Company: RGNX
Filing Date: 2025-03-13
Form Type: POS AM
Source: 0001193125-25-053998
Chunk: 0

Company: REGENXBIO Inc.
Filing Date: 2025-03-13
Form: POS AM
Chunk 0
---
As filed with the Securities and Exchange Commission on March 13, 2025 Registration No. 333-269086 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 POST-EFFECTIVE AMENDMENT NO. 2 TO FORM S-3 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 REGENXBIO Inc. (Exact name of registrant as specified in its charter)

| Delaware                        |     | 47-1851754            |
| (State or other jurisdiction of 
 incorporation or organization)  |     | -IRS Employer         
 Identification Number |

9804 Medical Center Drive Rockville, Maryland 20850 (240) 552-8181 (Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices) Curran Simpson President and Chief Executive Officer REGENXBIO Inc. 9804 Medical Center Drive Rockville, Maryland 20850 (240) 552-8181 (Name, address, including zip code, and telephone number, including area code, of agent for service) With copies to:

| Patrick J. Christmas                          
 Executive Vice President, Chief Legal Officer 
 REGENXBIO Inc. 9804 Medical                   
 Center Drive Rockville, Maryland 20850        
 (240) 552-8181                                |     | Kerry Shannon Burke                
 Matthew C. Franker                 
 Covington & Burling LLP            
 One CityCenter 850 Tenth           
 Street N.W. Washington, D.C. 20001 
 (202) 662-6000                     |

Approximate date of commencement of proposed sale to the public:From time to time after this registration statement becomes effective. If the only securities being registered on this form are being offered pursuant to dividend or interest reinvestment plans, please check the following box. ☐ If any of the securities being registered on this form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, other than securities offered only in connection with dividend or interest reinvestment plans, check the following box. ☒ If this form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐ If this form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the