Luxeptinib

Highlights Progress in TUSCANY Clinical Trial of Tuspetinib in AML Triple Frontline TherapySAN DIEGO and TORONTO, May 08, 2025 (GLOBE NEWSWIRE) -- Aptose Biosciences Inc. (“Aptose” or the “Company”) (TSX: APS and 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), today announced financial results for the first quarter ended March 31, 2025, and provided a corporate update. “Our TUSCANY clinical trial of tuspetinib in combination with venetoclax (VEN) and azacitidine (AZA) for frontline treatment of newly diagnosed acute myeloid leukemia (AML) continues to deliver robust safety and response data, with support and enthusiasm from our clinical investigators,” said William G. Rice, Ph.D., Chairman, President and Chief Executive Officer of Aptose. “We recently escalated the TUS dose to 80 mg from the initial dose of 40 mg in the TUS+VEN+AZA triplet therapy. Three patients receiving the initial dose of 40 mg and three patients receiving the 80 mg dose all have achieved complete remissions (CRs*) and continue on treatment. We are especially encouraged that two patients having highly adverse TP53 mutations have achieved objective responses and remain on treatment.” Key Corporate Highlights Tuspetinib Data Reported from First Two Cohorts of TUSCANY Phase 1/2 Trial - Tuspetinib based TUS+VEN+AZA triplet therapy is being advanced in the TUSCANY Phase 1/2 trial with the goal of creating a one-of-a-kind frontline therapy for newly diagnosed AML patients that is safe and active across diverse AML populations (mutation agnostic triplet frontline therapy), including patients without FLT3 mutations (wildtype FLT3). Data from the first two cohorts, with a 40 mg or 80 mg dose of tuspetinib in the TUS+VEN+AZA combination, reveal promising clinical safety and antileukemic activity (press release here). In the first cohort, our newly diagnosed AML patients received the initial 40 mg dose of TUS as part of the TUS+VEN+AZA combination. No safety concerns or dose limiting toxicities (DLTs) were observed. Three patients experienced rapid bone marrow blast reductions to achieve CRs; one having biallelic mutated TP53, complex karyotype (CK) chromosomal abnormalities, and wildtype FLT3; one having an IDH2 mutation wildtype FLT3; and one having FLT3-ITD and mutated NPM1. Clinical sites or central labs reported all these patients also achieved MRD-negative status. The fourth patient at the 40 mg dose of TUS, did not achieve a complete remission and discontinued the study. The first three patients continue on treatment. In the second cohort, three newly diagnosed AML patients having diverse mutation profiles have received the 80 mg dose of TUS, as part of the TUS+VEN+AZA combination. To date, no safety concerns or DLTs have been reported. All patients at the 80 mg dose of TUS rapidly achieved CRs; one patient with biallelic TP53 mutations and a complex karyotype and wildtype FLT3 status, a second patient having mutated DDX41 and wildtype FLT3 status, and a third patient having FLT3-ITD and NPM1 mutations. All three patients at the 80 mg dose of TUS are early in their course of treatment, are expected to achieve normal blood count recovery as their leukemia is resolved, and MRD status will be monitored as the patients move through their courses of therapy. OTC Exchange - Aptose common shares (“the Common Shares”) are now listed for trading on the OTC Markets (OTC) under the ticker “APTOF,” in addition to the Company’s continued listing on the Toronto Stock Exchange (TSX) under the symbol “APS”. This significantly expands Aptose accessibility for U.S.-based investors and enhances overall share liquidity by enabling trading through U.S. broker-dealers. Listing on the OTC Markets is part of Aptose’s strategy to align with TSX capital markets while increasing visibility and participation from the U.S. investment community. Aptose’s Common Shares were delisted from The Nasdaq Stock Market effective April 2, 2025 because of non-compliance with the Exchange’s equity requirements. Completed and Planned Value-Creating Milestones 2025: 1H Reported safety and efficacy with 40mg TUS+VEN+AZAReported safety and efficacy with 80mg TUS+VEN+AZA 2025: European Hematology Association (EHA) Report maturing data from TUS+VEN+AZA triplet study 2025: American Society of Hematology (ASH) Report response rate and durability of TUS+VEN+AZA tripletSelect TUS dose for TUS+VEN+HMA triplet Ph 2/3 PIVOTAL trialsPrepare for initiation of Ph 2/3 PIVOTAL program FINANCIAL RESULTS OF OPERATIONSAptose Biosciences Inc.Statements of Operations Data(unaudited)($ in thousands, except for share and per share data) Quarter endedMarch 31, 2025 2024 Expenses: Research and development$2,364 $6,445 General and administrative 3,097 3,315 Operating expenses 5,461 9,760 Other (loss) income, net (82) 120 Net loss$(5,543) $(9,640) Net loss per share, basic and diluted$(2.61) $(22.02) Weighted average number ofcommon shares outstanding used incomputing net loss per share, basicand diluted 2,126,287 437,750 Net loss for the quarter ended March 31, 2025 decreased by $4.1 million to $5.5 million, as compared to $9.6 million for the comparable period in 2024. Aptose Biosciences Inc.Balance Sheet Data(unaudited)($ in thousands) March 31,2025 