Ownership Submission
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 *
Rosebay Medical Co L.P.
   2. Issuer Name and Ticker or Trading Symbol
INFINITY PHARMACEUTICALS, INC. [INFI] 		5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director __X__ 10% Owner
_____ Officer (give title below) _____ Other (specify below)
(Last)
(First)
(Middle)
C/O NORTH BAY ASSOCIATES, 14000 QUAIL SPRINGS PARKWAY #2200		 3. Date of Earliest Transaction (Month/Day/Year)
01/07/2009
(Street)

OKLAHOMA CITY, OK 73134		 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 01/07/2009   P   1,000,000 A $ 15 3,000,000 D (1)  

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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 Purchase Warrants (right to buy) $ 15 (2) (3) 01/07/2009   P(1)   500,000   01/07/2009 07/01/2010 Common Stock 500,000 (2) 500,000 D  
Stock Purchase Warrants (right to buy) $ 20 (2) (4) 01/07/2009   P(1)   1,000,000   01/07/2009 07/01/2011 Common Stock 1,000,000 (2) 1,000,000 D  
Stock Purchase Warrants (right to buy) $ 30 (2) (5) 01/07/2009   P(1)   1,500,000   01/07/2009 07/02/2012 Common Stock 1,500,000 (2) 1,500,000 D  

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
Rosebay Medical Co L.P.
C/O NORTH BAY ASSOCIATES
14000 QUAIL SPRINGS PARKWAY #2200
OKLAHOMA CITY, OK 73134		     X    

Signatures

 /s/ Stephen A. Ives, as Vice President of Rosebay Medical Company, Inc., Rosebay Medical Company L.P.?s general partner   01/09/2009
**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) These securities were purchased pursuant to the Securities Purchase Agreement between the Issuer, Purdue Pharma L.P. and Purdue Pharmaceutical Products L.P., dated November 19, 2008 (the "Securities Purchase Agreement"). These securities were distributed by Purdue Pharma L.P. and Purdue Pharmaceutical Products L.P. to the Reporting Person and Beacon Company, the ultimate parents of Purdue Pharma L.P. and Purdue Pharmaceutical Products L.P., via a series of distributions to each entity's limited partner until it reached the Reporting Person.
(2) The Stock Purchase Warrants to purchase Issuer's Common Stock (the "Warrants") were acquired as part of a private placement by the Issuer in accordance with the Securities Purchase Agreement. These Warrants were distributed by Purdue Pharma L.P. and Purdue Pharmaceutical Products L.P. to the Reporting Person and Beacon Company, the ultimate parents of Purdue Pharma L.P. and Purdue Pharmaceutical Products L.P., via a series of distributions to each entity's limited partner until it reached the Reporting Person.
(3) The Warrants have the following exercise prices: (a) $15.00 per share from January 7, 2009 until September 30, 2009, (b) $16.25 per share from October 1, 2009 until January 3, 2010, (c) $17.50 per share from January 4, 2010 until March 31, 2010, (d) $18.75 per share from April 1, 2010 until June 30, 2010, and (e) $20.00 per share on July 1, 2010.
(4) The Warrants have the following exercise prices: (a) $20.00 per share from January 7, 2009 until September 30, 2010, (b) $22.50 per share from October 1, 2010 until January 2, 2011, (c) $25.00 per share from January 3, 2011 until March 31, 2011, (d) $27.50 per share from April 1, 2011 until June 30, 2011, and (e) $30.00 per share on July 1, 2011.
(5) The Warrants have the following exercise prices: (a) $30.00 per share from January 7, 2009 until October 2, 2011, (b) $32.50 per share from October 3, 2011 until January 2, 2012, (c) $35.00 per share from January 3, 2012 until April 1, 2012, (d) $37.50 per share from April 2, 2012 until July 1, 2012, and (e) $40.00 per share on July 2, 2012.

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