Company: RGNX
Filing Date: 2025-03-13
Form Type: POS AM
Source: 0001193125-25-053998
Chunk: 5

Company: REGENXBIO Inc.
Filing Date: 2025-03-13
Form: POS AM
Chunk 5
---
 additional financing and out ability to obtain additional financing; |

| • |     | our expectations regarding the outcome of legal proceedings; |

| • |     | our expectations regarding recent regulatory developments in the United States and foreign countries; and |

ii

| • |     | changes in the financial markets and banking system that may affect the ability and terms on which we may obtain                                    
 financing and our ability to accurately predict how long our existing cash resources will be sufficient to fund our anticipated operating expenses. |

You should carefully read the section of this prospectus and the applicable prospectus supplement entitled “Risk Factors” as well as the “Risk Factors” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” sections included in our filings with the SEC that are incorporated herein by reference for a discussion of other important factors that may cause our actual results to differ materially and adversely from those projected in the forward-looking statements. The actual results or developments anticipated may not be realized or, even if substantially realized, they may not have the expected consequences to or effects on us or our businesses or operations. Such statements are not guarantees of future performance and actual results or developments may differ materially and adversely from those projected in the forward-looking statements. Any forward-looking statement made by us in this prospectus and the information incorporated by reference herein speaks only as of the date of the respective document. Except as required by law, we disclaim any duty to update or revise any of these forward-looking statements after the date such statements are made, or to update the reasons actual results could differ materially from those anticipated in these forward-looking statements, even if new information becomes available in the future. iii

ABOUT THIS PROSPECTUS This prospectus is part of a registration statement on Form S-3that we filed with the Securities and Exchange Commission (the “SEC”) using a shelf registration process. Under this shelf registration process, we may, from time to time, offer or sell any combination of the securities described in this prospectus in one or more offerings, up to a total amount of $300,000,000. This prospectus provides you with a general description of the securities we may offer. Each time we offer securities under this registration statement, we will describe in a prospectus supplement, which will be delivered with this prospectus, specific information about the offering and the terms of the particular securities offered. The specific terms of the offered securities may vary from the general terms of the securities described in this prospectus, and accordingly the description of the securities contained in this prospect