Sec Form 4 Filing - Huyett William @ IRONWOOD PHARMACEUTICALS INC - 2019-04-01

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 Huyett William 2. Issuer Name and Ticker or Trading Symbol IRONWOOD PHARMACEUTICALS INC [ IRWD] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) Chief Operating Officer (Last) (First) (Middle) C/O IRONWOOD PHARMACEUTICALS, INC., 301 BINNEY STREET 3. Date of Earliest Transaction (MM/DD/YY) 04/01/2019 (Street) CAMBRIDGE, MA02142 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 Class A Common Stock 04/01/2019 D 85,312 D 26,063 D Class A Common Stock 04/01/2019 A 1,483 A 27,546 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 Employee Stock Option (Right to Buy) $ 13.6 ( 3 ) 04/01/2019 D 232,032 ( 3 ) ( 4 ) 01/02/2028 Class A Common Stock 232,032 ( 3 ) 105,468 D Employee Stock Option (Right to Buy) $ 11.49 ( 3 ) 04/01/2019 D 242,579 ( 3 ) ( 5 ) 01/29/2029 Class A Common Stock 242,579 ( 3 ) 16,171 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Huyett William C/O IRONWOOD PHARMACEUTICALS, INC. 301 BINNEY STREET CAMBRIDGE, MA02142 Chief Operating Officer Signatures /s/ Conor Kilroy, Attorney-in-Fact 04/03/2019 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Represents the disposition of 85,312 restricted stock units in connection with the separation (the "Separation") of Cyclerion Therapeutics, Inc. ("Cyclerion") from Ironwood Pharmaceuticals, Inc. ("Ironwood") in exchange for restricted stock units representing the right to receive shares of Cyclerion Common Stock. ( 2 )In connection with the Separation, the reporting person received 1,483 restricted stock units as a result of the adjustment of existing Ironwood restricted stock units held by the reporting person prior to the Separation. This award vests as shares of Class A Common Stock on May 9, 2019. ( 3 )Represents options to purchase Ironwood Class A Common Stock awarded to the reporting person prior to the Separation. In connection with the Separation, the unvested portion of the Ironwood option award was replaced with options to purchase shares of Cyclerion Common Stock. The exercise price of the vested portion of the Ironwood option award has been adjusted, and the reporting person received additional options to purchase shares of Cyclerion Common Stock, to preserve the pre-Separation intrinsic value of the vested portion of the Ironwood option award. ( 4 )The remaining 105,468 shares are presently exercisable in full. ( 5 )The remaining 16,171 shares are presently exercisable in full.

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