Offer to Purchase for Cash
All Outstanding Shares of Common Stock
(Including the Associated Rights to Purchase Series A Junior Participating Preferred Stock)
of

MEDAREX, INC.

at

$16.00 NET PER SHARE

Pursuant to the Offer to Purchase dated July 28, 2009

by

PUMA ACQUISITION CORPORATION

a wholly owned subsidiary of

BRISTOL-MYERS SQUIBB COMPANY

THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE
AT 12:00 MIDNIGHT, NEW YORK CITY TIME, ON MONDAY, AUGUST 24, 2009,
UNLESS THE OFFER IS EXTENDED.

July 28, 2009

To Brokers, Dealers, Commercial Banks, Trust Companies and Other Nominees:

We have been engaged by Puma Acquisition Corporation, a New Jersey corporation (“Purchaser”) and a wholly owned subsidiary of Bristol-Myers Squibb Company, a Delaware corporation (“Parent”), to act as Dealer Manager in connection with Purchaser’s offer to purchase (the “Offer”) all outstanding shares of common stock, par value $0.01 per share, including all rights to purchase Series A Junior Participating Preferred Stock issued pursuant to the Rights Agreement dated as of May 23, 2001, between Medarex, Inc. (the “Company”) and Continental Stock Transfer & Trust Company, as amended from time to time (the “Shares”), of the Company, a New Jersey corporation, that are not already owned by Parent and its subsidiaries, at a purchase price of $16.00 per Share net to the seller in cash, without interest and less any required withholding taxes, upon the terms and subject to the conditions set forth in the Offer to Purchase, dated July 28, 2009 (the “Offer to Purchase”), and the related Letter of Transmittal enclosed herewith.

For your information and for forwarding to your clients for whom you hold Shares registered in your name or in the name of your nominee, we are enclosing the following documents:

1. The Offer to Purchase;

2. The Letter of Transmittal for your use in accepting the Offer and tendering Shares and for the information of your clients, together with “Guidelines for Certification of Taxpayer Identification Number on Substitute Form W-9” providing information relating to backup federal income tax withholding;

3. A Notice of Guaranteed Delivery to be used to accept the Offer if the Shares and all other required documents cannot be delivered to Mellon Investor Services LLC (the “Depositary”) by the Expiration Date (as defined in the Offer to Purchase) or if the procedure for book-entry transfer cannot be completed by the Expiration Date;

4. The Company’s Solicitation/Recommendation Statement on Schedule 14D-9;

5. A form of letter which may be sent to your clients for whose accounts you hold Shares registered in your name or in the name of your nominee, with space provided for obtaining such clients’ instructions with regard to the Offer; and

6. A return envelope addressed to the Depositary for your use only.

Certain conditions to the Offer are described in “The Tender Offer — Section 15 — Certain Conditions of the Offer” in the Offer to Purchase.

We urge you to contact your clients as promptly as possible. Please note that the Offer and withdrawal rights will expire at 12:00 Midnight, New York City time, on Monday, August 24, 2009, unless the Offer is extended. Previously tendered Shares may be withdrawn at any time until the Offer has expired and, if Purchaser has not accepted such Shares for payment by September 26, 2009, such Shares may be withdrawn at any time after that date until Purchaser accepts Shares for payment.

For Shares to be properly tendered pursuant to the Offer, (a) the share certificates or confirmation of receipt of such Shares under the procedure for book-entry transfer, together with a properly completed and duly executed Letter of Transmittal, including any required signature guarantees, or an “Agent’s Message” (as defined in the Offer to Purchase) in the case of book-entry transfer, and any other documents required in the Letter of Transmittal, must be timely received by the Depositary or (b) the tendering stockholder must comply with the guaranteed delivery procedures, all in accordance with the Offer to Purchase and Letter of Transmittal.

Purchaser will not pay any fees or commissions to any broker or dealer or other person (other than the Depositary and the Information Agent as described in the Offer to Purchase) for soliciting tenders of Shares pursuant to the Offer. Purchaser will, however, upon request, reimburse brokers, dealers, commercial banks and trust companies for reasonable and necessary costs and expenses incurred by them in forwarding materials to their customers. Purchaser will pay all stock transfer taxes applicable to its purchase of Shares pursuant to the Offer, subject to Instruction 6 of the Letter of Transmittal.

Any inquiries you may have with respect to the Offer should be addressed to the Information Agent or the undersigned at the addresses and telephone numbers set forth on the back cover of the Offer to Purchase. Additional copies of the enclosed materials may be obtained from the Information Agent.

Very truly yours,

J.P. Morgan Securities Inc.

Nothing contained herein or in the enclosed documents shall constitute you the agent of the Purchaser, the Dealer Manager, the Information Agent or the Depositary or any affiliate of any of them or authorize you or any other person to use any document or make any statement on behalf of any of them in connection with the Offer other than the enclosed documents and the statements contained therein.

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