Material Event (Form 8-K)

On April 16, 2026, Atossa Therapeutics, Inc. (the "Company") announced that on April 13, 2026, the Company entered into a Settlement Agreement (the "Settlement Agreement") with Intas Pharmaceuticals Ltd. ("Intas") and Jina Pharmaceuticals, Inc., which is intended to resolve patent disputes related to Endoxifen-related intellectual property, including pending proceedings before the U.S. Patent and Trademark Office Patent Trial and Appeal Board ("PTAB").

As previously disclosed by the Company, the PTAB proceedings include challenges brought by Intas against two patents owned by the Company. Pursuant to the Settlement Agreement, the parties have agreed to seek termination of the PTAB proceedings identified in the Settlement Agreement. In the event any such proceeding is not terminated in its entirety, the applicable parties have agreed not to participate further in such proceeding, or in any related appeal, in each case subject to and in accordance with the terms of the Settlement Agreement.

The Settlement Agreement also includes mutual covenants pursuant to which the parties have agreed not to challenge, directly or indirectly, specified Endoxifen-related patents and patent applications owned or controlled by the other parties, subject to limited exceptions set forth in the Settlement Agreement.

In addition, the Settlement Agreement preserves the Company's ability to continue developing and commercializing Z-endoxifen base in the Company's principal areas of focus of oncology, endocrine dysfunction disorders and muscular dystrophy-related diseases. The Settlement Agreement also establishes agreed allocations between the parties with respect to certain other Endoxifen-related fields and formulations.

Upon anticipated termination by the PTAB of the proceedings, the Company's two issued patents titled, "Methods for Making and Using Endoxifen" (U.S. Patents Nos. 11,261,151 and 12,071,391), that are subject to such proceedings, are expected to remain issued and fully enforceable against other third parties.

The Company believes the Settlement Agreement helps reduce uncertainty arising from the pending challenges to the Company's patent portfolio and supports continued execution of the Company's strategic development plans for Z-endoxifen base in its core therapeutic areas.