Company: RGNX
Filing Date: 2025-03-13
Form Type: POSASR
Source: 0001193125-25-053917
Chunk: 37

Company: REGENXBIO Inc.
Filing Date: 2025-03-13
Form: POSASR
Chunk 37
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 sold, based on the bids submitted, and whether a bidder’s individual bids would be accepted, prorated or rejected. For example, in the case of debt security, the clearing spread could be indicated as a number of
“basis points” above an index treasury note.

Upon completion of such an electronic auction process, securities will be
allocated based on prices bid, terms of bid or other factors. The final offering price at which securities would be sold and the allocation of securities among bidders would be based in whole or in part on the results of the Internet or other
electronic bidding process or auction.

General Information

Underwriters, dealers and agents may engage in transactions with or perform services for us in the ordinary course of their businesses for
which they may receive customary fees and reimbursement of expenses. We may have a material relationship with the underwriters, dealers or agents. We will describe the nature of such relationship in the applicable prospectus supplement.

Under the securities laws of some states, the securities offered by this prospectus may be sold in those states only through registered or
licensed brokers or dealers. The specific terms of any lock-up provisions in respect of any given offering will be described in the applicable prospectus supplement.

Underwriters, dealers and agents may be entitled, under agreements entered into with us, to be indemnified by us against certain liabilities,
including liabilities under the Securities Act. Our underwriters, dealers and agents, or their affiliates, may be customers of, engage in transactions with or perform services for us, in the ordinary course of business.

LEGAL MATTERS

The validity of the shares of common stock offered by this prospectus will be passed upon for us by Covington & Burling LLP,
Washington, D.C. Counsel for any underwriters, dealers or agents will be named in the applicable prospectus supplement.

EXPERTS

The financial statements and management’s assessment of the effectiveness of internal control over financial
reporting (which is included in Management’s Report on Internal Control over Financial Reporting) incorporated in this prospectus by reference to the Annual Report on Form 10-K for the year ended
December 31, 2023 have been so incorporated in reliance on the report of PricewaterhouseCoopers LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

27

Common Stock

Preferred Stock

Warrants

Debt Securities

Rights

Units

PROSPECTUS

March 13, 2025

PART II INFORMATION NOT REQUIRED