otherwise support the Offer?

Yes. The directors and executive officers of Micromet and certain of their
affiliated funds have entered into tender and support agreements with us and
Amgen pursuant to which, among other things, those stockholders have agreed to
tender their Shares in the Offer. Excluding options and warrants to purchase
Shares that are exercisable within 60 days of January 25, 2012, the directors,
executive officers and affiliated funds that are party to such tender and
support agreements beneficially owned, in the aggregate, 7,041,552 Shares (or
7.6% of all outstanding Shares) as of January 25, 2012. Including options and
warrants to purchase Shares that are exercisable within 60 days of January 25,
2012, such directors, executive officers and affiliated funds beneficially
owned, in the aggregate, 12,986,468 Shares (or 13.2% of all outstanding Shares
after giving effect to the exercise of such options and warrants) as of January
25, 2012. See Section 11 : “The Merger Agreement; Other Agreements.”

If I tender my Shares, when and how will I get paid?

If the conditions to the Offer as set forth in Section 15 : “Conditions to
the Offer” are satisfied or waived and we consummate the Offer and accept your
Shares for payment, you will be entitled to an amount equal to the number of
Shares you tendered into the Offer multiplied by the Offer Price, net to you in
cash, without interest, less any applicable withholding taxes, promptly (and in
any event within three business days after our acceptance of such Shares). We
will pay for your validly tendered and not properly withdrawn Shares by
depositing the aggregate Offer Price therefor with the Depositary, which will
act as your agent for the purpose of receiving payments from us and transmitting
such payments to you. In all cases, payment for tendered Shares will be made
only after timely receipt by the Depositary of (i) certificates representing
such Shares or a confirmation of a book-entry transfer of such Shares as
described in Section 3 : “Procedures for Accepting the Offer and Tendering
Shares : Book-Entry Transfer,” (ii) a properly completed and duly executed
Letter of Transmittal, together with any required signature guarantees or, in
the case of book-entry transfer of Shares, either such Letter of transmittal or
an Agent’s Message in lieu of such Letter of Transmittal and (iii) any other
required documents for such Shares. See Section 1 : “Terms of the Offer” and
Section 2 : “Acceptance for Payment and Payment for Shares.”

What is the Top-Up Option and when could it be exercised?

Micromet has granted to us and Amgen an option (the “Top-Up Option”) to
purchase from Micromet the number of newly-issued Shares (the “Top-Up Option
Shares”) equal to the lesser of (i) the number of Shares that, when added to the
number of Shares owned by Amgen and its subsidiaries at the time of exercise of
the Top-Up Option, constitutes one Share more than 90% of the total number of
Shares that would be outstanding immediately after the issuance of all Shares
subject to the Top-Up Option on a fully diluted basis (which total number is the
number of Shares issued and outstanding plus the number of Shares which Micromet
would be required to issue pursuant to any then outstanding options, warrants or
other rights to acquire Shares (including the Top-Up Option) regardless of
whether or not then vested) or (ii) the aggregate number of Shares that Micromet
is authorized to issue under its certificate of incorporation but that are not
issued and outstanding (and are not subscribed for or otherwise committed to be
issued) at the time of exercise of the Top-Up Option. The Top-Up Option may be
exercised by us or Amgen, in whole or in part, at any time on or after the
Acceptance Time, in our sole discretion; provided, however,
that the obligation of Micromet to deliver Top-Up Option Shares upon the
exercise of the Top-Up Option is subject to the condition, unless waived by
Micromet, that immediately following the exercise of the Top-Up Option, the
number of Shares owned in the aggregate by us and Amgen constitutes at least one
Share more than 90% of the number of Shares that would be outstanding
immediately after the issuance of all Top-Up Option Shares. The aggregate
purchase price payable for the Top-Up Option Shares will be determined by
multiplying the number of Top-Up Option Shares by the Offer Price.

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See Section 11 : “The Merger Agreement; Other Agreements : The Merger
Agreement : Top-Up Option” and Section 12 : “Purpose of the Offer; Plans for
Micromet.”

What will happen to my stock options in the Offer?

The Offer is being made for all outstanding Shares, and not for options to
purchase Shares granted pursuant to any of Micromet’s equity incentive plans
(each such option, a “Micromet Option”). Micromet Options may not be tendered
into the Offer. If you wish to tender Shares underlying Micromet Options, you
must first exercise your Micromet Options (to the extent exercisable) in
accordance with their terms in sufficient time to tender the Shares received
into the Offer.

At the Effective Time, each outstanding Micromet Option, whether vested or
unvested, will be cancelled and converted into only the right to receive,
without interest, after giving effect to any accelerated vesting at the
Effective Time contemplated under the Merger Agreement or under the terms of any
employment agreement or individual award agreement, for the portion of each
Micromet Option that is (i) vested and exercisable as of the Effective Time, an
amount in cash equal to the product of (A) the excess, if any, of (1) the Offer
Price over (2) the exercise price per share of such vested portion of the
Micromet Option, and (B) the number of Shares underlying the vested portion of
such Micromet Option, and (ii) not vested at the Effective Time, an amount in
cash equal to the product of (A) the excess, if any, of (1) the Offer Price over
(2) the exercise price per share of such unvested portion of the Micromet
Option, and (B) the number of Shares underlying such unvested portion of the
Micromet Option (in each case, such product, less applicable withholdings, the
“Option Payment Amount”).

For the portion of each Micromet Option that is vested and exercisable as of
the Effective Time, the Option Payment Amount will be payable to the holder of
such option as soon as reasonably practicable, but no later than the second
payroll period, after the Effective Time. For the portion of each Micromet
Option that is not vested and exercisable as of the Effective Time, the Option
Payment Amount in respect of such cancelled and converted unvested portion of
the Micromet Option will be subject to the same vesting schedule and other
relevant terms applicable to the Micromet Option as in effect before the
Effective Time. The Option Payment Amount will be payable to the holder thereof
no later than the second payroll period after the applicable vesting date of
such payment, subject to the holder’s continued employment through the vesting
date, or earlier termination without “cause” (including because of the holder’s
death or disability) or resignation for “good reason” (in each case within the
meaning of the applicable Micromet equity plan or individual employment
agreement), in which case the Option Payment Amount will be payable to the
holder thereof by no later than the second payroll period after the date of such
termination or resignation. Any Option Payment Amount in respect of a cancelled
and converted unvested portion of a Micromet Option that remains outstanding and
unvested as of December 15, 2012 will vest on December 15, 2012, and such Option
Payment Amount will be paid to the holder no later than December 31, 2012. Any
partial accelerated vesting, pursuant to an individual employment agreement or
award agreement, will be applied pro rata, on a grant by grant basis, to each
vesting tranche subject to such accelerated vesting, such that the portion of
each such vesting tranche that is not accelerated will be subject to the same
vesting schedule in effect as of the date of the Merger Agreement. In addition,
the portion of each Micromet Option that is not vested as of the Effective Time
and which is held by a non-employee member of the Micromet Board will be subject
to accelerated vesting and become exercisable in full upon the Effective Time
and cashed-out in the same manner as other vested Micromet Options. See Section
11 : “The Merger Agreement; Other Agreements : Treatment of Micromet Equity
Awards.”

What are the U.S. federal income tax consequences of the Offer and
the Merger?

The receipt of cash by you in exchange for your Shares pursuant to the Offer
or the Merger (or pursuant to the exercise of appraisal rights in accordance
with Delaware law) will be a taxable transaction for U.S. federal income tax
purposes if you are a United States Holder (as defined in Section 5 : “Certain
Material U.S. Federal Income Tax Consequences of the Offer and the Merger”). In
general, you will recognize gain or loss equal to the

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difference between your adjusted tax basis in Shares that you tender into the
Offer or exchange in the Merger (or retain for exercise of appraisal rights) and
the amount of cash you receive for such Shares. If you are a United States
Holder and you hold your Shares as a capital asset, the gain or loss that you
recognize will be a capital gain or loss and will be treated as a long-term
capital gain or loss if you have held such Shares for more than one year. If you
are a Non-United States Holder (as defined in Section 5 : “Certain Material U.S.
Federal Income Tax Consequences of the Offer and the Merger”), you will
generally not be subject to U.S. federal income tax on gain recognized on Shares
you tender into the Offer or exchange in the Merger (or retain for exercise of
appraisal rights). You should consult your tax advisor about the
particular tax consequences to you of tendering your Shares into the Offer,
exchanging your Shares in the Merger or exercising appraisal rights.

See Section 5 : “Certain Material U.S. Federal Income Tax Consequences of the
Offer and the Merger” for a discussion of certain material U.S. federal income
tax consequences of tendering Shares into the Offer or exchanging Shares in the
Merger or exercising appraisal rights.

To whom should I talk if I have additional questions about the Offer?

You may call Georgeson Inc., the Information Agent, toll-free at (888)
877-5360.

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To the Holders of Shares of Common Stock of Micromet, Inc.:

INTRODUCTION

The Offer is being made pursuant to the Merger Agreement by and among Amgen,
Micromet and us. We are offering to purchase all of the issued and outstanding
Shares at the Offer Price, without interest, less any applicable withholding
taxes, upon the terms and subject to the conditions set forth in the Offer.

The Offer and the withdrawal rights will expire at the Expiration Date,
unless the Offer is extended or the Merger Agreement has been earlier terminated
in accordance with its terms. Under no circumstances will interest be paid with
respect to the purchase of Shares pursuant to the Offer, regardless of any
extension of the Offer or any delay in making payment for Shares.

If you are a record owner of Shares and you tender such Shares directly to
the Depositary in accordance with the terms of this Offer, we will not charge
you brokerage fees, commissions or, except as set forth in Instruction 6 of the
Letter of Transmittal, stock transfer taxes on the sale of Shares pursuant to
the Offer. However, if you do not complete and sign the Internal Revenue Service
Form W-9 that is enclosed with the Letter of Transmittal (or other applicable
form), you may be subject to backup withholding at the applicable statutory rate
on the gross proceeds payable to you. See Section 3 : “Procedures for Accepting
the Offer and Tendering Shares : Backup Withholding.” Stockholders with Shares
held in street name by a broker, dealer, bank, trust company or other nominee
should consult with such nominee to determine if they will be charged any
service fees or commissions. We will pay all charges and expenses of the
Depositary, the Information Agent and Moelis & Company LLC (the
“Dealer-Manager”) incurred in connection with the Offer. See Section 18 : “Fees
and Expenses.”

Subject to the provisions of the Merger Agreement, as soon as practicable
following the consummation of the Offer, we, Amgen and Micromet will cause the
Merger to be consummated by filing with the Secretary of State of the State of
Delaware a certificate of merger or a certificate of ownership and merger, as
applicable (in either case, the “Certificate of Merger”), in accordance with the
relevant provisions of the DGCL. The Merger will become effective upon the
filing of the Certificate of Merger or at such later time as Amgen and Micromet
agree in writing and specify in the Certificate of Merger, at which time
Micromet will become the Surviving Corporation and a wholly-owned subsidiary of
Amgen. At the Effective Time, each Share then outstanding (other than Shares
that are held by any stockholders who properly demand appraisal in connection
with the Merger as described in Section 17 : “Certain Legal Matters; Regulatory
Approvals : Appraisal Rights”) will be converted into the right to receive the
Offer Price, without interest, less any applicable withholding taxes, except for
Shares then owned by Amgen, Micromet or any of their respective wholly-owned
subsidiaries, which Shares will be cancelled and retired and will cease to
exist, and no consideration will be delivered in exchange therefor.

Section 11 : “The Merger Agreement; Other Agreements” more fully describes
the Merger Agreement. Certain material U.S. federal income tax consequences of
the sale of Shares pursuant to the Offer and the exchange of Shares pursuant to
the Merger are described in Section 5 : “Certain Material U.S. Federal Income
Tax Consequences of the Offer and the Merger.”

After careful consideration, the Micromet Board has unanimously (1)
determined that the Merger Agreement and the transactions contemplated by the
Merger Agreement are advisable, fair to and in the best interests of Micromet
and its stockholders, (2) approved, and declared advisable, the Merger
Agreement, the Offer, the Merger and the transactions contemplated by the Merger
Agreement in accordance with the requirements of Delaware law and (3) resolved
to recommend that Micromet’s stockholders accept the Offer and tender their
Shares to us pursuant to the Offer, and, to the extent required by applicable
law, adopt the Merger Agreement.

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A more complete description of the Micromet Board’s reasons for authorizing
and approving the Merger Agreement and the transactions contemplated thereby,
including the Offer and the Merger, is set forth in the Schedule 14D-9 that is
being filed with the SEC and, together with this Offer to Purchase, the Letter
of Transmittal and other related materials, mailed to Micromet’s stockholders in
connection with the Offer. Stockholders should carefully read the information
set forth in the Schedule 14D-9 in its entirety.

The Offer is not subject to any financing condition.

The Offer is conditioned upon: the Minimum Condition and the HSR Condition,
as well as other customary conditions. See Section 15 : “Conditions to the
Offer.”

According to Micromet, as of January 25, 2012, there were (a) 92,375,454
issued and outstanding Shares, (b) outstanding Micromet Options to purchase
14,017,356 Shares and (c) warrants to purchase 7,766,046 Shares (“Micromet
Warrants”). Assuming that all Shares described in (b) and (c) in the preceding
sentence are issued and that no other Shares were or are issued after January
25, 2012, there would be 114,158,856 Shares outstanding and the Minimum
Condition would be satisfied if at least 57,079,429 Shares are validly tendered
and not withdrawn prior to the Expiration Date.

If the Minimum Condition is satisfied and we accept for payment and pay for
the Shares tendered into the Offer, we will be entitled to elect or designate a
number of directors, rounded up to the next whole number, to the Micromet Board
that is equal to the product of (a) the total number of directors on the
Micromet Board (after giving effect to the directors elected or designated by
us) multiplied by (b) the percentage that the aggregate number of Shares
beneficially owned by Amgen, us and any of our affiliates bears to the total
number of Shares then outstanding, and Micromet will, upon our request at any
time following the purchase of and payment for Shares pursuant to the Offer,
take all actions necessary to (i) appoint to the Micromet Board the individuals
designated by us and permitted to be so designated as described above,
including, but not limited to, promptly filling vacancies or newly created
directorships on the Micromet Board, promptly increasing the size of the
Micromet Board (including by amending Micromet’s bylaws if necessary so as to
increase the size of the Micromet Board) and/or promptly securing the
resignations of the number of its incumbent directors as are necessary or
desirable to enable our designees to be so elected or designated to the Micromet
Board, and (ii) cause our designees to be so appointed at such time. Micromet
will, upon our request following the Acceptance Time, cause directors designated
by us to constitute the same percentage (rounded up to the next whole number) as
is on the Micromet Board of each committee of the Micromet Board to the extent
permitted by applicable law and the rules of the NASDAQ.

Pursuant to the Merger Agreement, in the event directors designated by us are
elected or appointed to the Micromet Board, until the Effective Time, Micromet
will cause the Micromet Board to maintain three directors who are members of the
Micromet Board on or prior to the date of the Merger Agreement and who are not
officers, directors or employees of Amgen, us or any of their or our affiliates,
each of whom shall be an “independent director” as defined by the rules of the
NASDAQ and eligible to serve on Micromet’s audit committee under the Exchange
Act and rules of the NASDAQ, and at least one of which will be an “audit
committee financial expert” as defined in Item 407(d)(5)(ii) and (iii) of
Regulation S-K (the “Continuing Directors”). After the Acceptance Time and prior
to the Effective Time, if our designees constitute a majority of the Micromet
Board, the affirmative vote of a majority of the Continuing Directors (in
addition to the approval rights of the Micromet Board or the stockholders of
Micromet as may be required by Micromet’s certificate of incorporation or bylaws
or by applicable law) will be required (i) for Micromet to amend or terminate
the Merger Agreement, (ii) to exercise or waive any of Micromet’s rights,
benefits or remedies under the Merger Agreement, if such action would adversely
affect, or would reasonably be expected to adversely affect, Micromet’s
stockholders (other than Amgen and us), (iii) to amend Micromet’s certificate of
incorporation or bylaws if such action would adversely affect the holders of
Shares (other than Amgen or us), or (iv) to take any other action of the
Micromet Board under or in connection with the Merger Agreement if such action
would materially and adversely affect, or would reasonably be expected to
materially and adversely affect, Micromet’s stockholders (other than Amgen or
us).

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As promptly as practicable after the Acceptance Time, we, Amgen and Micromet
expect to consummate the Merger in accordance with the DGCL. At the Effective
Time, our directors immediately prior to the Effective Time will be the only
directors of the Surviving Corporation.

The Merger is subject, to the extent required by applicable law, to the
adoption of the Merger Agreement by the affirmative vote of the holders of at
least a majority of the then-outstanding Shares; however, if the Minimum
Condition is satisfied, we will have sufficient Shares to adopt the Merger
Agreement without action by any other stockholders. This Offer to Purchase does
not constitute a solicitation of proxies, and we are not soliciting proxies at
this time.

If we acquire at least 90% of the then-outstanding Shares, including pursuant
to the Top-Up Option, if applicable, we may effect the Merger under the
“short-form” merger provisions of Section 253 of the DGCL without any vote of
stockholders. If we and our affiliates do not own, by virtue of the Offer or
otherwise, 90% or more of the issued and outstanding Shares, we may elect to
approve the Merger under the “long-form” merger provision of Section 251 of the
DGCL, which requires that the Merger Agreement be adopted by Micromet’s
stockholders. In that case, adoption of the Merger Agreement requires the
affirmative vote of holders of a majority of the outstanding Shares. Thus, if
the Minimum Condition and the other conditions to the Offer are satisfied and
the Offer is completed, we would have sufficient voting power to adopt the
Merger Agreement without the affirmative vote of any other stockholder of
Micromet. Amgen has agreed to vote, or cause to be voted, all Shares held by it
and its subsidiaries in favor of the adoption of the Merger Agreement. See
Section 11 : “The Merger Agreement; Other Agreements : Actions in Connection
with Long-Form Merger” and Section 17 : “Certain Legal Matters; Regulatory
Approvals : “Short-Form” Merger.”

No appraisal rights are available to the holders of Shares in connection with
the Offer. However, if the Merger is consummated, each holder of Shares (that
did not tender such Shares into the Offer) at the Effective Time who has neither
voted in favor of the Merger nor consented to the Merger in writing, and who
otherwise complies with the applicable statutory procedures under Section 262 of
the DGCL, will be entitled to receive a judicial determination of the fair value
of the holder’s Shares (exclusive of any element of value arising from the
accomplishment or expectation of the Merger) and to receive payment of such
judicially determined amount in cash, together with such rate of interest, if
any, as the Delaware court may determine for Shares held by such holder. This
value may be more or less than, or equal to, the Offer Price. See Section 17 :
“Certain Legal Matters; Regulatory Approvals : Appraisal Rights.”

This Offer to Purchase and the Letter of Transmittal contain
important information that should be read carefully before any decision is made
with respect to the Offer.

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THE TENDER OFFER

1.

Terms of the Offer.

Upon the terms and subject to the conditions to the Offer (including, if the
Offer is extended or amended, the terms and conditions of such extension or
amendment), we will accept for payment and pay for all Shares validly tendered
and not properly withdrawn prior to the Expiration Date as permitted under
Section 4 : “Withdrawal Rights.” As of the date of this Offer to Purchase, the
associated preferred share purchase rights do not trade separately from the
shares of Micromet common stock. Accordingly, by tendering Shares you are
automatically tendering a similar number of associated preferred share purchase
rights. If, however, the associated preferred share purchase rights separate
from the shares of Micromet common stock, tendering stockholders will be
required to deliver certificates evidencing the preferred share purchase rights
with the shares of Micromet common stock (or confirmation of book-entry
transfer, if available, of such preferred share purchase rights) in order to
validly tender such shares in the Offer.

The Offer is not subject to any financing condition. The Offer is conditioned
upon: the Minimum Condition and the HSR Condition, as well as other customary
conditions. See Section 15 : “Conditions to the Offer.”

We expressly reserve the right from time to time to waive any of the
conditions described in Section 15 : “Conditions to the Offer,” to increase the
Offer Price or to make any other changes in the terms and conditions of the
Offer, except that we will not, without the prior written consent of Micromet,
(i) decrease the Offer Price, (ii) change the form of consideration payable in
the Offer, (iii) decrease the maximum number of Shares sought to be purchased in
the Offer, (iv) impose additional conditions to the Offer, (iv) amend or modify
any of the conditions to the Offer in a manner that adversely affects, or
reasonably would be expected to adversely affect, any holder of Shares, (v)
waive or change the Minimum Condition or (vi) extend or otherwise change the
Expiration Date in a manner other than as required or permitted by the Merger
Agreement.

Pursuant to the Merger Agreement and in accordance with Rule 14d-11 under the
U.S. Securities Exchange Act of 1934, as amended (the “Exchange Act”), we may
elect to provide a subsequent offering period (and one or more extensions
thereof) following the Expiration Date. If we elect to provide a subsequent
offering period, it will be an additional period of time, following the
Expiration Date, during which stockholders may tender any Shares not previously
tendered into the Offer prior to the Expiration Date (or Shares previously
tendered and later withdrawn prior to the Expiration Date) and not withdrawn. If
we elect to provide a subsequent offering period, (i) it will remain open for
such period or periods as we will specify of neither less than three business
days nor more than 20 business days, (ii) Shares may be tendered in the same
manner as was applicable to the Offer except that any Shares tendered during
such period may not be withdrawn pursuant to Rule 14d-7(a)(2) under the Exchange
Act, (iii) we will immediately accept and promptly pay for Shares as they are
tendered and (iv) the price per Share will be the same as the Offer Price. For
purposes of the Offer as provided under the Exchange Act, a “business day” means
any day other than a Saturday, Sunday or a U.S. federal holiday and consists of
the time period from 12:01 a.m. through 12:00 midnight, New York City time.

A subsequent offering period, if one is provided, is not an extension of the
Offer. If we do elect to provide a subsequent offering period, we will make a
public announcement of such election no later than 9:00 a.m., New York City
time, on the next business day after the Expiration Date.

The Merger Agreement separately provides that we are required to extend the
Offer for periods of not more than five business days each, or such other number
of business days as we, Amgen and Micromet may agree, but not beyond the End
Date, in order to permit the satisfaction of all remaining conditions (subject
to our right to waive any condition to the Offer (other than the Minimum
Condition) in accordance with the Merger Agreement), if at any scheduled
Expiration Date any condition to the Offer has not been satisfied or waived
(other than the Minimum Condition, which we may not waive) or for any period or
periods required by applicable law or any interpretation or position of the SEC
or its staff or NASDAQ or its staff, provided that (1) we will extend the then
current Expiration Date until the first business day on which the Offer can be
accepted under applicable law and (2) we are not obligated to extend the Offer
beyond the End Date.

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If we extend the Offer, are delayed in our acceptance for payment of Shares,
are delayed in payment after the Acceptance Time or are unable to accept Shares
for payment pursuant to the Offer for any reason, then, without prejudice to our
rights under the Offer, the Depositary may retain tendered Shares on our behalf,
and such Shares may not be withdrawn except to the extent that tendering
stockholders are entitled to withdrawal rights as described in this Offer to
Purchase under Section 4 : “Withdrawal Rights.” However, our ability to delay
the payment for Shares that we have accepted for payment is limited by Rule
14e-1(c) under the Exchange Act, which requires us to promptly pay the
consideration offered or return the securities deposited by or on behalf of
stockholders promptly after the termination or withdrawal of the Offer.

If we make a material change in the terms of the Offer or the information
concerning the Offer or if we waive a material condition of the Offer, we will
disseminate additional tender offer materials and extend the Offer if and to the
extent required by Rules 14d-4(d)(1), 14d-6(c) and 14e-1 under the Exchange Act
and the interpretations thereunder. The minimum period during which an offer
must remain open following material changes in the terms of an offer or
information concerning an offer, other than a change in price or a change in
percentage of securities sought, will depend upon the facts and circumstances,
including the relative materiality of the terms or information changes and the
appropriate manner of dissemination. In a published release, the SEC has stated
that, in its view, an offer should remain open for a minimum of five business
days from the date the material change is first published, sent or given to
stockholders, and that if material changes are made with respect to information
that approaches the significance of price and the percentage of securities
sought, a minimum period of 10 business days may be required to allow for
adequate dissemination to stockholders and investor response. In accordance with
the foregoing view of the SEC and the applicable law, if, prior to the
Expiration Date, and subject to the limitations of the Merger Agreement, we
change the number of Shares being sought or the consideration offered pursuant
to the Offer, and if the Offer is scheduled to expire at any time earlier than
the 10th business day from the date that notice of such change is first
published, sent or given to stockholders, the Offer will be extended at least
until the expiration of such 10th business day.

