July 29, 1999

Exhibit 10.6
Confidential treatment requested

Seattle Genetics, Inc.
00000 00^xx Xxxxxx XX
Xxxxxxx, Xxxxxxxxxx 00000
(000) 000-0000 (Fax)

July 29, 1999

Xxxxxxx-Xxxxx Squibb Company
P.O. Box 4000
Princeton, New Jersey 08543-4000

    This letter sets forth the agreement of Xxxxxxx-Xxxxx Squibb Company ("BMS") and Seattle Genetics, Inc. ("SGI") to amend that certain License Agreement dated March 30, 1998 between BMS and SGI (the "Agreement") as set forth herein.

    For good and valuable consideration, the receipt and sufficiency of which is hereby acknowledged, the parties agree as follows:

    1.  Section 5.2(b) is hereby amended to add the following phrase at the beginning of Section 5.2(b):

"5.2(b) Except as set forth in subsections 5.2(i) and 5.2(j),..."

    2.  A new Section 5.2(i) relating to use of the peptidic linker technology is added to the Agreement, which shall read in its entirety as follows:

"5.2(i) With respect to Products covered by Licensed Technology relating only to [*], at the rate of [*]%

    3.  A new Section 5.2(j) relating to use of BR96 technology is added to the Agreement, which shall read in its entirety as follows:

"5.2(j) With respect to Products covered by Licensed Technology relating to the use of BR96 with any active agent other than [dox], at the rate of [*]%."

    4.  BMS hereby acknowledges and agrees that SGI has completed, to the satisfaction of BMS, all of the milestones set forth in Section 13.2 of the Agreement.

    5.  Table 5 of Exhibit A to the Agreement shall be amended to add the following U.S. Patent:

Application Number		Patent Number		Descriptions		License Type
		5,773,435		Prodrugs for betalactamase.		Exclusive

    6.  All other terms and conditions of the Agreement shall remain unchanged and in full force and effect.

[*]   Confidential treatment requested

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    BMS and SGI, intending to be legally bound, have caused this Amendment to be executed by their authorized representatives below.

		SEATTLE GENETICS, INC.
		By:		/s/ X. XXXXX FELL
		Name:		X. Xxxxx Xxxx
		Title:		President

ACKNOWLEDGED AND AGREED TO:
XXXXXXX-XXXXX SQUIBB COMPANY
		By: /s/ XXXXXXX XXXXXXX
Name:		Xxxxxxx Xxxxxxx
Title:		Vice President and Senior Counsel
		August 10, 1999

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