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Aptose Receives Fast Track Designation for HM43239 in

SAN DIEGO and TORONTO, May 04, 2022 (GLOBE NEWSWIRE) — Aptose Biosciences Inc. (“Aptose” or the “Company”) (NASDAQ: APTO, TSX: APS), a clinical-stage precision oncology company developing kinase inhibitors for treating hematological malignancies, today announced that the U.S. Food and Drug Administration (FDA) has granted Fast Track Designation to HM43239, an oral myeloid kinoma inhibitor, for the treatment of patients with relapsed or refractory acute myeloid (R/R). leukemia (AML) with FLT3 mutation. Currently, an international Phase 1/2 clinical trial is underway for HM43239 in the R/R AML patient population. HM43239 received orphan drug designation from the FDA for the treatment of acute myeloid leukemia in 2018.

“Fast Track status recognizes the potential of HM43239 to address an unmet need in AML patient populations and supports our efforts as we progress it towards a potential registration study,” said William G. Rice, Ph.D., President and CEO. “HM43239, which potently inhibits all tested forms of FLT3 and SYK and JAK-driven pathways, has already delivered complete remissions in a wide variety of patients with relapsed or refractory AML in a Phase 1/2 clinical trial in course, including patients who have previously failed other FLT3 inhibitory agents. The Fast Track designation will help facilitate drug development.

About the Fast Track designation

Fast Track is a process designed to facilitate the development and expedite the review of drugs to treat serious conditions and address an unmet medical need. The goal is to get important new drugs to the patient sooner. Once a drug receives Fast Track designation, early and frequent communication between the FDA and the sponsor is encouraged throughout the drug development and review process. The frequency of communication ensures that questions and issues are resolved quickly, often leading to earlier patient approval and access to medications. Visit the FDA website for more information.

About HM43239

HM43239 is a potent, genotype-independent oral small molecule inhibitor of a constellation of kinases active in myeloid malignancies and known to be involved in tumor proliferation, treatment resistance and differentiation. Currently under development for the treatment of patients with acute myeloid leukemia (AML), HM43239 is a potent inhibitor of FLT3, SYK, mutant forms of cKIT, JAK1/2 and other kinases. Regarding FLT3, HM43239 is very active live against internal tandem duplication (ITD) of FLT3, as well as resistance-conferring tyrosine kinase domain (TKD) D835 and gatekeeper (F691) mutations. invivo Murine xenograft models suggest superior antitumor activity and favorable tolerance compared to established kinase inhibitor in AML, including gilteritinib (FLT3 inhibitor) and entospletinib (SYK inhibitor). Besides, live xenograft models suggest synergy with inhibitors of DNMT, BCL-2 and other key therapeutic targets, highlighting the combinatorial optionality of HM43239 in AML. In an ongoing international Phase 1/2 clinical trial, HM43239 achieved complete remissions in a variety of patients with relapsed or refractory AML and continues to be a well-tolerated oral agent.

About Aptose

Aptose Biosciences is a clinical-stage biotechnology company engaged in the development of personalized therapies addressing unmet medical needs in oncology, with an initial focus on hematology. The Company’s pipeline of small molecule cancer therapeutics includes products designed to provide single-agent efficacy and to enhance the efficacy of other cancer therapies and regimens without overlapping toxicities. The Company has two clinical-stage investigational products in development for hematological malignancies: HM43239, an oral myeloid kinome inhibitor in an international phase 1/2 trial in patients with relapsed or refractory acute myeloid leukemia (AML); and luxeptinib, an oral, lymphoid and myeloid kinome inhibitor, in a Phase 1 a/b trial in patients with relapsed or refractory B-cell malignancies who have failed or are intolerant to standard therapies, and in a trial of separate Phase 1 a/b in patients with relapsed or refractory AML or high-risk myelodysplastic syndrome (MDS). For more information, visit www.aptose.com.

Forward-looking statements

This press release contains forward-looking statements within the meaning of Canadian and United States securities laws, including, but not limited to, statements regarding the clinical potential and development of HM43239 and statements relating to the growth, plans, goals, expectations and intentions of the Company and other statements including words such as “continue”, “expect”, “intend”, “will”, “hope”, “should”, “could”, “could”, “potential” and other similar expressions. These statements reflect our current views regarding future events and are subject to risks and uncertainties and are necessarily based on a number of estimates and assumptions which, although considered reasonable by us, are inherently subject to change. important business, economic, competitive, political changes and social uncertainties and hazards. 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. These factors could include, among others: our ability to obtain capital required for research and operations; the risks inherent in early-stage drug development, including demonstration of efficacy; development time/cost and 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; inability of new manufacturers to produce acceptable GMP batches in sufficient quantities; unexpected manufacturing defects; the potential impact of the COVID-19 pandemic and other risks detailed from time to time in our 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 forth in the section titled “Risk Factors” in our filings with Canadian securities regulators and the United States Securities and Exchange Commission under should these forward-looking statements prove to be incorrect, the actual results may differ 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 undertake no 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 place undue reliance on forward-looking statements due to the inherent uncertainty therein.

For more information, please contact:

Aptose Biosciences Inc. LifeSci Advisors, LLC
Susan Pietropaolo Dan Ferry, General Manager
Corporate Communication and Investor Relations 617-535-7746
201-923-2049 [email protected]
[email protected]