X0609 4 2026-08-25 false 0001590877 REGENXBIO Inc. RGNX 0002023732 Ciongoli Gregory Austin false C/O REGENXBIO INC. 9804 MEDICAL CENTER DRIVE ROCKVILLE MD 20850 true false false false false Common Stock 2026-08-25 4 A false 15432.00 0.00 A 15432.00 D Common Stock 2026-08-26 4 P false 49196.00 9.1411 A 64628.00 D Common Stock 2026-08-27 4 P false 53407.00 9.356 A 118035.00 D Stock Options (Right to buy) 8.91 2026-08-25 4 A false 69609.00 0.00 A 2027-08-25 2036-08-25 Common Stock 69609.00 69609.00 D 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. 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. 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. 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. /s/ Patrick J. Christmas as attorney-in-fact 2026-08-27