APTO News & Events

Aptose Biosciences featured clinical data for its lead compound tuspetinib combined with standard dosing of venetoclax and azacitidine 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. 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 spectrum; High-quality clinical responses: 90% across 40, 80 and 120 mg dose levels, 100% at the higher 80 mg and 120 mg dose levels, Observed in FLT3-WT, FLT3-ITD, and NPM1c genetic subgroups, Observed in biallelic TP53/complex karyotype and RAS adverse genetic subgroups, Observed in AML with MDS-related mutations; MRD negativity: 78% by central flow cytometry in responding subjects; TUS targets VEN resistance mechanisms; inhibits kinase-driven abnormal signaling; Two subjects transitioned to stem cell transplantation and both returned for TUS maintenance; TUS+VEN+AZA triplet therapy was well tolerated with no dose-limiting toxicities across all evaluable TUS dose levels; 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.

Aptose Biosciences announced data from its Phase 1/2 TUSCANY trial in newly diagnosed AML patients treated with tuspetinib in combination with standard of care dosing venetoclax and azacitidine in an oral presentation at the European Hematology Association Congress, being held June 12-15, 2025, in Milan, Italy. The TUS+VEN+AZA triplet is being developed as a mutation agnostic frontline therapy to treat large, mutationally diverse populations of newly diagnosed AML patients who are ineligible to receive induction chemotherapy. Dr. Gabriel Mannis, Associate Professor of Medicine, Stanford University School of Medicine, and an investigator in the TUSCANY study, reported safety and efficacy data from the first two dose cohorts at 40 mg of TUS or 80 mg of TUS in the TUS+VEN+AZA triplet. Dr. Mannis also noted three patients were rapidly enrolled on the third dose cohort of 120 mg TUS in the TUS+VEN+AZA triplet, and that no DLTs have been observed to date. The oral presentation at EHA included updated safety, complete remission, minimal residual disease assessments, and longer duration of follow-up: Title: TUSCANY Study of Safety and Efficacy of Tuspetinib Plus Standard of Care Venetoclax and Azacitidine in Study Participants with Newly Diagnosed AML Ineligible for Induction Chemotherapy. Key findings: To date, ten newly diagnosed AML patients have received the TUS+VEN+AZA combination: Four received the 40 mg dose of TUS, three received the 80 mg dose of TUS, and three received the 120 mg dose of TUS; At the initial dose of 40 mg TUS, with patients on longest duration of drug: Three subjects achieved CRs and were MRD-negative, including Patient with FLT3-ITD; Patient with FLT3-WT; Patient with TP53/CK. At the 80 mg TUS dose level: All three patients already achieved composite complete remissions; A TP53-mutated/CK AML patient achieved an early CRi; Too early in treatment for final MRD assessment. At the 120 mg TUS dose level: All three patients at the 120 mg TUS dose level remain on therapy; Too early in treatment for formal response and MRD assessments; Regardless of mutation status, TUS is active in newly diagnosed AML patients. MRD-negative responses achieved across diverse genetic populations, including adverseTP53 mutations and CK. Responses continue to evolve, and the triplet continues to be well tolerated with no DLTs. TUS can be administered safely with standard-of-care dosing of VEN/AZA. TUS PK properties not altered by VEN, AZA, antifungals or food. No prolonged myelosuppression in Cycle 1 in the absence of AML. No treatment-related deaths; all 10 subjects treated to date remain alive. No treatment related QTc prolongation, CPK elevations, differentiation syndrome or non-hematologic SAEs.

Aptose Biosciences reported updated and new data from Aptose's Phase 1/2 TUSCANY trial in newly diagnosed acute myeloid leukemia patients dosed with a 40 mg or 80 mg dose of tuspetinib in combination with standard of care dosing of venetoclax and azacitidine. The TUS+VEN+AZA triplet is being developed as a safe and mutation agnostic frontline therapy to treat large, mutationally diverse populations of newly diagnosed AML patients who are ineligible to receive induction chemotherapy. Earlier this year, Aptose announced the initiation of the TUSCANY trial and dosing in newly diagnosed AML patients at an initial dose of 40 mg TUS in the first cohort of four patients. The second cohort of patients is now receiving 80 mg TUS. 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. To date, four newly diagnosed AML patients received the initial dose of TUS as part of the combination. Notably, a patient with biallelic TP53 mutations and a complex karyotype and FLT3-wildtype achieved a complete remission (CR) and the clinical site reported no measurable residual disease in this patient. One FLT3-wildtype patient having an IDH-2 mutation achieved a CR and MRD-negative status. Another FLT3-wildtype patient achieved a CRi during Cycle 1 and MRD-negative status. The first three patients continue on treatment, while a fourth patient did not respond at this 40 mg dose level of TUS and was discontinued. The 40 mg dose of the TUS+VEN+AZA triplet remains safe, and no dose-limiting toxicities have been reported. To date, three newly diagnosed AML patients having diverse mutation profiles have received the 80 mg of TUS, as part of the TUS+VEN+AZA combination. The 80 mg TUS dose has been considered the optimal dose that has demonstrated safety and consistent blood exposure levels that exert potent antileukemic activity. All patients achieved blast reductions in Cycle 1 that met the criteria for complete remissions and continue on treatment. Notably, another TP53-mutated/CK and FLT3-wildtype patient achieved blast reductions that met CRi criteria in Cycle 1 and is now receiving additional therapy in Cycle 2. The second patient, having FLT3-wildtype status, achieved a CR. The third patient, having FLT3-ITD and NPM1 mutations and entering the trial with a 75% bone marrow blast count, achieved a CRi. All three patients are early in their course of treatment and are expected to show further improvements in their disease status as they are all continuing with treatment, and MRD status will be monitored as the patients move through their courses of therapy. The 80 mg dose of TUS, as part of the TUS+VEN+AZA triplet, continues to show favorable safety with no dose-limiting toxicities having been reported. "The treatment paradigm for AML is shifting to triplet combination therapy," said Rafael Bejar, CMO. "We have always maintained that tuspetinib, with its notable safety profile and ability to treat the larger, difficult-to-treat AML populations with high-risk mutations, could be an ideal drug for a triplet combination therapy in the frontline setting. With the majority of patients already achieving complete responses -- including early responses in patients with adverse mutations -- the clinical findings to date are bearing that out."

Aptose Biosciences announced that the Nasdaq Hearings Panel has determined to delist the common shares of the Company from The Nasdaq Stock Market. Under the terms of the Panel's December 17, decision in this matter, the Company was required to demonstrate compliance with the Exchange's equity requirement in Listing Rule 5550(b)(1) on or before March 31. As indicated in the Decision, March 31st represented the full extent of the Panel's discretion to grant continued listing while the Company was non-compliant with the Equity Rule. On March 31, through its advisor, the Company confirmed that it had been unable to regain compliance with the Equity Rule by that date. Accordingly, the Panel has determined to delist the Company's common shares from Nasdaq and will suspend trading in those securities effective at the open of business on April 2, 2025. The Company and board will review all available options, including an appeal to the determination, but will continue to execute its business plan and will seek to list on a U.S. national Securities Exchange at the appropriate time. Aptose's shares remain listed on TSX under the symbol "APS".