EXHIBIT 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 11, 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
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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
