UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549


                                  SCHEDULE 13G
                                (Amendment No. 1)


                    Under the Securities Exchange Act of 1934




                             SEATTLE GENETICS, INC.
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                                (Name of Issuer)


                    COMMON STOCK, PAR VALUE $0.001 PER SHARE
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                         (Title of Class of Securities)


                                    812578102
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                                 (CUSIP Number)


                                December 31, 2005
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             (Date of Event Which Requires Filing of this Statement)


Check the  appropriate box to designate the rule pursuant to which this Schedule
13G is filed:

                [ ] Rule 13d-1(b)
                [X] Rule 13d-1(c)
                [ ] Rule 13d-1(d)


*The  remainder of this cover page shall be filled out for a reporting  person's
initial filing on this form with respect to the subject class of securities, and
for any  subsequent  amendment  containing  information  which  would  alter the
disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the  Securities  Exchange  Act of
1934 ("Act") or otherwise  subject to the liabilities of that section of the Act
but  shall be  subject  to all other  provisions of  the Act  (however, see  the
Notes).





CUSIP No. 812578102
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(1)     Names of Reporting Persons.  I.R.S. Identification Nos. of Above Persons
        (entities only):

                Jonathan Gallen
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(2)     Check the Appropriate Box if a Member of a Group (See Instructions)

          (a)                            (b)
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(3)     SEC Use Only
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(4)     Citizenship or Place of Organization:  United States
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Number of Shares Beneficially Owned
   by Each Reporting Person With       (5) Sole Voting Power:        2,050,000*
                                           -------------------------------------
                                       (6) Shared Voting Power:              0
                                           -------------------------------------
                                       (7) Sole Dispositive Power:   2,767,550*
                                           -------------------------------------
                                       (8) Shared Dispositive Power:         0
                                           -------------------------------------
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(9)     Aggregate Amount Beneficially Owned by Each Reporting Person:
                2,767,550*
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(10)    Check if  the Aggregate Amount  in Row (9) Excludes Certain  Shares (See
        Instructions):   N/A
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(11)    Percent of Class Represented by Amount in Row (9):   6.5%*
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(12)    Type of Reporting Person (See Instructions):    IA, IN
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*   As of December 31, 2005, Ahab Partners, L.P. ("Ahab"),  Ahab  International,
Ltd.  ("International") and various private investment accounts (the "Accounts")
held in the aggregate  2,767,550  shares of common  stock,  par value $0.001 per
share (the "Shares"),  of Seattle Genetics,  Inc. Jonathan Gallen possesses sole
power to vote and direct the  disposition  of 2,050,000  Shares held by Ahab and
International.  In  addition,  Mr.  Gallen  possesses  sole  power to direct the
disposition  of  717,550  Shares  held  by the  Accounts.  Accordingly,  for the
purposes of Rule 13d-3 under the  Securities  Exchange Act of 1934,  as amended,
Mr. Gallen is deemed to beneficially own 2,767,550 Shares, or 6.5% of the Shares
deemed issued and outstanding as of December 31, 2005.






Item 1(a).  Name Of Issuer:  Seattle Genetics, Inc.

Item 1(b).  Address of Issuer's Principal Executive Offices:  
            21823 30th Drive SE, Bothell, Washington  98021


Item 2(a).  Name of Person Filing:  Jonathan Gallen*

Item 2(b).  Address  of  Principal  Business  Office  or,  if  None,  Residence:
            299 Park Avenue, New York, New York 10171

Item 2(c).  Citizenship:  United States

Item 2(d).  Title of Class of Securities:   Common Stock,  par value  $0.001 per
            share

Item 2(e).  CUSIP No.:  812578102


Item 3.     If  This  Statement Is  Filed  Pursuant  to Sections 240.13d-1(b) or
            240.13d-2(b) or (c), check whether the Person Filing is a:

            Not Applicable.


Item 4.     Ownership

            (a) Amount Beneficially Owned (as of December 31, 2005):  2,767,550*

            (b) Percent of Class (as of December 31, 2005):             6.5%*

            (c) Number of Shares as to which the person has:

               (i)   sole power to vote or to direct the vote         2,050,000*

               (ii)  shared power to vote or to direct the vote       0

               (iii) sole power to dispose or to direct the
                     disposition of                                   2,767,550*

               (iv)  shared power to dispose or to direct the
                     disposition of                                  0


---------------------------
*   As of December 31, 2005, Ahab Partners,  L.P. ("Ahab"), Ahab  International,
Ltd.  ("International") and various private investment accounts (the "Accounts")
held in the aggregate  2,767,550  shares of common  stock,  par value $0.001 per
share (the "Shares"),  of Seattle Genetics,  Inc. Jonathan Gallen possesses sole
power to vote and direct the  disposition  of 2,050,000  Shares held by Ahab and
International.  In  addition,  Mr.  Gallen  possesses  sole  power to direct the
disposition  of  717,550  Shares  held  by the  Accounts.  Accordingly,  for the
purposes of Rule 13d-3 under the  Securities  Exchange Act of 1934,  as amended,
Mr. Gallen is deemed to beneficially own 2,767,550 Shares, or 6.5% of the Shares
deemed issued and outstanding as of December 31, 2005.





Item 5.  Ownership of Five Percent or Less of a Class

         Not Applicable.


Item 6.  Ownership of More Than Five Percent on Behalf of Another Person

         Not Applicable.


Item 7.  Identification  and  Classification  of the  Subsidiary  Which Acquired
         the Security Being Reported on by the Parent Holding Company or Control
         Person

         Not Applicable.


Item 8.  Identification and Classification of Members of the Group

         Not Applicable.


Item 9.  Notice of Dissolution of Group

         Not Applicable.


Item 10.  Certification

          By  signing  below I  certify  that,  to the best of my knowledge  and
belief, the securities  referred to above were not acquired and are not held for
the purpose of or with the effect of changing or influencing  the control of the
issuer of the  securities  and were not acquired and  are not held in connection
with or as a participant in any transaction having that purpose or effect.



                                    SIGNATURE


         After reasonable inquiry and to the best of my knowledge and  belief, I
certify that the information  set forth in this statement is  true, complete and
correct.


                                             January 25, 2006


                                             /s/Jonathan Gallen
                                             -----------------------------------
                                             Jonathan Gallen,  in  his  capacity
                                             as the investment manager for  Ahab
                                             Partners, L.P., Ahab International,
                                             Ltd. and the Accounts



      Attention: Intentional misstatements or omissions of fact constitute
                Federal criminal violations (See 18 U.S.C. 1001)