Additional Field Force Agreement ? Amendment to Extend the Decision to Renew Joint Funding for 2005

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Exhibit 10.10

Millennium Pharmaceuticals, Inc.
40 Landsdowne Street
Cambridge, Massachusetts 02139
617.679.7000
www.millennium.com

Confidential Materials omitted and filed separately with the
Securities and Exchange Commission. Asterisks denote such omissions.

September 17, 2004

Paul Feirstein
ACS Sales and Marketing
Schering Corporation
2000 Galloping Hill Road
Kenilworth, NJ 07033

Re:

Additional Field Force Agreement — Amendment to Extend the Decision to Renew Joint Funding for 2005

Dear Paul:

        Schering and Millennium are parties to the Addendum to the Collaboration Agreement among Millennium Pharmaceuticals, Inc., Schering Corporation and Schering-Plough, Ltd., effective June 1, 2003 ("Additional Field Force Agreement"). Any defined terms used herein shall have the meaning set forth in the Additional Field Force Agreement. Pursuant to a discussion at the quarterly JSC meeting on September 10, the JSC agreed to the following amendments to the Additional Field Force Agreement in