Repligen grants 2,466 RSUs to CAO Hughes

Repligen’s chief accounting officer received a 2,466 RSU grant and had 277 shares withheld to cover taxes upon RSU release.

Rhea-AI Filing Summary

REPLIGEN CORP (RGEN) reported insider equity activity by Chief Accounting Officer Violetta Hughes. On March 5, 2026, she received a grant of 2,466 restricted stock units, each representing a contingent right to one share of common stock that vests in equal annual installments over four years. On September 1, 2026, 277 shares of common stock were withheld by Repligen to satisfy tax withholding obligations arising from the release of restricted stock units, at a reference value of $170.02 per share.

Insider Trade Summary

2 transactions reported

Mixed 2 txns

Insider Hughes Violetta

Role CHIEF ACCOUNTING OFFICER

Type	Security	Shares	Price	Value
Tax Withholding	Common Stock F2	277	$170.02	$47K
Grant/Award	Common Stock F1	2,466	$0.00	$0.00

Holdings After Transaction: Common Stock — 6,331 shares (Direct)

Footnotes (2)

1. F1. Ms. Hughes was awarded 2,466 restricted stock units. Each restricted stock unit represents a contingent right to receive one share of Repligen Corporation's Common Stock. The restricted stock units vest in equal annual installments over a four-year period beginning on the first anniversary of the grant date. The restricted stock units may be settled only by delivering shares of Repligen Corporation's Common Stock, and thus, the grant is being reported in Table 1 as allowed per SEC guidance.
2. F2. 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.

Key Figures

Restricted stock units granted: 2,466 units Vesting period: 4 years Shares withheld for taxes: 277 shares +2 more

5 metrics

Restricted stock units granted 2,466 units Grant to Chief Accounting Officer on March 5, 2026

Vesting period 4 years RSUs vest in equal annual installments starting on the first anniversary of grant

Shares withheld for taxes 277 shares Shares of common stock withheld on September 1, 2026 for tax withholding on RSU release

Reference value per share for tax withholding $170.02 per share Value applied to the 277 shares withheld on September 1, 2026

RSU-to-share ratio 1 share per unit Each restricted stock unit represents a contingent right to receive one share of common stock

Key Terms

restricted stock units, contingent right, tax withholding obligations

3 terms

restricted stock units financial

"Ms. Hughes was awarded 2,466 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.

contingent right financial

"Each restricted stock unit represents a contingent right to receive one share"

tax withholding obligations financial

"to satisfy the tax withholding obligations of the reporting person"

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What equity award did Repligen (RGEN) grant to Violetta Hughes?

Repligen granted 2,466 restricted stock units to Chief Accounting Officer Violetta Hughes on March 5, 2026. Each restricted stock unit represents a contingent right to receive one share of Repligen’s common stock, subject to vesting conditions.

How do the 2,466 RSUs granted by RGEN vest?

The 2,466 restricted stock units vest in equal annual installments over four years, beginning on the first anniversary of the March 5, 2026 grant date. Vesting delivers one share of Repligen common stock for each vested unit.

How many RGEN shares were withheld for taxes from the RSU release?

Repligen withheld 277 shares of common stock to satisfy Chief Accounting Officer Violetta Hughes’s tax withholding obligations that arose upon the release of restricted stock units. The withholding was reported at $170.02 per share.

Were the Repligen (RGEN) transactions under a Rule 10b5-1 trading plan?

The filing indicates no Rule 10b5-1 plan for these transactions. The document-level checkbox affirming trades under a Rule 10b5-1 plan is not marked, and there is no footnote stating that the transactions were executed under such a plan.

How will the RSUs granted by RGEN to Violetta Hughes be settled?

The restricted stock units may be settled only by delivering shares of Repligen Corporation’s common stock. Because settlement must be in shares, the grant is reported in the non-derivative (Table 1) section consistent with SEC guidance.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 09/02/2026 - 04:18 PM EDT Accepted by SEC EDGAR 09/02/2026 - 04:18 PM EDT 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).

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^*

Hughes Violetta

(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)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	CHIEF ACCOUNTING OFFICER

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
03/05/2026

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	03/05/2026		A		2,466(1)	A	$0	6,608	D
Common Stock	09/01/2026		F		277(2)	D	$170.02	6,331	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. Ms. Hughes was awarded 2,466 restricted stock units. Each restricted stock unit represents a contingent right to receive one share of Repligen Corporation's Common Stock. The restricted stock units vest in equal annual installments over a four-year period beginning on the first anniversary of the grant date. The restricted stock units may be settled only by delivering shares of Repligen Corporation's Common Stock, and thus, the grant is being reported in Table 1 as allowed per SEC guidance.

2. 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.

Remarks:

	/s/ Meghan Stapleton (Attorney in Fact)	09/02/2026
	** 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)