EXHIBIT 99(a)
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 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: February 23, 2000
BIOTECHNOLOGY VALUE FUND, L.P.
By: BVF Partners L.P., its general partner
By: BVF Inc., its general partner
By: /s/ Xxxx X. Xxxxxxx
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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 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
