GRI Bio (NASDAQ: GRI) boosts at-the-market common stock offering to $60M

Rhea-AI Filing Summary

GRI Bio, Inc. is updating its at-the-market stock offering to permit sales of up to $60,000,000 of common stock through H.C. Wainwright & Co. as sales agent.

The company has already sold shares for an aggregate purchase price of $12,639,002.84 under the existing program. As of January 29, 2026, its public float was approximately $86.6 million, based on 1,445,015 shares of common stock held by non-affiliates. The stock last traded at $4.11 per share on the Nasdaq Capital Market on January 28, 2026.

Filed pursuant to Rule 424(b)(5)

Registration No. 333-279348

PROSPECTUS SUPPLEMENT

(To Prospectus Supplements Dated May 20, 2024, July 19, 2024, July 26, 2024, December 20, 2024, May 5, 2025, May 23, 2025 and January 9, 2026, to Prospectus Dated May 16, 2024)

GRI BIO, INC.

Up to $60,000,000

Common Stock

This prospectus supplement amends, supplements, and supersedes certain information contained in the prospectus supplement dated May 20, 2024, and its accompanying prospectus dated May 16, 2024, as supplemented by our prospectus supplements dated July 19, 2024, July 26, 2024, December 20, 2024, May 5, 2025, May 23, 2025 and January 9, 2026 (collectively, the “Prior Prospectuses”), relating to the offer and sale of our common stock, par value $0.0001 per share (the “Common Stock”) through H.C. Wainwright & Co., LLC (“Wainwright”), as sales agent, in “at the market offerings” as defined in Rule 415 promulgated under the Securities Act of 1933, as amended, pursuant to the At the Market Offering Agreement with Wainwright dated as of May 20, 2024, as amended by Amendment No. 1 to At the Market Offering Agreement with Wainwright dated as of January 29, 2026 and effective as of January 28, 2026 (the “Sales Agreement”).

As of January 29, 2026, the aggregate market value of our outstanding Common Stock held by non-affiliates (the “public float”) calculated for purposes of General Instruction I.B.6 of Form S-3, was approximately $86.6 million based on 1,445,015 shares of outstanding Common Stock as of January 29, 2026, which number excludes 14 shares held by affiliates, and a price of $59.92 per share, which was the price at which our Common Stock was last sold on the Nasdaq Capital Market on December 4, 2025. As of the date of this prospectus supplement, shares of Common Stock with an aggregate purchase price of $12,639,002.84 have previously been sold pursuant to the Sales Agreement.

We are filing this prospectus supplement to amend the Prior Prospectuses to update the amount of shares we are eligible to sell pursuant to such prospectus. We are increasing the amount of shares of Common Stock we may offer and sell under the Sales Agreement to an aggregate offering price of up to $60,000,000 from time to time through Wainwright, which does not include the shares of Common Stock having an aggregate gross sales price of $12,639,002.84 that were sold pursuant to the Prior Prospectuses to date.

Our Common Stock is listed on the Nasdaq Capital Market under the symbol “GRI”. On January 28, 2026, the last reported sale price of our Common Stock on the Nasdaq Capital Market was $4.11 per share.

Investing in our securities involves a high degree of risk. You should review carefully the risks and uncertainties under the heading “Risk Factors” on page 5 of the prospectus dated May 16, 2024, on page S-7 of the prospectus supplement filed on May 20, 2024, and the other documents that are incorporated by reference to this prospectus supplement.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities, or determined if this prospectus is accurate or complete. Any representation to the contrary is a criminal offense.

H.C. Wainwright & Co.

The date of this prospectus supplement is January 29, 2026

FAQ

What does GRI Bio (GRI) disclose in this new prospectus supplement?

GRI Bio updates its at-the-market offering program, allowing sales of up to $60,000,000 in common stock through H.C. Wainwright. This supplement amends earlier prospectuses tied to the same program and reflects shares already sold plus the expanded capacity.

How large is GRI Bio’s updated at-the-market common stock offering?

The company may now offer and sell up to $60,000,000 of common stock through its at-the-market program. This amount is in addition to shares previously sold for an aggregate purchase price of $12,639,002.84 under the same Sales Agreement with H.C. Wainwright.

How much stock has GRI Bio already sold under the Sales Agreement?

GRI Bio has previously sold shares of common stock with an aggregate purchase price of $12,639,002.84 under the at-the-market Sales Agreement. The new supplement increases the potential future offering capacity to $60,000,000 of additional common stock.

What is GRI Bio’s public float and share count as referenced here?

As of January 29, 2026, GRI Bio’s public float was approximately $86.6 million, based on 1,445,015 shares of common stock held by non-affiliates. This calculation used a reference price of $59.92 per share from December 4, 2025.

On which exchange is GRI Bio’s stock listed and what was the recent price?

GRI Bio’s common stock is listed on the Nasdaq Capital Market under the symbol “GRI”. On January 28, 2026, the last reported sale price of its common stock was $4.11 per share.

Who is acting as sales agent for GRI Bio’s at-the-market offering?

H.C. Wainwright & Co., LLC is the sales agent for GRI Bio’s at-the-market common stock offering, operating under an At the Market Offering Agreement originally dated May 20, 2024 and amended effective January 28, 2026.