10
CUSIP No. 04033A 10 0 13G
EXHIBIT 99.A
------------
AGREEMENT TO FILE JOINTLY
We, the undersigned, hereby express our agreement that the attached
Schedule 13G and all subsequent amendments thereto executed by both of us
are filed on behalf of each of us.
HOECHST XXXXXX XXXXXXX, INC.
March 17, 1998 /s/ Xxxxxxx X. Xxxxxx
--------------------------- -------------------------------------
(Date) (Name and Title)
Xxxxxxx X. Xxxxxx
Vice President and Secretary
HMR PHARMA, INC.
March 17, 1998 /s/ Xxxxxxx X. Xxxxxx
--------------------------- -------------------------------------
(Date) (Name and Title)
Xxxxxxx X. Xxxxxx
Vice President and Secretary
