REGENXBIO (RGNX) director exercises options, withholds shares for taxes

Rhea-AI Filing Summary

REGENXBIO Inc. director Kenneth T. Mills reported exercising stock options for 225,000 shares of common stock on January 27, 2026 at an exercise price of $13.09 per share. These options were originally granted in 2016 and had fully vested prior to exercise.

To cover the option exercise price and related taxes, 221,753 shares of common stock were withheld by the company at a reference price of $13.41 per share, and the filing states there was no open-market sale involved. After these transactions, Mills directly beneficially owned 486,118 shares of REGENXBIO common stock.

Insider Trade Summary

225,000 shares exercised/converted

Mixed 3 txns

Insider Mills Kenneth T.

Role Director

Type	Security	Shares	Price	Value
Exercise	Stock Options (Right to Buy)	225,000	$0.00	--
Exercise	Common Stock	225,000	$13.09	$2.95M
Tax Withholding	Common Stock	221,753	$13.41	$2.97M

Holdings After Transaction: Stock Options (Right to Buy) — 225,000 shares (Direct); Common Stock — 707,871 shares (Direct)

Footnotes (1)

1. 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.

Form 4 Insider Transactions: What Each Field Means →

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^*

Mills Kenneth T.

(Last) (First) (Middle)

C/O REGENXBIO INC.

9804 MEDICAL CENTER DRIVE

(Street)

ROCKVILLE MD 20850

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
REGENXBIO Inc. [ RGNX ]

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

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

3. Date of Earliest Transaction (Month/Day/Year)
01/27/2026

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	01/27/2026		M(1)		225,000	A	$13.09	707,871	D
Common Stock	01/27/2026		F(2)		221,753	D	$13.41	486,118	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
Stock Options (Right to Buy)	$13.09	01/27/2026		M			225,000	(1)	01/28/2026	Common Stock	225,000	$0.00	225,000	D

Explanation of Responses:

1. 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.

2. 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.

Remarks:

	/s/ Patrick J. Christmas as attorney-in-fact	01/29/2026
	** 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.

FAQ

What insider transaction did REGENXBIO (RGNX) report for Kenneth T. Mills?

REGENXBIO director Kenneth T. Mills exercised stock options for 225,000 common shares on January 27, 2026. The options were previously granted in 2016 and fully vested, converting into common stock as part of routine equity compensation.

How many REGENXBIO (RGNX) shares does Kenneth T. Mills own after this Form 4?

After the reported transactions, Kenneth T. Mills beneficially owned 486,118 shares of REGENXBIO common stock directly. This figure reflects the shares received from the option exercise, net of the shares withheld to cover the exercise price and associated tax obligations.

Were any REGENXBIO (RGNX) shares sold on the open market in this filing?

No open-market sale occurred. The filing explains that 221,753 common shares were withheld by REGENXBIO to satisfy the option exercise price and taxes, using the January 27, 2026 closing price, rather than being sold in market transactions.

What was the exercise price of Kenneth T. Mills’s REGENXBIO (RGNX) stock options?

The stock options exercised by Kenneth T. Mills had an exercise price of $13.09 per share. These options covered 225,000 common shares and were originally granted in 2016, with vesting beginning in January 2017 and continuing in monthly installments thereafter.

Why were 221,753 REGENXBIO (RGNX) shares withheld in this insider transaction?

The 221,753 common shares were withheld to cover the exercise price and applicable taxes from the option exercise. The number of shares was calculated using REGENXBIO’s January 27, 2026 closing stock price, and the filing clarifies this did not involve an open-market sale.

How did the REGENXBIO (RGNX) stock options held by Kenneth T. Mills vest?

The option for 225,000 shares vested with 25% becoming exercisable on January 28, 2017. The remaining shares vested in equal monthly installments over the following 36 months, resulting in the entire grant being fully exercisable before the January 2026 transaction.