[Form 4] REGENXBIO Inc. Insider Trading Activity

Rhea-AI Filing Summary

Chan Mitchell, the Chief Financial Officer of REGENXBIO Inc. (RGNX), reported a non-derivative disposition on 09/01/2025. The filing shows 4,901 shares of common stock were withheld to satisfy taxes upon the vesting of restricted stock units originally granted on September 16, 2024, using a withholding price of $8.93 (based on the closing price on August 29, 2025). After the withholding, the reporting person beneficially owns 53,968 shares directly. The Form 4 was signed by an attorney-in-fact on behalf of the reporting person on 09/03/2025.

Positive

• RSUs vested for the reporting person, indicating planned compensation delivery occurred as documented
• Reporting person retains 53,968 shares directly after the withholding, preserving ongoing ownership stake

Negative

• 4,901 shares were disposed of (withheld), reducing the reported share count
• Withholding used closing price of $8.93, reflecting tax settlement at that valuation rather than potential higher market prices

Insights

Corporate Governance Expert

TL;DR: Routine tax-withholding sale following RSU vesting; no indication of new purchases or strategic change.

The Form 4 documents a customary practice where shares are withheld to cover tax obligations tied to restricted stock unit vesting. The disposition code 'F' and the explanation confirm the shares were not sold on the open market but withheld to pay taxes related to RSUs granted on September 16, 2024. The remaining direct beneficial ownership of 53,968 shares remains in the reporting person's name, and there is no evidence in this filing of additional transfers, pledges, or derivative activity.

Compensation Analyst

TL;DR: Compensation-related withholding reduced reported share count by 4,901 shares at a $8.93 per-share valuation.

The entry clarifies the withholding amount was calculated using the issuer's closing price on August 29, 2025, which is standard for payroll tax withholding associated with RSU vesting. This transaction reflects routine executive compensation administration rather than a discretionary sale or sign of market view. No change to outstanding derivative holdings is reported in this filing.

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

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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^*

Chan Mitchell

(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)

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

3. Date of Earliest Transaction (Month/Day/Year)
09/01/2025

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	09/01/2025		F		4,901(1)	D	$8.93	53,968	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 shares of common stock withheld to pay taxes upon the vesting of restricted stock units originally granted to the reporting person on September 16, 2024. The number of shares withheld was determined based on the closing price of the issuer's common stock on August 29, 2025.

Remarks:

	/s/ Patrick J. Christmas as attorney-in-fact	09/03/2025
	** 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 transaction did Chan Mitchell report on Form 4 for RGNX?

The Form 4 reports that 4,901 shares of common stock were withheld to pay taxes upon the vesting of restricted stock units on 09/01/2025.

Why were shares withheld according to the filing?

The filing explains the shares were withheld to pay taxes resulting from the vesting of RSUs originally granted on September 16, 2024.

What was the withholding price used for the tax payment?

The number of shares withheld was determined using the issuer's closing price of $8.93 on August 29, 2025.

How many shares does the reporting person own after this transaction?

After the withholding, the reporting person beneficially owns 53,968 shares of REGENXBIO common stock.

Does this Form 4 show any option exercises or derivative transactions?

No; Table II for derivative securities shows no transactions. The filing only reports a non-derivative withholding in Table I.