EXHIBIT A AGREEMENT REGARDING JOINT FILING -------------------------------- The undersigned, Biotechnology Value Fund, L.P., a Delaware limited partnership, and BVF Partners L.P., a Delaware limited partnership, and BVF Inc., a Delaware corporation,...Exhibit A • May 1st, 1998 • Biotechnology Value Fund L P Et Al • Investment advice
The undersigned, Biotechnology Value Fund, L.P., a Delaware limited partnership, and 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 subsequent amendments or supplements thereto shall also be filed on behalf of each of them.
