Exhibit A

CUSIP No. 501570 10 5 13G

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 KYTHERA Biopharmaceuticals, Inc.

Dated: February 7, 2014

PROSPECT VENTURE PARTNERS III, L.P.
By:	Prospect Management Co. III, L.L.C.
Its:	General Partner
/s/ David Schnell
David Schnell, M.D.
Managing Member
PROSPECT MANAGEMENT CO. III, L.L.C.
/s/ Russell C. Hirsch
Managing Member
/s/ David Schnell
David Schnell, M.D.
/s/ Russell C. Hirsch
Russell C. Hirsch, M.D., Ph.D.

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