Aptose Presents Highlights from Clinical Update Webcast Featuring Latest Available Data on AML Drug Tuspetinib

• Tuspetinib (TUS) Combination with Venetoclax (VEN) Clinical Findings Highlighted  
• TUS Targets VEN Resistance Mechanisms to Re-sensitize VEN Failure Patients to VEN
• 44% ORR with TUS/VEN in Difficult-to-Treat VEN Failure R/R AML Patients
• 48% ORR with TUS/VEN in Heavily Pre-treated R/R AML Patients
• Consistent Favorable Safety with TUS Single Agent and TUS/VEN Doublet

SAN DIEGO and TORONTO, Oct. 30, 2023 (GLOBE NEWSWIRE) -- Aptose Biosciences Inc. (“Aptose” or the “Company”) (NASDAQ: APTO, TSX: APS), a clinical-stage precision oncology company developing highly differentiated oral kinase inhibitors to treat hematologic malignancies, released highlights from a clinical update event held today, October 30, 2023, in conjunction with the European School of Haematology (ESH) 6^th International Conference: Acute Myeloid Leukemia “Molecular and Translational”: Advances in Biology and Treatment, being held in Estoril, Portugal (the “ESH 2023 Conference”).

The webcast event featured a comprehensive review of up-to-date clinical data for Aptose’s lead compound tuspetinib (TUS) by Rafael Bejar, MD, PhD, Aptose’s Chief Medical Officer, and featured Naval G. Daver, MD, Professor, Director Leukemia Research Alliance Program, Department of Leukemia, The University of Texas MD Anderson Cancer Center, Houston, TX. Dr. Daver is the lead investigator on Aptose’s APTIVATE trial of tuspetinib and is recognized for significant achievements in the development of novel acute myeloid leukemia (AML) treatments, including several combination therapies.

Tuspetinib (TUS) is a once-daily, oral, precision targeted kinase inhibitor that suppresses select kinases that drive the proliferation of AML. These key kinase targets include the SYK, FLT3, JAK1/2, mutant forms of KIT, RSK2, and the TAK1-TAB1 kinases operative in AML, while other kinases are avoided to promote safety.

AML care has shifted toward venetoclax (VEN) containing combination regimens and a new population of difficult-to-treat VEN relapsed patients (“VEN failures”) is emerging. Tuspetinib’s safety, activity, mechanism of action, and convenient dosing make it ideal for combination therapy. Importantly, TUS directly targets VEN resistance mechanisms (suppresses mutated FLT3, mutated KIT, SYK and mutated JAK1/2 of the JAK/STAT pathway, RSK2 of the RAS/MAPK pathway, key oncogenic growth and proliferation signals, and MCL-1 expression). This means that TUS targets pathways and may lead to re-sensitizing VEN-resistant cells to VEN when given in combination. TUS/VEN may safely and successfully treat these VEN failures, as we already have observed clinically, and an accelerated approval path may be available for VEN failure relapsed or refractory (R/R) AML patients treated with TUS/VEN.