[Form 4] REPLIGEN CORP Insider Trading Activity

Rhea-AI Filing Summary

Repligen Corporation reporting person Olivier Loeillot, who is listed as both a Director and the Chief Executive Officer, recorded a sale of common stock on 10/02/2025. The filing shows 1,248 shares were disposed of at a price of $145.23 per share, with 42,939 shares remaining beneficially owned after the transaction. The reported sale represents shares withheld by the issuer to satisfy tax withholding obligations arising from the release of restricted stock units, not an open-market purchase or voluntary sale. The Form 4 was signed on 10/06/2025 by an attorney-in-fact on behalf of the reporting person.

Positive

• Timely disclosure of the transaction via a filed Form 4
• Transaction explained as tax-withholding for released restricted stock units, clarifying the nature of the disposition

Negative

• Insider ownership reduced by 1,248 shares, lowering direct holdings
• Potential short-term signaling as market observers may view any insider share reduction unfavorably

Insights

Corporate Governance Analyst

TL;DR: CEO/director recorded a tax-withholding share disposition of 1,248 shares; remaining holding stays material at 42,939 shares.

Olivier Loeillot is reported as both CEO and a director and the transaction is described as shares withheld to meet tax withholding from released restricted stock units. That mechanism is administrative: shares are surrendered to cover taxes rather than sold in a discretionary cash-raising trade.

The main dependency is the compensation structure and timing of RSU releases; this action reduces outstanding beneficial ownership by 1,248 shares today while leaving 42,939 shares held. Monitor subsequent filings for scheduled vesting events or additional withholding transactions within the next 12 months.

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
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Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Loeillot Olivier

(Last) (First) (Middle)

C/O REPLIGEN CORPORATION

41 SEYON ST., BLDG 1, STE 100

(Street)

WALTHAM MA 02453

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
REPLIGEN CORP [ RGEN ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	Chief Executive Officer

3. Date of Earliest Transaction (Month/Day/Year)
10/02/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	10/02/2025		F		1,248(1)	D	$145.23	42,939	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. Represents the number of shares withheld by the Issuer to satisfy tax withholding obligations of the reporting person that arose upon the release of restricted stock units.

	/s/ Jennifer Carmichael (Attorney in Fact)	10/06/2025
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

What did Repligen insider Olivier Loeillot report on Form 4 (RGEN)?

The Form 4 reports a disposition of 1,248 shares at $145.23 per share on 10/02/2025, with 42,939 shares owned after the transaction.

Why were the 1,248 shares disposed of according to the filing?

The filing states the shares were withheld by the issuer to satisfy tax withholding obligations arising upon the release of restricted stock units.

Does this Form 4 indicate a market sale by the CEO of Repligen (RGEN)?

No. The reported disposition is described as tax withholding related to RSU release, not a voluntary open-market sale for cash.

How much did the withheld shares fetch per share?

The withholding transaction price is reported as $145.23 per share.

Who signed the Form 4 and when was it signed?

The Form 4 was signed by Jennifer Carmichael (Attorney in Fact) on 10/06/2025.