December 31,2024 Cash, cash equivalents and restricted cashequivalents$4,743 $6,707 Working capital 651 5,053 Total assets 7,467 10,127 Long-term liabilities 8,542 10,193 Accumulated deficit (546,510) (540,967) Shareholders’ deficit (7,393) (4,543) Total cash, cash equivalents and restricted cash equivalents as of March 31, 2025 were $4.7 million. Based on current operations, the Company expects that cash on hand and available capital provides the Company with sufficient resources to fund planned Company operations including research and development until the end of May 2025. The Company is proactively implementing financing and cost reduction efforts to extend its cash runway. As of May 1, 2025, we had 2,552,429 Common Shares issued and outstanding. In addition, there were 38,736 Common Shares issuable upon the exercise of outstanding stock options and there were 1,267,585 Common Shares issuable upon the exercise of the outstanding warrants. RESEARCH AND DEVELOPMENT EXPENSES Research and development expenses for the three months ended March 31, 2025 and 2024 were as follows: Quarter ended (in thousands) March 31,2025 March 31,2024 Program costs – Tuspetinib$1,479 $3,923 Program costs – Luxeptinib 98 208 Program costs – APTO-253 - 22 Personnel related expenses 646 1,924 Stock-based compensation 141 328 Depreciation of equipment - 10 Total$2,364 $6,445 Research and development expenses decreased by $4.1 million to $2.3 million for the quarter ended March 31, 2025, as compared to $6.4 million for the comparable period in 2024. Changes to the components of our research and development expenses presented in the table above are primarily as a result of the following events: Program costs for tuspetinib were $1.5 million for the quarter ended March 31, 2025, compared with $3.9 million for the comparable period in 2024. The lower program costs for tuspetinib in the current period are attributable to reduced activity in our APTIVATE clinical trial, reduced manufacturing activity, and related expenses. Program costs for luxeptinib decreased by approximately $0.1 million primarily due to lower clinical trial and manufacturing activities. Program costs for APTO-253 were zero. This was due to the Company’s decision to discontinue further development of APTO-253. Personnel-related expenses decreased by $1.3 million due to lower headcount for research and development personnel in the current quarter. Stock-based compensation decreased by approximately $0.2 million in the quarter ended March 31, 2025, primarily due stock options forfeited and/or vested in prior periods that are no longer being expensed resulting in lower expense in the current period. 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 www.aptose.com. Forward Looking Statements This press release contains forward-looking statements within the meaning of Canadian and U.S. securities laws, including, but not limited to, statements regarding the Company’s clinical development plans, the clinical potential, anti-cancer activity, therapeutic potential and applications and safety profile of tuspetinib, clinical trials, upcoming milestones, financing activities, expectations regarding capital available to the Company to fund planned Company operations, the Company’s cash runway, use of proceeds from financings, and statements relating to the Company’s plans, objectives, expectations and intentions and other statements including words such as “continue”, “expect”, “intend”, “will”, “hope”, “should”, “would”, “may”, “potential” 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; 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 and economic conditions; unexpected manufacturing defects, the evolving regulatory and political landscape and the funding of government programs and other risks detailed from time-to-time in our ongoing current reports, quarterly filings, annual information forms, annual reports and 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 PietropaoloCorporate Communications & Investor Relations201-923-2049spietropaolo@aptose.com

Tuspetinib Triple Drug Frontline Therapy Advancing in TUSCANY Clinical Trial Results to Date Highlight TUS Potential as an Ideal Third Drug to Include in AML Triplet Therapy Aptose Signs Debt Conversion Agreement with Hanmi SAN DIEGO and TORONTO, March 28, 2025 (GLOBE NEWSWIRE) -- Aptose Biosciences Inc. (“Aptose” or the “Company”) (NASDAQ: APTO, TSX: APS), 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), today announced financial results for the year ended December 31, 2024, and provided a corporate update. "During 2024 and into 2025, we continue to advance our lead investigational drug tuspetinib in combination with venetoclax (VEN) and azacitidine (AZA) for frontline treatment of newly diagnosed acute myeloid leukemia (AML),” said William G. Rice, Ph.D., Chairman, President and Chief Executive Officer of Aptose. “Tuspetinib brings favorable safety and broad activity across AML genetic subtypes to the TUS+VEN+AZA triplet therapy, which already has achieved complete remissions (CRs) in difficult-to-treat and underserved TP53-mutated/CK AML and FLT3-wildtype AML patients in our ongoing TUSCANY trial. We look forward to sharing more data as the trial evolves.” Key