If, prior to the Expiration Date, we increase the consideration being
paid for Shares, such increased consideration will be paid to all stockholders
whose Shares are purchased in the Offer, whether or not such Shares were
tendered before the announcement of such increase in consideration.

Any extension, delay, termination, waiver or amendment of the Offer will be
followed as promptly as practicable by public announcement thereof, such
announcement in the case of an extension to be made no later than 9:00 a.m., New
York City time, on the next business day after the previously scheduled
Expiration Date. Subject to applicable law (including Rules 14d-4(d), 14d-6(c)
and 14e-1 under the Exchange Act, which require that material changes be
promptly disseminated to stockholders in a manner reasonably designed to inform
them of such changes) and without limiting the manner in which we may choose to
make any public announcement, we will have no obligation to publish, advertise
or otherwise communicate any such public announcement other than by issuing a
press release to a national news service.

Micromet has provided us with Micromet’s stockholder list and security
position listings for the purpose of disseminating the Offer to holders of
Shares. This Offer to Purchase and the Letter of Transmittal will be mailed to
record holders of Shares whose names appear on Micromet’s stockholder list and
will be furnished, for subsequent transmittal to beneficial owners of Shares, to
brokers, dealers, commercial banks, trust companies and other nominees whose
names, or the names of whose nominees, appear on the stockholder list or, if
applicable, who are listed as participants in a clearing agency’s security
position listing.

2.

Acceptance for Payment and Payment for Shares.

Upon the terms and subject to the conditions to the Offer (including, if the
Offer is extended or amended, the terms and conditions of any such extension or
amendment), we will accept for payment and will promptly (and in any event
within three business days) thereafter pay for all Shares validly tendered and
not properly withdrawn prior to the Expiration Date pursuant to the Offer.

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In all cases, payment for Shares accepted for payment pursuant to the Offer
will be made only after timely receipt by the Depositary of:

the certificates evidencing such Shares (“Share Certificates”) or
confirmation (a “Book-Entry Confirmation”) of a book-entry transfer of such
Shares into the Depositary’s account at The Depository Trust Company (the
“Book-Entry Transfer Facility”) pursuant to the procedures set forth in Section
3 : “Procedures for Accepting the Offer and Tendering Shares” and, if the
preferred share purchase rights separate from the Shares under the terms of the
Rights Agreement, certificates for such preferred share purchase rights (or a
confirmation of book-entry transfer, if available, of such preferred share
purchase rights into the Depositary’s account at the Book-Entry Transfer
Facility);

a properly completed and duly executed Letter of Transmittal, together with
any required signature guarantees or, in the case of book-entry transfer of
Shares, either such Letter of Transmittal or an Agent’s Message in lieu of such
Letter of Transmittal; and

any other documents required by the Letter of Transmittal.

Accordingly, tendering stockholders may be paid at different times depending
upon when Share Certificates or Book-Entry Confirmations with respect to their
Shares are actually received by the Depositary.

For purposes of the Offer, we will be deemed to have accepted for payment,
and thereby purchased, Shares validly tendered and not properly withdrawn, if
and when we give oral or written notice to the Depositary of our acceptance for
payment of such Shares pursuant to the Offer. Upon the terms and subject to the
conditions to the Offer, payment for Shares accepted for payment pursuant to the
Offer will be made by deposit of the Offer Price therefor with the Depositary,
which will act as agent for tendering stockholders for the purpose of receiving
payments from us and transmitting such payments to tendering stockholders of
record whose Shares have been accepted for payment. If, for any reason
whatsoever, acceptance for payment of any Shares tendered pursuant to the Offer
is delayed, or we are unable to accept for payment Shares tendered pursuant to
the Offer, then, without prejudice to our rights under the Offer, the Depositary
may, nevertheless, on our behalf, retain tendered Shares, and such Shares may
not be withdrawn, except to the extent that the tendering stockholders are
entitled to withdrawal rights as described in Section 4 : “Withdrawal Rights”
and as otherwise required by Rule 14e-1(c) under the Exchange Act.

Under no circumstances will interest with respect to the Shares
purchased pursuant to the Offer be paid, regardless of any extension of the
Offer or delay in making such payment.

All questions as to the validity, form, eligibility (including time
of receipt) and acceptance for payment of any tender of Shares will be
determined by us in our sole discretion. We reserve the absolute right to reject
any and all tenders determined by it not to be in proper form or the acceptance
for payment of which may, in the opinion of our counsel, be unlawful.

Shares tendered by a Notice of Guaranteed Delivery will not be deemed
validly tendered for purposes of satisfying the Minimum Condition unless and
until Shares underlying such Notice of Guaranteed Delivery are delivered to the
Depositary or unless otherwise mutually agreed by us and Micromet.

If any tendered Shares are not accepted for payment for any reason pursuant
to the terms and conditions of the Offer, or if Share Certificates are submitted
evidencing more Shares than are tendered, Share Certificates evidencing
unpurchased or untendered Shares will be returned, without expense, to the
tendering stockholder (or, in the case of Shares tendered by book-entry transfer
into the Depositary’s account at the Book-Entry Transfer Facility pursuant to
the procedure set forth in Section 3 : “Procedures for Accepting the Offer and
Tendering Shares,” such Shares will be credited to an account maintained at the
Book-Entry Transfer Facility), in each case, promptly following the expiration
or termination of the Offer.

We reserve the right to transfer or assign in whole or in part from time to
time to Amgen or one or more direct or indirect wholly-owned subsidiaries of
Amgen the right to purchase all or any Shares tendered pursuant

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to the Offer, but any such transfer or assignment will not relieve us of our
obligations under the Offer and will in no way prejudice your rights to receive
payment for Shares validly tendered and not withdrawn pursuant to the Offer.

3.

Procedures for Accepting the Offer and Tendering Shares.

Valid Tender of Shares. No alternative, conditional or contingent
tenders will be accepted. In order for a Micromet stockholder to validly tender
Shares pursuant to the Offer, the stockholder must follow one of the following
procedures:

for Shares held as physical certificates, the certificates representing
tendered Shares (including, if the preferred share purchase rights separate from
the Shares under the terms of the Rights Agreement, certificates for the
preferred share purchase rights), a properly completed and duly executed Letter
of Transmittal, together with any required signature guarantees, and any other
documents required by the Letter of Transmittal, must be received by the
Depositary at one of its addresses set forth on the back cover of this Offer to
Purchase before the Expiration Date (unless the tender is made during a
subsequent offering period, if one is provided, in which case the certificates
representing Shares, the Letter of Transmittal and other documents must be
received before the expiration of such subsequent offering period);

for Shares held in book-entry form, either a properly completed and duly
executed Letter of Transmittal, together with any required signature guarantees,
or an Agent’s Message in lieu of such Letter of Transmittal, and any other
required documents, must be received by the Depositary at one of its addresses
set forth on the back cover of this Offer to Purchase, and such Shares
(including, if the preferred share purchase rights separate from the Shares
under the terms of the Rights Agreement, such preferred share purchase rights)
must be delivered according to the book-entry transfer procedures described
below under “Book-Entry Transfer” and a Book-Entry Confirmation must be received
by the Depositary, in each case before the Expiration Date (unless the tender is
made during a subsequent offering period, if one is provided, in which case the
Letter of Transmittal or an Agent’s Message in lieu of such Letter of
Transmittal, and other documents must be received before the expiration of such
subsequent offering period); or

the tendering stockholder must comply with the guaranteed delivery procedures
described below under “Guaranteed Delivery” before the Expiration Date.

The term “Agent’s Message” means a message, transmitted by the Book-Entry
Transfer Facility to, and received by, the Depositary and forming a part of a
Book-Entry Confirmation, that states that the Book-Entry Transfer Facility has
received an express acknowledgment from the participant in the Book-Entry
Transfer Facility tendering the Shares that are the subject of such Book-Entry
Confirmation, that such participant has received and agrees to be bound by the
terms of the Letter of Transmittal and that we may enforce such agreement
against such participant.

Book-Entry Transfer. The Depositary will establish an account with
respect to the Shares at the BookEntry Transfer Facility for purposes
of the Offer within two business days after the date of this Offer to Purchase.
Any financial institution that is a participant in the system of the
BookEntry Transfer Facility may make a bookentry delivery of
Shares by causing the BookEntry Transfer Facility to transfer such
Shares into the Depositary’s account at the BookEntry Transfer
Facility in accordance with the BookEntry Transfer Facility’s
procedures for such transfer. However, although delivery of Shares may be
effected through bookentry transfer at the BookEntry
Transfer Facility, either a properly completed and duly executed Letter of
Transmittal, together with any required signature guarantees, or an Agent’s
Message and any other required documents (for example, in certain circumstances,
a completed Form W-9 that is included in the Letter of Transmittal) must, in any
case, be received by the Depositary at one of its addresses set forth on the
back cover of this Offer to Purchase prior to the Expiration Date, or the
tendering stockholder must comply with the guaranteed delivery procedure
described below. Delivery of documents to the
Book
Entry Transfer Facility does not constitute delivery to
the Depositary.

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Signature Guarantees. No signature guarantee is required on the
Letter of Transmittal if:

the Letter of Transmittal is signed by the registered holder (which term, for
purposes of this Section 3, includes any participant in the Book-Entry Transfer
Facility’s systems whose name appears on a security position listing as the
owner of the Shares) of the Shares tendered therewith, unless such holder has
completed either the box entitled “Special Delivery Instructions” or the box
entitled “Special Payment Instructions” on the Letter of Transmittal; or

Shares tendered pursuant to such Letter of Transmittal are for the account of
a financial institution (including most commercial banks, savings and loan
associations and brokerage houses) that is a member of or participant in a
recognized “Medallion Program” approved by the Securities Transfer Association
Inc., including the Security Transfer Agents Medallion Program (STAMP), the
Stock Exchange Medallion Program (SEMP) and the New York Stock Exchange
Medallion Signature Program (MSP), or any other “eligible guarantor
institution,” as such term is defined in Rule 17Ad-15 under the Exchange Act
(each, an “Eligible Institution” and, collectively, the “Eligible
Institutions”).

In all other cases, all signatures on a Letter of Transmittal must be
guaranteed by an Eligible Institution. See Instructions 1 and 5 of the Letter of
Transmittal. If a Share Certificate is registered in the name of a person or
persons other than the signer of the Letter of Transmittal, or if payment is to
be made or delivered to, or a Share Certificate not accepted for payment or not
tendered is to be issued in the name of or returned to, a person other than the
registered holder(s), then the Share Certificate must be endorsed or accompanied
by appropriate duly executed stock powers, in either case signed exactly as the
name(s) of the registered holder(s) appears on the Share Certificate, with the
signature(s) on such Share Certificate or stock powers guaranteed by an Eligible
Institution as provided in the Letter of Transmittal. See Instructions 1 and 5
of the Letter of Transmittal.

Guaranteed Delivery. If a stockholder desires to tender Shares
pursuant to the Offer and the Share Certificates evidencing such stockholder’s
Shares are not immediately available or such stockholder cannot deliver the
Share Certificates and all other required documents to the Depositary prior to
the Expiration Date, or such stockholder cannot complete the procedure for
delivery by book-entry transfer on a timely basis, such Shares may nevertheless
be tendered; provided that all of the following conditions are satisfied:

such tender is made by or through an Eligible Institution;

a properly completed and duly executed Notice of Guaranteed Delivery,
substantially in the form made available by us, is received prior to the
Expiration Date by the Depositary as provided below; and

the Share Certificates (or a Book-Entry Confirmation) evidencing all tendered
Shares, in proper form for transfer, in each case together with a properly
completed and duly executed Letter of Transmittal, together with any required
signature guarantees (or, in the case of book-entry transfer of Shares, either
such Letter of Transmittal or an Agent’s Message in lieu of such Letter of
Transmittal), and any other documents required by the Letter of Transmittal are
received by the Depositary within three NASDAQ trading days after the date of
execution of such Notice of Guaranteed Delivery.

A Notice of Guaranteed Delivery may be delivered by overnight courier or
mailed to the Depositary and must include a guarantee by an Eligible Institution
in the form set forth in the form of Notice of Guaranteed Delivery made
available by us. In the case of Shares held through the Book-Entry Transfer
Facility, the Notice of Guaranteed Delivery must be delivered to the Depositary
by a participant by means of the confirmation system of the Book-Entry Transfer
Facility.

Shares tendered by a Notice of Guaranteed Delivery will not be deemed
validly tendered for purposes of satisfying the Minimum Condition unless and
until Shares underlying such Notice of Guaranteed Delivery are delivered to the
Depositary unless otherwise mutually agreed by us and Micromet.

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The method of delivery of Shares, the Letter of Transmittal and all
other required documents, including delivery through the Book-Entry Transfer
Facility, is at the election and risk of the tendering stockholder. Shares will
be deemed delivered only when actually received by the Depositary (including, in
the case of a book-entry transfer, by Book-Entry Confirmation). If delivery is
by mail, then registered mail with return receipt requested, properly insured,
is recommended. In all cases, sufficient time should be allowed to ensure timely
delivery.

The tender of Shares pursuant to any one of the procedures described above
will constitute the tendering stockholder’s acceptance of the terms and
conditions of the Offer, as well as the tendering stockholder’s representation
and warranty that such stockholder has the full power and authority to tender
and assign the Shares tendered, as specified in the Letter of Transmittal, and
that when the Acceptance Time occurs, we will acquire good and unencumbered
title, free and clear of all liens, restrictions, charges and encumbrances and
not subject to any adverse claims. Our acceptance for payment of Shares tendered
pursuant to the Offer will constitute a binding agreement between the tendering
stockholder and us upon the terms and subject to the conditions to the Offer.

Determination of Validity. All questions as to the validity, form,
eligibility (including time of receipt) and acceptance for payment of any tender
of Shares will be determined by us in our sole discretion. We reserve the
absolute right to reject any and all tenders we determine not to be in proper
form or the acceptance for payment of which may, in the opinion of our counsel,
be unlawful. We also reserve the absolute right to waive any defect or
irregularity in the tender of any Shares of any particular stockholder, whether
or not similar defects or irregularities are waived in the case of other
stockholders. No tender of Shares will be deemed to have been validly made until
all defects and irregularities have been cured or waived to our satisfaction.
None of us, the Depositary, the Information Agent, the Dealer-Manager or any
other person will be under any duty to give notification of any defects or
irregularities in tenders or incur any liability for failure to give any such
notification. Our interpretation of the terms and conditions of the Offer
(including the Letter of Transmittal and the instructions thereto) will be
determined by us in our sole discretion.

Appointment as Proxy. By executing the Letter of Transmittal (or
taking action resulting in the delivery of an Agent’s Message) as set forth
above, unless Shares relating to such Letter of Transmittal or Agent’s Message
are properly withdrawn pursuant to the Offer, the tendering stockholder will
irrevocably appoint our designees, and each of them, as such stockholder’s
attorneys-in-fact and proxies in the manner set forth in the Letter of
Transmittal, each with full power of substitution, to the full extent of such
stockholder’s rights with respect to the Shares tendered by such stockholder and
accepted for payment by us and with respect to any and all other Shares or other
securities or rights issued or issuable in respect of such Shares. All such
proxies will be considered coupled with an interest in the tendered Shares. Such
appointment will be effective if and when, and only to the extent that, we
accept such Shares for payment pursuant to the Offer. Upon such appointment, all
prior powers of attorney, proxies and consents given by such stockholder with
respect to such Shares or other securities or rights will, without further
action, be revoked and no subsequent powers of attorney, proxies, consents or
revocations may be given by such stockholder (and, if given, will not be deemed
effective) with respect thereto. Each of our designees will thereby be empowered
to exercise all voting and other rights with respect to such Shares and other
securities or rights, including in respect of any annual, special or adjourned
meeting of Micromet’s stockholders or otherwise, as such designee in its sole
discretion deems proper. We reserve the right to require that, in order for
Shares to be deemed validly tendered, immediately upon the occurrence of the
Acceptance Time, we must be able to exercise full voting, consent and other
rights with respect to such Shares and other securities and rights, including
voting at any meeting of stockholders.

The foregoing powers of attorney and proxies are effective only upon
acceptance for payment of Shares pursuant to the Offer. The Offer does not
constitute a solicitation of proxies, absent a purchase of Shares, for any
meeting of Micromet’s stockholders.

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Micromet Options and Micromet Warrants. The Offer is made only for
outstanding Shares and is not made for any Micromet Options or Micromet
Warrants. See Section 11 : “The Merger Agreement; Other Agreements : The Merger
Agreement : Treatment of Micromet Equity Awards” for a description of the
treatment of the Micromet Options and Micromet Warrants.

Backup Withholding. To prevent federal “backup withholding” with
respect to payment of the Offer Price of Shares purchased pursuant to the Offer,
each stockholder (including any stockholder that tenders Shares into the Offer
pursuant to the book-entry transfer procedures described above in this Section
3) must provide the Depositary with its correct taxpayer identification number
and certify that it is not subject to backup withholding by completing the Form
W-9 that is included in the Letter of Transmittal or by otherwise certifying
such stockholder’s exemption from backup withholding. See Instruction 8 set
forth in the Letter of Transmittal and Section 5 : “Certain Material U.S.
Federal Income Tax Consequences of the Offer and the Merger” of this Offer to
Purchase for a more detailed discussion of backup withholding.

4.

Withdrawal Rights.

Except as otherwise provided in this Section 4, tenders of Shares made
pursuant to the Offer are irrevocable. Shares tendered pursuant to the Offer may
be withdrawn at any time prior to the Expiration Date. Thereafter, tenders of
Shares are irrevocable, except that they may also be withdrawn after April 2,
2012, which is the 60th day from the commencement of the Offer, unless such
Shares have already been accepted for payment by us pursuant to the Offer.

For a withdrawal to be proper and effective, a written notice of withdrawal
must be timely received by the Depositary at one of its addresses set forth on
the back cover page of this Offer to Purchase. Any such notice of withdrawal
must specify the name of the person who tendered the Shares to be withdrawn, the
number of Shares to be withdrawn and the name of the registered holder of such
Shares, if different from that of the person who tendered such Shares. If Share
Certificates evidencing Shares to be withdrawn have been delivered or otherwise
identified to the Depositary, then, prior to the physical release of such Share
Certificates, the serial numbers shown on such Share Certificates must be
submitted to the Depositary and the signature(s) on the notice of withdrawal
must be guaranteed by an Eligible Institution, unless such Shares have been
tendered for the account of an Eligible Institution. If Shares have been
tendered pursuant to the procedure for book-entry transfer as set forth in
Section 3 : “Procedures for Accepting the Offer and Tendering Shares :
Book-Entry Transfer,” any notice of withdrawal must also specify the name and
number of the account at the Book-Entry Transfer Facility to be credited with
the withdrawn Shares.

If we extend the Offer, are delayed in our acceptance for payment of Shares
or are unable to accept Shares for payment pursuant to the Offer for any reason,
then, without prejudice to our rights under the Offer, the Depositary may,
nevertheless, on our behalf, retain tendered Shares, and such Shares may not be
withdrawn except to the extent that tendering stockholders are entitled to
withdrawal rights as described in this Section 4 and as otherwise required by
Rule 14e-1(c) under the Exchange Act.

Any Shares properly withdrawn will thereafter be deemed not to have been
validly tendered for purposes of the Offer. However, withdrawn Shares may be
re-tendered at any time prior to the Expiration Date by following one of the
procedures described in Section 3 : “Procedures for Accepting the Offer and
Tendering Shares : Valid Tender of Shares.”

No withdrawal rights will apply to Shares tendered in any subsequent offering
period that we elect to provide (as described in more detail in Section 1 :
“Terms of the Offer”) or to Shares previously tendered into the Offer and
accepted for payment.

All questions as to the form and validity (including time of receipt) of any
notice of withdrawal will be determined by us in our sole discretion. None of
us, the Depositary, the Information Agent, the Dealer-Manager or any other
person will be under any duty to give notification of any defects or
irregularities in any notice of withdrawal or incur any liability for failure to
give any such notification.

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5.

Certain Material U.S. Federal Income Tax Consequences of the Offer
and the Merger.

The following is a summary of certain material U.S. federal income tax
consequences of the Offer and the Merger to holders whose Shares are purchased
pursuant to the Offer or whose Shares are converted into the right to receive
cash in the Merger (or pursuant to the exercise of appraisal rights in
accordance with Delaware law). This summary is not a comprehensive description
of all U.S. federal income tax considerations that may be relevant to the Offer
and the Merger. The discussion applies only to holders that hold their Shares as
capital assets, and may not apply to Shares received pursuant to the exercise of
employee stock options or otherwise as compensation, Shares held as part of a
“straddle,” “hedge,” “conversion transaction,” constructive sale or other
integrated transaction, holders that purchase or sell Shares as part of a wash
sale for tax purposes, holders in special tax situations (such as dealers in
securities or currencies, traders in securities that elect to use a
mark-to-market method of accounting for their securities holdings, banks,
insurance companies, tax-exempt organizations, U.S. expatriates, “controlled
foreign corporations” or “passive foreign investment companies”), or United
States Holders (as defined below) whose functional currency is not the U.S.
dollar. This discussion does not address any aspect of U.S. federal gift or
estate tax, or state, local or foreign taxation.

If a partnership holds Shares, the tax treatment of a partner in the
partnership generally will depend on the status of the partner and the tax
treatment of the partnership. Partners in partnerships holding Shares should
consult their tax advisors with regard to the U.S. federal income tax
consequences of exchanging Shares pursuant to the Offer or the Merger.

THE MATERIAL U.S. FEDERAL INCOME TAX CONSEQUENCES SET FORTH BELOW ARE
BASED ON CURRENT LAW. BECAUSE INDIVIDUAL CIRCUMSTANCES MAY DIFFER, EACH HOLDER
SHOULD CONSULT SUCH HOLDER’S OWN TAX ADVISOR TO DETERMINE THE APPLICABILITY OF
THE RULES DISCUSSED BELOW TO SUCH HOLDER AND THE PARTICULAR TAX EFFECTS OF THE
OFFER AND THE MERGER TO SUCH HOLDER, INCLUDING THE APPLICATION AND EFFECT OF
U.S. FEDERAL ESTATE AND GIFT, STATE, LOCAL AND OTHER TAX LAWS.

United States Holders. For purposes of this discussion, the term
“United States Holder” means a beneficial owner of Shares that is, for U.S.
federal income tax purposes:

a citizen or resident of the United States;

a domestic corporation;

an estate whose income is subject to United States federal income taxation
regardless of its source; or

a trust if (i) a court within the United States is able to exercise primary
supervision over the administration of the trust and one or more United States
persons have the authority to control all substantial decisions of the trust or
(ii) the trust has validly elected to be treated as a “United States person”
under applicable Treasury regulations.

The receipt of cash for Shares pursuant to the Offer or the Merger (or
pursuant to the exercise of appraisal rights) will be a taxable transaction for
U.S. federal income tax purposes. In general, a United States Holder will
recognize gain or loss in an amount equal to the difference between such United
States Holder’s adjusted federal income tax basis in such Shares sold pursuant
to the Offer or converted into the right to receive cash in the Merger (or
appraised in an appraisal proceeding by the Delaware Court of Chancery) and the
amount of cash received therefor. Gain or loss must be determined separately for
each block of Shares (i.e., Shares acquired at the same cost in a single
transaction) sold pursuant to the Offer or converted into the right to receive
cash in the Merger. Such gain or loss will be capital gain or loss (other than,
with respect to the exercise of appraisal rights, amounts, if any, that are or
are deemed to be interest for federal income tax purposes, which amounts will be
taxed as ordinary income) and will be long-term capital gain or loss if, on the
date of sale (or, if applicable, the date of the Merger), such Shares were held
for more than one year. Long-term capital gains recognized by an individual
generally will be taxed at preferential rates. Net capital losses may be subject
to limits on deductibility.

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Non-United States Holders. For purposes of this discussion, the term
“Non-United States Holder” means a beneficial owner of Shares that is not a
United States person for U.S. Federal income tax purposes.

In general, a Non-United States Holder will not be subject to U.S. federal
income tax on gain recognized on Shares sold pursuant to the Offer or converted
into the right to receive cash in the Merger (or appraised in an appraisal
proceeding by the Delaware Court of Chancery) unless:

the gain is “effectively connected” with the Non-United States Holder’s
conduct of a trade or business in the United States, and the gain is
attributable to a permanent establishment that such holder maintains in the
United States, if that is required by an applicable income tax treaty as a
condition for subjecting such holder to U.S. taxation on a net income basis;

the Non-United States Holder is an individual present in the United States
for 183 or more days in the taxable year of the sale and certain other
conditions exist; or

Micromet is or has been a United States real property holding corporation for
U.S. federal income tax purposes and the Non-United States Holder held, directly
or indirectly, at any time during the five-year period ending on the date of
sale (or, if applicable, the date of the Merger), more than 5% of Shares and
such holder is not eligible for any treaty exemption.

