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 the Amendment containing the information required by Schedule
13D, 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 24, 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 VENTURE PARTNERS, 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
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Xxxx X. Xxxxxxx
President
BVF INC.
By: /s/ Xxxx X. Xxxxxxx
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Xxxx X. Xxxxxxx
President
