AGREEMENT

Pursuant to Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, as amended, the undersigned hereby agree that only one statement containing the information required by Schedule 13G need be filed with respect to the ownership by each of the undersigned of the shares of Common Stock of Insmed Incorporated.

Dated: March 8, 2011

PROSPECT VENTURE PARTNERS III, L.P.
By:	Prospect Management Co. III, L.L.C.
Its:	General Partner

/s/ Lori Hoover-Simotas  

Lori Hoover-Simotas 

Attorney-in-Fact 

PROSPECT MANAGEMENT CO. III, L.L.C.
 

/s/ Lori Hoover-Simotas  

Lori Hoover-Simotas 

Attorney-in-Fact 

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