Exhibit 99.1
CERTIFICATION PURSUANT TO
18 U.S.C. SECTION 1350,
AS ADOPTED PURSUANT TO
SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002
In connection with the Quarterly Report of Abgenix, Inc. (the “Company”) on Form 10-Q for the period ending September 30, 2002, as filed with the Securities and Exchange Commission on the date hereof (the “Report”), I hereby certify, pursuant to 18 U.S.C. § 1350, as adopted pursuant to § 906 of the Sarbanes-Oxley Act of 2002, that:
(1) The Report fully complies with the requirements of section 13(a) of the Securities Exchange Act of 1934; and
(2) The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.
November 14, 2002 | /s/ RAYMOND M. WITHY |
| Raymond M. Withy, Ph.D. |
| President and Chief Executive Officer |
| (Principal Executive Officer) |
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