Company: RGNX
Filing Date: 2025-03-13
Form Type: POSASR
Source: 0001193125-25-053917
Chunk: 42

Company: REGENXBIO Inc.
Filing Date: 2025-03-13
Form: POSASR
Chunk 42
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 in this registration statement or prospectus that was a part of this registration statement or made in any such document immediately prior to such effective date.

(5) That, for the purpose of determining liability of the registrant under the Securities Act of 1933 to any purchaser in the initial
distribution of the securities, in a primary offering of securities of the undersigned registrant pursuant to this registration statement, regardless of the underwriting method used to sell the securities to the purchaser, if the securities are
offered or sold to such purchaser by means of any of the following communications, the undersigned registrant will be a seller to the purchaser and will be considered to offer or sell such securities to such purchaser:

(i) Any preliminary prospectus or prospectus of the undersigned registrant relating to the offering required to be filed
pursuant to Rule 424;

(ii) Any free writing prospectus relating to the offering prepared by or on behalf of the
undersigned registrant or used or referred to by the undersigned registrant;

(iii) The portion of any other free writing
prospectus relating to the offering containing material information about the undersigned registrant or its securities provided by or on behalf of the undersigned registrant; and

(iv) Any other communication that is an offer in the offering made by the undersigned registrant to the purchaser.

(6) That, for purposes of determining any liability under the Securities Act of 1933, each filing of the registrant’s annual report
pursuant to Section 13(a) or 15(d) of the Securities Exchange Act of 1934 (and, where applicable, each filing of an employee benefit plan’s annual report pursuant to Section 15(d) of the Securities Exchange Act of 1934) that is
incorporated by reference in the registration statement shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

(7) In connection with offerings of securities to existing security holders pursuant to warrant or rights
where any securities not taken by security holders are to be reoffered to the public, to supplement the prospectus, after the expiration of the subscription period for a warrant or rights offering, to set forth the results of the subscription

II-4

offer, the transactions by the underwriters during the subscription period, the amount of unsubscribed securities to be purchased by the underwriters, and the