AGREEMENT REGARDING JOINT FILING

EXHIBIT 1

AGREEMENT REGARDING JOINT FILING

                The undersigned, Biotechnology Value Fund, L.P., a Delaware limited partnership, Biotechnology Value Fund II, L.P., a Delaware limited partnership, BVF Investments, L.L.C., a Delaware limited liability company, Investment 00, X.X.X., xx Xxxxxxxx limited liability company, BVF Partners L.P., a Delaware limited partnership, and BVF Inc., a Delaware corporation, hereby agree and acknowledge that the information required by Schedule 13G, to which this Agreement is attached as an exhibit, is filed on behalf of each of them. The undersigned further agree that any amendments or supplements thereto shall also be filed on behalf of each of them.

Dated:		October 13, 2006
		BIOTECHNOLOGY VALUE FUND, L.P.
		By:		BVF Partners L.P., its general partner
				By:		BVF Inc., its general partner
						By:		/s/  XXXX X. XXXXXXX
								Xxxx X. Xxxxxxx President
		BIOTECHNOLOGY VALUE FUND II, L.P.
		By:		BVF Partners L.P., its general partner
				By:		BVF Inc., its general partner
						By:		/s/  XXXX X. XXXXXXX
								Xxxx X. Xxxxxxx President
		BVF INVESTMENTS, L.L.C.
		By:		BVF Partners L.P., its manager
				By:		BVF Inc., its general partner
						By:		/s/  XXXX X. XXXXXXX
								Xxxx X. Xxxxxxx President
		INVESTMENT 10, L.L.C.
		By:		BVF Partners L.P., its attorney-in-fact
				By:		BVF Inc., its general partner
						By:		/s/  XXXX X. XXXXXXX
								Xxxx X. Xxxxxxx President
		BVF PARTNERS L.P.
		By:		BVF Inc., its general partner
						By:		/s/  XXXX X. XXXXXXX
								Xxxx X. Xxxxxxx President
		BVF INC.
						By:		/s/  XXXX X. XXXXXXX
								Xxxx X. Xxxxxxx President