Changes in Beneficial Ownership · 4

Repligen Corporation

RGENNASDAQEQUITYCurrent

Changes in Beneficial Ownership

Filed Sep 22, 2026Accepted Sep 22, 2026, 4:07 PM EDTFiling CIK 730272Accession 0001628280-26-063026

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Structured filing — 4

wk-form4_1790107640.xml

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Filing details

Report period: 2026-09-21
Issuer: REPLIGEN CORP
Issuer CIK: 0000730272
Trading symbol: RGEN
Rule 10b5-1 indication: Checked

Reporting owner 1

Name: Loeillot Olivier
Reporting owner CIK: 0001995525
Relationship: Director · Officer
Officer title: Chief Executive Officer
Address: C/O REPLIGEN CORPORATION, 41 SEYON ST., BLDG 1, STE 100, WALTHAM, MA, 02453

Non-derivative transactions

Non-derivative transactions · 2 reported rows
Security	Transaction date	Code	Amount	A / D	Price (USD)	Owned after	Ownership
Common Stock	2026-09-21	M · Form 4^[F1]	5,426	A	141.79	53,795	D
Common Stock	2026-09-21	S · Form 4^[F1]	5,426	D	180	48,369	D

Table key

M · Form 4: Exempt derivative exercise or conversion under Rule 16b-3
A: Acquired
D: Direct
S · Form 4: Sale on the market or privately

Derivative transactions

Derivative transactions · 1 reported row
Security	Conversion / exercise price (USD)	Transaction date	Code	Amount	A / D	Price (USD)	Exercisable	Expires	Underlying security	Underlying shares	Owned after	Ownership
Stock Option (Right to Buy)	141.79	2026-09-21	M · Form 4^[F1]	5,426	D	0	2027-09-03	2034-09-03	Common Stock	5,426	5,426	D

Table key

M · Form 4: Exempt derivative exercise or conversion under Rule 16b-3
D: Direct

Footnotes

F1: The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on August 19, 2025.↩ 1 ↩ 2 ↩ 3

Signature 1

Signed: /s/ Jennifer Carmichael (Attorney in Fact)
Date: 2026-09-22

Company context

Repligen Corporation is a global life sciences company that develops and commercializes highly innovative bioprocessing technologies and systems that enable efficiencies in the process of manufacturing biological drugs. We are “inspiring advances in bioprocessing” for the customers we serve, primarily biopharmaceutical drug developers and contract development and manufacturing organizations (CDMOs) worldwide. Our focus areas are Filtration and Fluid Management, Chromatography, Process Analytics and Proteins. Our corporate headquarters are located in Waltham, Massachusetts, and the majority of our manufacturing sites are in the U.S., with additional key sites in Estonia, Germany, Ireland, the Netherlands and Sweden. For more information about the company see our website at www.repligen.com, and follow us on LinkedIn.

Current securities

RGENNASDAQ · EQUITY · Current

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