“Effectively connected” gains that are recognized by a corporate Non-United
States Holder also may be subject, under certain circumstances, to an additional
“branch profits tax” at a 30% rate or at a lower rate if such holder is eligible
for the benefits of an income tax treaty that provides for a lower rate.

Micromet has not been, is not and does not anticipate becoming a United
States real property holding corporation before the date of sale (or, if
applicable, the date of the Merger) for U.S. federal income tax purposes.

Information Reporting and Backup Withholding. Payments made to a
noncorporate United States Holder in connection with the Offer or the Merger
generally will be subject to information reporting and may be subject to “backup
withholding”. See Section 3 : “Procedure for Accepting the Offer and Tendering
Shares : Backup Withholding” of this Offer to Purchase.

Backup withholding generally applies if a United States Holder (i) fails to
provide an accurate taxpayer identification number or (ii) in certain
circumstances, fails to comply with applicable certification requirements. A
Non-United States Holder generally will be exempt from information reporting and
backup withholding if it certifies on an Internal Revenue Service Form W-8BEN
that it is not a U.S. person, or otherwise establishes an exemption in a manner
satisfactory to the Depositary.

Backup withholding is not an additional tax and may be refunded by the
Internal Revenue Service to the extent it results in an overpayment of tax.
Certain persons generally are entitled to exemption from information reporting
and backup withholding, including corporations. Certain penalties apply for
failure to provide correct information and for failure to include reportable
payments in income. Each holder should consult with his or her own tax advisor
as to his or her qualification for exemption from backup withholding and the
procedure for obtaining such exemption. Tendering United States Holders may be
able to prevent backup withholding by completing the Form W-9 that is included
in the Letter of Transmittal or, in the case of Non-United States Holders, a
Form W-8BEN.

6.

Price Range of Shares; Dividends.

The Shares are listed on the NASDAQ under the symbol “MITI.” The Shares have
been listed on the NASDAQ since May 9, 2006.

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The following table sets forth, for the calendar quarters indicated, the high
and low closing prices per Share on the NASDAQ as reported on the
NASDAQ(1):

High

Low

Year Ending December 31, 2012:

First Quarter (through February 1, 2012)

$10.96

$7.37

Year Ended December 31, 2011:

First Quarter

$

8.37

$

4.82

Second Quarter

7.07

5.28

Third Quarter

6.42

4.37

Fourth Quarter

7.24

4.68

Year Ended December 31, 2010:

First Quarter

$

8.83

$

6.68

Second Quarter

8.33

5.32

Third Quarter

7.30

6.01

Fourth Quarter

8.54

6.48

(1)

Source: Bloomberg L.P.

According to Micromet, as of January 25, 2012, there were (a) 92,375,454
issued and outstanding Shares, (b) outstanding Micromet Options to purchase
14,017,356 Shares and (c) Micromet Warrants to purchase 7,766,046 Shares.

The Offer Price of $11.00 per Share represents an approximate:

33% premium to the closing price per Share reported on the NASDAQ on January
25, 2012, the last day before we announced the execution of the Merger Agreement
and the Offer;

52% premium to the closing price per Share reported on the NASDAQ on December
23, 2011, the last closing price 30 days before the day we announced the
execution of the Merger Agreement and the Offer;

24% premium over the 52-week-high intraday price per Share reported on the
NASDAQ for the period ended January 25, 2012, the last day before we announced
the execution of the Merger Agreement and the Offer; and

34%, 58%, 86% and 87% over the volume-weighted average trading prices for the
Shares for the one-month, three-month, six-month and twelve-month periods ending
on the last day before we announced the execution of the Merger Agreement and
the Offer.

On February 1, 2012, the last trading day before we commenced the Offer, the
closing price of Shares reported on the NASDAQ was $10.94 per Share. We
encourage you to obtain a recent quotation for Shares in deciding whether to
tender your Shares. See Section 6 : “Price Range of Shares; Dividends.”

Stockholders are urged to obtain current market quotations for Shares
before making a decision with respect to the Offer.

Micromet has never declared or paid cash dividends with respect to the
Shares. Under the terms of the Merger Agreement, Micromet is not permitted to
declare or pay any dividend in respect of the Shares without Amgen’s prior
written consent. See Section 11 : “The Merger Agreement; Other Agreements : The
Merger Agreement : Conduct of Business of Micromet.”

7. Certain Information Concerning Micromet.

Except as otherwise set forth in this Offer to Purchase, the information
concerning Micromet contained in this Offer to Purchase has been taken from or
based upon publicly available documents and records on file with

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the SEC and other public sources and is qualified in its entirety by
reference thereto. None of us, Amgen, the Information Agent and the
Dealer-Manager take responsibility for the accuracy or completeness of the
information contained in such documents and records or for any failure by
Micromet to disclose events that may have occurred or may affect the
significance or accuracy of any such information but that are unknown to us,
Amgen, the Information Agent and the Dealer-Manager.

General. Micromet is a Delaware corporation incorporated in 1998.
The principal executive offices of Micromet are located at 9201 Corporate
Boulevard, Suite 400, Rockville, Maryland, 20850 and the telephone number is
(240) 752-1420.

As described in the joint press release announcing the execution of the
Merger Agreement, issued by Amgen and Micromet on January 26, 2012 and filed by
Micromet with the SEC on Schedule 14D-9 on such date, Micromet is a
biopharmaceutical company focused on the discovery, development and
commercialization of innovative antibody-based therapies for the treatment of
cancer. Micromet is advancing a robust pipeline of novel therapeutics based on
its proprietary BiTE ® (Bispecific T cell Engager) technology. BiTE
antibodies are designed to direct the body’s cytotoxic, or cell-destroying, T
cells against tumor cells, and represent a new therapeutic approach to cancer
therapy. Typically, antibodies cannot engage T cells because T cells lack the
appropriate receptors for binding antibodies. BiTE antibodies have been shown to
bind T cells to tumor cells, ultimately killing the tumor cells.

Micromet’s lead product candidate, blinatumomab, is a BiTE antibody in Phase
2 clinical development for acute lymphoblastic leukemia (“ALL”). Blinatumomab is
also in clinical development for the treatment of non-Hodgkin’s lymphoma
(“NHL”), and could have applications in other hematologic malignancies.

Blinatumomab has demonstrated encouraging single-agent activity in both adult
and pediatric patients with ALL as well as adult patients with NHL, and is
currently under investigation in five trials:

Two Phase 2 trials for adult patients with relapsed/refractory ALL

Phase 1/2 trial for pediatric patients with relapsed/refractory ALL

Phase 2 trial for adult ALL patients with minimal residual disease

Phase 1 trial for adult patients with relapsed/refractory NHL

Available Information. Micromet files annual, quarterly and current
reports, proxy statements and other information with the SEC. Micromet’s SEC
filings are available to the public over the Internet at the SEC’s website at
www.sec.gov. You may also read and copy any document Micromet files with the SEC
at the SEC’s Public Reference Room at 100 F Street, N.E., Washington, D.C.
20549. Please call the SEC at 1-800-SEC-0330 for further information on the
public reference rooms. Micromet maintains a website at www.micromet.com. These
website addresses are not intended to function as hyperlinks, and the
information contained on Micromet’s website and on the SEC’s website is not
incorporated by reference in this Offer to Purchase and you should not consider
it a part of this Offer to Purchase.

8. Certain Information Concerning Purchaser and Amgen.

Purchaser. We are a Delaware corporation and a wholly-owned
subsidiary of Amgen and were formed solely for the purpose of engaging in the
transactions contemplated by the Merger Agreement, including the Offer and the
Merger. To date, we have not carried on any activities other than those related
to our formation, the Merger Agreement, the Offer and the Merger. We have
minimal assets and liabilities other than the contractual rights and obligations
as set forth in the Merger Agreement. Following the consummation of the Offer
and the satisfaction or waiver of the remaining conditions set forth in the
Merger Agreement, we will merge with and into Micromet, with Micromet continuing
as the Surviving Corporation. Our principal executive offices are located at One
Amgen Center Drive, Thousand Oaks, California, 91320-1799. Our business
telephone number is (805) 447-1000.

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Amgen. Amgen is a Delaware corporation. The business address of
Amgen is One Amgen Center Drive, Thousand Oaks, California, 91320-1799. The
business telephone number for Amgen is (805) 447-1000. Amgen is the world’s
largest independent biotechnology medicines company. Amgen discovers, develops,
manufactures and markets medicines for grievous illnesses. Amgen focuses solely
on human therapeutics and concentrates on innovating novel medicines based on
advances in cellular and molecular biology. Amgen’s mission is to serve
patients.

Additional Information. Certain information concerning the directors
and executive officers of Amgen is set forth in Annex A to this Offer to
Purchase and certain information concerning our directors and executive officers
is set forth in Annex B to this Offer to Purchase.

Except as set forth elsewhere in this Offer to Purchase (including Section 10
: “Background of the Offer; Past Contacts, Transactions, Negotiations and
Agreements with Micromet”, Section 11 : “The Merger Agreement; Other
Agreements”, Annex A and Annex B): (i) neither we nor Amgen nor, to our
knowledge or the knowledge of Amgen after reasonable inquiry, any of the persons
or entities listed in Annex A or Annex B, or any associate or affiliate of the
foregoing, beneficially owns or has a right to acquire any Shares or any other
equity securities of Micromet, (ii) neither we nor Amgen nor, to our knowledge
or the knowledge of Amgen after reasonable inquiry, any of the persons or
entities referred to in clause (i) has effected any transaction in the Shares or
any other equity securities of Micromet during the 60-day period preceding the
date of this Offer to Purchase, (iii) neither we nor Amgen nor, to our knowledge
or the knowledge of Amgen after reasonable inquiry, any of the persons listed on
Annex A or Annex B, has any contract, arrangement, understanding or relationship
with any other person with respect to any securities of Micromet, (iv) during
the two years prior to the date of this Offer to Purchase, there have been no
transactions between us and Amgen, its subsidiaries or, to our knowledge or the
knowledge of Amgen after reasonable inquiry, any of the persons listed in Annex
A and Annex B, on the one hand, and Micromet or any of its executive officers,
directors or affiliates, on the other hand, (v) during the two years prior to
the date of this Offer to Purchase, there have been no negotiations,
transactions or contracts between us, Amgen, our or its subsidiaries or, to our
knowledge or the knowledge of Amgen after reasonable inquiry, any of the persons
listed in Annex A and Annex B, on the one hand, and Micromet or any of its
executive officers, directors or affiliates, on the other hand, concerning a
merger, consolidation or acquisition, a tender offer or other acquisition of
securities, an election of directors or a sale or other transfer of a material
amount of assets, (vi) there are no present or proposed material agreements,
arrangements, understandings or relationships between us, Amgen or any of our or
its respective executive officers, directors or affiliates, on the one hand, and
Micromet or any of its executive officers, directors or affiliates, on the other
hand and (vii) during the past five years, neither we nor Amgen has been
convicted in a criminal proceeding (excluding traffic violations or similar
misdemeanors) or been a party to any judicial or administrative proceeding
(except for matters that were dismissed without sanction or settlement) that
resulted in a judgment, decree or final order enjoining it from future
violations of, or prohibiting activities subject to, U.S. federal or state
securities laws, or a finding of any violation of U.S. federal or state
securities laws.

Available Information. Pursuant to Rule 14d-3 under the Exchange
Act, we and Amgen have filed with the SEC a Tender Offer Statement on Schedule
TO (as amended, which we refer to as the “Schedule TO”), of which this Offer to
Purchase forms a part, and exhibits to the Schedule TO and such documents are
available to the public over the Internet at the SEC’s website at www.sec.gov.
You may also read and copy any document filed by us and/or Amgen with the SEC at
the SEC’s Public Reference Room at 100 F Street, N.E., Washington, D.C. 20549.
Please call the SEC at 1-800-SEC-0330 for further information on the public
reference rooms. Amgen maintains a website at www.amgen.com. These website
addresses are not intended to function as hyperlinks, and the information
contained on Amgen’s website and on the SEC’s website is not incorporated by
reference in this Offer to Purchase and you should not consider it a part of
this Offer to Purchase.

9. Source and Amount of Funds.

The total amount of funds required by us to consummate the Offer and purchase
all outstanding Shares in the Offer and to provide funding in connection with
the Merger is approximately $1.16 billion, plus related fees and expenses.
Amgen, our parent company, will provide us with sufficient funds to purchase all
Shares validly

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tendered in the Offer and will provide funding for our acquisition of the
remaining Shares in the Merger. Amgen expects to fund such cash requirements
from its available cash. The Offer is not subject to any financing condition.

We do not believe that our financial condition is relevant to a decision by a
holder of Shares whether to tender Shares and accept the Offer because (i) the
consummation of the Offer is not subject to any financing condition, (ii) the
Offer is being made for all Shares solely for cash, (iii) if the Offer is
consummated, we will acquire all remaining Shares in the Merger for the same
cash price as was paid in the Offer (i.e., the Offer Price) and (iv) we, through
Amgen, have sufficient funds available to purchase all Shares validly tendered
and not properly withdrawn pursuant to the Offer and to provide funding for the
Merger in light of Amgen’s financial capacity in relation to the amount of
consideration payable.

10. Background of the Offer; Past Contacts, Transactions,
Negotiations and Agreements with Micromet.

References to Amgen below in certain cases may be references to us or other
entities that are affiliates of Amgen.

Background of the Offer

Amgen regularly evaluates its business and plans and considers a variety of
transactions to enhance its business. Amgen has considered a number of
alternatives for developing its businesses, including partnerships and
acquisitions of other companies and businesses. As part of this process,
beginning in late 2010 Amgen engaged in discussions with Micromet in order to
find transactions to enhance its profile in technologies for treating cancer.
These discussions led to a July 2011 collaboration between Amgen and Micromet on
the research of BiTE ® antibodies in solid tumors (referred to herein
as the Solid Tumor Collaboration). Shortly after the discussions commenced,
Amgen began to examine Micromet as a potential acquisition target based on
Micromet’s capabilities and the determination that Micromet’s assets would be
complementary in the development of novel therapeutics for the treatment of
grievous illnesses.

On April 5, 2011, Dr. Roger Perlmutter, Executive Vice President, Research
and Development of Amgen, Dr. Iain Dukes, Vice President, External R&D of
Amgen, Mrs. Erin Lavelle, Executive Director, Business Development of Amgen, and
Mr. Michael Flaschen, Executive Director, External R&D of Amgen, met in New
York City with Dr. Christian Itin, Chief Executive Officer of Micromet, Dr.
Patrick Baeuerle, Chief Science Officer of Micromet and Dr. Jens Hennecke,
Senior Vice President, Business Development of Micromet, to discuss the ongoing
collaboration negotiations. At that meeting, representatives of Amgen introduced
the idea of a strategic transaction with Micromet. Dr. Itin indicated that at
the time Micromet was focused on completing the proposed collaboration on new
BiTE antibodies. As a result, Amgen did not make an offer at that time, but
instead continued to pursue the Solid Tumor Collaboration, while its senior
management continued to discuss internally potential strategic options regarding
Micromet.

On May 18, 2011, Dr. Dukes met with Dr. Michael Carter, a member of the
Micromet Board, in Rhode Island, for a purpose unrelated to Micromet and Dr.
Dukes raised the subject of an acquisition of Micromet by Amgen. Dr. Carter
expressed his views that the Micromet Board might be willing to entertain an
appropriate acquisition offer by Amgen and indicated that he would raise the
matter with the Chairman of the Micromet Board, Mr. David Hale.

Amgen engaged Moelis & Company LLC and Moelis & Company UK LLP as of
June 17, 2011 to act as its financial advisors for a potential acquisition of
Micromet.

On July 11, 2011, Amgen and Micromet AG, a wholly-owned subsidiary of
Micromet, entered into, and Micromet announced, the Solid Tumor Collaboration.

On July 14, 2011, Drs. Perlmutter and Dukes met with Mr. Hale and Mr. Joseph
Slattery, another member of the Micromet Board, in San Diego to express Amgen’s
interest in a potential transaction and indicated that Amgen was planning to
prepare a non-binding proposal letter for an acquisition.

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On July 18, 2011, Amgen’s senior management team agreed to proceed with a
non-binding proposal to Micromet and Mr. Kevin W. Sharer, Amgen’s Chairman of
the Board and Chief Executive Officer, sent a letter to Mr. Hale indicating
Amgen’s proposal for an acquisition of Micromet at a price of $9.00 per Share in
cash.

On July 25, 2011, Dr. Dukes called Dr. Carter seeking information on the
status of Micromet’s response to Amgen’s proposal. Dr. Carter informed Dr. Dukes
that Micromet had a meeting of the Micromet Board the next day with its
financial advisor, Goldman, Sachs & Co. (referred to herein as Goldman
Sachs), to assess Amgen’s proposal.

On July 26, 2011, representatives of Goldman Sachs contacted Mr. David
Piacquad, Vice President, Strategy and Corporate Development of Amgen, to
indicate that Micromet was not interested in a transaction at that price level.

On July 28, 2011, the Amgen Board met and discussed a possible acquisition of
Micromet. At this meeting, Amgen’s management discussed its views on Micromet
and the Amgen Board asked questions about Micromet. After these discussions, the
Amgen Board authorized Amgen’s senior management to enter into an agreement to
acquire Micromet upon certain conditions including completion of due diligence
and definitive agreements.

On August 1, 2011, Dr. Perlmutter contacted Mr. Hale to indicate that Amgen
remained interested in a transaction and would like to conduct additional due
diligence on Micromet. At that time, Mr. Hale indicated he would convey that
interest to the Micromet Board at its meeting later that week. Dr. Perlmutter
and Mr. Hale then discussed the possibility of a face-to-face meeting in
mid-August.

Mr. Hale followed up with Dr. Perlmutter following Micromet’s Board of
Directors meeting on August 3, 2011 and confirmed the opportunity for a limited
due diligence discussion to determine whether Amgen could increase its offer
price if Amgen would enter into a confidentiality agreement with a standstill
with Micromet.

On August 5, 2011, Dr. Itin contacted Dr. Perlmutter to coordinate the due
diligence session and proposed the meeting in San Francisco. Dr. Itin and
Micromet provided Amgen with a proposed agenda for the due diligence session and
draft confidentiality agreement and Dr. Perlmutter submitted a due diligence
request list and proposed attendee list to Dr. Itin. The parties negotiated the
scope of the diligence meeting and confidentiality agreement over the next few
days and entered into the confidentiality agreement on August 18, 2011.

The parties met on August 18, 2011 in San Francisco for a due diligence
session to discuss potential sources of additional value that would permit Amgen
to increase its offer price. Among those in attendance for Amgen were Drs.
Perlmutter and Dukes, Mr. Piacquad, Dr. Sean Harper, Senior Vice President,
Global Development and Corporate Chief Medical Officer of Amgen, Dr. Paul
Eisenberg, Senior Vice President, Global Regulatory Affairs and Safety of Amgen,
Dr. Roy Baynes, Vice President, Global Development Hematology/Oncology of Amgen,
Ms. Alison Moore, Vice President, Process & Product Engineering of Amgen,
and Mr. Jonathan Porter, Director, Commercial Global Marketing of Amgen. Those
in attendance for Micromet included Drs. Itin, Baeuerle and Hennecke, Dr. Ulrich
Grau, Chief Operating Officer of Micromet, Dr. Jan Fagerberg, Chief Medical
Officer of Micromet, and a representative of Goldman Sachs.

On August 29, 2011, Amgen’s senior management team met and discussed the
results of the August 18th meeting and, following discussion of certain
questions decided to continue discussions with Micromet for a transaction at
$9.00 per Share.

On September 1, 2011, Dr. Perlmutter called Mr. Hale and reiterated Amgen’s
proposal to acquire Micromet at a price of $9.00 per Share. Mr. Hale indicated
that he was disappointed that Amgen was unwilling to raise its offer price
following the due diligence meeting and that the Micromet Board had determined
that $9.00 per share was not an appropriate value for Micromet stockholders, but
that he would take that proposal back to the Micromet Board.

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Mr. Hale responded to Dr. Perlmutter on September 9, 2011 to indicate that
Micromet’s Board had determined that $9.00 was not an adequate acquisition price
for Micromet and the Board was disappointed that Amgen did not find increased
value through the diligence discussion in San Francisco.

Mr. Sharer sent a letter, dated September 19, 2011, to Mr. Hale indicating
that Amgen continued to propose a price for Micromet at $9.00 per Share.

On September 22, 2011, a representative of Goldman Sachs spoke with Robert A.
Bradway, Chief Operating Officer of Amgen, and again conveyed the Micromet
Board’s unwillingness to proceed with discussions at $9.00 per share and their
disappointment that Amgen did not find increased value as a result of the
diligence discussions in San Francisco. Goldman Sachs agreed to call Amgen after
discussing the matter further with the Micromet Board.

On September 29, 2011, representatives of Goldman Sachs spoke with Mr.
Piacquad and confirmed that Micromet would further respond to Amgen’s offer
after Micromet’s Board meeting scheduled for the following week.

On October 11, 2011, representatives of Goldman Sachs on behalf of Micromet’s
Board contacted Mr. Piacquad to reject the $9.00 per Share offer, but
communicated that Micromet might still entertain a potential transaction with
Amgen at a substantially higher price. The representatives of Goldman Sachs also
indicated that Micromet was pursuing licensing and collaboration transactions.
Over the next several weeks, Amgen and its advisors spent a significant amount
of time in an effort to determine whether Amgen would be willing to increase its
proposal and ways to structure any such proposal.

On October 28, 2011, Mr. Sharer sent a letter to Mr. Hale indicating that
Amgen was willing to increase the price in its proposal by acquiring Micromet in
a transaction in which Amgen would pay a fixed amount equal to $9.00 per Share
in cash plus a contingent value component paying up to $3.00 more per Share in
$1.00 increments contingent on the achievement of certain commercial sales and
regulatory milestones for blinatumumab if they occurred within certain time
periods extending out to 2017.

On November 3, 2011, representatives from Goldman Sachs contacted Mr.
Piacquad to indicate that Micromet’s Board had decided not to pursue the October
28, 2011 proposal from Amgen.

On November 22, 2011, representatives from Goldman Sachs had a conversation
with Mr. Piacquad and Dr. Dukes in which Mr. Piacquad and Dr. Dukes indicated
that Amgen would not submit a cash offer at a substantially higher price. The
representatives of Goldman Sachs indicated that Mr. Hale might be willing to
present to the Micromet Board an all cash offer at a price below the $12.00 per
Share in total potential consideration reflected in Amgen’s last offer. Goldman
Sachs also communicated that the Micromet Board had not formally agreed to enter
into discussions at a price below $12.00 per Share.

On December 7 and December 16, 2011, Amgen’s senior management team reviewed
the transaction and discussed the financial implications of a revised offer.
Amgen’s senior management agreed to submit a revised offer of $10.75 per Share
on December 19, 2011.

On December 21, 2011, Mr. Piacquad and Dr. Dukes contacted Mr. Hale to
discuss the potential acquisition and communicated that Amgen was potentially
willing to increase the fixed price portion of its earlier proposal, but that
Amgen desired entering into a transaction containing only a fixed price
component at $10.75 per Share. Mr. Hale indicated that he would need to convene
the Micromet Board to consider this proposal.

On January 3, 2012, Mr. Hale responded to Mr. Piacquad and Dr. Dukes that the
Micromet Board would not accept $10.75 per Share; however, Mr. Hale indicated
that Micromet’s Board would be willing to work toward a transaction and work
with Amgen on due diligence if Amgen would raise its price to $11.00 per Share.
Mr. Piacquad and Dr. Dukes agreed to review a price of $11.00 per Share with
Amgen’s senior management.

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On January 5, 2012, Amgen’s senior management team received an update from
Mr. Piacquad and agreed to proceed with an offer price of $11.00 per Share
subject to Amgen Board approval before entering into a definitive agreement. On
the same day, Mr. Piacquad and Dr. Dukes verbally agreed to a purchase price of
$11.00 per Share with Mr. Hale subject to completion of Amgen’s due diligence,
negotiation of mutually acceptable transaction documentation and approval by the
Amgen Board and the Micromet Board. As a follow-up, Amgen and Micromet entered
into an amendment to their confidentiality agreement to change certain matters
relating to the process of contacting Micromet personnel and Amgen provided
Micromet a due diligence request list.

On January 6, 2012, Amgen’s legal counsel, Sullivan & Cromwell LLP (which
we refer to herein as S&C), provided to Micromet’s legal counsel, Cooley LLP
(which we refer to herein as Cooley) an initial draft of the Merger Agreement.

