Ownership Submission
FORM 3
 UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF 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 *
  Ridgeback Capital Investments L.P.
 2. Date of Event Requiring Statement (Month/Day/Year)
02/02/2010		 3. Issuer Name and Ticker or Trading Symbol
IRONWOOD PHARMACEUTICALS INC [IRWD]
(Last)
(First)
(Middle)
430 PARK AVENUE, 12TH FLOOR		 4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director __X__ 10% Owner
_____ Officer (give title below) _____ Other (specify below)
5. If Amendment, Date Original Filed(Month/Day/Year)
02/02/2010
(Street)

NEW YORK, NY 10022		 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 Beneficially Owned
1.Title of Security
(Instr. 4)		 2. Amount of Securities Beneficially Owned
(Instr. 4)		 3. Ownership Form: Direct (D) or Indirect (I)
(Instr. 5)		 4. Nature of Indirect Beneficial Ownership
(Instr. 5)
Class B Common Stock (2) 10,389,262
D (1)
 

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly. SEC 1473 (7-02)
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Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 4)		 2. Date Exercisable and Expiration Date
(Month/Day/Year)		 3. Title and Amount of Securities Underlying Derivative Security
(Instr. 4)		 4. Conversion or Exercise Price of Derivative Security 5. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 5)		 6. Nature of Indirect Beneficial Ownership
(Instr. 5)
Date Exercisable Expiration Date Title Amount or Number of Shares

Reporting Owners

Reporting Owner Name / Address Relationships
Director 10% Owner Officer Other
Ridgeback Capital Investments L.P.
430 PARK AVENUE
12TH FLOOR
NEW YORK, NY 10022		     X    
Ridgeback Capital Investments Ltd.
430 PARK AVENUE
12TH FLOOR
NEW YORK,, NY 10022		     X    
Ridgeback Capital Management LP
430 PARK AVENUE
12TH FLOOR
NEW YORK, NY 10022		     X    

Signatures

/s/ Bud Holman, Attorney-in-Fact 02/08/2010
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 5(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) Ridgeback Capital Investments L.P. owns all of the securities reported herein directly. Ridgeback Capital Investments Ltd. is the general partner of Ridgeback Capital Investments L.P. Pursuant to an investment management agreement, Ridgeback Capital Management LP maintains investment and voting power with respect to the securities held or controlled by Ridgeback Capital Investments Ltd. Wayne Holman, an individual, controls Ridgeback Capital Management LP. Ridgeback Capital Management LP, Ridgeback Capital Investments Ltd. and Wayne Holman do not own any securities reported herein directly and disclaim beneficial ownership of any of the securities covered by this statement, except to the extent of any pecuniary interest therein.
(2) Shares of Class B Common Stock are convertible at any time, at the holder's election, and automatically upon transfer, on a one-for-one basis into shares of Class A Common Stock.

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