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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(Print or Type Responses)

1. Name and Address of Reporting Person * Daniel D Ronald   2. Issuer Name and Ticker or Trading Symbol INFINITY PHARMACEUTICALS, INC. [INFI] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) __X__ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O MCKINSEY & CO., 55 EAST 52ND STREET, 21ST FLOOR 3. Date of Earliest Transaction (Month/Day/Year) 09/12/2006 (Street) NEW YORK, NY 10022 4. If Amendment, Date Original Filed(Month/Day/Year) 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 (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 09/12/2006   A   13,261 (1) A (2) 13,261 (1) D

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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

Stock Option (right to buy)

$ 15.04

09/12/2006

A

28,125 (1)

(3)

09/12/2016

Common Stock

28,125 (1)

$ 0

28,125 (1)

D

Stock Option (right to buy)

$ 3.48 (6)

09/12/2006

A

2,210 (1)

(4)

06/12/2016

Common Stock

2,210 (1)

(5)

2,210 (1)

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Daniel D Ronald C/O MCKINSEY & CO. 55 EAST 52ND STREET, 21ST FLOOR NEW YORK, NY 10022	X

Signatures

/s/ D. Ronald Daniel		09/13/2006
**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)	Reflects a 1-for-4 reverse stock split, which became effective on September 12, 2006.
(2)	Received in exchange for 60,000 shares of Infinity Discovery, Inc. ("IPI") common stock in connection with the merger of IPI into Infinity Pharmaceuticals, Inc. (the "Merger") based on a conversion ratio of 0.88411.
(3)	The option vests as to 9,375 of the shares on the first anniversary of the grant date, which grant date was September 12, 2006, and the remainder in quarterly installments of 2,343 shares beginning at the end of the first quarter thereafter, provided that the holder continues to serve as a director.
(4)	The option vests as to 552 shares on June 12, 2006, 184 shares on June 30, 2006 and the remainder in equal monthly installments through February 2007.
(5)	Received in the Merger in exchange for a stock option to acquire 10,000 shares of IPI common stock for $0.77 per share based on a conversion ratio of 0.88411.
(6)	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.

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