On January 7, 2012, Micromet made available to Amgen an on-line data room
containing due diligence information and Amgen commenced due diligence on these
documents.

On January 9, 2012, Amgen and Micromet met in Cooley’s offices in San
Francisco to conduct further due diligence on Micromet while various of the
attendees at the meeting were in San Francisco to attend the J.P. Morgan
Healthcare Conference. Amgen participants included Drs. Perlmutter, Harper,
Eisenberg and Dukes, Mr. Piacquad, Ms. Moore and Dr. Susie Jun, Executive
Medical Director, Global Development of Amgen and Mr. Peter Sandor, Vice
President, Global Marketing of Amgen. Those in attendance for Micromet included
Mr. Hale (for a portion of the meeting) and Drs. Itin and Hennecke as well as
representatives from Goldman Sachs.

From that point forward, until January 25, 2012, representatives of Amgen
continued to perform a due diligence investigation of Micromet. During this
time, Amgen, Micromet and their representatives held numerous due diligence
calls and Micromet added materials to its online data room on an ongoing basis.
In addition, several representatives from Amgen and Micromet also met in person
and via telephone on January 13, 2012 to discuss various due diligence
questions.

On January 11, 2012, Cooley provided S&C with a draft of the Merger
Agreement. S&C responded with comments on this draft on January 15, 2012.
Cooley responded with comments to this draft on January 18, 2012 and
representatives of Amgen, S&C and Cooley had a telephone conference the
following day on January 19, 2012 to discuss open issues, including issues
related to the ability of the Micromet Board to change its recommendation, the
triggers to the payment of the termination fee, the amount of the termination
fee, the exceptions to the definition of Material Adverse Effect and the
calculation of the Minimum Condition. On January 20, 2012, Cooley provided
S&C with additional comments to the Merger Agreement, and, later that night,
S&C provided Cooley with a revised draft of the Merger Agreement.

On January 20, 2012, the Amgen Board met with Amgen’s management, including
its General Counsel, to discuss the current state of the negotiations with
Micromet. Management discussed its analysis of the transaction with the Amgen
Board, the financial analyses of Micromet and the proposed transaction. At this
meeting, the Amgen Board discussed the material terms of transaction. The Amgen
Board asked questions of management and after discussing the terms of the
transaction authorized management to continue discussions with Micromet and to
enter into a transaction with Micromet.

From January 22, 2012 through January 25, 2012, representatives from Amgen,
S&C, Cooley and Micromet had a series of telephone conversations to discuss
certain open issues related to the Merger Agreement, exchanged drafts of the
Merger Agreement and negotiated the Merger Agreement.

On January 23, 2012, Mr. Hale had a conversation with Mr. Piacquad and
communicated the Micromet Board’s request for an increase in the offer price to
$11.50 per share based on the increase in Micromet’s stock price since late
December 2011 and the reduction in the premium to the current market price. Mr.
Piacquad indicated that he believed that Amgen was offering fair value for
Micromet but would need to consult with other

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senior management before responding to the proposal. Later on the same day,
after discussions with senior management of Amgen and its financial advisors,
Mr. Piacquad contacted Mr. Hale and indicated that Amgen was not prepared to
increase its price above $11.00 per Share. Mr. Hale responded that he would take
that response to the Micromet Board the next day.

On January 24, 2012, Mr. Hale contacted Mr. Piacquad and indicated that he
believed that Micromet would be prepared to continue moving forward at $11.00
per Share, but that an issue that was being discussed among counsel relating to
certain of the circumstances under which the termination fee would become
payable would need to be resolved favorably to Micromet.

On January 25, 2012, following the close of trading on the NASDAQ, Micromet
informed Amgen that at a meeting of the Micromet Board, the Micromet Board had
unanimously (i) approved, and declared advisable, the Merger Agreement and the
transactions contemplated by the Merger Agreement, including the Offer and the
Merger, upon the terms and subject to the conditions set forth therein, (ii)
determined that the Merger Agreement and the transactions contemplated thereby
are fair to, and in the best interests of, Micromet and its stockholders and
(iii) resolved to recommend that Micromet’s stockholders accept the Offer,
tender their Shares into the Offer and, to the extent required by applicable
law, adopt the Merger Agreement. Later on January 25, 2012, the Merger Agreement
was executed and delivered on behalf of each of Amgen, Purchaser and Micromet.
The following morning, on January 26, 2012, Amgen and Micromet issued a joint
press release announcing the execution of the Merger Agreement.

On February 2, 2012, Purchaser commenced the Offer described in this Offer to
Purchase. Micromet’s description of its review process is contained in the
Schedule 14D-9.

Past Contacts, Transactions, Negotiations and Agreements with
Micromet

On July 11, 2011, Amgen entered into a Collaboration and License Agreement
with Micromet under which the two parties agreed to collaborate on the research
of BiTE antibodies against three undisclosed solid tumor targets and the
subsequent development and commercialization of BiTE antibodies against up to
two of these targets, to be selected by Amgen. Amgen paid an up-front payment of
10 million, or $14.5 million using the exchange rate as of the payment date, of
which 4 million (or $5.7 million using the exchange rate as of the payment
date) was an advanced payment to Micromet for research and development services
to be performed by Micromet and the remaining 6 million (or $8.5 million using
the exchange rate as of the payment date) was designated as the license fee
relating to the license of BiTE antibody technology and know-how. Micromet has
been primarily responsible for the generation and pre-clinical research of the
BiTE antibodies, and Amgen will lead the clinical development, manufacturing,
and commercialization of any products resulting from the collaboration. Micromet
is eligible to receive up to a total of 342 million in milestone payments in
connection with the development and sale of BiTE antibodies against the first
target selected by Amgen, as follows: 7 million in pre-clinical milestones, 35
million in clinical milestones, and 300 million in milestones related to
product approval and achievement of certain sales thresholds. Micromet is also
eligible to receive an additional cash payment upon initiation of the program,
as well as milestones, royalties and development funding comparable to the first
program. The combined potential payments to Micromet from both programs,
excluding reimbursement of research and development costs, are approximately
695 million. Micromet has not recognized any milestone revenue under this
Collaboration and License Agreement to date.

The Collaboration and License Agreement contains termination provisions
whereby Amgen may terminate the agreement upon 90 days’ notice. There are also
provisions for termination for material breach that either party may invoke
according to the terms of the agreement.

11. The Merger Agreement; Other Agreements.

The Merger Agreement

The following is a summary of certain provisions of the Merger Agreement.
This summary does not purport to be complete and is qualified in its entirety by
reference to the full text of the Merger Agreement, a copy of

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which is filed as Exhibit (d)(1) to the Schedule TO, which is incorporated
herein by reference. Copies of the Merger Agreement and the Schedule TO, and any
other filings that we make with the SEC with respect to the Offer or the Merger,
may be obtained in the manner set forth in Section 8 : “Certain Information
Concerning Purchaser and Amgen : Available Information.” Stockholders and other
interested parties should read the Merger Agreement for a more complete
description of the provisions summarized below.

Explanatory Note Regarding the Merger Agreement

The Merger Agreement is included to provide you with information
regarding its terms. Factual disclosures about Amgen, us and Micromet or any of
their respective affiliates contained in this Offer to Purchase or in their
respective public reports filed with the SEC, as applicable, may supplement,
update or modify the factual disclosures about Amgen, us and Micromet or any of
their respective affiliates contained in the Merger Agreement. The
representations, warranties and covenants made in the Merger Agreement by Amgen,
us and Micromet were qualified and subject to important limitations agreed to by
Amgen, us and Micromet in connection with negotiating the terms of the Merger
Agreement. In particular, in your review of the representations and warranties
contained in the Merger Agreement and described in this summary, it is important
to bear in mind that the representations and warranties were negotiated with the
principal purposes of establishing the circumstances in which a party to the
Merger Agreement may have the right not to consummate the Offer or the Merger if
the representations and warranties of the other party prove to be untrue due to
a change in circumstance or otherwise, and allocating risk between the parties
to the Merger Agreement, rather than establishing matters as facts. The
representations and warranties may also be subject to a contractual standard of
materiality different from those generally applicable to stockholders and
reports and documents filed with the SEC, and in some cases were qualified by
disclosures set forth in schedules that were provided by each party to the other
but are not publicly filed as part of the Merger Agreement. Moreover,
information concerning the subject matter of the representations and warranties,
which do not purport to be accurate as of the date of this Offer to Purchase,
may have changed since the date of the Merger Agreement and subsequent
developments or new information qualifying a representation or warranty may have
been included in this Offer to Purchase.

The Offer

The Merger Agreement provides that we will commence the Offer as promptly as
practicable but in no event more than ten business days after the date of the
Agreement, and that, subject to the satisfaction of the Minimum Condition and
other conditions that are described in Section 15 : “Conditions to the Offer,”
Amgen will cause us to accept for payment, and we will accept for payment, all
Shares validly tendered and not properly withdrawn pursuant to the Offer
promptly after the Expiration Date. The initial Expiration Date will be 12:00
midnight, New York City time, at the end of Thursday, March 1, 2012.

Terms and Conditions of the Offer

Our obligations to accept for payment, and pay for, any Shares tendered
pursuant to the Offer are subject to the conditions set forth in Section 15 :
“Conditions to the Offer.” The Offer conditions are for the sole benefit of
Amgen and us, and we or Amgen may waive, in whole or in part, any condition to
the Offer from time to time, in our or its sole discretion, provided that we may
not waive the Minimum Condition, or amend or modify any of the other conditions
in the Offer in a manner that adversely affects, or reasonably would be expected
to adversely affect, any Micromet stockholders, in each case, without the prior
written consent of Micromet.

Extensions of the Offer; Subsequent Offering Period

The Merger Agreement provides that we will extend the Offer (a) for periods
of not more than five business days each or such other number of business days
as we, Amgen and Micromet may agree, but not beyond the End Date, in order to
permit the satisfaction of all remaining conditions (subject to our right to
waive any

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condition to the Offer (other than the Minimum Condition) in accordance with
the Merger Agreement), if on any scheduled Expiration Date any condition to the
Offer has not been satisfied or waived (other than the Minimum Condition, which
we may not waive), and (b) for any period or periods required by applicable law
or any interpretation or position of the SEC or its staff or NASDAQ or its
staff, provided that (1) we will extend the then current Expiration Date until
the first business day on which the Offer can be accepted under applicable law
and (2) we are not obligated to extend the Offer beyond the End Date. We may
also elect to provide a subsequent offering period of neither less than three
business days nor more than 20 business days, during which time Micromet’s
stockholders whose Shares have not been tendered prior to the Expiration Date
(or whose Shares were tendered and later withdrawn prior to the Expiration Date)
may tender, but not withdraw, their Shares and receive the Offer Price.

Micromet Board Recommendation

The Micromet Board has, at a meeting duly called and held, unanimously (i)
determined that the Merger Agreement and the transactions contemplated by the
Merger Agreement are advisable, fair to and in the best interests of Micromet
and its stockholders, (ii) approved, and declared advisable, the Merger
Agreement, the Offer, the Merger and the transactions contemplated by the Merger
Agreement in accordance with the requirements of Delaware law and (iii) resolved
to recommend that Micromet’s stockholders accept the Offer and tender their
Shares to us pursuant to the Offer, and, to the extent required by applicable
law, adopt the Merger Agreement (item (iii), the “Micromet Board
Recommendation”).

Micromet’s Board of Directors

Upon the Acceptance Time and all times thereafter, we will be entitled to
elect or designate a number of directors, rounded up to the next whole number,
to the Micromet Board that is equal to the product of (a) the total number of
directors on the Micromet Board (after giving effect to the directors elected or
designated by us) multiplied by (b) the percentage that the aggregate number of
Shares beneficially owned by Amgen, us and any of our affiliates bears to the
total number of Shares then outstanding, and Micromet will, upon our request at
any time following the purchase of and payment for Shares pursuant to the Offer,
take all actions necessary to (i) appoint to the Micromet Board the individuals
designated by us and permitted to be so designated as described above,
including, but not limited to, promptly filling vacancies or newly created
directorships on the Micromet Board, promptly increasing the size of the
Micromet Board (including by amending Micromet’s bylaws if necessary so as to
increase the size of the Micromet Board) and/or promptly securing the
resignations of the number of its incumbent directors as are necessary or
desirable to enable our designees to be so elected or designated to the Micromet
Board, and (ii) cause our designees to be so appointed at such time. Micromet
will, upon our request following the Acceptance Time, cause directors designated
by us to constitute the same percentage (rounded up to the next whole number) as
is on the Micromet Board of each committee of the Micromet Board to the extent
permitted by applicable law and the rules of the NASDAQ.

In the event that directors designated by us are elected or designated to the
Micromet Board, until the Effective Time, Micromet will cause the Micromet Board
to maintain the Continuing Directors. After the Acceptance Time and prior to the
Effective Time, if our designees constitute a majority of the Micromet Board,
the affirmative vote of a majority of the Continuing Directors will (in addition
to the approval rights of the Micromet Board or the stockholders of Micromet as
may be required by Micromet’s certificate of incorporation or bylaws or by
applicable law) be required (i) for Micromet to amend or terminate the Merger
Agreement, (ii) to exercise or waive any of Micromet’s rights, benefits or
remedies under the Merger Agreement, if such action would adversely affect, or
would reasonably be expected to adversely affect, Micromet’s stockholders (other
than Amgen or us), (iii) to amend Micromet’s certificate of incorporation or
bylaws if such action would adversely affect the holders of Shares (other than
Amgen or us), or (iv) to take any other action of the Micromet Board under or in
connection with the Merger Agreement if such action would materially and
adversely affect, or would reasonably be expected to materially and adversely
affect, Micromet’s stockholders (other than Amgen or us).

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Top-Up Option

Pursuant to the Merger Agreement, Micromet has granted to us and Amgen the
Top-Up Option, which is an option that we or Amgen may, but are not obligated
to, exercise, to purchase from Micromet the Top-Up Option Shares. The Top-Up
Option may be exercised by us or Amgen, in whole or in part, at any time on or
after the Acceptance Time, in our or its sole discretion, until the earlier to
occur of the Effective Time and the termination of the Merger Agreement in
accordance with its terms; provided, however, that the obligation of Micromet to
deliver Top-Up Option Shares upon the exercise of the Top-Up Option is subject
to the condition, unless waived by Micromet, that immediately following the
exercise of the Top-Up Option, the number of Shares owned in the aggregate by
Amgen and us constitutes at least one Share more than 90% of the number of
Shares that would be outstanding immediately after the issuance of all Top-Up
Option Shares.

The Top-Up Option is intended to expedite the timing of the consummation of
the Merger (after consummation of the Offer, at which time Micromet would be a
majority-owned subsidiary of Amgen, which would have the requisite voting power
to cause stockholder adoption of the Merger Agreement, even without exercise of
the Top-Up Option) by permitting the Merger to occur pursuant to Delaware’s
“short-form” merger statute, Section 253 of the DGCL, without any vote of
Micromet’s stockholders.

The aggregate purchase price payable for the Top-Up Option Shares will be
determined by multiplying the number of Top-Up Option Shares by the Offer Price.
Such purchase price may be paid by Amgen or us, at our election, (i) in cash or
(ii) by (x) paying in cash an amount equal to not less than the aggregate par
value of the Top-Up Option Shares and (y) payment of the balance by executing
and delivering to Micromet a promissory note (with full recourse to Amgen), with
such terms as specified in the Merger Agreement, having a principal amount equal
to the difference between the aggregate purchase price and the amount paid in
cash.

The Merger

The Merger Agreement provides that, following the consummation of the Offer,
subject to the terms and conditions of the Merger Agreement, and in accordance
with the DGCL, at the Effective Time:

we will be merged with and into Micromet and, as a result of the Merger, our
separate corporate existence will cease;

Micromet will be the Surviving Corporation in the Merger and will become a
wholly-owned subsidiary of Amgen; and

all of our property, assets, rights, privileges, immunities, powers and
franchises and those of Micromet will vest in Micromet as the Surviving
Corporation, and all of our debts, liabilities, obligations and duties and those
of Micromet will become the debts, liabilities and duties of Micromet as the
Surviving Corporation.

Certificate of Incorporation; Bylaws; Directors and Officers of the
Surviving Corporation.
Unless otherwise determined by Amgen prior to the
Effective Time, at the Effective Time, (i) the certificate of incorporation of
the Surviving Corporation will be amended and restated in its entirety to be
identical to our certificate of incorporation as in effect immediately prior to
the Effective Time, (ii) the bylaws of the Surviving Corporation will be amended
and restated to conform to our bylaws as in effect immediately prior to the
Effective Time and (iii) the directors and officers of the Surviving Corporation
immediately after the Effective Time will be the respective individuals who are
designated as our directors and officers immediately prior to the Effective
Time.

Merger Closing Conditions. Our obligations and the obligations of
Amgen, on the one hand, and Micromet, on the other hand, to effect the Merger
are each subject to the satisfaction of each of the following conditions:

the adoption of the Merger Agreement by the affirmative vote of the holders
of at least a majority of the then outstanding Shares, if required by applicable
law;

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no temporary restraining order, preliminary or permanent injunction or other
order preventing the consummation of the Merger shall have been issued by any
governmental body of competent jurisdiction and remain in effect, and there
shall not be any applicable action taken, or any applicable law or order
promulgated, entered, enforced, enacted, issued or deemed applicable to the
Offer or the Merger that directly or indirectly prohibits, or makes illegal, the
acceptance of or payment for Shares, or the consummation of the Offer or the
Merger illegal; and

the occurrence of the Acceptance Time.

Merger Consideration. At the Effective Time, each Share then
outstanding (other than Shares that are held by any stockholders who properly
demand appraisal in connection with the Merger as described in Section 17 :
“Certain Legal Matters; Regulatory Approvals : Appraisal Rights”) (each, an
“Eligible Share”) will be converted into the right to receive the Offer Price,
without interest, less any applicable withholding taxes, except for Shares then
owned by Amgen, Micromet or any of their respective wholly-owned subsidiaries,
which Shares will be cancelled and retired and will cease to exist, and no
consideration will be delivered in exchange therefor.

Payment for Shares. Before the Effective Time, Amgen will designate
a bank or trust company reasonably acceptable to Micromet to make payment of the
consideration payable in the Merger (the “Paying Agent”). At the Effective Time
and from time to time thereafter to the extent necessary, we or Amgen will
deposit or cause to be deposited with the Paying Agent, for the benefit of
holders of Eligible Shares, cash in immediately available funds necessary to pay
the aggregate consideration payable in the Merger.

As soon as reasonably practicable after the Effective Time and in no event
later than three business days thereafter, the Paying Agent will send to each
holder of Shares (other than Shares then owned by Amgen, Micromet or any of
their respective wholly-owned subsidiaries) a letter of transmittal and
instructions advising the stockholders how to surrender Eligible Shares
represented by Share Certificates or book-entry (“Micromet Book-Entry Shares”)
in exchange for the consideration payable in the Merger, which is an amount per
Share in cash equal to the Offer Price. The Paying Agent will pay the
consideration payable in the Merger to the holders of Eligible Shares upon (1)
surrender of a Share Certificate, together with a letter of transmittal, duly
completed and validly executed in accordance with the instructions therein, and
such other documents as may be required pursuant to such instructions or (2)
delivery to the Paying Agent of an Agent’s Message in respect of Micromet
Book-Entry Shares (or such other evidence, if any, of transfer as the Paying
Agent may reasonably request). Interest will not be paid or accrue in respect of
the consideration payable in the Merger. The Surviving Corporation will reduce
the amount of any consideration payable in the Merger paid to the stockholders
by any applicable withholding taxes.

If any cash deposited with the Paying Agent is not claimed within 180 days
following the Effective Time, such cash will be returned to the Surviving
Corporation, upon its demand, and any stockholders who have not theretofore
complied with Share exchange procedures in the Merger Agreement will thereafter
look only to the Surviving Corporation for payment of their claims for the
consideration payable in the Merger, without interest, less any applicable
withholding taxes. Notwithstanding the foregoing, neither the Surviving
Corporation nor the Paying Agent will be liable to any holder of Shares for any
consideration payable in the Merger delivered in respect of such Shares to a
public official pursuant to abandoned property, escheat or other similar
applicable law.

The transmittal instructions will include instructions if the stockholder has
lost a Share Certificate or if it has been stolen or destroyed. The stockholder
will have to provide an affidavit to that fact and, if required by Amgen, post a
bond in a customary amount and upon such terms as may be required by Amgen as
indemnity against any claim that may be made against it in respect of such Share
Certificate.

Treatment of Micromet Equity Awards

Micromet has represented to us that it currently has outstanding Micromet
Options that are exercisable for an aggregate of 14,017,356 Shares.

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At the Effective Time, each outstanding Micromet Option, whether vested or
unvested, will be cancelled and converted into only the right to receive,
without interest, after giving effect to any accelerated vesting at the
Effective Time contemplated under the Merger Agreement or under the terms of any
employment agreement or individual award agreement, for the portion of each
Micromet Option that is (i) vested and exercisable as of the Effective Time, an
amount in cash equal to the product of (A) the excess, if any, of (1) the Offer
Price over (2) the exercise price per share of such vested portion of the
Micromet Option, and (B) the number of Shares underlying the vested portion of
such Micromet Option, and (ii) not vested at the Effective Time, an amount in
cash equal to the product of (A) the excess, if any, of (1) the Offer Price over
(2) the exercise price per share of such unvested portion of the Micromet
Option, and (B) the number of Shares underlying such unvested portion of the
Micromet Option (in each case, such product, less applicable withholdings, the
“Option Payment Amount”).

For the portion of each Micromet Option that is vested and exercisable as of
the Effective Time, the Option Payment Amount will be payable to the holder of
such option as soon as reasonably practicable, but no later than the second
payroll period, after the Effective Time. For the portion of each Micromet
Option that is not vested and exercisable as of the Effective Time, the Option
Payment Amount in respect of such cancelled and converted unvested portion of
the Micromet Option will be subject to the same vesting schedule and other
relevant terms applicable to the Micromet Option as in effect before the
Effective Time. The Option Payment Amount will be payable to the holder thereof
no later than the second payroll period after the applicable vesting date of
such payment, subject to the holder’s continued employment through the vesting
date, or earlier termination without “cause” (including because of the holder’s
death or disability) or resignation for “good reason” (in each case within the
meaning of the applicable Micromet equity plan or individual employment
agreement), in which case the Option Payment Amount will be payable to the
holder thereof by no later than the second payroll period after the date of such
termination or resignation. Any Option Payment Amount in respect of a cancelled
and converted unvested portion of a Micromet Option that remains outstanding and
unvested as of December 15, 2012 will vest on December 15, 2012, and such Option
Payment Amount will be paid to the holder no later than December 31, 2012. Any
partial accelerated vesting, pursuant to an individual employment agreement or
award agreement, will be applied pro rata, on a grant by grant basis, to each
vesting tranche subject to such accelerated vesting, such that the portion of
each such vesting tranche that is not accelerated will be subject to the same
vesting schedule in effect as of the date of the Merger Agreement. In addition,
the portion of each Micromet Option that is not vested as of the Effective Time
and which is held by a non-employee member of the Micromet Board will be subject
to accelerated vesting and become exercisable in full upon the Effective Time
and cashed-out in the same manner as other vested Micromet Options.

Treatment of Micromet Warrants

Micromet has represented to us that it currently has outstanding warrants
that are exercisable for an aggregate of 7,766,046 Shares. Any holder of a
warrant that exercises such warrant prior to the Expiration Date will receive
Shares which such holder may tender into the Offer in the same manner as any
other holder of Shares. Any warrant that remains outstanding following the
Expiration Date will be treated in accordance with the terms of the applicable
warrant. The Merger Agreement provides that following the closing of the
transactions, Amgen will cause the Surviving Corporation to assume, exchange or
make payment with respect to all outstanding warrants of Micromet and will take
all actions necessary and required to comply with the terms of Micromet’s
warrants.

Representations and Warranties

The Merger Agreement contains representations and warranties of Amgen, us and
Micromet.

