Tuspetinib

SAN DIEGO and TORONTO, Dec. 19, 2025 (GLOBE NEWSWIRE) -- Aptose Biosciences Inc. (“Aptose” or the “Company”) (TSX: APS; OTC: APTOF) announced today that it will be rescheduling its upcoming special meeting of shareholders, originally scheduled to be held on January 16, 2026 (the “Meeting”), to a later date to be announced. Aptose will hold the rescheduled Meeting as soon as practicable in January 2026. No changes are expected to be made to the record date of the Meeting, being the close of business on December 12, 2025, or to the matters to be put before shareholders at the Meeting, including the previously announced continuance of Aptose from the Canada Business Corporations Act to the Business Corporations Act (Alberta) (“ABCA”) (the “Continuance”) and the subsequent acquisition by HS North America Ltd., a wholly owned subsidiary of Hanmi Pharmaceutical Co. Ltd. (together, the “Hanmi Purchasers”), by way of a statutory plan of arrangement under the ABCA (the “Arrangement” and, together with the Continuance, the “Transaction”). Aptose has determined to reschedule the Meeting after it receives final clearance of the proxy statement from the United States Securities and Exchange Commission (“SEC”). Following the clearance from the SEC, Aptose will announce the new date, time and virtual details for the Meeting. Aptose intends to mail to all shareholders, and to make available under its profile on SEDAR+ at www.sedarplus.ca and EDGAR at www.sec.gov, the proxy statement, form of proxy, letter of transmittal along with any additional required disclosure in connection with the Meeting. On December 12, 2025, Aptose obtained an interim order from the Court of King’s Bench of Alberta (the “Court”) authorizing the holding of the Meeting and matters relating to the conduct of the Meeting. The Company’s board of directors unanimously recommends that the holders of Aptose common shares vote FOR the special resolutions approving the Continuance and the Arrangement at the Meeting. About Aptose Aptose Biosciences Inc. 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 www.aptose.com. Forward Looking Statements This news release contains “forward-looking information” and “forward-looking statements” (collectively, “forward-looking information”) within the meaning of applicable securities laws. This information includes, but is not limited to, statements concerning our objectives, our strategies to achieve those objectives, as well as statements made with respect to management’s beliefs, plans, estimates, projections and intentions, and similar statements concerning anticipated future events, results, circumstances, performance or expectations that are not historical facts. In some cases, forward-looking information can be identified by the use of forward-looking terminology such as “expects”, “estimates”, “outlook”, “forecasts”, “projection”, “prospects”, “intends”, “anticipates”, “believes”, or variations of such words and phrases or statements that certain actions, events or results “may”, “could”, “would”, “might”, “will”, “will be taken”, “occur” or “be achieved”. In addition, any statements that refer to expectations, intentions, projections or other characterizations of future events or circumstances contain forward-looking information. Statements containing forward-looking information are not historical facts but instead represent management’s expectations, estimates and projections regarding future events or circumstances. Forward-looking information in this news release include, among other things, statements relating to Aptose’s business in general; statements relating to the postponed Meeting and the timing thereof, the expected impact on the record date, the clearance from the SEC and the timing thereof the mailing of the proxy statement, form of proxy, letter of transmittal along with any additional required disclosure in connection with the Meeting and the timing thereof. Risks and uncertainties related to the transactions contemplated by the Transaction include, but are not limited to: the possibility that the Transaction will not be completed on the terms and conditions, or on the timing, currently contemplated, and that it may not be completed at all, due to a failure to obtain or satisfy, in a timely manner or otherwise, required regulatory, shareholder and Court approvals and other conditions to the completion of the Transaction or for other reasons; the risk that competing offers or acquisition proposals will be made; the negative impact that the failure to complete the Transaction for any reason could have on the price of the common shares of Aptose or on the business of Aptose; Hanmi Purchaser’s failure to pay the cash consideration at completion of the Transaction; the business of Aptose may experience significant disruptions, including loss of employees due to transaction related uncertainty, industry conditions or other factors; risks relating to employee retention; the risk of regulatory changes that may materially impact the business or the operations of Aptose; risks related to the diversion of management’s attention from Aptose’s ongoing business operations while the Transaction is pending; and other risks and uncertainties affecting Aptose, including those described in filings and reports Aptose may make from time to time with the Canadian securities authorities. Although we have attempted to identify important risk factors that could cause actual results to differ materially from those contained in forward-looking information, there may be other risk factors not presently known to us or that we presently believe are not material that could also cause actual results or future events to differ materially from those expressed in such forward-looking information. There can be no assurance that such information will prove to be accurate, as actual results and future events could differ materially from those anticipated in such information. No forward-looking statement is a guarantee of future results. Accordingly, you should not place undue reliance on forward-looking information, which speaks only as of the date made. The forward-looking information contained in this news release represents the Company’s expectations as of the date of this news release (or as the date they are otherwise stated to be made) and are subject to change after such date. However, the Company disclaims any intention or obligation or undertaking to update or revise any forward-looking information whether as a result of new information, future events or otherwise, except as required under applicable securities laws in Canada. All of the forward-looking information contained in this news release is expressly qualified by the foregoing cautionary statements. This announcement is for informational purposes only and does not constitute an offer to purchase or a solicitation of an offer to sell, or an offer to sell or a solicitation of an offer to buy, common shares of Aptose. For further information, please contact: Aptose Biosciences Inc. Susan Pietropaolo Corporate Communications & Investor Relations 201-923-2049 spietropaolo@aptose.com Released December 19, 2025

