Company: RGNX
Filing Date: 2025-06-13
Form Type: S-3
Source: 0001193125-25-140870
Chunk: 2

Company: REGENXBIO Inc.
Filing Date: 2025-06-13
Form: S-3
Chunk 2
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, dated June 13, 2025

PRELIMINARY PROSPECTUS

Up to 268,096 Shares of Common Stock

This prospectus relates to the resale of up to 268,096 shares of common stock, par value $0.0001 per share (the “Shares”), of
REGENXBIO Inc. (the “Company,” “we,” “our” or “us”) by the selling stockholder named in this prospectus (the “Selling Stockholder”). The Shares are issuable to the Selling Stockholder upon the
exercise of a warrant to purchase up to 268,096 Shares (the “Warrant”) at an exercise price of $14.92 per share, which Warrant was issued in a private placement in connection with the Loan Agreement, dated May 16, 2025, by and between
REGENXBIO RS LLC, a wholly owned subsidiary of ours, and an affiliate of HealthCare Royalty Management, LLC.

We are registering the
resale of the Shares on behalf of the Selling Stockholder, which it may offer and sell from time to time pursuant to this prospectus. We are not selling any securities under this prospectus and will not receive any of the proceeds from the sale of
the Shares by the Selling Stockholder. We will receive proceeds of up to approximately $4.0 million upon the exercise in full of the Warrant by the Selling Stockholder for cash. For more information related to the Selling Stockholder, please
refer to the section of this prospectus titled “The Selling Stockholder.”

The Selling Stockholder may sell the Shares at
fixed prices, at prevailing market prices at the time of sale or at prices negotiated with the purchasers to or through underwriters, broker-dealers, agents, or through any other means described in the section of this prospectus titled “Plan of Distribution.” The Selling Stockholder will pay any discounts, commissions, and fees of underwriters, selling brokers, dealer managers or similar securities industry professionals incurred by such Selling Stockholder in disposing of the
Shares covered by this prospectus. We will bear all costs, expenses and fees in connection with the registration of the Shares.

Our
common stock is listed on The Nasdaq Global Select Market under the symbol “RGNX.” On June 12, 2025, the last reported sale price of our common stock was $10.20.

Investing in our securities involves significant risks. Before buying our securities, you should carefully read and