Some of the representations and warranties in the Merger Agreement made by
Micromet are qualified as to “materiality” or “Material Adverse Effect.” For
purposes of the Merger Agreement, an event, occurrence, violation, inaccuracy,
circumstance or other matter will be deemed to have a “Material Adverse Effect”
on Micromet and its subsidiaries taken as a whole if such event, occurrence,
violation, inaccuracy, circumstance or

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other matter had or would reasonably be likely to have a material adverse
effect on (a) the assets, liabilities, business, financial condition or results
of operations of Micromet and its subsidiaries taken as a whole or (b) the
ability of Micromet to consummate the transactions contemplated by the Merger
Agreement; provided, however, that none of the following shall be deemed in and
of themselves, either alone or in combination, to constitute, and none of the
following shall be taken into account in determining whether there is, or would
reasonably likely to be, a Material Adverse Effect on Micromet and its
subsidiaries:

any change in the market price or trading volume of the Shares (provided,
however, that this exception will not apply to the underlying causes of any such
change or prevent any of such underlying causes from being taken into account in
determining whether a Material Adverse Effect has occurred);

any event, occurrence, circumstance, change or effect arising from the
announcement or pendency of the transactions contemplated by the Merger
Agreement to the extent attributable to the identity of Amgen;

any event, circumstance, change or effect in the national, European or
international economy, biopharmaceutical industry or financial markets generally
unless such event, circumstance, change or effect materially and
disproportionately impacts Micromet and its subsidiaries, taken as a whole,
compared to other participants in the biopharmaceutical industry;

any event, occurrence, circumstance, change or effect arising directly or
indirectly from or otherwise relating to any act of terrorism, war, national or
international calamity or any other similar event unless such event,
circumstance, change or effect materially and disproportionately impacts
Micromet and its subsidiaries, taken as a whole, compared to other participants
in the biopharmaceutical industry;

the failure of Micromet or its subsidiaries to meet internal or analysts’
expectations or projections or the results of operations (provided, however,
that this exception will not apply to the underlying causes of any such failure
or prevent any of such underlying causes from being taken into account in
determining whether a Material Adverse Effect has occurred);

any adverse effect arising directly from or otherwise directly relating to
the termination, at Amgen’s request, of any or all employee plans intended to
qualify under Section 401(k) of Internal Revenue Code of 1986, as amended, in
accordance with the terms of the Merger Agreement or the failure of Micromet or
any of its subsidiaries to take any action that Micromet and its subsidiaries
are specifically prohibited from taking prior to the Acceptance Time pursuant to
the provision in the Merger Agreement relating to the operation of Micromet’s
business and that was not consented to by Amgen; or

any event, circumstance, change or effect arising directly or indirectly from
or otherwise relating to any change in, or any compliance with or action taken
for the purpose of complying with, applicable law or United States generally
accepted accounting principles (“GAAP”) (or interpretations of applicable law or
GAAP), unless such event, circumstance, change or effect materially and
disproportionately impacts Micromet and its subsidiaries, taken as a whole,
compared to other participants in the biopharmaceutical industry.

In the Merger Agreement, Micromet has made customary representations and
warranties to Amgen and us with respect to, among other things:

the due organization, valid existence, good standing and qualification to do
business of Micromet and its subsidiaries;

Micromet’s capitalization;

Micromet’s SEC filings;

Micromet’s financial statements;

the absence of certain changes or events;

title to assets;

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real property and equipment;

intellectual property matters, including the absence of infringement of
rights of others;

material contracts and the absence of any defaults under material contracts;

the absence of certain material undisclosed liabilities;

compliance with applicable laws;

compliance with regulatory requirements, including possession of all
governmental licenses and permits necessary to conduct its business;

compliance with domestic and international anti-bribery laws;

disclosure of Micromet’s communications with certain governmental bodies;

tax matters, including filings of material tax returns and payment of
material taxes;

employee benefit matters, including the status of employee benefit plans;

environmental matters, including compliance of Micromet and its subsidiaries
with applicable environmental laws;

insurance coverage;

the absence of certain undisclosed transactions with affiliates;

the absence of any material litigation or other legal proceedings, claims or
investigations;

corporate authorization and validity of the Merger Agreement;

the inapplicability of any anti-takeover law to the Merger Agreement and the
Offer, the Merger and the other transactions contemplated by the Merger
Agreement;

stockholder votes required to adopt the Merger Agreement, if adoption is
required;

the absence of any conflict between the execution of the Merger Agreement and
the consummation of the Offer and the Merger, on the one hand, and the
organizational or governing documents or certain agreements of Micromet and its
subsidiaries or applicable laws, on the other hand;

required government filings, approvals and notices;

an amendment to the Rights Agreement to exempt the transactions contemplated
by the Merger Agreement;

the receipt by the Micromet Board of a fairness opinion from Goldman, Sachs
& Co.;

parties entitled to financial advisory fees based on Micromet’s arrangements;
and

the accuracy of information supplied by Micromet for inclusion in this Offer
to Purchase, and the absence of material untrue statements or omissions in the
Schedule 14D-9 and any proxy or information statement relating to the Merger.

In the Merger Agreement, we and Amgen have made customary representations and
warranties to Micromet with respect to, among other things:

the organization, valid existence, good standing and qualification to do
business of Amgen and us;

corporate authorization and validity of the Merger Agreement;

the absence of any conflict between the execution of the Merger Agreement and
the consummation of the Offer and the Merger, on the one hand, and our
organizational or governing documents and those of Amgen, applicable laws or
certain of our agreements and those of Amgen, on the other hand;

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required government filings, approvals and notices;

the accuracy of information supplied by Amgen and us for inclusion in the
Schedule 14D-9 and any proxy or information statement relating to the Merger,
and the absence of material untrue statements or omissions in this Offer to
Purchase;

absence of litigation;

availability of funds necessary to perform our respective obligations under
the Merger Agreement, including the payment of the aggregate Offer Price and
consideration payable in the Merger; and

lack of ownership of Shares by Parent, us or our affiliates.

None of the representations and warranties contained in the Merger Agreement
survive the consummation of the Merger.

Conduct of Business of Micromet

The Merger Agreement provides that, except (i) as required or otherwise
contemplated under the Merger Agreement, (ii) with the written consent of Amgen
or (iii) as previously disclosed to Amgen in connection with entering into the
Merger Agreement, during the period from the date of the Merger Agreement and
until the earlier of the Acceptance Time and the termination of the Merger
Agreement, Micromet will, and will cause each of its subsidiaries to, conduct
its business and operations (A) in the ordinary course and in substantially the
same manner as previously conducted and (B) using its commercially reasonable
efforts to maintain compliance with applicable law and the requirements of its
material contracts. During such time, Micromet will use commercially reasonable
efforts to preserve intact components of its current business organization,
including keeping available the services of current officers and key employees
and use commercially reasonable efforts to maintain its relations and good will
with its suppliers and customers and governmental bodies; provided, however,
that Micromet and its subsidiaries are not obligated to put in place any new
retention programs or to include additional personnel in existing retention
programs.

In addition, during the same period, except (i) as required or otherwise
contemplated under the Merger Agreement, (ii) with the written consent of Amgen
or (iii) as previously disclosed to Amgen in connection with entering into the
Merger Agreement, Micromet will not, and will not permit any of its subsidiaries
to, take certain actions (subject to certain further exceptions to the
individual restrictions set forth in the Merger Agreement, including in certain
circumstances exceptions relating to Micromet’s ordinary course of business
consistent with past practice), including the following:

declare, accrue, set aside or pay any dividend or make any other distribution
in respect of any shares of Micromet’s capital stock, or repurchase, redeem or
otherwise reacquire any shares of Micromet’s capital stock, other than dividends
or distributions by a subsidiary of Micromet to Micromet or another subsidiary
of Micromet;

sell, issue, grant or authorize the issuance or grant of any security, any
right to acquire any security or any instrument convertible into or exchangeable
for any security of Micromet or any of its subsidiaries, except issuances upon
the valid exercise of Micromet Options or Micromet Warrants outstanding as of
the date of the Merger Agreement;

split, combine or reclassify any of the outstanding shares of capital stock
of Micromet or enter into any agreement with respect to voting of any of the
capital stock of Micromet or its subsidiaries or any securities convertible into
or exchangeable for such capital stock;

other than as contemplated by the Merger Agreement or to the extent required
by applicable law, (1) enter into, establish, adopt, modify, amend or terminate
any employee plan or any employment, consulting, collective bargaining, bonus or
other incentive compensation, health or other welfare, pension, retirement,

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severance, deferred compensation or any other compensation or benefit plan
with, for or in respect of any director, officer, other employee or consultant
that would constitute an employee plan under the Merger Agreement had it been in
effect on the date of the Merger Agreement, (2) grant any new awards under any
employee plan, (3) take any action to amend, modify or waive any of its rights
under, or accelerate the vesting criteria or vesting requirements of payment of
any compensation or benefit under, any employee plan, (4) increase in any manner
the compensation, bonuses, severance pay or any other benefits of any employee
or director of Micromet or its subsidiaries, (5) pay any bonus to any employee
or director of Micromet or its subsidiaries, except for such individual’s unpaid
2011 annual bonus, (6) promote any employee or hire any employee or engage any
temporary employee or independent contractor other than a replacement hire to
fill an existing position as previously disclosed to us that (i) was vacated as
a result of attrition and (ii) is for a position for which total annual
compensation is less than $100,000 or 100,000, (7) take any action to
accelerate the vesting or payment, or fund or in any other way secure the
payment, of compensation or benefits under any employee plan, to the extent not
already provided in any such employee plan, (8) change any actuarial or other
assumptions used to calculate funding obligations with respect to any employee
plan or change the manner in which contributions to such plans are made or the
basis on which such contributions are determined, except as may be required by
GAAP or applicable law or (9) issue or forgive any loans to any employee or
director of Micromet or its subsidiaries; provided, however, that Micromet and
its subsidiaries may provide routine, reasonable salary increases to
non-executive employees in the ordinary course of business in amount not to
exceed 6% per individual and 4% in the aggregate salary amount for all
individuals, may amend any employee plans to the extent required by applicable
law and may accelerate bonus payments for eligible directors, officers or other
employees of Micromet or its subsidiaries whose employment is terminated before
payment of annual bonuses for the year of termination, in accordance with bonus
plans existing on the date of the Merger Agreement;

amend, modify or waive any provision of or permit the adoption of any
amendment to its certificate of incorporation or bylaws or other charter or
organizational documents or the Rights Agreement;

form any subsidiary, acquire any equity interest or other interest in any
other entity or enter into any joint venture, partnership, limited liability
corporation or similar arrangement;

incur any indebtedness for borrowed money or issue any debt securities or
warrants or other rights to acquire debt securities of Micromet or any of its
subsidiaries, or assume, guarantee or endorse the obligations of any other
person, in the case of any of the foregoing, involving an aggregate principal
amount or potential guaranteed amount in excess of $25,000 individually or
$125,000 in the aggregate, or otherwise incur or modify any material
indebtedness or liability;

pre-pay any long-term debt or accelerate or delay any material payments or
the collection of payment due to Micromet;

make capital expenditures other than (1) capital expenditures set forth in
the Micromet’s capital expense budget provided to us and (2) capital
expenditures not provided for in such budget that do not exceed $50,000
individually and $250,000 in the aggregate during any calendar quarter;

acquire, lease, license or sublicense any material right or other material
asset from any other person or sell or otherwise dispose of, or lease, license
or sublicense, any material right or other material asset to any other person,
or waive or relinquish, abandon, allow to lapse or encumber (except encumbrances
permitted by the Merger Agreement) any material right or material asset or enter
into any discussion relating to the foregoing with respect to blinatumomab, or
MT103;

lend money or make capital contributions to or make investments in, any
person, except as required under Micromet’s parent guarantee of its
subsidiaries’ obligations or for short term borrowings in the ordinary course of
business;

enter into, amend, waive any provision of, modify in any material respect or
terminate any material contract;

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enter into, modify, amend or terminate any contract or waive, release or
assign any rights or claims thereunder, if the result of such action would be
reasonably likely to adversely affect MT103 in any material respect;

make or change any material tax election, settle or compromise any material
tax liability, claim or assessment, change any actual tax accounting period,
change or consent to any change in any tax accounting method, file any amended
material tax return, enter into any closing agreement, surrender any right to
claim a material tax refund, waive or extend or consent to any extension or
waiver of the statute of limitations period applicable to any material taxes,
tax claim or assessment, or incur any material liability for tax outside of the
ordinary course of business;

commence any legal proceeding, except (1) routine matters in the ordinary
course of business and consistent with past practices, (2) where Micromet
reasonably determines in good faith that the failure to commence suit would
result in a material impairment of a valuable aspect of its business (after
consultation with Amgen) or (3) in connection with a breach of the Merger
Agreement or any other agreements contemplated thereby;

settle any legal proceeding, except for settlements that result solely in a
monetary obligation involving payment by Micromet or its subsidiaries of (1) not
more than the amount specifically reserved in accordance with GAAP with respect
to such legal proceeding on Micromet’s balance sheet or (2) not more than
$500,000 in the aggregate (in addition to any amounts funded through insurance
policies);

change any of its methods of accounting or accounting practices in any
material respect unless required by GAAP or by applicable law;

dispose of any MT103 drug substance or drug product inventory (“MT103
Inventory”), including any expired MT103 Inventory, except and only to the
extent required by applicable law or contracts entered into by Micromet or its
subsidiaries prior to the date of the Merger Agreement;

enter into any collective bargaining, agreement to form a work council or
other union or similar agreement or commit to enter into any such agreements,
except as required by applicable law; and

agree or commit to take any of the foregoing actions.

No Solicitation

Micromet has agreed that, during the period from the date of the Merger
Agreement until the earlier of the Acceptance Time and the termination of the
Merger Agreement, neither it nor its subsidiaries nor any of their
representatives, directly or indirectly, will:

solicit, initiate or knowingly induce, facilitate or encourage the submission
or announcement of any Acquisition Proposal (as defined below) (including by
granting any waiver under Section 203 of the DGCL) or any inquiry or indication
of interest that could reasonably be expected to lead to an Acquisition
Proposal;

furnish any information regarding Micromet or any of its subsidiaries to any
person in connection with or in response to an Acquisition Proposal or an
inquiry or indication of interest that could reasonably be expected to lead to
an Acquisition Proposal;

participate or engage in discussions or negotiations with any person with
respect to any Acquisition Proposal or an inquiry or indication of interest that
could reasonably be expected to lead to an Acquisition Proposal;

approve, endorse or recommend any Acquisition Proposal; or

enter into any letter of intent, term sheet, merger agreement, acquisition
agreement, option agreement or similar document or any contract contemplating or
otherwise relating to any Acquisition Proposal.

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However, prior to the Acceptance Time, Micromet is not prohibited from
furnishing nonpublic information regarding itself and its subsidiaries to, or
entering into discussions with, any person in response to a bona-fide written
Acquisition Proposal that is submitted after the date of the Merger Agreement to
Micromet by such person (and not withdrawn) if (1) none of Micromet, its
subsidiaries or any representative of Micromet or its subsidiaries breached or
took any action inconsistent with the immediately foregoing paragraph or the
provisions relating to an Adverse Change Recommendation (as described below),
(2) the Micromet Board concludes in good faith that such bona-fide written
Acquisition Proposal would reasonably be expected to lead to a Superior Offer
(as defined below) and, after consulting with its outside legal counsel, that
the failure to take such action would reasonably constitute a breach of the
fiduciary duties of the Micromet Board to the Micromet stockholders under
applicable law, (3) at least two business days prior to furnishing any nonpublic
information to, or entering into discussions with, the person delivering the
Acquisition Proposal, Amgen receives written notice from Micromet of the
identity of such person and of Micromet’s intention to furnish nonpublic
information to, or enter into discussions with, such person, and Micromet
receives from such person an executed confidentiality agreement in a customary
form that is no less favorable to Micromet than the confidentiality agreement
entered into by Micromet and Amgen (which Micromet may negotiate with the person
during the two business day notice period), and (4) Micromet concurrently
furnishes all such nonpublic information to Amgen (to the extent such nonpublic
information has not been previously furnished or made available by Micromet to
Amgen or its representatives).

For purposes of the Merger Agreement, “Acquisition Proposal” means any offer
or proposal (other than an offer or proposal made or submitted by Amgen)
contemplating any Acquisition Transaction, which is defined as any transaction
or series of transactions (other than the transactions contemplated by the
Merger Agreement), involving (1) any merger, consolidation, business combination
or similar transaction involving Micromet or any of its subsidiaries, (2) any
direct or indirect sale, license, lease, transfer, exchange or other disposition
(including any license, collaboration, disposition or revenue-sharing
arrangement), in one transaction or a series of transactions, including by
merger, consolidation, business combination, share exchange, joint venture,
extraordinary dividend, recapitalization, corporate reorganization or otherwise,
of any business or assets (including MT103 or any other BiTE antibody)
representing, or that would represent after giving effect to the transaction,
20% or more of the assets, net revenues or net income of Micromet or any of its
subsidiaries, (3) any issuance, sale or other disposition, in one transaction or
series of transactions, including by way of merger, consolidation, business
combination, share exchange, joint venture or any similar transaction, of
securities (or options, rights or warrants to purchase, or securities
convertible into or exchangeable for, such securities) representing 15% or more
of the voting power of Micromet (or 20% or more of the voting power of any of
Micromet’s subsidiaries), (4) any transaction, including any tender offer or
exchange offer, that if consummated would result in or would reasonably be
expected to result in any person or group beneficially owning 15% or more of the
voting power of Micromet (or in the case of Micromet’s subsidiaries, 20% or more
of the voting power of such subsidiaries) or in which any person or group will
acquire the right to acquire beneficial ownership of 15% or more of the
outstanding voting power of Micromet (or in the case of Micromet’s subsidiaries,
20% or more of the voting power of any such subsidiary), or (5) any combination
of the foregoing.

For purposes of the Merger Agreement, “Superior Offer” means an unsolicited,
bona-fide written Acquisition Proposal made by a third party after the date of
the Merger Agreement and not resulting from a breach of Micromet’s
non-solicitation obligations described above pursuant to which such third party
would acquire 80% or more of the voting power of Micromet or the assets of
Micromet and its subsidiaries on a consolidated basis on terms that the Micromet
Board determines, in its good faith judgment, after consultation with its
outside legal counsel and its financial advisor of nationally recognized
reputation, to be more favorable to Micromet’s stockholders than the terms of
the Offer and the Merger and is reasonably capable of being completed on the
terms proposed taking into account all relevant factors, including the terms and
conditions of the Acquisition Proposal, including price, form of consideration,
closing conditions, anticipated timing of consummation of the transaction, and
for which financing, if a cash transaction, is not a condition to the
consummation of the purchase transaction and is reasonably determined to be
available by the Micromet Board.

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During the period from the date of the Merger Agreement until the earlier of
the Acceptance Time and the termination of the Merger Agreement, Micromet has
agreed to promptly (and in no event later than twenty-four hours after receipt
of any Acquisition Proposal, any inquiry or indication of interest that could
reasonably be expected to lead to an Acquisition Proposal or any request for
nonpublic information) advise Amgen orally and in writing of any Acquisition
Proposal, any inquiry or indication of interest that could reasonably be
expected to lead to an Acquisition Proposal or any request for nonpublic
information relating to Micromet or any of its subsidiaries, including (a) the
identity of the person making or submitting such Acquisition Proposal, inquiry,
indication of interest or request and (b) a copy of all written materials and
communications provided in connection with such Acquisition Proposal, inquiry,
indication of interest or request submitted by any person during such period.

As of the date of the Merger Agreement, Micromet and its subsidiaries agreed
to immediately cease and cause to be terminated any existing discussions with
any person that relate to any Acquisition Proposal or any inquiry or indication
of interest that could lead to an Acquisition Proposal and to promptly (but in
no event later than five days after the date of the Merger Agreement) demand
that each person that has executed a confidentiality agreement with Micromet or
any of its subsidiaries or any of its affiliates or representatives prior to the
date of the Merger Agreement with respect to such person’s consideration of a
possible Acquisition Proposal or equity investment at any time after January 1,
2011 (other than agreements that have expired by their terms) to immediately
return or destroy (which destruction must be certified in writing by such person
to Micromet) all confidential information furnished by Micromet or any of its
subsidiaries or any of its affiliates or representatives prior to the date of
the Merger Agreement to such person, its subsidiaries or any of its or their
affiliates or representatives. Micromet has agreed to, except as determined by
the Micromet Board in good faith after consultation with outside counsel that
the failure to take such action would constitute a breach of fiduciary duties of
the Micromet Board to the Micromet stockholders under applicable law, not to
release or permit the release during the period from the date of the Merger
Agreement until the earlier of the Acceptance Time and the termination of the
Merger Agreement of any person from, or to waive or permit the waiver of any
provision of, the Rights Agreement or any confidentiality, “standstill”, or
similar agreement to which Micromet or any of its subsidiaries is a party and
will use its commercially reasonable efforts to enforce or cause to enforced
each such agreement at the request of Amgen.

Micromet Board’s Recommendation; Adverse Recommendation Changes

The Micromet Board has made the Micromet Board Recommendation that the
holders of the Shares accept the Offer, tender their Shares into the Offer and,
if required by applicable law, adopt the Merger Agreement. The Micromet Board
has also agreed to include the Micromet Board Recommendation in the Schedule
14D-9 and consented to the inclusion of the Micromet Board Recommendation in
this Offer to Purchase and documents related to the Offer.

In addition, except as expressly permitted by the non-solicitation provisions
of the Merger Agreement, neither the Micromet Board nor any committee thereof
may:

withdraw (or modify in a manner adverse to Amgen or us), or publicly propose
to withdraw (or modify in a manner adverse to Amgen or us), the Micromet Board
Recommendation or approve, recommend or declare advisable, or propose publicly
to approve, recommend or declare advisable, any Acquisition Proposal (any such
action, an “Adverse Change Recommendation”); or

approve, recommend or declare advisable, or propose or resolve to approve,
recommend or declare advisable, or allow Micromet or any of its subsidiaries to
execute or enter into any contract constituting or related to, or that is
intended to or would be reasonably likely to lead to, any Acquisition
Transaction, or requiring, or reasonably likely to cause, Micromet to abandon,
terminate, delay or fail to consummate, or that would otherwise materially
impede, interfere with or be inconsistent with, the transactions contemplated by
the Merger Agreement.

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However, at any time prior to the Acceptance Time, the Micromet Board may
make an Adverse Change Recommendation if:

Micromet is not in breach of the non-solicitation provisions of the Merger
Agreement;

the Micromet Board determines in good faith, after consultation with
Micromet’s outside legal counsel, that the failure to make the Adverse Change
Recommendation would constitute a breach of the fiduciary duties of the Micromet
Board to Micromet’s stockholders under applicable law;

Amgen shall have received from Micromet prior written notice of Micromet’s
intention to make an Adverse Change Recommendation at least four business days
prior to making any Adverse Change Recommendation (a “Change of Recommendation
Notice”);

if the decision to make an Adverse Change Recommendation is not in connection
with an Acquisition Proposal, then Micromet must have complied with the
following requirements: (a) Micromet must have given Amgen the four business
days after Amgen’s receipt of the Change of Recommendation Notice to propose
revisions to the terms of the Merger Agreement or make other proposals and must
have negotiated in good faith with Amgen (and caused its representatives to
negotiate with Amgen) with respect to such proposed revisions or other
proposals, if any, and (b) after considering the results of negotiations with
Amgen and taking into account the proposals made by Amgen, if any, and after
consultation with its outside legal counsel, the Micromet Board must have
determined, in good faith, that the failure to make the Adverse Change
Recommendation would constitute a breach of fiduciary duties of the Micromet
Board to Micromet’s stockholders under applicable law; and

if the decision to make an Adverse Change Recommendation is in connection
with an Acquisition Proposal, then Micromet must have complied with the
following requirements: (a) prior to giving effect to clauses (b) through (d)
below, the Micromet Board must have determined, in good faith, that such
Acquisition Proposal is a Superior Offer, (b) Micromet must have provided to
Amgen the material terms and condition of such Acquisition Proposal and copies
of all material documents relating to such Acquisition Proposal in accordance
with the provisions described under “No Solicitation” above, (c) Micromet must
have given Amgen four business days after Amgen’s receipt of the Change of
Recommendation Notice to propose revisions to the terms of the Merger Agreement
or make other proposals, if any, and shall have negotiated in good faith with
Amgen (and caused its representatives to negotiate with Amgen) with respect to
Amgen’s proposed revisions or other proposals, if any, so that the Acquisition
Proposal would no longer constitute a Superior Offer and (d) after considering
the results of negotiations with Amgen and taking into account the proposals
made by Amgen, if any, and after consultation with its outside legal counsel,
the Micromet Board must have determined, in good faith, that such Acquisition
Proposal remains a Superior Offer and that the failure to make the Adverse
Change Recommendation would constitute a breach of fiduciary duties of the
Micromet Board to Micromet’s stockholders.

Issuance of any “stop, look and listen” communication by or on behalf of
Micromet which does no more than comply with the requirements of Rule 14d-9(f)
shall not in and of itself be considered an Adverse Change Recommendation that
requires the giving of a Change of Recommendation Notice or compliance with the
procedures described in the paragraph above. Neither Micromet nor the Micromet
Board is permitted to recommend that Micromet’s stockholders tender any
securities in connection with any tender or exchange offer or otherwise approve,
endorse or recommend any Acquisition Proposal, unless in each case, in
connection therewith, the Micromet Board effects an Adverse Change
Recommendation in accordance with the terms of the Merger Agreement.

