Joint Filer Information

Names:	Deerfield Mgmt, L.P., Deerfield Management Company, L.P., Deerfield Partners, L.P., Deerfield International Master Fund, L.P.

Address:	780 Third Avenue, 37th Floor New York, NY 10017

Designated Filer:	James E. Flynn

Issuer and Ticker Symbol:	Auxilium Pharmaceuticals, Inc. [AUXL]

Date of Earliest Transaction Required to be Reported:	January 29, 2015

The undersigned, Deerfield Mgmt, L.P., Deerfield Management Company, L.P., Deerfield Partners, L.P. and Deerfield International Master Fund, L.P., are jointly filing the attached Statement of Changes in Beneficial Ownership on Form 4 with James E. Flynn with respect to the beneficial ownership of securities of Auxilium Pharmaceuticals, Inc.

Signatures:

DEERFIELD MGMT, L.P. By: J.E. Flynn Capital, LLC, General Partner By: /s/ Jonathan Isler Jonathan Isler, Attorney-In-Fact	DEERFIELD PARTNERS, L.P. By: Deerfield Mgmt, L.P., General Partner By: J.E. Flynn Capital, LLC, General Partner By: /s/ Jonathan Isler Jonathan Isler, Attorney-In-Fact

DEERFIELD MANAGEMENT COMPANY, L.P. By: Flynn Management LLC, General Partner By: /s/ Jonathan Isler Jonathan Isler, Attorney-In-Fact	DEERFIELD INTERNATIONAL MASTER FUND, L.P. By: Deerfield Mgmt, L.P., General Partner By: J.E. Flynn Capital, LLC, General Partner By: /s/ Jonathan Isler Jonathan Isler, Attorney-In-Fact

AUXILIUM PHARMACEUTICALS INC 4