X0609 4 2025-12-31 false 0001590877 REGENXBIO Inc. RGNX 0001346164 Simpson Curran false C/O REGENXBIO INC. 9804 MEDICAL CENTER DRIVE ROCKVILLE MD 20850 true true false false Chief Executive Officer false Common Stock 2025-12-31 4 A false 951.00 6.9955 A 343418.00 D Common Stock 2026-06-30 4 A false 1453.00 10.18 A 344871.00 D Common Stock 2026-07-01 4 F false 6818.00 13.09 D 338053.00 D The reporting person is voluntarily reporting the acquisition of shares of the Issuer's common stock pursuant to the REGENXBIO Inc. Employee Stock Purchase Plan ("ESPP") for the ESPP purchase period of July 1, 2025 through December 31, 2025. This transaction is exempt under Rule 16b-3(c). In accordance with the ESPP, these shares were purchased based on 85% of the closing price of the Issuer's common stock on July 1, 2025. The reporting person is voluntarily reporting the acquisition of shares of the Issuer's common stock pursuant to the ESPP for the ESPP purchase period of January 1, 2026 through June 30, 2026. This transaction is exempt under Rule 16b-3(c). In accordance with the ESPP, these shares were purchased based on 85% of the closing price of the Issuer's common stock on June 30, 2026. Represents shares of common stock withheld to pay taxes upon the vesting of restricted stock units originally granted to the reporting person on July 1, 2024. The number of shares withheld was determined based on the closing price of the issuer's common stock on July 1, 2026. /s/ Patrick J. Christmas as attorney-in-fact 2026-07-06