Actions in Connection with Long-Form Merger

Unless the Merger is consummated in accordance with the “short-form” merger
provisions of Section 253 of the DGCL, following the Acceptance Time, Amgen
and/or its affiliates may, as the holders of a majority of the

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issued and outstanding Shares, elect to approve the Merger under the
“long-form” merger provision of Section 251 of the DGCL which requires that the
Merger Agreement be adopted by Micromet’s stockholders. Adoption of the Merger
Agreement requires the affirmative vote of holders of a majority of the
outstanding Shares. Thus, if the Minimum Condition and the other conditions to
the Offer are satisfied and the Offer is completed, we would have sufficient
voting power to adopt the Merger Agreement without the affirmative vote of any
other stockholder of Micromet. Amgen has agreed to vote, or cause to be voted,
all Shares held by it and its subsidiaries in favor of the adoption of the
Merger Agreement.

Micromet has agreed that, if the adoption of the Merger Agreement by holders
of Shares is required to consummate the Merger, then, subject to its right to
make an Adverse Change Recommendation or consider certain alternative
Acquisition Proposals (as described above), as promptly as practicable following
the Expiration Date, Micromet will: (i) take all action necessary under all
applicable law to call, give notice of and hold a meeting of the holders of
Shares to vote on the adoption of the Merger Agreement and approval of the
Merger (the “Micromet Stockholders’ Meeting”) and (ii) prepare and file with the
SEC a proxy statement and use all reasonable efforts to respond to any comments
of the SEC or its staff and to cause the proxy statement to be mailed to
Micromet’s stockholders as promptly as practicable.

Employee Matters

For a period commencing upon the Effective Time and continuing through the
end of the year in which the Effective Time occurs, Amgen will provide to each
Micromet employee who continues to be employed by Amgen, the Surviving
Corporation or any subsidiary thereof (the “Continuing Employees”) total
compensation (including employee benefits other than equity based compensation
and retention benefits and based on bonus opportunity rather than actual bonus
payments) that is at least substantially comparable in the aggregate to the
compensation provided to such Continuing Employees immediately prior to the
execution of this Agreement. In addition, Continuing Employees will be eligible
for certain severance benefits.

Amgen will, or will cause the Surviving Corporation to and instruct its
subsidiaries to, as applicable, assume the liability for accrued personal, sick
or vacation time and allow Continuing Employees to use such accrued personal,
sick or vacation time in accordance with the practice and policies of Micromet
and its Subsidiaries, as applicable to each such Continuing Employee immediately
before the Effective Time, subject to the cap on vacation accrual set forth in
Amgen’s vacation policy and subject to applicable law. Any accrued but unused
personal, sick or vacation time of each such Continuing Employee in excess of
80% of such cap will be paid by Amgen, the Surviving Corporation (or any other
Subsidiaries of Amgen) as soon as practicable to such Continuing Employee at
such employee’s compensation rate in effect as of the Effective Time.

In addition, Amgen agrees that all Continuing Employees will be eligible to
continue to participate in the Surviving Corporation’s health and welfare
benefit plans to the extent that they were eligible to participate in such plans
prior to the closing; provided, however, that if Amgen or the Surviving
Corporation terminates any such health or welfare benefit plan, then (upon
expiration of any appropriate transition period) Amgen will use commercially
reasonable efforts to cause the Continuing Employees to be eligible to
participate in Amgen’s health and welfare benefit plans, to substantially the
same extent as similarly situated employees of Amgen (taking into account job
location). To the extent that service is relevant for eligibility, vesting or
allowances (including paid time off) under any health or welfare benefit plan of
Amgen and/or the Surviving Corporation, then Amgen will use commercially
reasonable efforts to cause such health or welfare benefit plan to (to the
extent that it would not result in any duplication of benefits), for purposes of
eligibility, vesting and allowances (including paid time off) but not for
purposes of benefit accrual or participation, credit Continuing Employees for
service prior to the Effective Time with Micromet to the same extent that such
service was recognized prior to the Effective Time under the corresponding
Micromet health or welfare benefit plan.

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Rule 14d-10(d) Matters

Micromet has agreed that, prior to the Acceptance Time, it will (acting
through the Compensation Committee of the Micromet Board) cause each employee
plan and company employee agreement pursuant to which consideration is payable
to any officer, director or employee who is a holder of any Micromet security to
be approved by the Compensation Committee of the Micromet Board (comprised
solely of “independent directors”) in accordance with the requirements of
Rule14d-10(d)(2) under the Exchange Act and the instructions thereto as an
“employment compensation, severance or other employee benefit arrangement”
within the meaning of Rule 14d-10(d)(2) under the Exchange Act and satisfy the
requirements of the non-exclusive safe harbor set forth in Rule 14(d)-10(d)(2)
of the Exchange Act.

Efforts to Close the Transaction

Each of Amgen and Micromet have agreed to cooperate with one another and use
(and cause their respective subsidiaries to use) its commercially reasonable
efforts to take or cause to be taken all actions, and do or cause to be done all
things, reasonably necessary, proper or advisable on its part under the Merger
Agreement and applicable law to consummate and make effective the Offer and the
other transactions contemplated by the Merger Agreement as soon as reasonably
practicable, including preparing and filing as promptly as reasonably
practicable all documentation to effect all necessary notices, reports and other
filings and to obtain as promptly as practicable all consents, registrations,
approvals, permits and authorizations necessary or advisable to be obtained from
any third party and/or governmental body in order to consummate the Offer and
the transactions contemplated by the Merger Agreement; provided, that, in
connection with obtaining any waivers or consents, Micromet will not agree to
any change to any Micromet contract that would be adverse to the interest of
Micromet, its subsidiaries or, after the Merger, Amgen without the prior written
consent of Amgen. Micromet and its subsidiaries will only be required to take or
commit to take any action, or agree to any condition or restriction in
connection with obtaining any consent, permit, authorization, waiver, clearance
or approval from any governmental body, if such action, commitment, agreement,
condition or restriction is binding on Micromet and its subsidiaries only in the
event that the Merger is consummated and then only with the prior written
consent of Amgen. Amgen is not required to agree to commit to any divestitures
or licenses or to proffer to, or agree to, sell or hold separate and agree to
sell, before or after the Effective Time, any assets, businesses, or interest in
any assets or businesses of Amgen, Micromet or any of their respective
affiliates (or to consent to any sale or license, or agreement to sell or
license by Micromet, of any of its assets or businesses) or to agree to any
changes or restrictions in the operations of any such assets or businesses in
each case to the extent such action would reasonably be expected to,
individually or in the aggregate, (i) restrict in any material respect or
otherwise negatively and materially impact the operation or ownership by Amgen,
the Surviving Corporation, Micromet and/or any of their respective subsidiaries
or affiliates of the Shares, the businesses or assets of the Surviving
Corporation, Micromet and/or their subsidiaries, taken as a whole or (ii)
restrict in any material respect or otherwise negatively and materially impact
the operations, businesses or assets of Amgen and its affiliates (excluding
Micromet and its subsidiaries), taken as a whole (with materiality for purposes
of this clause (ii) being determined assuming Amgen and its affiliates, taken as
a whole, were the size of Micromet and its subsidiaries, taken as a whole).

Amgen and Micromet have also agreed (1) to make an appropriate filing under
the HSR Act and (2) to the extent required, to make filings pursuant to Section
35 et seq. of the German Act Against Restraints of Competition
(Gesetz gegen Wettbewerbsbeschr 164nkungen) (the “GWB”) and other
antitrust laws.

We and Amgen, on the one hand, and Micromet, on the other hand, have agreed
to (i) give the other parties prompt notice of the making or commencement of any
request, inquiry, investigation, action or legal proceeding by or before any
governmental body with respect to the Offer, the Merger or the other
transactions contemplated by the Merger Agreement, (ii) keep the other parties
reasonably informed as to the status of any such request, inquiry,
investigation, action or legal proceeding, (iii) promptly inform the other
parties of any communication to or from the United States Federal Trade
Commission (the “FTC”), the United States Department of Justice (the “DOJ”) or
any other governmental body to the extent regarding the Offer, the Merger or the
other transactions

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contemplated by the Merger Agreement or regarding any such request, inquiry,
investigation, action or legal proceeding, and provide a copy of all written
communications and (iv) pull and refile any notice under the HSR Act only if the
other parties agree.

Subject to legal requirements relating to the sharing of information, Amgen
and Micromet will have the right to review in advance, and to the extent
practicable each will consult the other on, all the information relating to
Amgen or Micromet, as the case may be, and any of their respective subsidiaries
that appear in any filing made with, or written material submitted to, any third
party and/or governmental body in connection with the Offer, the Merger and the
other transactions contemplated by the Merger Agreement and will incorporate all
comments reasonably proposed by Amgen or Micromet, as the case may be. However,
in this context, Amgen and Micromet are not obligated to share with each other
any documents or materials that contain confidential or proprietary information
(including any so called 4(c) or 4(d) documents) and may instead submit such
information directly to the third party and/or governmental body, unless a
review of the confidential and proprietary information would be material in
connection with any second request (or similar process outside of the United
States), in which case Amgen and Micromet will share their confidential and
proprietary information solely with each other’s outside antitrust counsel, who
may not further disclose the information to Amgen or Micromet. In such case,
Amgen and Micromet would also enter into a joint defense agreement. In addition,
except as may be prohibited by any governmental body or by any legal
requirement, in connection with such request, inquiry, investigation, action or
legal proceeding in respect of the transactions contemplated by the Merger
Agreement, we, Amgen and Micromet will permit authorized representatives of the
other party to be present at each meeting or conference relating to such
request, inquiry, investigation, action or legal proceeding and to have access
to and be consulted in connection with any document, opinion or proposal made or
submitted to any governmental body in connection with such request, inquiry,
investigation, action or legal proceeding.

Takeover Statute

Micromet has agreed that if any state takeover law or similar law may become,
or may purport to be, applicable to the transactions contemplated by the Merger
Agreement, Micromet and the Micromet Board will grant such approvals and take
such actions as are necessary so that the transactions contemplated by the
Merger Agreement may be consummated as promptly as practicable on the terms and
conditions contemplated by the Merger Agreement and otherwise act to eliminate
the effect of any such takeover law or similar law on any of the transactions
contemplated by the Merger Agreement.

Indemnification and Insurance

Amgen has agreed that, it will, and will cause the Surviving Corporation to,
from the Effective Time until the sixth anniversary of the Effective Time:

to the fullest extent that Micromet and its subsidiaries would have been
permitted to under applicable law and their respective certificates of
incorporation or by-laws or other organizational documents, indemnify, defend
and hold harmless each director and officer of Micromet or any of its
subsidiaries as of the date of the Merger Agreement in his or her capacity as an
officer or director of Micromet or any of its subsidiaries, to the extent
arising out of or pertaining to any and all matters pending, existing or
occurring at or prior to the Effective Time, including any such matter arising
under any claim with respect to the transactions contemplated by the Merger
Agreement; and

maintain in effect, for the benefit of each director and officer of Micromet
or any of its subsidiaries as of the date of the Merger Agreement with respect
to their acts and omissions occurring prior to the Effective Time, the existing
policy of directors’ and officers’ liability insurance maintained by Micromet as
of the date of the Merger Agreement on terms with respect to coverage,
deductibles and amounts no less favorable than the policy existing at the time
of the Merger Agreement and Micromet may purchase a six-year “tail” policy for
the existing policy, except that the amount either Amgen or the Surviving
Corporation is required to expend in any one year is subject to a cap.

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Other Covenants

The Merger Agreement contains other customary covenants, including covenants
relating to securityholder litigation, public announcements and access,
confidentiality, matters with respect to Section 16 of the Exchange Act and the
rules and regulations thereunder, stock exchange delisting and deregistration.

Termination of the Merger Agreement

The Merger Agreement may be terminated at any time prior to the Effective
Time:

by mutual written consent of Amgen and Micromet;

by either Amgen or Micromet by written notice to the other if the Offer
expires without the acceptance for payment of Shares pursuant to the Offer,
provided that such termination right is not available to any party if a breach
by such party of any provision of the Merger Agreement proximately caused the
failure of the acceptance for payment of Shares pursuant to the Offer (such
termination, an “Expiration Date Termination”);

by either Amgen or Micromet by written notice to the other if a court of
competent jurisdiction or other governmental body issues a final and
nonappealable order, decree or ruling, or takes any other action, having the
effect of permanently restraining, enjoining or otherwise prohibiting the
acceptance for payment of Shares pursuant to the Offer or the Merger or making
consummation of the Offer or the Merger illegal;

by Amgen by written notice to Micromet at any time prior to the Acceptance
Time, if, whether or not permitted to do so, (i) the Micromet Board makes an
Adverse Change Recommendation, or approves or recommends an Acquisition
Proposal, (ii) Micromet enters into any letter of intent, agreement in principle
or definitive agreement with respect to any Acquisition Proposal, (iii) Micromet
fails to include the Micromet Board Recommendation in the Schedule 14D-9, or
(iv) the Micromet Board fails to publicly reaffirm the Micromet Board
Recommendation within ten days after receipt of a written request by Amgen to
provide such reaffirmation following a publicly made Acquisition Proposal (such
termination, an “Adverse Change Recommendation Termination”);

by Micromet by written notice to Amgen if we terminate the Offer without
having accepted any Shares for payment thereunder, provided that such
termination right is not available to Micromet if a breach by Micromet of any
provision of the Merger Agreement proximately caused the occurrence of the event
which gave rise to such termination right;

by either Amgen or Micromet by written notice to the other if the Acceptance
Time does not occur on or prior to the close of business on the date that is the
End Date; provided that such termination right is not available to either party
if a breach of any provision of the Merger Agreement by such party proximately
caused the failure of the Acceptance Time to have occurred (such termination, an
“End Date Termination”);

by Micromet by written notice to Amgen at any time prior to the Acceptance
Time, in order to accept a Superior Offer and enter into the Specified Agreement
(as defined below) relating to such Superior Offer, if (i) such Superior Offer
did not result from any breach of the provisions described under “No
Solicitation” above, (ii) the Micromet Board, after satisfying all of the
requirements with respect to an Adverse Change Recommendation, authorizes
Micromet to enter into a binding written definitive acquisition agreement
providing for the consummation of a transaction constituting a Superior Offer
(the “Specified Agreement”) and (iii) Micromet pays the termination fee
described below immediately prior to, and enters into the Specified Agreement
concurrently with, the termination of the Merger Agreement (such termination, a
“Superior Offer Termination”);

by Amgen by written notice to Micromet at any time prior to the Acceptance
Time, (i) if a breach of any representation or warranty or failure to perform
any covenant or obligation contained in the Merger Agreement on the part of
Micromet occurs that would cause a failure of the conditions to the Offer to

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exist and such breach remains uncured by Micromet at the earlier of the End
Date and forty-five days after Amgen gives Micromet notice of such breach and
Micromet is continuing to use its reasonable best efforts to cure the breach or
(ii) if Micromet materially breaches any of its obligations with respect to the
provisions described under “No Solicitation” above (the termination described in
this clause (ii), a “Micromet Breach Termination”); or

by Micromet by written notice to Amgen at any time prior to the Acceptance
Time if a breach in any material respect of any representation or warranty or
failure to perform in any material respect any covenant or obligation contained
in the Merger Agreement on the part of Amgen occurs, in each case if such breach
or failure has prevented or would reasonably be expected to prevent Amgen or us
from consummating the transactions contemplated by the Merger Agreement and such
breach remains uncured by Amgen at the earlier of the End Date and forty-five
days after Micromet gives Amgen notice of such breach and Amgen is continuing to
use its reasonable best efforts to cure the breach.

Effects of Termination

If the Merger Agreement is terminated in accordance with its terms, the
Merger Agreement will be of no further force or effect, subject to certain
designated provisions of the Merger Agreement that survive, including the effect
of termination, expenses and termination fee and other miscellaneous provisions
and the confidentiality agreement between Amgen and Micromet, which will remain
in full force and effect in accordance with its terms. The termination of the
Merger Agreement does not relieve any party from any liability for any willful
breach of the Merger Agreement prior to the date of the termination.

Termination Fees

Micromet has agreed to pay Amgen a termination fee of $40 million (the
“Termination Fee”) if:

(i) (A) the Merger Agreement is terminated by Amgen or Micromet pursuant to
an Expiration Date Termination or an End Date Termination, (B) after the date of
the Merger Agreement and at or prior to the time of the termination of the
Merger Agreement, an Acquisition Proposal is publicly made, commenced or
submitted or announced and not withdrawn, and (C) Micromet consummates or is
subject to a Specified Acquisition Transaction (as defined below) within 365
days after such termination or Micromet or any of its representatives signs a
definitive agreement within 365 days after such termination providing for a
Specified Acquisition Transaction; or

(ii) the merger Agreement is terminated (A) by Amgen pursuant to (x) an
Adverse Change Recommendation Termination or (y) a Micromet Breach Termination
or

(iii) by Micromet pursuant to a Superior Offer Termination.

A “Specified Acquisition Transaction” is defined as any transaction or series
of transactions involving:

(a) any merger, consolidation, business combination or similar transaction
involving Micromet or any of its subsidiaries,

(b) any direct or indirect sale, license, lease, transfer, exchange or other
disposition (including any license, collaboration, disposition or
revenue-sharing arrangement), in one transaction or a series of transactions,
including by merger, consolidation, business combination, share exchange, joint
venture, extraordinary dividend, recapitalization, corporate reorganization or
otherwise, of any business or assets (including MT103 or any other BiTE
antibody) representing, or that would represent after giving effect to the
transaction, 50% or more of the consolidated assets, net income or net revenues
of Micromet and its subsidiaries; provided that if the Specified Acquisition
Transaction is for a license or collaboration, such transaction will only be
deemed a Specified Acquisition Transaction if it is entered into with a person
or its affiliates that had publicly made an Acquisition Proposal after the date
of the Merger Agreement and prior to the termination of the Merger Agreement,

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(c) any issuance, sale, or other disposition, in one transaction or a series
of transactions, including by way of merger, consolidation, business
combination, share exchange, joint venture or any similar transaction, of
securities (or options, rights or warrants to purchase, or securities
convertible into or exchangeable for, such securities) representing 50% or more
of the voting power of Micromet,

(d) any transaction, including any tender offer or exchange offer, that if
consummated would result in or would reasonably be expected to result in any
person or group beneficially owning 50% or more of the voting power of Micromet
or in which any person or group shall acquire the right to acquire beneficial
ownership of 50% or more of the outstanding voting power of Micromet, or

(e) any combination of the foregoing.

Any Termination Fee will be paid as follows: (A) in the case of clause (i)
above, upon the earlier of two business days after the entry into an agreement
with respect to a Specific Acquisition Transaction or concurrent with the
consummation of a Specified Acquisition Transaction, (B) in the case of clause
(ii) above, within two business days following termination of the Merger
Agreement or (C) in the case of clause (iii) above, concurrently with the
termination of the Merger Agreement as a condition to the effectiveness of such
termination.

Specific Performance

We, Amgen and Micromet are entitled to seek an injunction or injunctions to
prevent breaches of the Merger Agreement and to enforce specifically the terms
and provisions thereof in addition to any other remedy to which they are
entitled under the terms of the Merger Agreement, at law or in equity.

Fees and Expenses

Except as provided in this Section 11 : “The Merger Agreement; Other
Agreements : The Merger Agreement : Termination Fees” all fees and expenses
incurred in connection with the Merger Agreement, the Offer, the Merger and the
other transactions contemplated by the Merger Agreement will be paid by the
party incurring such fees and expenses.

Governing Law

The Merger Agreement is governed by Delaware law.

Other Agreements

Employment Agreements

The following summary description of the Employment Agreement Amendments and
the Award Agreement is qualified in its entirety by reference to such employment
agreements and award agreement, which Amgen has filed as exhibits (d)(2), (d)(3)
and (d)(4) to the Schedule TO, which you may examine and copy as set forth in
“Section 8 : Certain Information Concerning Purchaser and Amgen” above.

On January 24, 2012, Micromet and Amgen entered into an amendment to
executive employment agreement with each of Dr. Jan Fagerberg, Senior Vice
President : Chief Medical Officer, and Prof. Dr. Patrick A. Baeuerle, Senior
Vice President : Chief Scientific Officer. The amendments entered into with each
of Dr. Fagerberg and Dr. Baeuerle, amend the employment agreements between
Micromet and Dr. Fagerberg and Dr. Baeuerle, respectively, each dated as of May
6, 2011 (collectively, the “Employment Agreement Amendments”). The effect of the
Employment Agreement Amendments is to change certain terms of Dr. Fagerberg’s
and Dr. Baeuerle’s employment with Micromet from and after the Effective Time.
Neither of the Employment Agreement Amendments will become effective until the
Effective Time. In addition, each of

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Dr. Fagerberg and Dr. Baeuerle have agreed that the changes pursuant to their
employment contemplated by the Employment Agreement Amendments will not
constitute “good reason” under their employment agreements.

Under the Employment Agreement Amendments, following the Effective Time, (i)
Dr. Fagerberg’s position and title will be Vice President, Global Development,
and Dr. Baeuerle’s position and title will be Vice President, Research, (ii) Dr.
Fagerberg’s and Dr. Baeuerle’s base salaries will be 275,834 and 302,356,
respectively, (iii) each of Dr. Fagerberg and Dr. Baeuerle will have an annual
bonus target equal to 40% of their respective base salaries, (iv) each will be
granted 10,000 restricted stock units under Amgen’s equity incentive plan, which
will vest fully on the second anniversary of the Effective Time, contingent upon
their remaining employed with Micromet through such date, and (v) beginning in
2013, they will each be eligible to receive annual long-term incentive equity
grants that are determined in accordance with Amgen’s annual grant guidelines.
In addition, under his Employment Agreement Amendment and a special retention
award agreement between Amgen and Dr. Baeuerle, dated as of January 24, 2012
(the “Award Agreement”), Dr. Baeuerle will be eligible for a $1,000,000 cash
retention bonus, which will vest fully on the second anniversary of the
Effective Time, contingent upon Dr. Baeuerle remaining employed with Micromet
through such date or his earlier termination without “cause” (as defined in the
Award Agreement) or upon his earlier death or disability.

The Tender and Support Agreements

The following summary description of the Tender and Support Agreements is
qualified in its entirety by reference to the form of Tender and Support
Agreement, which Amgen has filed as exhibit (d)(5) to the Schedule TO, which you
may examine and copy as set forth in “Section 8 : Certain Information Concerning
Purchaser and Amgen” above.

Concurrently with entering into the Merger Agreement, we and Amgen entered
into Tender and Support Agreements with the directors and executive officers of
Micromet and certain of their affiliated funds (the “Supporting Stockholders”).
Based upon information provided by the Supporting Stockholders and Micromet,
excluding options and warrants to purchase Shares that are exercisable within 60
days of January 25, 2012, the Supporting Stockholders beneficially owned, in the
aggregate, 7,041,552 Shares (or 7.6% of all outstanding Shares) as of January
25, 2012. Including options and warrants to purchase Shares that are exercisable
within 60 days of January 25, 2012, the Supporting Stockholders beneficially
owned, in the aggregate, 12,986,468 Shares (or 13.2% of all outstanding Shares
after giving effect to the exercise of such options and warrants) as of January
25, 2012.

Pursuant to the Tender and Support Agreements, each Supporting Stockholder
agreed to validly tender (or cause to be tendered) in the Offer any and all
Shares of which such Supporting Stockholder is the record or beneficial owner
and any additional Shares with respect to which such Supporting Stockholder
becomes the record or beneficial owner after the date of its Tender and Support
Agreement and prior to the earlier of (i) the date upon which the Merger
Agreement is validly terminated or (ii) the Effective Time (the “Support
Period”) (collectively, the “Subject Shares”) pursuant to the terms of the Offer
as promptly as practicable, but no later than ten business days following
commencement of the Offer. If such Supporting Stockholder has not received all
documents or instruments required to be delivered pursuant to the terms of the
Offer by such time, such Supporting Stockholder has agreed to tender (or cause
to be tendered) the Subject Shares within two business days following the
receipt of such documents or instruments, but in any event prior to the initial
Expiration Date.