TUS+VEN+AZA triplet frontline therapy demonstrates high rates of efficacy and MRD-negative remissions in newly diagnosed AML patients with diverse mutationsSafety continues to be a notable hallmark of TUS-based therapies100% response rate (CR/CRh) at the two higher dose levels (80 and 120 mg TUS dose)CR/CRh observed in FLT3 wildtype subjects, representing ~70% of AML patientsCR/CRh observed in AML with TP53/complex karyotype, RAS, and MDS-related mutations SAN DIEGO and TORONTO, Dec. 06, 2025 (GLOBE NEWSWIRE) -- Aptose Biosciences Inc. (“Aptose” or the “Company”) (NASDAQ: APTO, TSX: APS), a clinical-stage precision oncology company developing highly differentiated targeted agents to treat hematologic malignancies, today featured clinical data for its lead compound tuspetinib (TUS) combined with standard dosing of venetoclax (VEN) and azacitidine (AZA) in a poster presentation at the 67th American Society of Hematology (ASH) Annual Meeting in Orlando, FL. Updated data from patients in the TUSCANY trial across all three cohorts, 40 mg, 80 mg or 120 mg TUS dose in TUS+VEN+AZA, reveal promising clinical safety and antileukemic activity and support the use of TUS in combination with standard of care treatment across a broad range of AML populations, including those with adverse mutations regardless of FLT3 mutation status. Poster title: “TUSCANY study demonstrates safety and efficacy of tuspetinib plus standard of care venetoclax and azacitidine in patients with newly diagnosed AML ineligible for induction chemotherapy” Key Findings and Messages: In newly diagnosed AML patients, TUS+VEN+AZA shows promising safety, tolerability and resilient efficacy, including MRD-negative remissions across a broad mutational spectrumHigh-quality clinical responses (CR/CRh): 90% across 40, 80 and 120 mg dose levels100% at the higher 80 mg and 120 mg dose levelsObserved in FLT3-WT, FLT3-ITD, and NPM1c genetic subgroupsObserved in biallelic TP53/complex karyotype and RAS adverse genetic subgroupsObserved in AML with MDS-related mutations MRD negativity: 78% by central flow cytometry in responding subjectsTUS targets VEN resistance mechanisms; inhibits kinase-driven abnormal signalingTwo subjects transitioned to stem cell transplantation and both returned for TUS maintenanceTUS+VEN+AZA triplet therapy was well tolerated with no dose-limiting toxicities (DLTs) across all evaluable TUS dose levels No DLTs including no prolonged myelosuppression for subjects in remission in Cycle 1No drug-related deaths, differentiation syndrome, QTc prolongation, or CPK elevation reported8/10 evaluable subjects experienced red cell and platelet transfusion independence for > 8 weeks after their best responseFebrile neutropenia was reported in 2 subjects (16.7%), with 1 subject related to TUS At the recently enrolled 160 mg dose level, preliminary findings show patients achieving early blast clearance with MRD-negativity and formal responses in the first few weeks of treatment (not included in poster data cut). “Tuspetinib, as part of a triple drug therapy, continues to perform well, achieving 100% clinical response in the two higher doses we have evaluated to date,” said Rafael Bejar, MD, PhD, Chief Medical Officer at Aptose. “We recently commenced treating patients at the highest dose level of 160 mg TUS and have already achieved early responses. With no dose-limiting toxicities and activity across diverse mutations, TUS+VEN+AZA targets AML’s greatest unmet needs and largest populations.” The ASH poster presentation is available here. About Tuspetinib Aptose’s lead compound tuspetinib is a convenient once daily oral agent that potently targets SYK, mutated and wild type forms of FLT3, mutated KIT, JAK1/2, and RSK2 kinases, while avoiding many typical toxicity concerns observed with other agents. The ongoing TUSCANY triplet Phase 1/2 study is designed to test various doses and schedules of TUS in combination with standard dosing of azacitidine and venetoclax in newly diagnosed patients with AML who are ineligible to receive induction chemotherapy. Data from the first three dose cohorts demonstrate safety, CRs and minimal residual disease (MRD) negativity across patients with diverse mutations. The early data showed that 9 out of 10 patients responded to the TUS triplet therapy, with 100% complete remission (CR/CRh) achieved in the 80mg and 120mg cohorts. Notably, patients with difficult-to-treat mutations in TP53, RAS and FLT3 genes also achieved a 100% CR/CRh rate. 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 without overlapping toxicities. The Company’s lead clinical-stage compound tuspetinib (TUS), is an oral kinase inhibitor that has demonstrated activity as 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 www.aptose.com. Forward Looking Statements This press release may contain forward-looking statements within the meaning of Canadian and U.S. securities laws, including, but not limited to, statements relating to the therapeutic potential of tuspetinib, its clinical development and safety profile including its tolerability and resilient efficacy, as well as 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 obtain the capital required for research and operations and to continue as a going concern; the inherent risks in early stage drug development including demonstrating efficacy; development time/cost and the regulatory approval process; the progress of our clinical trials; our ability to find and enter into agreements with potential partners; our ability to attract and retain key personnel; changing market conditions; inability of new manufacturers to produce acceptable batches of GMP in sufficient quantities; unexpected manufacturing defects; 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 spietropaolo@aptose.com