Corporate Highlights Tuspetinib Phase 1/2 TUSCANY Trial Well Under Way with Responses Noted - Tuspetinib based TUS+VEN+AZA triplet therapy is being advanced in the TUSCANY Phase 1/2 trial with the goal of creating an improved frontline therapy for newly diagnosed AML patients that is active across diverse AML populations (mutation agnostic triplet frontline therapy), including FLT3-wildtype AML. This activity differentiates TUS from other drugs in development. In January 2025, Aptose announced initiation of dosing in the first TUSCANY trial cohort with the starting dose of 40 mg TUS in combination with standard-of-care doses of VEN+AZA. At 40 mg TUS, the triplet therapy achieved complete remissions (CRs) in difficult-to-treat TP53-muated AML and FLT3-wildtype AML patients, including a measurable residual disease (MRD) negative remission (press release here). In February 2025, amid the promising early results and favorable safety from patients treated at the 40 mg dose level, the Cohort Safety Review Committee (CSRC) monitoring the TUSCANY trial approved escalating to 80 mg TUS in the triplet therapy (press release here). Subjects have now begun treatment at the 80 mg TUS dose level of the triplet therapy and further recruitment is under way. No significant safety concerns have been reported to date, including no prolonged myelosuppression of subjects in remission. This TUS+VEN+AZA triplet therapy study in newly diagnosed AML was supported with robust safety and efficacy data from the TUS single agent dose escalation study and the TUS+VEN doublet APTIVATE study in relapsed or refractory (R/R) AML, both of which were completed during 2024 after treating more than 170 patients.Financing Activity – During 2024, Aptose completed several financings for a total of approximately $37 million to support the TUS-based TUS+VEN+HMA triplet therapy development for AML. This included a $10 million loan Facility Agreement with Hanmi Pharmaceutical Co. Ltd. (“Hanmi”). Subsequently in March 2025, Hanmi and Aptose executed a Debt Conversion Agreement to convert a portion of the debt into equity, subject to Hanmi owning no more than 19.99% of the issued and outstanding common shares of Aptose. Therefore, an amount of $1.5 million has been converted into 409,063 common shares as of this date. Beyond the $10 million, Aptose and Hanmi are negotiating a new tuspetinib co-development collaboration agreement intended to provide additional funding to accelerate clinical development of tuspetinib. Aptose licensed tuspetinib from Hanmi Pharmaceutical in November 2021.Aptose Signs CRADA with NCI – In December, Aptose announced that it entered into a Cooperative Research and Development Agreement (“CRADA”) with the National Cancer Institute (NCI), part of the National Institutes of Health (press release here). Under the CRADA, the NCI and Aptose will collaborate on the clinical development of TUS, an inhibitor of key signaling kinases involved in myeloid malignancies, in the NCI Cancer Therapy Evaluation Program (CTEP) sponsored myeloMATCH trials employing combinations of targeted therapy for the treatment of molecularly defined AML and myelodysplastic syndromes (MDS) populations. These trials will be conducted by NCI's National Clinical Trials Network (NCTN), with the participation of the NCI Community Oncology Research Program (NCORP) in the U.S. and Canada.Aptose Meets Nasdaq Minimum Bid Compliance – Earlier this month, Aptose announced that it received a written notification from the Listing Qualifications Department of The Nasdaq Stock Market, LLC notifying the Company that it is in compliance with Nasdaq’s minimum bid price requirement (press release here). On March 14, 2025, Nasdaq confirmed that, for ten consecutive business days, the closing bid price of the Company’s common shares has been $1.00 per share or greater. Accordingly, the Company has regained compliance with Listing Rule 5550(a)(2). Separately, Aptose is not in compliance with the $2.5 million shareholders equity requirement and is operating under an exception granted by the Nasdaq Hearing Panel, which provides Aptose additional time to regain compliance, although there is no assurance that the Company will successfully achieve full compliance with the Nasdaq shareholders equity requirement. Completed and Planned Value-Creating Milestones 2024 Accomplishments Completed $10 million loan from Hanmi as Advance on CollaborationCompleted $8 million S-1 financingExecuted CRADA with NCI MyeloMATCH for tuspetinib in AML/MDSInitiated dosing of TUS+VEN+AZA triplet therapy in newly diagnosed AML patients in TUSCANY trialASH: Reported CR/Safety from APTIVATE TUS and TUS+VEN trialASH: Reported dosing accrual from TUS+VEN+AZA triplet therapy trial 2025: 1H Demonstrated safety and efficacy with 40mg TUS+VEN+AZA in triplet therapy trialDosing 80mg TUS in TUS+VEN+AZA dose cohort in triplet therapy trialExecuted Debt Conversion agreement with HanmiExpect to report CR/MRD/Safety data from TUS+VEN+AZA triplet therapy trialExpect to execute Hanmi/Aptose CollaborationEHA2025 Congress - Report maturing data readout from TUS+VEN+AZA triplet therapy trial 2025: 2H Select optimal TUS doses for TUS+VEN+HMA triplet therapy Ph 2/3 pivotal trialsPrepare for