The Tender and Support Agreements further provide that, during the Support
Period, each Supporting Stockholder will, at any meeting of the holders of
Shares, vote (or cause to be voted) such Supporting Stockholder’s Subject Shares
(A) in favor of (i) the Merger, the execution and delivery by Micromet of the
Merger Agreement and the adoption and approval of the Merger Agreement and the
terms thereof and (ii) each of the other transactions contemplated by the Merger
Agreement; (B) against any action or agreement that would result in a breach of
any representation, warranty, covenant or obligation of Micromet in the Merger
Agreement; and (C) against the following actions (other than the Merger and the
other transactions contemplated by the Merger Agreement): (i) any Acquisition
Proposal; (ii) any amendment to Micromet’s certificate of incorporation or
bylaws; (iii) any material

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change in the capitalization of Micromet or Micromet’s corporate structure;
and (iv) any other action which would impede, interfere with, delay, postpone,
discourage or adversely affect the Merger, the Tender and Support Agreement or
any of the other transactions contemplated by the Merger Agreement.

In furtherance of the Supporting Stockholder covenants under the Tender and
Support Agreements, each Supporting Stockholder has delivered to Amgen a proxy
whereby it agreed, during the Support Period, to appoint and constitute Amgen
and any designee of Amgen, and each of them, the attorneys and proxies of the
Supporting Stockholder, with full power of substitution and resubstitution, to
the full extent of the Supporting Stockholder’s rights with respect to (i) the
outstanding shares of capital stock of Micromet owned of record by the
Supporting Stockholder as of the date of the proxy, which shares are specified
on the final page of the proxy, and (ii) any and all other shares of capital
stock of Micromet which the Supporting Stockholder may acquire on or after the
date of the proxy.

Each Supporting Stockholder agreed pursuant to its Tender and Support
Agreement that it will not enter into any tender, voting or other such
agreement, or grant a proxy or power of attorney, with respect to any of the
Subject Shares that is inconsistent with its Tender and Support Agreement or
otherwise taken any other action with respect to any of the Subject Shares that
would in any way restrict, limit or interfere with the performance of any of the
Supporting Stockholder’s obligations under its Tender and Support Agreement or
any of the actions contemplated thereby.

The Tender and Support Agreements and all rights and obligations of the
parties thereunder, including the proxy, shall terminate, and no party shall
have any rights or obligations thereunder and the Tender and Support Agreement
shall become null and void on, and have no further effect as of the earlier of
(i) the date upon which the Merger Agreement is validly terminated, or (ii) the
date upon which the Merger becomes effective.

Confidentiality Agreement

The following summary description of the Confidentiality Agreement is
qualified in its entirety by reference to such Confidentiality Agreement and
Amendment No. 1 to such Confidentiality Agreement, which Amgen has filed as
exhibits (d)(6) and (d)(7) to the Schedule TO, which you may examine and copy as
set forth in “Section 8 : Certain Information Concerning Purchaser and Amgen”
above.

Amgen and Micromet entered into a confidentiality agreement, effective as of
August 11, 2011 (as amended, the “Confidentiality Agreement”). Under the terms
of the Confidentiality Agreement, Amgen agreed that, subject to certain
exceptions, any non-public information regarding Micromet and its subsidiaries
or affiliates furnished to Amgen or its representatives would, for a period of
eighteen months from the date of the Confidentiality Agreement, be kept
confidential and used by Amgen and its representatives solely for the purpose of
considering, evaluating and negotiating a possible transaction between Amgen and
Micromet and would be kept confidential except as provided in the
Confidentiality Agreement. The confidentiality agreement also includes a
standstill provision that was subject to certain exceptions.

12. Purpose of the Offer; Plans for Micromet.

Purpose of the Offer

We are making the Offer pursuant to the Merger Agreement in order to acquire
control of, and ultimately following the Merger, the entire equity interest in,
Micromet while allowing Micromet’s stockholders an opportunity to receive the
Offer Price promptly by tendering their Shares into the Offer. If the Offer is
consummated, we, Amgen and Micromet expect to consummate the Merger as promptly
as practicable in accordance with the DGCL. At the Effective Time, Micromet will
become a wholly-owned subsidiary of Amgen.

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Holders of Shares who tender their Shares into the Offer will cease to have
any equity interest in Micromet and will no longer participate in the future
growth of Micromet. If the Merger is consummated, the current holders of Shares
will no longer have an equity interest in Micromet and instead will only have
the right to receive an amount in cash equal to the Offer Price or, to the
extent that holders of Shares are entitled to and have properly demanded
appraisal in connection with the Merger, the amounts to which such holders of
Shares are entitled in accordance with Delaware law.

As soon as possible after the consummation of the Offer, we, Amgen and
Micromet expect to consummate the Merger pursuant to the Merger Agreement.
Pursuant to the Merger Agreement, at any time on or after the Acceptance Time,
we may exercise the Top-Up Option to purchase from Micromet, subject to certain
limitations, the Top-Up Option Shares in order to merge us into Micromet without
any vote of Micromet’s stockholders in accordance with Section 253 of the DGCL.
However, the obligation of Micromet to deliver Top-Up Option Shares upon the
exercise of the Top-Up Option is subject to the conditions, unless waived by
Micromet, that immediately following the exercise of the Top-Up Option, the
number of Shares owned in the aggregate by Amgen and us constitutes at least one
Share more than 90% of the number of Shares that would be outstanding
immediately after the issuance of all Top-Up Option Shares. We intend to
exercise the Top-Up Option if it is exercisable and such exercise is necessary
in order for us to be able to effect such a “short-form” merger. See Section 11
: “The Merger Agreement; Other Agreements : The Merger Agreement : Top-Up
Option” and Section 17 : “Certain Legal Matters; Regulatory Approvals :
“Short-Form” Merger.”

If, after the Acceptance Time, we and our affiliates do not own, by virtue of
the Offer or otherwise, 90% or more of the issued and outstanding Shares, we may
elect to require Micromet to effect the Merger under the “long-form” merger
provision of Section 251 of the DGCL which requires that the Merger Agreement be
adopted by Micromet’s stockholders. Adoption of the Merger Agreement requires
the affirmative vote of holders of a majority of the outstanding Shares. Thus,
if the Minimum Condition and the other conditions to the Offer are satisfied and
the Offer is completed, we would have sufficient voting power to adopt the
Merger Agreement without the affirmative vote of any other stockholder of
Micromet. Amgen has agreed to vote, or cause to be voted, all Shares held by it
and its affiliates in favor of the adoption of the Merger Agreement. No interest
will be paid for Shares acquired in the Merger. See Section 11 : “The Merger
Agreement; Other Agreements : Actions in Connection with Long-Form Merger” and
Section 17 : “Certain Legal Matters; Regulatory Approvals : “Short-Form”
Merger.”

Plans for Micromet

The Merger Agreement provides that, following the consummation of the Offer
and subject to the conditions set forth in the Merger Agreement, we will be
merged with and into Micromet and that, following the Merger and until
thereafter amended, our certificate of incorporation as in effect immediately
prior to the Effective Time will be the certificate of incorporation of the
Surviving Corporation and at the Effective Time our bylaws will be the bylaws of
the Surviving Corporation until thereafter amended.

Our directors immediately prior to the Effective Time will become the only
directors of the Surviving Corporation at the Effective Time and our officers at
such time will become the only officers of the Surviving Corporation. See
Section 11 : “The Merger Agreement; Other Agreements : The Merger Agreement :
Certificate of Incorporation; Bylaws; Directors and Officers of the Surviving
Corporation.”

We will continue to evaluate the business and operations of Micromet during
the pendency of the Offer and the Merger and will take such actions as we deem
appropriate under the circumstances then existing. Thereafter, we intend to
review such information as part of a comprehensive review of Micromet’s
business, operations, capitalization and management with a view to optimizing
development of Micromet’s potential in conjunction with Amgen’s existing
businesses. We expect that all aspects of Micromet’s business will be fully
integrated into Amgen. However, plans may change based on further analysis
including changes in Micromet’s business, corporate structure, charter, bylaws,
capitalization, board of directors, management, officers, indebtedness or

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dividend policy, although, except as disclosed in this Offer to Purchase, we
and Amgen have no current plans with respect to any of such matters.

Except as described above or elsewhere in this Offer to Purchase, neither we
nor Amgen has any present plans or proposals that would relate to or result in
(i) any extraordinary transaction involving Micromet or any of its subsidiaries
(such as a merger, reorganization or liquidation), (ii) any purchase, sale or
transfer of a material amount of assets of Micromet or any of its subsidiaries,
(iii) any change in the Micromet Board or management of Micromet, (iv) any
material change in Micromet’s capitalization or dividend rate or policy or
indebtedness, (v) any other material change in Micromet’s corporate structure or
business, (vi) any class of equity securities of Micromet being delisted from a
national securities exchange or ceasing to be authorized to be quoted in an
automated quotation system operated by a national securities association or
(vii) any class of equity securities of Micromet becoming eligible for
termination of registration pursuant to Section 12(g) of the Exchange Act.

13. Certain Effects of the Offer.

Market for Shares. The purchase of Shares pursuant to the Offer will
reduce the number of holders of Shares and the number of Shares that might
otherwise trade publicly, which could adversely affect the liquidity and market
value of the remaining Shares held by stockholders other than Amgen and its
affiliates. Neither Amgen nor its affiliates can predict whether the reduction
in the number of Shares that might otherwise trade publicly would have an
adverse or beneficial effect on the market price for, or marketability of,
Shares or whether such reduction would cause future market prices to be greater
or less than the Offer Price.

NASDAQ Listing. Depending upon the number of Shares purchased
pursuant to the Offer, the Shares may no longer meet the requirements for
continued listing on the NASDAQ. According to the published NASDAQ guidelines,
the NASDAQ would consider delisting the Shares if, among other things, the total
number of holders of Shares falls below 400 or the number of publicly held
Shares falls below 750,000. Shares held by officers or directors of Micromet or
their immediate families, or by any beneficial owner of 10% or more of such
Shares, ordinarily will not be considered as being “publicly held” for this
purpose. According to Micromet, as of January 25, 2012, 92,375,454 Shares were
issued and outstanding. If, as a result of the purchase of Shares pursuant to
the Offer or otherwise, the Shares no longer meet the requirements of the NASDAQ
for continued listing and such listing is discontinued, the market for Shares
could be adversely affected.

If the NASDAQ were to delist the Shares, it is possible that Shares would
continue to trade on another securities exchange or in the over-the-counter
market and that price or other quotations would be reported by such exchange or
other sources. The extent of the public market for Shares and the availability
of such quotations would depend, however, upon such factors as the number of
stockholders and/or the aggregate market value of the publicly traded Shares
remaining at such time, the interest in maintaining a market in Shares on the
part of securities firms, the possible termination of registration under the
Exchange Act (as described below), and other factors. We cannot predict whether
the reduction in the number of Shares that might otherwise trade publicly would
have an adverse or beneficial effect on the market price or marketability of
Shares or whether it would cause future market prices to be greater or less than
the Offer Price. Trading in Shares will cease upon the Effective Time if trading
has not ceased earlier as discussed above.

After the consummation of the Offer, Amgen may cause Micromet to take all
action to be treated as a “controlled company,” as defined by Rule 5615(c) of
the NASDAQ Rules (or any successor provision), which means that Micromet would
be exempt from the requirement that the Micromet Board be composed of a majority
of “independent directors” and the related rules covering the independence of
directors serving on the nominating and corporate governance committee and the
compensation committee of the Micromet Board. The controlled company exemption
does not modify the independence requirements for Micromet’s audit committee or
the requirements of the Merger Agreement relating to independent directors and
the independent director committee. See Section 11 : “The Merger Agreement;
Other Agreements : The Merger Agreement : Micromet Board of Directors.”
Following the purchase of Shares in the Offer and the satisfaction or waiver of
the remaining conditions, we expect to consummate the Merger, following which no
Shares will be publicly owned.

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Exchange Act Registration. The Shares are currently registered under
the Exchange Act. As a result, Micromet currently files periodic reports on
account of the Shares. Following the purchase of Shares in the Offer and the
satisfaction of the remaining conditions, we expect to complete the Merger,
following which the Shares will no longer be publicly owned. Following the
consummation of the Merger, we intend to take steps to cause the termination of
the registration of Shares under the Exchange Act as promptly as practicable and
may in the future take steps to cause the suspension of all of Micromet’s
reporting obligations under the Exchange Act. Pursuant to the rules of the SEC
and the views expressed by the SEC staff, Micromet may terminate its Exchange
Act registration and suspend its reporting obligations on account of the Shares
if (i) the outstanding Shares are not listed on a national securities exchange,
(ii) there are fewer than 300 holders of record of Shares and (iii) Micromet is
not otherwise required to furnish or file reports under the Exchange Act. Such
termination and suspension, once effective, would reduce the information that
Micromet must furnish to its stockholders and to the SEC. The deregistration of
the Shares, once effective, would make certain provisions of the Exchange Act,
including the short-swing profit recovery provisions of Section 16(b) of the
Exchange Act and the requirement of furnishing a proxy statement or information
statement in connection with stockholders’ meetings or actions in lieu of a
stockholders’ meeting pursuant to Section 14(a) or 14(c) of the Exchange Act and
the related requirement to furnish an annual report to stockholders, no longer
applicable with respect to the Shares. In addition, if the Shares are no longer
registered under the Exchange Act, the requirements of Rule 13e-3 under the
Exchange Act with respect to “going private” transactions would no longer be
applicable to Micromet. Furthermore, the ability of Micromet’s affiliates and
persons holding restricted securities to dispose of such securities pursuant to
Rule 144 or Rule 144A under the Securities Act of 1933, as amended, could be
impaired or eliminated. If registration of the Shares under the Exchange Act
were terminated, the Shares would no longer be eligible for NASDAQ reporting or
for continued inclusion on the list of the Board of Governors of the Federal
Reserve System (the “Federal Reserve Board”) for margin securities.

Margin Regulations. The Shares are currently “margin securities”
under the regulations of the Federal Reserve Board, which has the effect, among
other things, of allowing brokers to extend credit using the Shares as
collateral. Depending upon factors similar to those described above regarding
listing and market quotations, following the Offer, the Shares may no longer
constitute “margin securities” for the purposes of the margin regulations of the
Federal Reserve Board, in which event the Shares would be ineligible as
collateral for margin loans made by brokers.

14. Dividends and Distributions.

As discussed in Section 11 : “The Merger Agreement; Other Agreements : The
Merger Agreement : Conduct of Business of Micromet,” the Merger Agreement
provides that, from the date of the Merger Agreement to the Acceptance Time,
without the prior written approval of Amgen, Micromet will not, and will not
allow its subsidiaries to, authorize or pay any dividends on or make any
distribution with respect to the outstanding Shares.

15. Conditions to the Offer.

Notwithstanding any other provisions of the Offer or the Merger Agreement, we
will not be required to accept for payment, and subject to the rules and
regulations of the SEC, including Rule 14e-1(c) under the Exchange Act (relating
to our obligation to pay for or return tendered Shares promptly after
termination or withdrawal of the Offer), will not be obligated to pay for, or
may delay acceptance or payment for, any Shares tendered pursuant to the Offer
if:

prior to the Expiration Date, the Minimum Condition shall not have been
satisfied;

the HSR Condition shall not have been satisfied;

if required under applicable law, the written approval of the Offer by the
German Federal Cartel Office under the GWB shall not have been given or the
review period applicable to the Offer under the GWB shall not have expired or
been terminated;

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(a) any of the representations and warranties of Micromet regarding its
organization, good standing and qualification, its capital structure, its
corporate authority, takeover statutes, votes required, its rights plan and the
fairness opinion given by its financial advisor were not true and correct in all
material respects as of the date of the Merger Agreement or are not true and
correct in all material respects as of the Expiration Date (disregarding all
Material Adverse Effect and other materiality qualifications in such
representations) as though made on and as of such date and time (except to the
extent that any such representation and warranty expressly speaks as of a
different date, in which case such representation and warranty shall speak as of
such different date) or (b) any of the other representations and warranties of
Micromet set forth in the Merger Agreement were not accurate in all respects as
of the date of the Merger Agreement or are not accurate in all respects at and
as of the Expiration Date (disregarding all Material Adverse Effect and other
materiality qualifiers in such representations) as though made on and as of such
date and time (except to the extent that any such representation and warranty
expressly speaks as of a different date), except that any inaccuracies in such
representations and warranties will be disregarded if the circumstances giving
rise to all such inaccuracies (considered collectively) do not constitute, and
would not reasonably be expected to have a Material Adverse Effect on Micromet
and its subsidiaries, taken as a whole;

Micromet shall not have performed or complied in all material respects with
all covenants and obligations it is required to comply with or to perform under
the Merger Agreement prior to the Expiration Date;

since the date of the Merger Agreement, there shall have occurred a Material
Adverse Effect or a change, event, circumstance or development shall have
occurred that is, individually or in the aggregate, reasonably likely to have a
Material Adverse Effect;

the Micromet Board withdraws or modifies the Micromet Board Recommendation in
a manner adverse to Amgen and us or accepts or recommends any Acquisition
Proposal;

any court of competent jurisdiction issues any temporary restraining order,
preliminary or permanent injunction or other order (or such order remains in
effect) preventing the consummation of the Offer or the Merger or an action is
taken, or any applicable law or order promulgated, entered, enforced, enacted,
issued or deemed applicable to the Offer or the Merger by any governmental body
which directly or indirectly prohibits, or makes illegal, the acceptance for
payment of or payment for Shares or the consummation of the Offer or the Merger;

a legal proceeding by a governmental body having authority over Amgen, us,
Micromet or any of its subsidiaries is pending which (i) challenges or seeks to
restrain or prohibit the consummation of the Offer or the Merger, (ii) seeks to
restrain or prohibit Amgen’s or its affiliates’ ownership or operation of the
business of Micromet or its subsidiaries, or of Amgen or its affiliates, or to
compel Amgen or any of its affiliates to dispose of or hold separate all or any
portion of the business or assets of Micromet or its subsidiaries or of Amgen or
its affiliates or (iii) seeks to impose or confirm material limitations on the
ability of Amgen or any of its affiliates to effectively exercise full rights of
ownership of the Shares; or

the Merger Agreement is validly terminated in accordance with its terms.

The foregoing conditions are for the sole benefit of Amgen and us and may be
waived by Amgen and us, in whole or in part at any time and from time to time,
in the sole discretion of Amgen and us; provided that the Minimum Condition may
be waived by Amgen and us only with the prior written consent of Micromet, which
may be granted or withheld in Micromet’s sole discretion. The failure by Amgen
or us at any time to exercise any of the foregoing rights will not be deemed a
waiver of any such right and each such right will be deemed an ongoing right
which may be asserted at any time and from time to time.

16. Adjustments to Prevent Dilution.

In the event that, notwithstanding Micromet’s covenant to the contrary (See
Section 11 : “The Merger Agreement; Other Agreements : The Merger Agreement :
Conduct of Business of Micromet”), between the

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date of the Merger Agreement and the Effective Time, Micromet changes the
number of Shares or securities convertible or exchangeable into or exercisable
for Shares issued and outstanding as a result of a reclassification, stock split
(including a reverse stock split), stock dividend or distribution,
recapitalization, merger, subdivision, issuer tender or exchange offer, or other
similar transaction, the Offer Price and the consideration payable in the Merger
shall be equitably adjusted.

17. Certain Legal Matters; Regulatory Approvals.

General

Except as described in this Section 17, we are not aware of any pending legal
proceeding relating to the Offer. Except as described in this Section 17, based
on our and Amgen’s review of publicly available filings by Micromet with the SEC
and other information regarding Micromet, we are not aware of any governmental
license or regulatory permit that appears to be material to Micromet’s business
that might be adversely affected by our acquisition of Shares as contemplated in
this Offer to Purchase or of any approval or other action by any governmental,
administrative or regulatory authority or agency, domestic or foreign, that
would be required for the acquisition or ownership of Shares by us as
contemplated in this Offer to Purchase. However, there can be no assurance that
any such approval or other action, if needed, would be obtained or would be
obtained without substantial conditions or that if such approvals were not
obtained or such other actions were not taken, adverse consequences might not
result to Micromet’s business, or certain parts of Micromet’s business might not
have to be disposed of, any of which could cause us to elect to terminate the
Offer without the purchase of Shares thereunder under certain conditions. See
Section 15 : “Conditions to the Offer.”

Litigation

On January 27, 2012, a putative class action lawsuit challenging the Merger,
captioned Rush v. Micromet, Inc., Case No. V358302, was filed in the
Circuit Court for Montgomery County, Maryland (the “Rush Case”). On January 30,
2012, a putative class action lawsuit challenging the Merger, captioned
Passes v. Micromet, Inc., Case No. 7198-VCP, was filed in the Court of
Chancery for the State of Delaware (the “Passes Case”). On January 30, 2012, a
putative class action lawsuit challenging the Merger, captioned Bohaychuck
v. Micromet, Inc.
, Case No. 7197-VCP, was filed in the Court of Chancery
for the State of Delaware (the “Bohaychuck Case”). On January 31, 2012, a
putative class action lawsuit challenging the Merger, captioned Volpe v.
Micromet, Inc.
, Case No. 7201-VCP, was filed in the Court of Chancery for
the State of Delaware (the “Volpe Case”). On February 1, 2012, a putative class
action lawsuit challenging the Merger, captioned Draper-Donaldson v.
Micromet, Inc.
, was filed in the Court of Chancery for the State of
Delaware (the “Draper-Donaldson Case”). On February 1, 2012, a putative class
action lawsuit challenging the Merger, captioned Wolf v. Micromet,
Inc.
, was filed in the Court of Chancery for the State of Delaware (the
“Wolf Case” and collectively with the Passes Case, Bohaychuck Case, Volpe Case,
Draper-Donaldson Case and the Rush Case, the “Stockholder Litigations”).

The Stockholder Litigations were each filed against us, Amgen, Micromet and
the individual members of the Micromet Board. The Stockholder Litigations each
generally allege, among other things, that the members of the Micromet Board
breached their fiduciary duties owed to the Micromet stockholders by approving
the proposed Merger for inadequate consideration, entering into the Merger
Agreement containing preclusive deal-protection devices, and failing to take
steps to maximize the value to be paid to the Micromet stockholders. Each of the
Stockholder Litigations also alleges claims for aiding and abetting such alleged
breaches of fiduciary duties. The Passes Case alleges the aiding and abetting
claim against Micromet only, whereas the Bohaychuck Case alleges this claim
against Micromet and Amgen, the Draper-Donaldson Case and Wolf Case allege this
claim against Amgen and us and the Rush Case and Volpe Case allege this claim
against us, Amgen and Micromet. The plaintiffs in each of the Stockholder
Litigations generally seek, among other things, declaratory and injunctive
relief concerning the alleged breaches of fiduciary duty, injunctive relief
prohibiting consummation of the proposed Merger, damages and attorneys’ fees and
costs, and other forms of relief.

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State Takeover Statutes

A number of states (including Delaware, where Micromet is incorporated) have
adopted takeover laws and regulations that purport, to varying degrees, to be
applicable to attempts to acquire securities of corporations that are
incorporated in such states or that have substantial assets, stockholders,
principal executive offices or principal places of business therein. To the
extent that certain provisions of certain of these state takeover statutes
purport to apply to the Offer or the Merger, we believe there are reasonable
bases for contesting such laws. In Edgar v. MITE Corp., the Supreme
Court of the United States invalidated on constitutional grounds the Illinois
Business Takeover Statute that, as a matter of state securities law, made
takeovers of corporations meeting certain requirements more difficult. However,
in 1987, in CTS Corp. v. Dynamics Corp. of America, the Supreme Court
held that the State of Indiana could, as a matter of corporate law,
constitutionally disqualify a potential acquiror from voting shares of a target
corporation without the prior approval of the remaining stockholders where,
among other things, the corporation is incorporated in, and has a substantial
number of stockholders in, the state. Subsequently, in TLX Acquisition Corp.
v. Telex Corp.
, a Federal District Court in Oklahoma ruled that the
Oklahoma statutes were unconstitutional insofar as they apply to corporations
incorporated outside Oklahoma in that they would subject such corporations to
inconsistent regulations. Similarly, in Tyson Foods, Inc. v.
McReynolds
, a Federal District Court in Tennessee ruled that four Tennessee
takeover statutes were unconstitutional as applied to corporations incorporated
outside Tennessee. This decision was affirmed by the United States Court of
Appeals for the Sixth Circuit.

Section 203 of the DGCL restricts an “interested stockholder” (including a
person who owns or has the right to acquire 15% or more of the corporation’s
outstanding voting stock) from engaging in a “business combination” (defined to
include mergers and certain other actions) with certain Delaware corporations
for a period of three years following the time such person became an interested
stockholder. These restrictions will not be applicable to us and Amgen because
the Micromet Board has unanimously approved the Offer, the Merger, the Merger
Agreement and the other transactions contemplated thereby, including for
purposes of Section 203.

