Repligen CEO sells $503K in stock under plan

Repligen’s CEO reported a 3,035-share planned sale and 2,842 shares withheld for taxes tied to RSU vesting.

Rhea-AI Filing Summary

REPLIGEN CORP (RGEN) reported that Chief Executive Officer and director Loeillot Olivier disposed of common stock in early September 2026. On September 4, he sold 3,035 shares of common stock at $165.90 per share in an open-market or private transaction, executed under a Rule 10b5-1 trading plan adopted on August 19, 2025. On September 3, 2,842 shares of common stock were withheld by the company to satisfy tax withholding obligations arising from the release of restricted stock units.

Insider Trade Summary 10b5-1

Net Seller: 3,035 shares

Net Sell 2 txns

Insider Loeillot Olivier

Role Chief Executive Officer

Sold 3,035 shs ($504K)

Type	Security	Shares	Price	Value
Sale	Common Stock F2	3,035	$165.90	$504K
Tax Withholding	Common Stock F1	2,842	$169.61	$482K

Holdings After Transaction: Common Stock — 48,369 shares (Direct)

Footnotes (2)

1. F1. Represents the number of shares withheld by the Issuer to satisfy the tax withholding obligations of the reporting person that arose upon the release of restricted stock units.
2. F2. 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.

Key Figures

Shares sold: 3,035 shares Sale price per share: $165.90 per share Gross proceeds from sale: $503,506.50 +3 more

6 metrics

Shares sold 3,035 shares Open-market or private sale of Repligen common stock on September 4, 2026

Sale price per share $165.90 per share Price for the 3,035 Repligen common shares sold on September 4, 2026

Gross proceeds from sale $503,506.50 3,035 shares sold at $165.90 per share on September 4, 2026

Shares withheld for taxes 2,842 shares Shares withheld on September 3, 2026 to satisfy tax withholding from RSU release

Value of shares withheld $482,031.62 2,842 shares valued at $169.61 per share for tax withholding on September 3, 2026

Rule 10b5-1 plan adoption date August 19, 2025 Trading plan under which the September 4, 2026 sale was executed

Key Terms

Rule 10b5-1 trading plan, restricted stock units, tax withholding obligations

3 terms

Rule 10b5-1 trading plan regulatory

"The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan"

A Rule 10b5-1 trading plan is a pre-arranged schedule that allows company insiders to buy or sell stock at specific times, even if they have inside information. It helps prevent accusations of unfair trading by making these transactions look planned and transparent, rather than sneaky or illegal.

restricted stock units financial

"obligations of the reporting person that arose upon the release of restricted stock units"

Restricted stock units are a type of company reward where employees are promised shares of stock, but they only fully own these shares after meeting certain conditions, like staying with the company for a set time. They matter because they can become valuable assets and are often used to motivate employees to help the company succeed.

tax withholding obligations financial

"withheld by the Issuer to satisfy the tax withholding obligations of the reporting person"

FAQ

What insider transactions did RGEN’s CEO report in this Form 4?

The CEO, Loeillot Olivier, reported a sale of 3,035 common shares on September 4, 2026, and a disposition of 2,842 shares on September 3, 2026, that were withheld by Repligen to cover his tax withholding obligations from restricted stock unit vesting.

At what price did the Repligen (RGEN) CEO sell shares?

On September 4, 2026, the CEO sold 3,035 common shares of Repligen at a price of $165.90 per share in an open-market or private transaction, as reported in the Form 4 filing.

Were the RGEN CEO’s stock sales under a Rule 10b5-1 plan?

Yes. The Form 4 states that the sales were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on August 19, 2025, and the Rule 10b5-1 checkbox on the form is affirmed.

Why were 2,842 Repligen (RGEN) shares disposed of on September 3, 2026?

The 2,842 shares reported on September 3, 2026, represent shares withheld by Repligen to satisfy the CEO’s tax withholding obligations that arose upon the release of restricted stock units, rather than a discretionary open-market sale.

How many Repligen (RGEN) shares did the CEO sell versus tax withholding shares?

The CEO sold 3,035 shares of common stock on September 4, 2026. Separately, 2,842 shares were withheld for taxes on September 3, 2026, in connection with restricted stock unit vesting, according to the Form 4.

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Available on EDGAR 09/08/2026 - 04:14 PM Accepted by SEC EDGAR 09/08/2026 - 04:13 PM Learn about SEC filing dates

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
Estimated average burden
hours per response:			0.5

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

X

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 MASSACHUSETTS 02453

(City) (State) (Zip)

UNITED STATES

(Country)

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

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
09/03/2026

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

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

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

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	09/03/2026		F		2,842(1)	D	$169.61	51,404	D
Common Stock	09/04/2026		S		3,035(2)	D	$165.9	48,369	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 the tax withholding obligations of the reporting person that arose upon the release of restricted stock units.

2. 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.

Remarks:

	/s/ Jennifer Carmichael (Attorney in Fact)	09/08/2026
	** 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.
* Form 4: SEC 1474 (03-26)