Shares in the St. Louis bioinformatics company were down 9.23 percent at $4.92 in mid-afternoon trading after starting the day at $.5.36. On Monday, the stock climbed 15 percent to close at $5.25 after the Pfizer news jolted investors. The shares closed at $4.80 the day before the announcement.
The two companies initially announced a wide area network partnership in January 2001 that Pfizer employ a "broad array" of Tripos' drug-discovery software tools, including the SYBYL and UNITY programs.
Details of the extended agreement were not disclosed.