EXHIBIT 10.81 CONFIDENTIAL Date: February 22, 1999 To: Stephen Evans-Freke Chairman and Chief Executive Officer cc: Susan Kanaya, Treasurer, SUGEN, Inc. Suzanne Hooper, Cooley Godward LLP From: Donald E. Nickelson Chairman of the Compensation...Modification of Letter Agreement • June 1st, 1999 • Sugen Inc • Biological products, (no disgnostic substances)
