Sec Form 4 Filing - Burke Thomas Joseph @ INFINITY PHARMACEUTICALS, INC. - 2006-09-12

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 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 Burke Thomas Joseph 2. Issuer Name and Ticker or Trading Symbol INFINITY PHARMACEUTICALS, INC. [ INFI] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) Assistant Treasurer (Last) (First) (Middle) C/O INFINITY PHARMACEUTICALS, INC., 780 MEMORIAL DRIVE 3. Date of Earliest Transaction (MM/DD/YY) 09/12/2006 (Street) CAMBRIDGE, MA02139 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ 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 (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 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 09/12/2006 A 10,306 ( 1 ) A 10,306 ( 1 ) D

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 (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 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 (MM/DD/YY) 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 Stock Option (Right to Buy) $ 1.72 ( 3 ) 09/12/2006 A 5,525 ( 1 ) ( 4 ) 05/05/2013 Common Stock 5,525 ( 1 ) ( 5 ) 5,525 ( 1 ) D Stock Option (Right to Buy) $ 1.72 ( 3 ) 09/12/2006 A 1,621 ( 1 ) ( 6 ) 03/25/2014 Common Stock 1,621 ( 1 ) ( 7 ) 1,621 ( 1 ) D Stock Option (Right to Buy) $ 2.04 ( 3 ) 09/12/2006 A 5,640 ( 1 ) ( 8 ) 05/10/2015 Common Stock 5,640 ( 1 ) ( 9 ) 5,640 ( 1 ) D Stock Option (Right to Buy) $ 2.04 ( 3 ) 09/12/2006 A 5,640 ( 1 ) ( 10 ) 05/10/2015 Common Stock 5,640 ( 1 ) ( 9 ) 5,640 ( 1 ) D Stock Option (Right to Buy) $ 2.04 ( 3 ) 09/12/2006 A 2,210 ( 1 ) ( 10 ) 06/07/2015 Common Stock 2,210 ( 1 ) ( 11 ) 2,210 ( 1 ) D Stock Option (Right to Buy) $ 3.48 ( 3 ) 09/12/2006 A 2,431 ( 1 ) ( 12 ) 03/31/2016 Common Stock 2,431 ( 1 ) ( 13 ) 2,431 ( 1 ) D Stock Option (Right to Buy) $ 3.48 ( 3 ) 09/12/2006 A 331 ( 1 ) ( 14 ) 03/31/2016 Common Stock 331 ( 1 ) ( 15 ) 331 ( 1 ) D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Burke Thomas Joseph C/O INFINITY PHARMACEUTICALS, INC. 780 MEMORIAL DRIVE CAMBRIDGE, MA02139 Assistant Treasurer Signatures /s/ Thomas Joseph Burke 09/13/2006 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Reflects a 1-for-4 reverse stock split, which became effective on September 12, 2006. ( 2 )Received in exchange for 46,628 shares of Infinity Discovery, Inc. ("IPI") common stock in connection with the merger of IPI into Infinity Pharmaceuticals, Inc. (the "Merger") based a conversion ratio of 0.88411. ( 3 )The exercise price reflects the exercise price of each option to purchase IPI common stock prior to the closing of the Merger divided by a conversion ratio of 0.88411, as adjusted to reflect the 1-for-4 reverse stock split. ( 4 )The option vests monthly in equal installments for four years, beginning on January 31, 2003. ( 5 )Received in the Merger in exchange for stock option to acquire 25,000 shares of IPI common stock for $0.38 per share based on a conversion ratio of 0.88411. ( 6 )The option vests monthly in equal installments for four years, beginning on January 31, 2004. ( 7 )Received in the Merger in exchange for stock option to acquire 7,336 shares of IPI common stock for $0.38 per share based on a conversion ratio of 0.88411. ( 8 )The option vests monthly in equal installments for six years, beginning on January 31, 2005. ( 9 )Received in the Merger in exchange for stock option to acquire 25,518 shares of IPI common stock for $0.45 per share based on a conversion ratio of 0.88411. ( 10 )The option vests monthly in equal installments for four years, beginning on January 31, 2005. ( 11 )Received in the Merger in exchange for stock option to acquire 10,000 shares of IPI common stock for $0.45 per share based on a conversion ratio of 0.88411. ( 12 )The option vests monthly in equal installments for four years, beginning on February 1, 2006. ( 13 )Received in the Merger in exchange for stock option to acquire 11,000 shares of IPI common stock for $0.77 per share based on a conversion ratio of 0.88411. ( 14 )The option vests monthly in equal installments for one year, beginning on February 1, 2006. ( 15 )Received in the Merger in exchange for stock option to acquire 1,500 shares of IPI common stock for $0.77 per share based on a conversion ratio of 0.88411.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

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