GRI Bio (NASDAQ: GRI) boosts $7.38M at-the-market common stock program

Rhea-AI Filing Summary

GRI Bio, Inc. is updating its at-the-market equity program to offer and sell up to $7,379,813 of common stock from time to time through H.C. Wainwright & Co. as sales agent under an existing sales agreement. This supplements earlier prospectus supplements and adjusts the amount the company may sell while remaining within the one-third public float limit set by General Instruction I.B.6 of Form S-3. The company notes that approximately $6,165,114 of common stock has already been sold under prior supplements, and that its public float was about $29.8 million based on 13,935,394 shares outstanding as of January 8, 2026. The common stock trades on the Nasdaq Capital Market under the symbol GRI, with a last reported sale price of $0.284 per share on January 8, 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 and May 23, 2025, to Prospectus Dated May 16, 2024)

GRI BIO, INC.

Up to $7,379,813

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 and May 23, 2025 (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 (the “Sales Agreement”).

As of January 9, 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 $29.8 million based on 13,935,394 shares of outstanding Common Stock as of January 8, 2026, of which 471 shares were held by affiliates, and a price of $2.14 per share, which was the price at which our Common Stock was last sold on the Nasdaq Capital Market on December 4, 2025.

We have sold an aggregate of approximately $2,560,431 of shares of Common Stock pursuant to General Instruction I.B.6 of Form S-3 during the prior 12-calendar month period that ends on and includes the date of this prospectus supplement.

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 $7,379,813 from time to time through Wainwright, which does not include the shares of Common Stock having an aggregate gross sales price of approximately $6,165,114 that were sold pursuant to the Prior Prospectuses to date. Pursuant to General Instruction I.B.6 of Form S-3, in no event will we sell securities in a public primary offering with a value exceeding one-third of our public float in any 12-month calendar period so long as our public float remains below $75.0 million. In the event that we may sell additional amounts under the Sales Agreement, we will file another prospectus supplement prior to making such additional sales.

Our Common Stock is listed on the Nasdaq Capital Market under the symbol “GRI”. On January 8, 2026, the last reported sale price of our Common Stock on the Nasdaq Capital Market was $0.284 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 9, 2026

FAQ

What is GRI Bio (GRI) offering in this new prospectus supplement?

GRI Bio is updating its at-the-market equity program to offer and sell up to $7,379,813 of its common stock from time to time through H.C. Wainwright & Co. as sales agent under an existing sales agreement.

How does this GRI (GRI) supplement relate to prior at-the-market offerings?

The supplement amends and supersedes certain information in prior prospectus supplements and increases the amount of common stock the company may sell under the sales agreement, in addition to approximately $6,165,114 of common stock already sold under those earlier supplements.

What limitation applies to GRI Bio’s (GRI) future primary offerings under Form S-3?

Under General Instruction I.B.6 of Form S-3, GRI Bio states it will not sell securities in a public primary offering with a value exceeding one-third of its public float in any 12-month period while its public float remains below $75.0 million.

What is GRI Bio’s (GRI) recent public float and share count?

As of January 9, 2026, the public float was approximately $29.8 million, based on 13,935,394 shares of common stock outstanding as of January 8, 2026, of which 471 shares were held by affiliates.

What was the recent trading price of GRI Bio (GRI) common stock?

On January 8, 2026, GRI Bio’s common stock last traded at $0.284 per share on the Nasdaq Capital Market.

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

H.C. Wainwright & Co., LLC is acting as sales agent under the at-the-market offering agreement dated May 20, 2024.

What risks does GRI Bio (GRI) highlight for this at-the-market program?

The company states that investing in its securities involves a high degree of risk and directs readers to the “Risk Factors” sections in its May 16, 2024 prospectus, the May 20, 2024 prospectus supplement, and other incorporated documents.