Mills Kenneth T. - 27 Jan 2026 Form 4 Insider Report for REGENXBIO Inc. (RGNX)

Role: Director
Signature: /s/ Patrick J. Christmas as attorney-in-fact
Issuer symbol: RGNX
Transactions as of: 27 Jan 2026
Net transactions value: -$28,458
Form type: 4
Filing time: 29 Jan 2026, 16:58:46 UTC
Previous filing: 03 Jun 2025
SEC: View on sec.gov

Reporting Owners (1)

Name	Relationship	Address	Signature	Signature date	CIK
Mills Kenneth T.	Director	C/O REGENXBIO INC., 9804 MEDICAL CENTER DRIVE, ROCKVILLE	/s/ Patrick J. Christmas as attorney-in-fact	29 Jan 2026	0001652824

Transactions Table

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Ownership	Footnotes
transaction	RGNX	Common Stock	Options Exercise	$2,945,250	+225,000	+47%	$13.09	707,871	27 Jan 2026	Direct	F1
transaction	RGNX	Common Stock	Tax liability	$2,973,708	-221,753	-31%	$13.41	486,118	27 Jan 2026	Direct	F2

Derivative Securities (e.g., puts, calls, warrants, options, convertible securities)

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Underlying Class	Amount	Exercise Price	Ownership	Footnotes
transaction	RGNX	Stock Options (Right to Buy)	Options Exercise	$0	-225,000	-50%	$0.000000	225,000	27 Jan 2026	Common Stock	225,000	$13.09	Direct	F1

* An asterisk sign (*) next to the price indicates that the price is likely invalid.

Explanation of Responses:

Id	Content
F1	The previously granted option, representing a right to purchase a total of 225,000 shares, became exercisable as follows: 25% of the shares subject to this option vested on January 28, 2017, and the balance vested in equal monthly installments over the 36 months thereafter.
F2	Represents shares of common stock withheld to satisfy the exercise price and pay taxes upon the exercise of options originally granted to the reporting person on January 28, 2016, which were set to expire on January 28, 2026. The number of shares withheld was determined based on the closing price of the issuer's common stock on January 27, 2026. The transaction did not involve any open-market sale of securities.

Content

The previously granted option, representing a right to purchase a total of 225,000 shares, became exercisable as follows: 25% of the shares subject to this option vested on January 28, 2017, and the balance vested in equal monthly installments over the 36 months thereafter.

Represents shares of common stock withheld to satisfy the exercise price and pay taxes upon the exercise of options originally granted to the reporting person on January 28, 2016, which were set to expire on January 28, 2026. The number of shares withheld was determined based on the closing price of the issuer's common stock on January 27, 2026. The transaction did not involve any open-market sale of securities.