X0306 4 2018-09-17 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 2018-09-17 4 S false 1515.00 70.46 D 339505.00 D Common Stock 2018-09-17 4 S false 100.00 71.10 D 339405.00 D Common Stock 2018-09-17 4 S false 624.00 73.04 D 338781.00 D Common Stock 2018-09-17 4 S false 1399.00 73.80 D 337382.00 D Common Stock 2018-09-17 4 S false 622.00 75.29 D 336760.00 D Common Stock 2018-09-17 4 S false 1450.00 76.72 D 335310.00 D Common Stock 2018-09-17 4 S false 900.00 77.88 D 334410.00 D Common Stock 2018-09-17 4 S false 400.00 78.73 D 334010.00 D Common Stock 2018-09-17 4 S false 200.00 79.45 D 333810.00 D Common Stock 2018-09-17 4 S false 300.00 81.12 D 333510.00 D This transaction was effected pursuant to a Rule 10b5-1 trading plan. This transaction was executed in multiple trades at prices ranging from $80.80 to $81.30. 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 $70.05 to $70.90. 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 $72.55 to $73.45. 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 $73.55 to $74.35. 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 $75.00 to $75.60. 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 $76.40 to $77.30. 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 $77.40 to $78.35. 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 $78.40 to $79.20. 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 $79.40 to $79.50. 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. /s/ Patrick J. Christmas as attorney-in-fact 2018-09-19