X0306 4 2021-01-25 false 0001590877 REGENXBIO Inc. RGNX 0001652824 Mills Kenneth T. C/O REGENXBIO INC. 9600 BLACKWELL ROAD, SUITE 210 ROCKVILLE MD 20850 true true false false President and CEO Common Stock 2021-01-25 4 M false 6500.00 0.85 A 287484.00 D Common Stock 2021-01-25 4 S false 315.00 42.64 D 287169.00 D Common Stock 2021-01-25 4 S false 974.00 44.05 D 286195.00 D Common Stock 2021-01-25 4 S false 5211.00 44.99 D 280984.00 D Employee Stock Option (Right to Buy) 0.85 2021-01-25 4 M false 6500.00 0.00 D 2024-09-23 Common Stock 6500.00 41170.00 D This transaction was effected pursuant to a Rule 10b5-1 trading plan. This transaction was executed in multiple trades at prices ranging from $42.49 to $42.72. The price reported above reflects the weighted average sale price. 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. This transaction was executed in multiple trades at prices ranging from $43.55 to $44.52. The price reported above reflects the weighted average sale price. 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. This transaction was executed in multiple trades at prices ranging from $44.55 to $45.00. The price reported above reflects the weighted average sale price. 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 previously granted option, representing a right to purchase a total of 708,200 shares, became exercisable as follows: 474,490 of the shares subject to the option are initial shares ("Initial Shares") and 233,710 of the shares subject to the option are contingent shares ("Contingent Shares"). 120,394 of the Initial Shares vested on September 17, 2014, 88,524 of the Initial Shares vested on September 17, 2015 and an additional 7,377 of the Initial Shares vested upon each month of continuous service to the Company thereafter. 25% of the Contingent Shares were deemed vested as of September 17, 2014 on January 13, 2015 due to a subsequent event. The remainder of the Contingent Shares vested over four years of service following September 17, 2014, with 25% of the remaining 75% of Contingent Shares having vested on September 17, 2015 and the remaining Contingent Shares having vested in 36 equal monthly installments thereafter. /s/ Patrick J. Christmas as attorney-in-fact 2021-01-27