Repligen (RGEN) COO uses 3,911 shares to cover tax withholding

Rhea-AI Filing Summary

Repligen Corporation’s Chief Operating Officer James Bylund reported two share dispositions that were automatically used to cover taxes on vesting stock awards, rather than open-market sales. On February 27, 2026, 1,478 common shares at $128.73 per share were withheld, and on March 2, 2026, 2,433 shares at $124.97 per share were withheld.

These shares were retained by the company to satisfy Bylund’s tax withholding obligations triggered by the release of restricted stock units. After the March 2 withholding, Bylund directly owned 17,609 Repligen common shares.

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

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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^*

Bylund James

(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)

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

3. Date of Earliest Transaction (Month/Day/Year)
02/27/2026

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	02/27/2026		F		1,478(1)	D	$128.73	20,042	D
Common Stock	03/02/2026		F		2,433(1)	D	$124.97	17,609	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)	03/03/2026
	** 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).
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FAQ

What insider transaction did Repligen (RGEN) report for James Bylund?

Repligen reported that COO James Bylund had shares withheld to cover taxes on vesting restricted stock units. Two Form 4 transactions show automatic tax-withholding dispositions of common stock, not open-market purchases or sales, in late February and early March 2026.

How many Repligen (RGEN) shares were withheld for James Bylund’s taxes?

A total of 3,911 Repligen common shares were withheld for taxes. This included 1,478 shares on February 27, 2026, and 2,433 shares on March 2, 2026, as part of automatic tax-withholding tied to restricted stock unit releases.

At what prices were Repligen (RGEN) shares withheld for James Bylund?

The tax-withholding share values were based on prices of $128.73 and $124.97 per share. On February 27, 2026, 1,478 shares were withheld at $128.73, and on March 2, 2026, 2,433 shares were withheld at $124.97, according to the Form 4 disclosure.

Did Repligen (RGEN) COO James Bylund sell shares in the open market?

The Form 4 shows no open-market sales by James Bylund. Instead, Repligen withheld shares to satisfy his tax obligations arising from restricted stock unit vesting, using transaction code F for tax-withholding dispositions rather than standard sale transactions.

How many Repligen (RGEN) shares does James Bylund own after these transactions?

After the March 2, 2026 tax-withholding disposition, James Bylund directly owned 17,609 Repligen common shares. This figure reflects his direct holdings reported following the latest automatic share withholding to cover tax obligations on released restricted stock units.

What does transaction code F mean in the Repligen (RGEN) Form 4?

Transaction code F on the Form 4 indicates payment of tax liability by delivering or withholding securities. For Repligen’s COO, it shows the issuer withheld common shares to cover taxes due upon the release of restricted stock units, rather than an elective stock sale.