**Exhibit No. 10.1**

**Confidential Materials omitted and filed separately with the Securities and ExchangeCommission.   Asterisks denote omissions.**

**AMENDMENT NO. 6**

**to**

**AGREEMENT**

**by and between**

**BAYER AG AND MILLENNIUM PHARMACEUTICALS, INC.**

        This is Amendment No. 6 ("Amendment No. 6") dated as of March 22, 2002 (the "Amendment Effective Date"), to the Agreement,dated as of September 22, 1998 (as amended, the "Agreement"), by and between Bayer AG, located at D 51368 Leverkusen, Germany andMillennium Pharmaceuticals, Inc., located at 75 Sidney Street, Cambridge, Massachusetts 02139. The Agreement has previously beenamended by Amendment No. 2 dated as of December 1, 1999, Amendment No. 3 dated as of September 18, 2000, Amendment No. 4 dated as ofDecember 1, 2000 and Amendment No. 5 dated as of September 7, 2001. The Parties acknowledge that there is no Amendment No. 1 to thisAgreement.

INTRODUCTION

        The Parties have determined that it is in their mutual best interests to amend the Agreement in the manner set forth below.

        1.        Use of Terms. Capitalized terms used herein and not defined herein shall have the respective meanings ascribed to suchterms in the Agreement.

        2.        Article I - Definitions.

        (a)        Section 1.8.    Section 1.8 of the Agreement is hereby amended by deleting Section         1.8 in its entirety and by substituting thefollowing in its place:

| "Section 1.8 "Bayer Returned QT Know-How" means Know-How owned or otherwise controlled by Bayer (as of the dateMillennium exercises the option under Section 3.2(d) with respect to the applicable Bayer Returned QT Know-How), inwhich Bayer has a licensable or sublicensable interest and which Bayer has developed or acquired as a result of theDiscovery Program and/or the Bayer Development Program, relating to (a) a Returned QT, the use of a Returned QT todiscover and develop Small Molecule Drugs, the treatment of diseases and/or conditions with Small Molecule Drugsthat interact with a Returned QT, and the Bayer Configured Assay relating to a Returned QT, and/or (b) the leadstructure under development by Bayer and related data (as more specifically set forth in Section 3.2(d))." |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

----

        3.    Provisions Relating to Specific QTs.    Notwithstanding Section 3.2(d)(ii), the parties agree that Millennium has validlyexercised its option under Section 3.2(d)(i) with respect to the following Returned QTs: [**]. Attached hereto as Exhibit A aresigned letters memorializing Millennium's exercise of its option under Section 3.2(d)(i) with respect to each of the above-notedReturned QTs. The effective date for the licenses granted as a result of Millennium's exercise of each of these options shall beMarch 22, 2002.

[Remainder of page intentionally left blank.]

2

----

        4.    General. In all other respects, the Agreement is hereby ratified and confirmed.

IN WITNESS WHEREOF, the Parties have executed this Amendment No. 6 as of the date set forth above.

|   |   | BAYER AG                         |
|--------|--------|----------------------------------|
|   |   | By:                         | /s/  Dr. Wolfgang Ehrenstein |
|   |   | Title:                      | /s/  Head of PL Department Health Care |
|   |   |                             |   |
|   |   | By:                         | /s/  Dr. Wolfgang Hartwig |
|   |   | Title:                      |   Executive VP for Research |
|   |   |                             |   |
|   |   | MILLENNIUM PHARMACEUTICALS, INC. |
|   |   | By:                         | /s/  Alan Crane |
|   |   | Title:                      | SVP Corporate Development |

3

----

**Exhibit AExercise Letters forBayer Returned QT Know-HowAnd Bayer Returned QT Patent Rights**

----

***[Form of Exercise Letters for Bayer Returned QT Know-Howand Bayer Returned QT Patent Rights]***

[Millennium Letterhead]

    [March ___, 2002]

Bayer AGPH-R L, Bldg. 0402Elberfeld, WuppertalD-42096, Germany

| Re:  | Option under Section 3.2(d) of Agreement by and between Bayer AG andMillennium Pharmaceuticals, Inc. dated September 22, 1998, as amended. |  |
|-----------|--------------------------------------------------------------------------------------------------------------------------------------------|--|

Dear                     :

Reference is made to the Agreement by and between Bayer AG ("Bayer") and Millennium Pharmaceuticals, Inc. ("MPI") dated September 22,1998, as amended (the "Agreement").

In accordance with Section 3.2(d)(ii) of the Agreement, Millennium hereby notifies Bayer of its exercise of the option set forth inSection 3.2(d)(i) with respect to Returned QT __. The specific Bayer Returned QT Know-How and Bayer Returned QT Patent Rightsrequested with respect to this Returned QT are ____________________________________________________________.

|   | Very truly yours, Ron Farquhar, Ph.D.Senior Program Director |  |
|--------|-------------------------------------------------------------------|--|