Statement of Changes in Beneficial Ownership (Form 4)

FORM 4 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 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES 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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(Print or Type Responses)

1. Name and Address of Reporting Person * Ciongoli Gregory Austin 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) (Last) (First) (Middle) C/O REGENXBIO INC., 9804 MEDICAL CENTER DRIVE 3. Date of Earliest Transaction (Month/Day/Year) 08/25/2026 (Street) ROCKVILLE, MD 20850 4. If Amendment, Date 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 (City) (State) (Zip) 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 08/25/2026 A 15,432(1) A $ 0 15,432 D Common Stock 08/26/2026 P 49,196 A $9.1411(2) 64,628 D Common Stock 08/27/2026 P 53,407 A $9.356(3) 118,035 D

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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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 Underlying Securities (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 of Derivative Security: 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)

$8.91

08/25/2026

A

69,609

08/25/2027(4)

08/25/2036

Common Stock

69,609

$ 0

69,609

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Ciongoli Gregory Austin C/O REGENXBIO INC. 9804 MEDICAL CENTER DRIVE ROCKVILLE, MD 20850	X

Signatures

/s/ Patrick J. Christmas as attorney-in-fact		08/27/2026
**Signature of Reporting Person		Date

Explanation of Responses:

*	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).
(1)	Represents shares of common stock underlying a time-based restricted stock unit award (RSU). 1/3rd of the shares subject to the RSU award shall vest on each of August 25, 2027, August 25, 2028 and August 25, 2029, while the recipient provides continuous service to the Issuer.
(2)	Represents shares purchased in an open-market transaction. The price reported in Column 4 is a weighted average price. This transaction was executed in multiple trades at prices ranging from $8.67 to $9.35. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer or a security holder of the issuer full information regarding the number of shares and prices at which the transaction was effected.
(3)	Represents shares purchased in an open-market transaction. The price reported in Column 4 is a weighted average price. This transaction was executed in multiple trades at prices ranging from $9.17 to $9.4525. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer or a security holder of the issuer full information regarding the number of shares and prices at which the transaction was effected.
(4)	The option will vest over a three year period, with 1/3rd of the option vesting on August 25, 2027 and the remaining portion of the option vesting in equal monthly installments over the 24 months thereafter, while the optionee provides continuous service to the Issuer.

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