Ph 2 portion of Ph 2 / Ph 3 pivotal programAmerican Society of Hematology (ASH) Update FINANCIAL RESULTS OF OPERATIONSAptose Biosciences Inc.Statements of Operations Data(unaudited)($ in thousands, except for share and per share data) Year ended December 31, 20242023Expenses: Research and development$15,103 $36,765 General and administrative 11,154 15,591 Operating expenses 26,257 52,356 Other income, net 827 1,149 Net loss$(25,430)$(51,207) Net loss per share, basic and diluted$(36.38)$(227.43)Weighted average number of common shares outstanding used in computing net loss per share, basic and diluted 698,980 225,154 Net loss for the year ended December 31, 2024 decreased by $25.8 million to $25.4 million, as compared to $51.2 million for the comparable period in 2023. Aptose Biosciences Inc.Balance Sheet Data(unaudited)($ in thousands) December 31, December 31, 2024 2023Cash, cash equivalents and restricted cash equivalents$6,707 $9,252 Working capital 5,071 (3,375)Total assets 10,127 12,989 Long-term liabilities 10,211 621 Accumulated deficit (540,967) (515,537) Shareholders’ deficit (4,543) (2,901) Total cash, cash equivalents and restricted cash equivalents as of December 31, 2024, were $6.7 million. Based on current operations, the Company expects that cash on hand and available capital provides the Company with sufficient resources to fund planned Company operations including research and development until April 2025.As of March 21, 2025, we had 2,552,429 Common Shares issued and outstanding. In addition, there were 39,219 Common Shares issuable upon the exercise of outstanding stock options and there were 1,267,585 Common Shares issuable upon the exercise of the outstanding warrants. RESEARCH AND DEVELOPMENT EXPENSES The research and development expenses for the years ended December 31, 2024 and 2023 were as follows: Year ended December 31,(in thousands)20242023Program costs – Tuspetinib$9,606 $24,925Program costs – Luxeptinib 422 3,510Program costs – APTO-253 (19) 40Personnel related expenses 4,735 6,878Stock-based compensation 346 1,373Depreciation of equipment 13 39Total$15,103 $36,765 Research and development expenses decreased by $21.7 million to $15.1 million for year ended December 31, 2024, as compared to $36.8 million for the comparable period in 2023. Changes to the components of our research and development expenses presented in the table above are primarily as a result of the following events: Program costs for tuspetinib were $9.6 million for the year ended December 31, 2024, compared with $24.9 million for the comparable period in 2023. The lower program costs for tuspetinib in the current year were due to reduced activity in our APTIVATE clinical trial, reduced manufacturing costs, and related expenses. In the comparable period in 2023, Tuspetinib program costs included the healthy volunteer study, which was completed in the same year.Program costs for luxeptinib decreased by approximately $3.1 million primarily due to lower clinical trial and manufacturing activities.Program costs for APTO-253 decreased by approximately $59 thousand. This reduction was due to the Company’s decision to discontinue further development of APTO-253.Personnel-related expenses decreased by $2.1M due to lower headcount 2024.Stock-based compensation decreased by approximately $1.0 million in the year ended December 31, 2024, primarily due to stock options granted with lower grant date fair values when compared to the options granted in the prior period, coupled with option forfeitures recorded in the current year. 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 www.aptose.com. Forward Looking Statements This press release contains forward-looking statements within the meaning of Canadian and U.S. securities laws, including, but not limited to, statements regarding the Company’s clinical development plans, the clinical potential, anti-cancer activity, therapeutic potential and applications and safety profile of tuspetinib, clinical trials, the enrollment in clinical trials and the data therefrom, the submission of a compliance plan to Nasdaq and available options to regain compliance, upcoming milestones and presentation of additional data, financing activities, expectations regarding capital available to the Company to fund planned Company operations, maintenance of the Nasdaq and TSX listings, use of proceeds from financings, the conversion of debt into equity contemplated by the Debt Conversion Agreement entered into with Hanmi, the negotiation of a co-development collaboration agreement with Hanmi, the collaboration with the NCI for the clinical development of tuspetinib and statements relating to the Company’s plans, objectives, expectations and intentions and other statements including words such as “continue”, “expect”, “intend”, “will”, “hope” “should”, “would”, “may”, “potential” 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; 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 and economic conditions; unexpected manufacturing defects, the evolving regulatory and political landscape and the funding of government programs and other risks detailed from time-to-time in our ongoing current reports, 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