FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person * Baker Brothers Life Sciences Capital (GP), LLC   2. Issuer Name and Ticker or Trading Symbol SEATTLE GENETICS INC /WA [SGEN] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) __X__ Director __X__ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 667 MADISON AVENUE, 17TH FLOOR 3. Date of Earliest Transaction (Month/Day/Year) 08/03/2006 (Street) NEW YORK, NY 10021 4. If Amendment, Date Original Filed(Month/Day/Year) 6. Individual or Joint/Group Filing(Check Applicable Line) ___ Form filed by One Reporting Person _X_ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock (1) (2) 08/03/2006   P   18,535 A $ 3.9967 3,729,500 I See Footnote (3) Common Stock (1) (2) 08/04/2006   P   17,793 A $ 4.0498 3,747,293 I See Footnote (3) Common Stock (1) (2) 08/07/2006   P   28,692 A $ 4.0341 3,775,985 I See Footnote (3)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Baker Brothers Life Sciences Capital (GP), LLC 667 MADISON AVENUE 17TH FLOOR NEW YORK, NY 10021	X	X
BAKER JULIAN 667 MADISON AVENUE NEW YORK, NY 10021		X
BAKER FELIX 667 MADISON AVENUE NEW YORK, NY 10021	X	X

Signatures

/s/ Julian C. Baker, as Managing Member of Baker Brothers Life Sciences Capital (GP), LLC		08/07/2006
**Signature of Reporting Person		Date
/s/ Julian C. Baker		08/07/2006
**Signature of Reporting Person		Date
/s/ Felix J. Baker		08/07/2006
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	In addition to Baker Brothers Life Sciences Capital (GP), LLC this form 4 is being filed jointly by Julian C. Baker, Felix J. Baker, each of whom has the same business address as Baker Brothers Life Sciences Capital (GP), LLC. and may be deemed to have a pecuniary interest in securities owned by it. Because of certain relationships with other security holders of the Issuer, the Reporting Persons have filed on Schedule 13D as if they were a member of a group with such shareholders. (Continued in footnote 2.)
(2)	However, the Reporting Persons disclaim that they and any other person or persons, including those persons with whom the Reporting Persons have filed a Schedule 13D, in fact constitute a "group" for purposes of Section 13(d)(3) of the Securities Exchange Act of 1934, as amended, or Rule 13d-5 thereunder or that they are the beneficial owners of securities owned by such other persons, and each of them disclaims beneficial ownership of securities reported herein except to the extent of their pecuniary interest, if any, therein. Felix J. Baker is a director of the Issuer.
(3)	Represents shares of common stock owned directly by Baker Brothers Life Sciences, LP., the sole general partner of which is Baker Brothers Life Sciences Capital, L.P., a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital (GP), LLC. Felix J. Baker and Julian C. Baker are the controlling members of Baker Brothers Life Sciences Capital (GP), LLC.

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