Aptose Announces Deferral of Interest Payment

SAN DIEGO and TORONTO, June 30, 2025 (GLOBE NEWSWIRE) -- Aptose Biosciences Inc. ("Aptose" or the "Company") (TSX: APS; OTC: APTOF), a clinical-stage precision oncology company developing a tuspetinib (TUS) based triple drug frontline therapy to treat patients with newly diagnosed acute myeloid leukemia (AML), announced that it has entered into an Interest Deferral Agreement (the “Agreement”) with Hanmi Pharmaceutical Co., Ltd. (“Hanmi”), whereby Hanmi has agreed to further defer the interest payment due under the loan facility agreement dated August 27, 2024 (the “2024 Loan Agreement”) between Aptose and Hanmi for the period commencing December 21, 2024 and ending on March 31, 2025 from June 27, 2025 to December 31, 2025 and to defer the interest due under the 2024 Loan Agreement for the period commencing March 31, 2025 and ending on June 30, 2025 to December 31, 2025.

About Aptose

Aptose Biosciences is a clinical-stage biotechnology company committed to developing precision medicines addressing unmet medical needs in oncology, with an initial focus on hematology. The Company's small molecule cancer therapeutics pipeline includes products designed to provide single agent efficacy and to enhance the efficacy of other anti-cancer therapies and regimens without overlapping toxicities. The Company’s lead clinical-stage compound tuspetinib (TUS), is an oral kinase inhibitor that has demonstrated activity as a monotherapy and in combination therapy in patients with relapsed or refractory acute myeloid leukemia (AML) and is being developed as a frontline triplet therapy in newly diagnosed AML. For more information, please visit .

Forward Looking Statements

This press release may contain forward-looking statements within the meaning of Canadian and U.S. securities laws, including statements relating but not limited to statements relating to the Company’s plans, objectives, expectations and intentions and other statements including words such as “continue”, “expect”, “intend”, “will”, “should”, “would”, “may”, and other similar expressions. Such statements reflect our current views with respect to future events and are subject to risks and uncertainties and are necessarily based upon a number of estimates and assumptions that, while considered reasonable by us are inherently subject to significant business, economic, competitive, political and social uncertainties and contingencies. Many factors could cause our actual results, performance or achievements to be materially different from any future results, performance or achievements described in this press release. Such factors could include, among others: our ability to negotiate a collaboration agreement to jointly develop tuspetinib with Hanmi, our ability to remain compliant with Nasdaq listing requirements and other risks detailed from time-to-time in our ongoing quarterly filings, annual information forms, annual reports and annual filings with Canadian securities regulators and the United States Securities and Exchange Commission.

Should one or more of these risks or uncertainties materialize, or should the assumptions set out in the section entitled "Risk Factors" in our filings with Canadian securities regulators and the United States Securities and Exchange Commission underlying those forward-looking statements prove incorrect, actual results may vary materially from those described herein. These forward-looking statements are made as of the date of this press release and we do not intend, and do not assume any obligation, to update these forward-looking statements, except as required by law. We cannot assure you that such statements will prove to be accurate as actual results and future events could differ materially from those anticipated in such statements. Investors are cautioned that forward-looking statements are not guarantees of future performance and accordingly investors are cautioned not to put undue reliance on forward-looking statements due to the inherent uncertainty therein.

For further information, please contact:

Aptose Biosciences Inc.                                          

Susan Pietropaolo                                                                                    

Corporate Communications & Investor Relations                         

201-923-2049