We are not aware of any other state takeover laws or regulations that are
applicable to the Offer or the Merger and has not attempted to comply with any
state takeover laws or regulations. If any government official or third party
should seek to apply any such state takeover law to the Offer or the Merger or
any of the other transactions contemplated by the Merger Agreement, we will take
such action as then appears desirable, which action may include challenging the
applicability or validity of such statute in appropriate court proceedings. In
the event it is asserted that one or more state takeover statutes are applicable
to the Offer or the Merger and an appropriate court does not determine that it
is or they are inapplicable or invalid as applied to the Offer or the Merger, we
might be required to file certain information with, or to receive approvals
from, the relevant state authorities or holders of Shares, and we might be
unable to accept for payment or pay for Shares tendered pursuant to the Offer,
or might be delayed in continuing or consummating the Offer or the Merger. In
such case, we may not be obligated to accept for payment or pay for any tendered
Shares. See Section 15 : “Conditions to the Offer.”

Antitrust Compliance

United States Antitrust Compliance. Under the HSR Act and the rules
that have been promulgated thereunder by the FTC, certain acquisition
transactions may not be consummated unless certain information has been
furnished to the Antitrust Division of the U.S. Department of Justice (the
“Antitrust Division”) and the FTC and certain waiting period requirements have
been satisfied. The initial waiting period for a cash tender offer is 15 days,
but this period may be shortened if the reviewing agency grants “early
termination” of the waiting period, or it may be lengthened if the acquiring
person voluntarily withdraws and re-files to allow a second 15-day waiting
period, or the reviewing agency issues a formal request for additional
information and documentary material. The purchase of Shares pursuant to the
Offer is subject to the HSR Act. The Antitrust Division and the FTC scrutinize
the legality under the antitrust laws of transactions such as the acquisition of

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Shares by us pursuant to the Offer. At any time before or after the
consummation of any such transactions, the Antitrust Division or the FTC could
take such action under the antitrust laws of the United States as it deems
necessary or desirable in the public interest, including seeking to enjoin the
purchase of Shares pursuant to the Offer or seeking divestiture of the Shares so
acquired or divestiture of assets of Amgen or Micromet. Private parties (as well
as individual States of the United States) may also bring legal actions under
the antitrust laws of the United States or state antitrust laws. We do not
believe that the consummation of the Offer will result in a violation of any
applicable antitrust laws. However, there can be no assurance that a challenge
to the Offer on antitrust grounds will not be made, or if such a challenge is
made, what the result would be.

Each of Micromet and Amgen will file by February 6, 2012 a Premerger
Notification and Report Form with the FTC and the Antitrust Division for review
in connection with the Offer. The initial waiting period applicable to the
purchase of Shares pursuant to the Offer will expire 15 days (or the next
business day) after the filing by Amgen is made.

German Antitrust Compliance. If required by law, the written
approval by the German Federal Cartel Office or the expiration of any applicable
waiting period would be a condition to our obligation to accept for payment and
pay for the Shares tendered pursuant to the Offer. We do not believe that the
Offer will require a filing with the German Federal Cartel Office nor do we
believe that the consummation of the Offer will meet the criteria for a
prohibition under the German Act against Restraints of Competition (Gesetz
gegen Wettbewerbsbeschr 164nkungen
). However, there can be no assurance that a
challenge to the Offer on antitrust grounds will not be made, or if such a
challenge is made, what the result would be.

Going Private Transactions

The SEC has adopted Rule 13e-3 under the Exchange Act, which is applicable to
certain “going private” transactions, and which may under certain circumstances
be applicable to the Merger or other business combination following the purchase
of Shares pursuant to the Offer in which we seek to acquire the remaining Shares
not then held by us. We believe that Rule 13e-3 under the Exchange Act will not
be applicable to the Merger because we were not, at the time the Merger
Agreement was executed, and are not, an affiliate of Micromet (for purposes of
the Exchange Act); it is anticipated that the Merger will be effected within one
year following the consummation of the Offer; and, in the Merger, stockholders
will receive the same price per Share as the Offer Price.

Rule 13e-3 under the Exchange Act would otherwise require, among other
things, that certain financial information concerning Micromet and certain
information relating to the fairness of the proposed transaction and the
consideration offered to minority stockholders be filed with the SEC and
disclosed to stockholders before the completion of a transaction.

Appraisal Rights

No appraisal rights are available to the holders of Shares in connection with
the Offer. However, if the Merger is consummated, each holder of Shares (that
did not tender such Shares into the Offer) at the Effective Time who has neither
voted in favor of the Merger nor consented to the Merger in writing, and who
otherwise complies with the applicable statutory procedures under Section 262 of
the DGCL, will be entitled to receive a judicial determination of the fair value
of such holder’s Shares (exclusive of any element of value arising from the
accomplishment or expectation of the Merger) and to receive payment of such
judicially determined amount in cash, together with such rate of interest, if
any, as the Delaware court may determine for Shares held by such holder (which
shall be, unless the court in its discretion determines otherwise for good cause
shown, compounded quarterly and shall accrue at 5% over the Federal Reserve
discount rate (including any surcharge) as established from time to time during
the period between the Effective Date and the date of payment of the judgment).

Any such judicial determination of the fair value of any Shares could be
based upon considerations other than, or in addition to, the price paid in the
Offer and the market value of such Shares. Holders of Shares should recognize
that the value so determined could be higher or lower than, or the same as, the
Offer Price or the

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consideration payable in the Merger (which is equivalent in amount to the
Offer Price). Moreover, we may argue in an appraisal proceeding that, for
purposes of such proceeding, the fair value of such Shares is less than such
amount. For the avoidance of doubt, the parties to the Merger Agreement have
agreed and acknowledged that, in any appraisal proceeding described in this
Offer to Purchase and to the fullest extent permitted by applicable law, the
fair value of Shares subject to the appraisal proceeding will be determined in
accordance with Section 262 of the DGCL without regard to the Top-Up Option, any
Shares issued through the exercise of the Top-Up Option or any cash or
promissory note delivered by us to Micromet in payment for such Shares issued
through the exercise of the Top-Up Option.

The foregoing summary of the appraisal rights of stockholders under the DGCL
does not purport to be a statement of the procedures to be followed by
stockholders desiring to exercise any appraisal rights in accordance with
Delaware law. The preservation and exercise of appraisal rights require strict
and timely adherence to the applicable provisions of Delaware law, which will be
set forth in their entirety in the proxy statement or information statement
disseminated in connection with the Merger, unless effected as a “short-form”
merger, in which case they will be set forth in a notice of merger to be sent to
stockholders. The foregoing discussion is not a complete statement of law
pertaining to appraisal rights in accordance with Delaware law and is qualified
in its entirety by reference to Delaware law.

You cannot exercise appraisal rights at this time. The information provided
above is for informational purposes only with respect to your alternatives if
the Merger is consummated. If you tender your Shares into the Offer, you will
not be entitled to exercise appraisal rights with respect to your Shares but,
instead, subject to the conditions to the Offer, you will receive the Offer
Price for your Shares.

“Short-Form” Merger

Section 253 of the DGCL provides that, if a parent company owns at least 90%
of the issued and outstanding shares of each class of a subsidiary’s stock
entitled to vote to adopt a merger agreement, the parent company may merge that
subsidiary with the parent company pursuant to the “short-form” merger
procedures without prior notice to, or the approval or consent of, the other
stockholders of the subsidiary. In order to consummate the Merger pursuant to
these provisions of the DGCL, we would have to own at least 90% of the issued
and outstanding Shares. If we are able to consummate the Merger pursuant to
these provisions of the DGCL, the consummation of the Merger would take place as
soon as practicable after the Acceptance Time, without any notice to or approval
or consent of the other holders of Shares. If we own, by virtue of the Offer or
otherwise, 90% or more of the issued and outstanding Shares, we, Amgen and
Micromet will take all necessary and appropriate action to cause the Merger to
become effective as soon as practicable in accordance with these “short-form”
merger procedures set forth in Section 253 of the DGCL.

18. Fees and Expenses.

We have retained the Depositary, the Information Agent and the Dealer-Manager
in connection with the Offer. Each of the Depositary and the Information Agent
will receive customary compensation, and the Depositary, Information Agent and
the Dealer-Manager will each receive, subject to certain limits, reimbursement
for reasonable out-of-pocket expenses.

As part of the services included in such retention, the Information Agent may
contact holders of Shares by personal interview, mail, electronic mail,
telephone and other methods of electronic communication and may request brokers,
dealers, commercial banks, trust companies and other nominees to forward the
Offer materials to beneficial holders of Shares.

Except as set forth above, we will not pay any fees or commissions to any
broker or dealer or other person for soliciting tenders of Shares pursuant to
the Offer. Brokers, dealers, commercial banks, trust companies or other nominees
will, upon request, be reimbursed by us for customary mailing and handling
expenses incurred by them in forwarding the Offer materials to their customers.

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19. Miscellaneous.

The Offer is not being made to (nor will tenders be accepted from or on
behalf of) holders of Shares in any jurisdiction in which the making of the
Offer or the acceptance thereof would not be in compliance with the securities,
“blue sky” or other laws of such jurisdiction. However, we may, in our
discretion, take such action as it may deem necessary to make the Offer comply
with the laws of such jurisdiction and extend the Offer to holders of Shares in
such jurisdiction in compliance with applicable laws.

No person has been authorized to give any information or to make any
representation on behalf of us not contained herein or in the Letter of
Transmittal, and, if given or made, such information or representation must not
be relied upon as having been authorized.

We and Amgen have filed with the SEC a Tender Offer Statement on Schedule TO
pursuant to Rule 14d-3 under the Exchange Act, furnishing certain additional
information with respect to the Offer, and may file amendments thereto. In
addition, a Solicitation/Recommendation Statement on Schedule 14D-9 is being
filed with the SEC by Micromet pursuant to Rule 14d-9 under the Exchange Act,
setting forth the recommendation of the Micromet Board with respect to the Offer
and the reasons for such recommendation and furnishing certain additional
related information, and Micromet may file amendments thereto. The Schedule TO
and the Schedule 14D-9, including their respective exhibits, and any amendments
to any of the foregoing, may be examined and copies may be obtained from the
SEC’s Public Reference Room at 100 F Street, N.E., Washington, D.C. 20549, or
may be accessed electronically on the SEC’s website at www.sec.gov and are
available from the Information Agent at the address and telephone number set
forth on the back cover of this Offer to Purchase.

ARMSTRONG ACQUISITION CORP.

February 2, 2012

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ANNEX A

CERTAIN INFORMATION REGARDING THE DIRECTORS

AND EXECUTIVE OFFICERS OF AMGEN INC.

Set forth in the table below are the name, current principal occupation and
material positions held during the past five years of each of the directors and
executive officers of Amgen. The business address of each director and executive
officer of Amgen is One Amgen Center Drive, Thousand Oaks, California
91320-1799. Each director and executive officer of Amgen is a citizen of the
United States of America, except for Fran §ois de Carbonnel, who is a citizen of
Switzerland, and Jonathan M. Peacock, who is a citizen of the United Kingdom.

During the past five years, to the best of our knowledge, none of the persons
listed below has been convicted in a criminal proceeding (excluding traffic
violations or similar misdemeanors) or been a party to any judicial or
administrative proceeding (except for matters that were dismissed without
sanction or settlement) that resulted in a judgment, decree or final order
enjoining him, her or it from future violations of, or prohibiting activities
subject to, U.S. federal or state securities laws, or a finding of any violation
of U.S. federal or state securities laws.

Name

Present Principal Occupation or Employment and Employment
History

Director Since

David Baltimore

President Emeritus and Robert Andrews Millikan Professor of Biology,

California Institute of Technology

(Academia)

2006 : Present

Director,

Amgen Inc.

(Biotechnology)

1999 : Present

Founder and Chairman of the Board of Directors,

Calimmune, Inc.

(Healthcare)

2008 : Present

Director,

Regulus Therapeutics Inc.

(Biopharmaceuticals)

2008 : Present

Director,

Immune Design Corp.

(Biotechnology)

2008 : Present

Director,

BB Biotech AG

(Investment Company)

2004 : March 2011

Director,

MedImmune, Inc.

(Biotechnology)

2003 : 2007

1999

Frank J. Biondi, Jr.

Senior Managing Director,

WaterView Advisors LLC

(Financial Services)

1999 : Present

2002

A-1


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Name

Present Principal Occupation or Employment and Employment
History

Director Since

Director,

Amgen Inc.

(Biotechnology)

2002 : Present

Director,

RealD Inc.

(Technology)

2010 : Present

Director,

Cablevision Systems Corp.

(Telecommunications, Media and Entertainment)

2005 : Present

Director,

Seagate Technology

(Technology)

2005 : Present

Director,

Hasbro, Inc.

(Toys and Games)

1999 : Present

Director,

Yahoo! Inc.

(Internet Services)

2008 : 2010

Director,

Harrahs Entertainment, Inc.

(Gaming)

2002 : 2008

Director,

The Bank of New York Mellon Corporation

(Financial Services)

1995 : 2008

Robert A. Bradway

President and Chief Operating Officer,

Amgen Inc.

(Biotechnology)

May 2010 : Present

Executive Vice President and Chief Financial Officer,

Amgen Inc.

(Biotechnology)

April 2007 : May 2010

Vice President, Operations Strategy,

Amgen Inc.

(Biotechnology)

2006 : April 2007

Director,

Amgen Inc.

(Biotechnology)

2011 : Present

2011

A-2


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Name

Present Principal Occupation or Employment and Employment
History

Director Since

Director,

Norfolk Southern Corporation

(Transportation)

2011 : Present

Fran §ois de Carbonnel

Director,

Amgen Inc.

(Biotechnology)

2008 : Present

Director,

Mazars Group

(Financial Services)

2011 : Present

Director,

Quilvest S.A.

(Financial Services)

2006 : Present

Director,

Pages Jaunes S.A.

(Publishing)

2004 : Present

2008

Director,

Ecofin Funds

(Financial Services)

2004 : Present

Director,

Thomson S.A.

(Media)

2007 : 2010

Vance D. Coffman

Director,

Amgen Inc.

(Biotechnology)

2007 : Present

Director,

Deere & Company

(Farm and Construction Machinery)

2004 : Present

Director,

3M Company

(Consumer Products)

2002 : Present

Director,

Bristol-Myers Squibb Company

(Pharmaceuticals)

1998 : 2007

2007

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Name

Present Principal Occupation or Employment and Employment
History

Director Since

Rebecca M. Henderson

John and Natty McArthur University Professor,

Harvard University

(Academia)

September 2011 : Present

Research Associate,

National Bureau of Academic Research

(Research)

1995 : Present

Senator John Heinz Professor of Environmental Management,

Harvard Business School

(Academia)

July 2009 : September 2011

Eastman Kodak LFM Professor of Management,

Massachusetts Institute of Technology

(Academia)

1999 : July 2009

2009

Director,

Amgen Inc.

(Biotechnology)

2009 : Present

Director,

IDEXX Laboratories, Inc.

(Technology)

2003 : Present

Director,

Ember Corporation

(Technology)

2001 : 2009

Frank C. Herringer

Director,

Amgen Inc.

(Biotechnology)

2004 : Present

Director,

Safeway Inc.

(Retail)

2008 : Present

Director,

Cardax Pharmaceuticals, Inc.

(Biotechnology)

2007 : Present

Director,

Aegon US Holding Corporation

(Insurance)

1999 : Present

2004

A-4


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Name

Present Principal Occupation or Employment and Employment
History

Director Since

Director,

The Charles Schwab Corporation

(Financial Services)

1996 : Present

Chairman of the Board,

Transamerica Corporation

(Financial Services)

1995 : Present

Gilbert S. Omenn

Professor of Internal Medicine, Human Genetics and Public Health and Director
of the Center for Computational Medicine and Bioinformatics,

University of Michigan

(Academia)

1997 : Present

1987

Affiliate Faculty Member,

Institute for Systems Biology

(Research)

2009 : Present

Director,

Amgen Inc.

(Biotechnology)

1987 : Present

Member, Scientific Advisory Board,

Galectin Therapeutics Inc.

(Pharmaceuticals)

2009 : Present

Director and Member, Scientific Advisory Board,

Armune BioSciences, Inc.

(Diagnostics)

2008 : Present

Member, Scientific Advisory Board,

Compendia Biosciences Inc.

(Biotechnology)

2007 : Present

Member, Scientific Advisory Board,

Innocentive Innovation Inc.

(Information Technology)

2006 : Present

Member, Scientific Advisory Board,

Motorola, Inc.

(Electronics)

1998 : 2010

Director,

Rohm & Hass Co.

(Chemicals)

1987 : 2009

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Name

Present Principal Occupation or Employment and Employment
History

Director Since

Director,

OccuLogix, Inc.

(Medical Services)

2005 : 2008

Judith C. Pelham

President Emeritus,

Trinity Health

(Healthcare)

2004 : Present

Director,

Amgen Inc.

(Biotechnology)

1995 : Present

1995

Director,

Zoll Medical Corporation

(Medical Products)

2011 : Present

Director,

Eclipsys Corporation

(Information Technology)

2009 : 2010

J. Paul Reason, USN (Retired)

Director,

Amgen Inc.

2001

(Biotechnology)

2001 : Present

Director,

Norfolk Southern Corporation

(Transportation)

2002 : Present

Director,

Todd Shipyards Corporation

(Shipbuilding)

2007 : 2011

Leonard D. Schaeffer

Senior Advisor,

TPG Capital

(Investment Management)

2006 : Present

Partner,

North Bristol Partners LLC

(Consulting)

2006 : Present

Director,

Amgen Inc.

(Biotechnology)

2004 : Present

2004

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Name

Present Principal Occupation or Employment and Employment
History

Director Since

Director,

Quintiles Transnational Corp.

(Clinical Research and Consulting)

2008 : Present

Chairman of the Board,

Surgical Care Affiliates, LLC

(Healthcare)

2007 : 2011

Director,

Allergan, Inc.

(Pharmaceuticals)

1993 : 2011

Kevin W. Sharer

Chief Executive Officer,

Amgen Inc.

(Biotechnology)

2000 : Present

Chairman of the Board of Directors,

Amgen Inc.

(Biotechnology)

2001 : Present

President,

Amgen Inc.

(Biotechnology)

2000 : 2010

Director,

Chevron Corporation

(Integrated Oil)

2007 : Present

Director,

Northrop Grumman Corporation

(Defense)

2003 : Present

Director,

3M Company

(Consumer Products)

2001 : 2007

1992

Ronald D. Sugar

Senior Advisor,

Northrop Grumman Corporation

(Defense)

2010 : Present

Senior Advisor,

Ares Management LLC

(Financial Services)

2010 : Present

2010

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of Contents

Name

Present Principal Occupation or Employment and Employment
History

Director Since

Chairman of the Board of Directors and Chief Executive Officer,

Northrop Grumman Corporation

(Defense)

2003 : 2009

Director,

Amgen Inc.

(Biotechnology)

2010 : Present

Director,

Apple Inc.

(Electronics)

2010 : Present

Director,

Air Lease Corporation

(Aircraft Leasing)

2010 : Present

Director,

Chevron Corporation

(Integrated Oil)

2005 : Present

David W. Beier

Senior Vice President, Global Government and Corporate Affairs,

Amgen Inc.

(Biotechnology)

2008 : Present

Senior Vice President, Global Government Affairs,

Amgen Inc.

(Biotechnology)

2003 : 2008

Director,

ARYx Therapeutics, Inc.

(Pharmaceuticals)

2008 : 2011

Not applicable (executive)

Fabrizio Bonanni

Executive Vice President, Operations,

Amgen Inc.

(Biotechnology)

August 2007 : Present

Senior Vice President, Manufacturing,

Amgen Inc.

(Biotechnology)

2004 : August 2007

Not applicable (executive)

A-8


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Name

Present Principal Occupation or Employment and Employment
History

Director Since

Anthony C. Hooper

Executive Vice President, Global Commercial Operations,

Amgen Inc.

(Biotechnology)

October 2011 : Present

Not applicable (executive)

Senior Vice President, Commercial Operations and President, U.S., Japan and
Intercontinental,

Bristol-Myers Squibb Company

(Pharmaceuticals)

March 2010 : October 2011

President, Americas,

Bristol-Myers Squibb Company

(Pharmaceuticals)

January 2009 : March 2010

President, U.S. Pharmaceuticals, Worldwide

Pharmaceuticals Group,

Bristol-Myers Squibb Company

(Pharmaceuticals)

2004 : January 2009

Brian M. McNamee

Senior Vice President, Human Resources,

Amgen Inc.

(Biotechnology)

2001: Present

Not applicable (executive)

Jonathan M. Peacock

Executive Vice President and Chief Financial Officer,

Amgen Inc.

(Biotechnology)

September 2010 : Present

Chief Financial and Administration Officer,

Novartis Pharmaceuticals AG

(Healthcare)

2005 : September 2010

Not applicable (executive)

Roger M. Perlmutter

Executive Vice President, Research and Development,

Amgen Inc.

(Biotechnology)

2001 : Present

Director,

StemCells, Inc.

(Biotechnology)

2000 : Present

Not applicable (executive)

Anna S. Richo

Senior Vice President and Chief Compliance Officer,

Amgen Inc.

(Biotechnology)

June 2008 : Present

Not applicable (executive)

A-9


Table
of Contents

Name

Present Principal Occupation or Employment and Employment
History

Director Since

Vice President, Law,

Amgen Inc.

(Biotechnology)

2003 : June 2008

David J. Scott

Senior Vice President, General Counsel and Secretary,

Amgen Inc.

(Biotechnology)

2004 : Present

Not applicable (executive)

A-10


Table
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ANNEX B

CERTAIN INFORMATION REGARDING THE DIRECTORS

AND EXECUTIVE OFFICERS OF PURCHASER

Set forth in the table below are the name, current principal occupation and
material positions held during the past five years of each of our directors and
executive officers. The business address of each such director and executive
officer is One Amgen Center Drive, Thousand Oaks, California 91320-1799. David
J. Scott is a citizen of the United States of America and Jonathan M. Peacock is
a citizen of the United Kingdom.

During the past five years, to the best of our knowledge, none of the persons
listed below has been convicted in a criminal proceeding (excluding traffic
violations or similar misdemeanors) or been a party to any judicial or
administrative proceeding (except for matters that were dismissed without
sanction or settlement) that resulted in a judgment, decree or final order
enjoining him or us from future violations of, or prohibiting activities subject
to, U.S. federal or state securities laws, or a finding of any violation of U.S.
federal or state securities laws.

Name and Position

Present Principal Occupation or Employment and
Employment History

Director Since

Jonathan M. Peacock

President, Chief Executive Officer and Director

Executive Vice President and Chief Financial Officer,

Amgen Inc.

(Biotechnology)

September 2010 : Present

Chief Financial and Administration Officer,

Novartis Pharmaceuticals AG

(Healthcare)

2005 : September 2010

January 2012

David J. Scott

Senior Vice President, General Counsel and Secretary and Director

Senior Vice President, General Counsel and Secretary,

Amgen Inc.

(Biotechnology)

2004 : Present

January 2012

B-1


Table
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ANY LETTER OF TRANSMITTAL TO BE DELIVERED TO THE
DEPOSITARY MAY ONLY BE SENT TO THE DEPOSITARY BY MAIL OR COURIER TO ONE OF THE
ADDRESSES SET FORTH BELOW AND MAY NOT BE SENT BY FACSIMILE TRANSMISSION. ANY
CERTIFICATES REPRESENTING SHARES AND ANY OTHER REQUIRED DOCUMENTS SENT BY A
STOCKHOLDER OF MICROMET OR SUCH STOCKHOLDER’S BROKER, DEALER, COMMERCIAL BANK,
TRUST COMPANY OR OTHER NOMINEE SHOULD BE SENT TO THE DEPOSITARY AS FOLLOWS:

If delivering by mail:

American Stock Transfer & Trust

Company, LLC

Operations Center

Attn: Reorganization Department

P.O. Box 2042

New York, New York 10272-2042

If delivering by hand or courier:

American Stock Transfer & Trust

Company, LLC

Operations Center

Attn: Reorganization Department

6201 15th Avenue

Brooklyn, New York 11219

Other Information:

Questions or requests for assistance or additional copies of this Offer to
Purchase, the Letter of Transmittal and/or the Notice of Guaranteed Delivery may
be directed to the Information Agent at its location and telephone numbers set
forth below. Stockholders may also contact their broker, dealer, commercial
bank, trust company or other nominee for assistance concerning the Offer.

The Information Agent for the Offer is:

Georgeson Inc.

199 Water Street, 26th Floor

New York, New York 10038

Banks and Brokers Call: (212) 440-9800

Call Toll Free: (888) 877-5360

The Dealer-Manager for the Offer is:

Moelis & Company LLC

399 Park Avenue, 5th Floor

New York, New York 10022

Call: (212) 883-3800

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