EX-32.1 7 rgen-ex32_1.htm EX-32.1

Exhibit 32.1

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 Annual Report on Form 10-K of Repligen Corporation (the “Company”) for the fiscal year ending December 31, 2025 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), the undersigned officers of the Company hereby certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that to their knowledge:

(1) The Report fully complies with the requirements of section 13(a) or 15(d) 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.

This certification is being provided pursuant to 18 U.S.C. 1350 and is not to be deemed a part of the Report, nor is it to be deemed to be “filed” for any purpose whatsoever.

Date: February 26, 2026 | By: | /S/ OLIVIER LOEILLOT
|  | Olivier Loeillot
|  | Chief Executive Officer
|  | (Principal executive officer)
Date: February 26, 2026 | By: | /S/ JASON K. GARLAND
|  | Jason K. Garland
|  | Chief Financial Officer
|  | (Principal financial officer)