Company: RGNX
Filing Date: 2025-03-13
Form Type: POSASR
Source: 0001193125-25-053917
Chunk: 33

Company: REGENXBIO Inc.
Filing Date: 2025-03-13
Form: POSASR
Chunk 33
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 changed; |

| • |     | market prices prevailing at the time of sale; |

| • |     | prices related to the prevailing market price; or |

| • |     | negotiated prices. |

The applicable prospectus supplement will set forth the method of distribution and the terms and conditions of the offering of such securities, including:

| • |     | the terms of the offering; |

| • |     | the names of any underwriters, dealers or agents; |

| • |     | the name or names of any managing underwriter or underwriters; |

| • |     | the purchase price of the securities and the proceeds to us from the sale; |

| • |     | any over-allotment or other options under which the underwriters may purchase additional shares of common stock 
 from us;                                                                                                        |

| • |     | any underwriting discounts, concessions, commissions or agency fees and other items constituting compensation to 
 underwriters, dealers or agents;                                                                                 |

| • |     | any discounts or concessions allowed or re-allowed or paid by 
 underwriters or dealers to other dealers;                     |

| • |     | any delayed delivery arrangements; |

| • |     | estimated offering expenses; or |

| • |     | any securities exchange or market on which the securities offered in the prospectus supplement may be listed. |

We may issue to our existing security holders, through a dividend or similar distribution, rights to purchase shares of our common stock or preferred stock, debt securities or units, which may or may not be transferable. In any distribution of rights to our existing security holders, if all of the underlying securities are not subscribed for, we may then sell the unsubscribed securities directly to third parties or may engage the services of one or more underwriters, dealers or agents, including standby underwriters, to sell the unsubscribed securities to third parties. The applicable prospectus supplement will describe the specific terms of any offering of our common stock or preferred stock through the issuance of rights, including, if applicable, the material terms of any standby underwriting or purchase arrangement. 24

Sale Through Underwriters or Dealers

If we use underwriters for a sale of securities, the underwriters will acquire the securities for their own account for resale to the public,
either on a firm commitment basis or a best efforts basis. The underwriters may resell the securities in one or more transactions, including negotiated transactions, at a fixed public offering price or at varying prices determined at the time of
sale