Company: RGNX
Filing Date: 2025-06-25
Form Type: 424B3
Source: 0001193125-25-146911
Chunk: 4

Company: REGENXBIO Inc.
Filing Date: 2025-06-25
Form: 424B3
Chunk 4
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 statement in the later-dated document modifies or supersedes the earlier statement.

You should read this
prospectus together with the additional information about our company to which we refer you in the section of this prospectus titled “Where You Can Find More Information.”

Neither we nor the Selling Stockholder has authorized anyone to provide you with information that is in addition to or different from that contained in this prospectus. We take no responsibility for, and can provide no assurance as to the reliability of, any information that others may provide. We will be offering to sell, and seeking offers to buy, our securities only in jurisdictions where such offers and sales are permitted. You should not assume that the information in this prospectus or any prospectus supplement or free writing prospectus that we have prepared or authorized is accurate as of any date other than the date of those documents, or that any information in documents that we have incorporated by reference is accurate except as of the date of such document, regardless of the time of delivery of this prospectus or any prospectus supplement or free writing prospectus, or the sale of any security hereunder. You should not consider this prospectus to be an offer or solicitation relating to the Shares in any jurisdiction in which such an offer or solicitation relating to the Shares is not authorized. Furthermore, you should not consider this prospectus to be an offer or solicitation relating to the Shares if the person making the offer or solicitation is not qualified to do so, or if it is unlawful for you to receive such an offer or solicitation.

We note that the representations, warranties, covenants and agreements made in any agreement or instrument that is
filed as an exhibit to any document that is incorporated by reference herein were made solely for the benefit of the parties to such agreement or instrument, including in some cases, for the purpose of allocating risk among the parties to such
agreements and instruments, and should not be deemed to be a representation, warranty or covenant to you. Moreover, such representations, warranties and covenants were accurate only as of the date when made. Accordingly, such representations,
warranties and covenants should not be relied on as accurately representing the current state of our affairs.

Unless the context
otherwise requires, throughout this prospectus, the words “REGENXBIO,” “Company” “we,” “our” or “us,” refer to REGENXBIO Inc.

AAVIATE, AFFINITY BEYOND, AFFINITY DUCHENNE,