QuickLinks -- Click here to rapidly navigate through this document

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, BVF Partners L.P., a Delaware limited partnership, and BVF Inc., a Delaware corporation, hereby agree and acknowledge that the information required by the Amendment to 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 further amendments or supplements thereto shall also be filed on behalf of each of them.

Dated:	February 12, 2003
	BIOTECHNOLOGY VALUE FUND, L.P.
	By:	BVF Partners L.P., its general partner
		By:	BVF Inc., its general partner
			By:	/s/ MARK N. LAMPERT
				Mark N. Lampert President
	BIOTECHNOLOGY VALUE FUND II, L.P.
	By:	BVF Partners L.P., its general partner
		By:	BVF Inc., its general partner
			By:	/s/ MARK N. LAMPERT
				Mark N. Lampert President
	BVF INVESTMENTS, L.L.C.
	By:	BVF Partners L.P., its manager
		By:	BVF Inc., its general partner
			By:	/s/ MARK N. LAMPERT
				Mark N. Lampert President
	BVF PARTNERS L.P.
	By:	BVF Inc., its general partner
			By:	/s/ MARK N. LAMPERT
				Mark N. Lampert President
	BVF INC.
			By:	/s/ MARK N. LAMPERT
				Mark N. Lampert President

QuickLinks

AGREEMENT REGARDING JOINT FILING

3 DIMENSIONAL PHARMACEUTICALS INC SC 13G/A