On August 18, 2025 Aptose Biosciences Inc. ("Aptose" or the "Company") (OTC: APTOF, TSX: APS), a clinical-stage precision oncology company developing the tuspetinib (TUS)-based triple drug frontline therapy to treat patients with newly diagnosed AML, reported a data update from the Phase 1/2 TUSCANY trial in newly diagnosed AML (Press release, Aptose Biosciences, AUG 18, 2025, View Source [SID1234655342]). The trial was initiated in December 2024, and the growing body of positive data includes the recently completed third cohort of 120 mg TUS in the TUS+VEN+AZA triplet therapy. Data to date from ten (10) patients across all three cohorts, 40 mg, 80 mg or 120 mg TUS dose in TUS+VEN+AZA, support the use of TUS with standard of care treatment across all AML populations, including those carrying mutations that are the most difficult to treat and those with mutated and unmutated (wildtype) FLT3 genes.

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The TUS+VEN+AZA triplet is being developed as a safe and well-tolerated mutation agnostic frontline therapy to treat large, mutationally diverse populations of newly diagnosed AML patients who are ineligible to receive induction chemotherapy. At the 120 mg TUS dose level in combination with VEN+AZA, as with the prior reported 40 mg and 80 mg TUS dose cohorts, no significant safety concerns or dose limiting toxicities (DLTs) have been observed in the TUSCANY trial, including no prolonged myelosuppression in Cycle 1 of subjects in remission, no reports of drug-related QTc prolongation or differentiation syndrome (DS), and no treatment-related deaths. Nine out of ten dosed patients remain on study across all dose cohorts and enrollment is being advanced to the 160 mg TUS dose level following the Cohort Safety Review Committee (CSRC) meeting.

"We already have data from three different TUS dose levels in the TUSCANY trial, and the data continue to strengthen at higher doses of TUS and over time. We are building a strong case for TUS+VEN+AZA as a triplet frontline therapy of choice to address a broad AML population, including subgroups with the most adverse of mutations," said William G. Rice, Ph.D., Chairman, President and Chief Executive Officer of Aptose.

Data highlights:

Comparison of CR/CRh1 Response rates2-5:

VEN+AZA2 TUS+VEN+AZA
All subjects 65% 90% (9/10)
NPM1-mutant 67% 100% (2/2)
FLT3-ITD 61% 100% (2/2)
TP53-mutant 52% 100% (2/2)

Comparison of MRD-negativity6 rates among All Subjects and among CR/CRh Responders3:

VEN+AZA2,3 TUS+VEN+AZA
Among All Subjects 23.4% 70% (7/10)
Among CR/CRh Responders 40.9% 78% (7/9)

Comparison of MRD-negativity rates among more difficult-to-treat Patient Subpopulations defined as Lower Benefit (TP53-mutated) and Intermediate Benefit (FLT3-ITD or RAS-mutated) relative to VEN+AZA5:

VEN+AZA3,5 TUS+VEN+AZA
Intermediate Benefit 27.9% 100% (3/3)
Lower Benefit 14.5% 100% (2/2)

TUS+VEN+AZA – CR/CRh and MRD-negativity rates among Subjects with Adverse Mutations:

TP53, FLT3-ITD, RAS mutations: Achieved CR/CRh and MRD-negativity
100% (5/5)

"As illustrated in the data highlights, the addition of TUS to VEN+AZA appears to boost response rates and MRD-negativity while maintaining favorable safety and tolerability," said Rafael Bejar, M.D., Ph.D., Chief Medical Officer of Aptose, "and the 100% CR/CRh and 100% MRD-negativity rates among the five biallelic TP53-mutant, FLT3-ITD, and RAS-mutant AML cases are exciting to see, as this can correlate with longer overall survival. We have observed a trend towards achieving CRs more quickly at the higher dose levels, so we are keen to see the activity as we advance into the 160 mg TUS dose cohort."

Key messages:

Addition of TUS to VEN+AZA demonstrates excellent CR/CRh rates
100% CR/CRh among all subjects treated at 80 mg and 120 mg TUS dose levels
Appear to be achieving CR earlier with 120 mg TUS than with 40 mg or 80 mg
Addition of TUS to VEN+AZA demonstrates excellent MRD-negativity rates
MRD-negativity in 7 of 9 (78%) already achieved in patients who responded to therapy
Expect patient survival to be extended with continued long-term treatment
Excellent safety and well tolerated with no dose-limiting toxicities (No DLT) at completed dose levels
Broad-spectrum activity including patients with adverse TP53, RAS and FLT3-ITD mutations
No loss of MRD-negativity observed to date, including in one patient with over 7 months of follow up
MRD-negativity and remissions continue to mature over time on therapy
No relapses reported to date and no treatment related deaths
The only non-responder was a patient at the initial TUS dose level (40 mg) that did not achieve TUS exposures previously associated with response
Additional data are included in the new Aptose corporate presentation here.

TUSCANY: TUS+VEN+AZA Triplet Phase 1/2 Study

The 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, durable, and well tolerated.

The TUSCANY triplet Phase 1/2 study, being conducted at 10 leading U.S. clinical sites by elite clinical investigators, is designed to test various doses and schedules of TUS in combination with standard dosing of AZA and VEN for patients with AML who are ineligible to receive induction chemotherapy. A convenient, once daily oral agent, TUS is being administered in 28-day cycles. Multiple U.S. sites are enrolling in the TUSCANY trial with anticipated enrollment of 18-24 patients by late 2025. Data will be released as it becomes available.

More information on the TUSCANY Phase 1/2 study can be found on www.clinicaltrials.gov (here: View Source).