Exhibit 99.1

Atossa Therapeutics Reports First Quarter 2026 Financial Results and Provides a Corporate Update

SEATTLE, WASHINGTON, May 8, 2026 — Atossa Therapeutics, Inc. (Nasdaq: ATOS) (Atossa or the Company), a clinical-stage biopharmaceutical company developing novel therapies in oncology and other areas of high unmet clinical need, today announces its financial results and provides an update on recent corporate developments for the first quarter ended March 31, 2026.

“During the quarter, we made meaningful progress advancing our (Z)-endoxifen development strategy across both oncology and rare disease indications,” stated Dr. Steven Quay, M.D., Ph.D., Atossa Therapeutics’ President and Chief Executive Officer. “We continued to advance (Z)-endoxifen in the clinic for the treatment of breast cancer, while also generating data to support its potential in rare diseases, including Duchenne Muscular Dystrophy (DMD) and McCune-Albright Syndrome. Importantly, we secured both Orphan Drug and Rare Pediatric Disease designations from the FDA for (Z)-endoxifen in DMD, and subsequently we’ve received Rare Pediatric Disease designation from the FDA for McCune-Albright Syndrome, reinforcing the potential of our programs in areas of high unmet need. Building on this momentum, we remain focused on identifying additional indications where our platform can deliver meaningful therapeutic benefit to patients with limited treatment options.”

Dr. Quay continued, “Our balance sheet remains strong, positioning us to continue to execute across our strategic plans, and deliver value to shareholders in upcoming quarters.”

First Quarter 2026 & Recent Highlights

Financial Results for the First Quarter Ended March 31, 2026

Operating Expenses. Total operating expenses were $9.9 million for the three months ended March 31, 2026, which was an increase of $2.5 million, from total operating expenses for the three months ended March 31, 2025 of $7.4 million. Factors contributing to the increased operating expenses in the three months ended March 31, 2026 are explained below.

Research & Development (R&D) Expenses. The following table provides a breakdown of major categories within R&D expenses for the three months ended March 31, 2026 and 2025, together with the dollar change and percentage change in those categories (dollars in thousands):



As (Z)-endoxifen is our only product candidate for which we currently incur R&D expenses, we have not further disaggregated R&D expenses by product candidate:

General and Administrative (G&A) Expenses. The following table provides a breakdown of major categories within G&A expenses for the quarter ended March 31, 2026 and 2025, together with the dollar change and percentage change in those categories (dollars in thousands):

Interest Income. Interest income of $0.3 million for the quarter ended March 31, 2026 represented a decrease of $0.4 million compared to the prior year period. The decrease was due primarily to lower average cash balances invested in our money market account during the current year period relative to the same period in the prior year.

About Atossa Therapeutics

Atossa Therapeutics, Inc. (Nasdaq: ATOS) is a clinical-stage biopharmaceutical company developing innovative medicines in oncology and other areas of significant unmet need. The Company’s lead product candidate, (Z)-endoxifen, is currently in development across several clinical settings.

(Z)-Endoxifen is a potent Selective Estrogen Receptor Modulator/Degrader (SERM/D) with demonstrated activity across multiple mechanisms of interest. Atossa is evaluating its potential applications in oncology and rare diseases. The Company’s proprietary oral formulation has shown a favorable safety profile and pharmacology distinct from tamoxifen, including ER-targeted effects and PKC inhibition. Atossa’s (Z)-endoxifen is not approved for any indication.

Atossa has received Orphan Drug Designation from the U.S. Food and Drug Administration (FDA) for (Z)-endoxifen for the treatment of Duchenne Muscular Dystrophy, as well as Rare Pediatric Disease (RPD) designation for (Z)-endoxifen for the treatment of both Duchenne Muscular Dystrophy and McCune-Albright Syndrome. Upon approval of a qualifying marketing application, drugs with RPD designation may be eligible for a Priority Review Voucher (PRV), which can be used to obtain priority review for a future application or may be sold or transferred to another sponsor. In the last 18–24 months, disclosed PRV sales have ranged from $100–$205 million.

Atossa’s (Z)-endoxifen program is supported by a growing global intellectual property portfolio, including multiple recently issued U.S. patents and numerous pending applications worldwide.

More information is available at https://atossatherapeutics.com.

Forward Looking Statements

This press release contains certain “forward-looking statements” within the meaning of applicable securities laws, including but not limited to, our 2026 outlook and our expectations regarding the Company’s development and regulatory strategy and related milestones, the potential indications that the Company may pursue for (Z)-endoxifen, the potential for (Z)-endoxifen to receive regulatory approval and the timing thereof, the Company's progress across its pipeline and potential commercialization, the strength of the Company's patent portfolio, the Company’s potential eligibility for and the value of a Rare Pediatric Disease Priority Review Voucher (PRV), and the potential market and growth opportunities for the Company. Words such as “expect,” “potential,” “continue,” “may,” “will,” “should,” “could,” “would,” “seek,” “intend,” “plan,” “estimate,” “anticipate,” “believe,” “design,” “predict,” “future,” or other similar expressions or statements regarding intent, belief or current expectations, are forward-looking statements.

Forward-looking statements in this press release are subject to risks and uncertainties that may cause actual results, outcomes, or the timing of actual results or outcomes to differ materially from those projected or anticipated, including, without limitation, risks and uncertainties associated with: our ability to successfully execute our strategy to shorten our clinical development timelines and pursue a DMD or McCune-Albright Syndrome indication or other indications for our lead program, (Z)-endoxifen; expected timing, completion and results of our preclinical studies, clinical trials, and research and development programs; the unpredictable relationship between preclinical study results and clinical study results; the timing or likelihood of regulatory filings and approvals; the outcome or timing of necessary regulatory approvals; our ability to receive orphan-drug exclusivity for (Z)-endoxifen for DMD; our ability to maintain compliance with Nasdaq listing requirements; our ability to establish and maintain intellectual property rights covering our products; the impact of general macroeconomic conditions on our business; our ability to raise capital; and other risks and uncertainties detailed from time to time in Atossa’s filings with the SEC, including, without limitation, its Annual Reports on Form 10-K and Quarterly Reports on Form 10-Q.

The market value of a PRV is variable and subject to a number of factors beyond our control and reported past PRV sale amounts are not necessarily indicative of PRV sale amounts in the future.

Forward-looking statements are presented as of the date of this press release. Except as required by law, we do not intend to update any forward-looking statements.

Investor & Media Contact

Investors: WaterSeid Partners, Inc. — [email protected]

Media: Elev8 New Media — [email protected]

ATOSSA THERAPEUTICS, INC.

CONDENSED CONSOLIDATED BALANCE SHEETS

(amounts in thousands, except share and per share data)

(Unaudited)

ATOSSA THERAPEUTICS, INC.

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS

(amounts in thousands, except share and per share data)

(Unaudited)