X0203 3 2010-02-02 0 0001446847 IRONWOOD PHARMACEUTICALS INC IRWD 0000937889 VENROCK ASSOCIATES 3340 HILLVIEW AVENUE PALO ALTO CA 94304 0 0 1 0 0001239243 VENROCK ASSOCIATES II LP 3340 HILLVIEW AVENUE PALO ALTO CA 94304 0 0 1 0 0001239244 VENROCK ENTERPRENEURS FUND LP 3340 HILLVIEW AVENUE PALO ALTO CA 94304 0 0 1 0 0001239245 VENROCK MANAGEMENT LLC 3340 HILLVIEW AVENUE PALO ALTO CA 94304 0 0 1 0 0001458177 VENROCK HEALTHCARE CAPITAL PARTNERS LP 3340 HILLVIEW AVENUE PALO ALTO CA 94304 0 0 1 0 0001479354 VHCP Co-Investment Holdings, LLC 3340 HILLVIEW AVENUE PALO ALTO CA 94304 0 0 1 0 0001479355 VHCP Management, LLC 3340 HILLVIEW AVENUE PALO ALTO CA 94304 0 0 1 0 0001465458 VR Management LLC 3340 HILLVIEW AVENUE PALO ALTO CA 94304 0 0 1 0 0001365618 Hove Anders D 3340 HILLVIEW AVENUE PALO ALTO CA 94304 0 0 1 0 Class B Common Stock 8731321 I By Funds Consists of 2,559,605 shares held directly by Venrock Associates ("VA"), 3,683,329 shares held directly by Venrock Associates II, L.P. ("VA2"), 48,387 shares held by Venrock Entrepreneurs Fund, L.P. ("VEF"), 2,017,021 shares held directly by Venrock Healthcare Capital Partners, L.P. ("VHCP"), 382,979 shares held directly by VHCP Co-Investment Holdings, LLC ("VHCP CI") and 40,000 shares held directly by VR Management, LLC ("VRM"). Bryan E. Roberts, a director of the Company, is a general partner of VA and VA2 and may be deemed to beneficially own these shares. Mr. Roberts disclaims beneficial ownership of these shares except to the extnet of his proportionate pecuniary interest therein. Venrock Management, LLC ("VM") is the general partner of VEF and may be deemed to beneficially own these shares. Mr. Roberts is a member of VM and may be deemed to beneficially own these shares. Mr. Roberts disclaims beneficial ownership of these shares except to the extent of his proportionate pecuniary interest therein. VHCP Management, LLC ("VHCPM") is the general partner of VHCP and the manager of VHCP CI and may be deemed to beneficially own these shares. Mr. Roberts and Anders D. Hove are members of VHCPM and may be deemed to beneficially own these shares. Messrs. Roberts and Hove disclaim beneficial ownership of these shares except to the extent of their proportionate pecuniary interest therein. Messrs. Roberts and Hove are members of VRM and may be deemed to beneficially own these shares. Messrs. Roberts and Hove disclaim beneficial ownership of these shares except to the extent of their proportionate pecuniary interest therein. /s/ David L. Stepp, Authorized Signatory 2010-02-02 /s/ David L. Stepp, Authorized Signatory 2010-02-02 /s/ David L. Stepp, Authorized Signatory 2010-02-02 /s/ David L. Stepp, Authorized Signatory 2010-02-02 /s/ David L. Stepp, as attorney-in-fact 2010-02-02 /s/ David L. Stepp, as attorney-in-fact 2010-02-02 /s/ David L. Stepp, as attorney-in-fact 2010-02-02 /s/ David L. Stepp, as attorney-in-fact 2010-02-02 /s/ David L. Stepp, as attorney-in-fact 2010-02-02