Regeneron Pharmaceuticals (REGN) 10-Q 2002 Q2 Quarterly report

Exhibit 99.1

CERTIFICATION OF CEO AND CFO 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 Regeneron Pharmaceuticals, Inc. (the “Company”) on Form 10-Q for the period ending June 30, 2002 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), Leonard S. Schleifer, M.D., Ph.D., as Chief Executive Officer of the Company, and Murray A. Goldberg, as Chief Financial Officer of the Company, each hereby certifies, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, to the best of his knowledge, 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 result of operations of the Company.

-s-  Leonard S. SchleiferLeonard S. Schleifer, M.D., Ph.D.
Chief Executive Officer
August 13, 2002

-s-  Murray A. GoldbergMurray A. Goldberg
Chief Financial Officer
August 13, 2002