Material Agreement (Form 8-K)

Item 1.01 Entry Into a Material Definitive Agreement.

On February 20, 2026, Atossa Therapeutics, Inc. (the "Company") entered into the At the Market Offering Agreement, dated February 20, 2026 (the "Sales Agreement"), with Rodman & Renshaw LLC (the "Sales Agent"), pursuant to which the Company may offer and sell from time to time up to $50,000,000 of shares of the Company's common stock, par value $0.18 per share (the "Shares"), through the Sales Agent as agent or principal. The offering and sale of the Shares has been registered under the Securities Act of 1933, as amended (the "Securities Act"), pursuant to the Company's Registration Statement on Form S-3(File No. 333-279367)(the "Registration Statement"), which was originally filed with the Securities and Exchange Commission ("SEC") on May 13, 2024 and declared effective by the SEC on May 23, 2024, the base prospectus contained within the Registration Statement, and a prospectus supplement that was filed with the SEC on February 20, 2026.

Sales of the Shares, if any, pursuant to the Sales Agreement, may be made in sales deemed to be an "at the market offering" as defined in Rule 415(a)(4) promulgated under the Securities Act, including sales made directly on or through The Nasdaq Capital Market or on any other existing trading market for the Company's common stock. The Company has no obligation to sell any of the Shares under the Sales Agreement, and may at any time suspend offers under the Sales Agreement or terminate the Sales Agreement. The Sales Agent will act as a sales agent and will use commercially reasonable efforts to sell on the Company's behalf all of the Shares requested to be sold by the Company, consistent with their normal trading and sales practices, on mutually agreed terms between the Sales Agent and the Company. The Company currently intends to use the proceeds of the offering, if any, for clinical development of its product candidates, working capital and general corporate purposes. The Company may also use a portion of the proceeds to license, acquire or invest in complementary businesses, technology, products or assets, however, it has no current commitments to do so.

The Sales Agreement contains customary representations, warranties and agreements by the Company, as well as indemnification obligations of the Company for certain liabilities under the Securities Act. Under the terms of the Sales Agreement, the Company will pay the Sales Agent a commission of up to 3.0% of the gross proceeds of Shares sold pursuant to the Sales Agreement. In addition, the Company has agreed to reimburse certain expenses incurred by the Sales Agent in connection with the offering. The Sales Agreement may be terminated by the Sales Agent or the Company at any time upon notice to the other party, as set forth in the Sales Agreement, or by the Sales Agent at any time.

This Current Report on Form 8-Kshall not constitute an offer to sell or a solicitation of an offer to buy any securities, nor shall there be any sale of these securities in any state or jurisdiction in which such an offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or other jurisdiction.

Gibson, Dunn & Crutcher LLP, counsel to the Company, has issued an opinion to the Company, dated February 20, 2026 regarding the validity of the Shares. A copy of the opinion is filed herewith as Exhibit 5.1.

The description of the material terms of the Sales Agreement is not intended to be complete and is qualified in its entirety by reference to the Sales Agreement, which is filed herewith as Exhibit 1.1 and incorporated herein by reference.