C ERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT , MARKED BY BRACKETS , HAS BEEN OMITTED AND FILED
SEPARATELY WITH THE S ECURITIES AND E XCHANGE C OMMISSION PURSUANT TO R ULE 24 B -2 OF THE S ECURITIES E XCHANGE A CT
OF 1934, AS AMENDED .
Exhibit 10.20
FOURTH AMENDMENT TO
SCREENING SERVICES AGREEMENT
This Fourth Amendment to Screening Services Agreement (this “TRAP Fourth Amendment”) is made and dated as of
March 6, 2002, (the “ Fourth Amendment Effective Date ”), by and between Sanwa Kagaku Kenkyusho Co., Ltd. , a Japanese
corporation (“ Sanwa ”) and Telik Inc. , a Delaware corporation (“ Telik ”).
RECITALS
A. Sanwa and Telik are parties to the Screening Services Agreement dated as of December 20, 1996, as amended by the
First Amendment to Screening Services Agreement dated September 24, 1997, the Second Amendment to Screening Services
Agreement dated October 29, 1998, and the Third Amendment to Screening Services Agreement and Master Amendment
Agreement, both dated February 14, 2001 (collectively, the “ TRAP Agreement ”).
B. Sanwa and Telik desire to execute this TRAP Fourth Amendment to reflect various changes they desire to make in the
research to be undertaken pursuant to the TRAP Agreement, including without limitation the [*] Lead Optimization Project
relating to [*] , and the amendments reflected herein are among the conditions to Sanwa paying Telik the amount set forth
herein.
NOW, THEREFORE, in consideration of the above recitals and for other good and valuable consideration, the adequacy
and receipt of which are hereby acknowledged, the parties hereby agree as follows:
1. Amendments . The TRAP Agreement is hereby amended as follows:
A. Section 1.4(a) is hereby revised by deleting the second through the fourth sentences of Section 1.4(a) and replacing
the deleted language with the following language:
For a period commencing on [*] and ending on [*] , Telik shall undertake, [*] , a Lead Optimization