Moleculin Biotech has reported a 37% preliminary blinded composite complete remission rate in 62 evaluable patients from Part A of the Phase 2/3 MIRACLE trial in relapsed or refractory acute myeloid leukemia. The same 37% rate was observed among 30 participants whose disease had previously failed a venetoclax-based first-line regimen, a population with particularly poor outcomes after relapse. Because the analysis remains blinded and combines patients receiving Annamycin plus cytarabine with patients receiving cytarabine and placebo, the new figures cannot be attributed to Annamycin and do not provide a treatment-versus-control comparison.
The updated results are therefore primarily a test of whether the trial’s pooled remission signal is holding as enrollment expands and includes more venetoclax-exposed patients. The decisive Part A analysis will come after the study is fully enrolled and unblinded, which Moleculin expects between December 2026 and February 2027.
The 37% remission signal remains encouraging, but blinded data cannot prove Annamycin’s benefit
Among the 62 evaluable patients, the preliminary complete remission rate was 24%, while the composite complete remission rate was 37%. Composite complete remission includes conventional complete remission as well as remissions in which blood-count recovery remains incomplete, including CRi or CRh. These broader response categories can still be clinically important because remission may allow some patients to proceed to stem cell transplantation or another consolidative treatment.
Thirty of the 62 evaluable participants, representing 48%, had previously received and failed a venetoclax-based regimen. Within that subgroup, the complete remission rate was 23% and the composite complete remission rate was 37%, almost identical to the pooled trial population. Moleculin interprets this similarity as evidence that prior venetoclax exposure has not eliminated the remission signal being observed in MIRACLE.
That interpretation must remain cautious because treatment assignments are still concealed. The 30 venetoclax-exposed patients include an unknown mixture of people receiving the 190 mg/m² Annamycin regimen, the 230 mg/m² regimen and the cytarabine-plus-placebo control. The 37% figure therefore shows that remission is occurring within this difficult subgroup, but it cannot establish how much of the activity came from Annamycin.
Moleculin compared the result with published outcomes showing an approximately 13% salvage remission rate and median overall survival of about 2.4 months after failure of first-line venetoclax-based therapy. That historical comparison provides context but is not equivalent to a randomized comparison. Differences in age, mutations, disease burden, prior treatment, remission definitions and the number of treatment cycles can materially affect outcomes between studies.
The current analysis also evaluates responses after only one treatment cycle. Some historical salvage datasets allow several cycles before determining the best response, making direct comparisons especially difficult. The more reliable evidence will come from the concurrent control arm when Part A is unblinded.
Earlier unblinded results favored both Annamycin doses over cytarabine alone
The July update follows a June interim analysis in the first 45 patients, when treatment assignments were unblinded for review. In that dataset, complete remission occurred in 43% of patients receiving 190 mg/m² Annamycin plus high-dose cytarabine and 36% receiving 230 mg/m² Annamycin plus cytarabine, compared with 12% in the cytarabine-plus-placebo group. Composite complete remission rates were 50%, 57% and 29%, respectively.
Those results provided the first randomized evidence that both Annamycin doses may improve remission rates beyond high-dose cytarabine alone. The Independent Data Monitoring Committee described a strong numerical trend favoring the experimental groups and recommended that both Annamycin doses remain in the study because their results were too similar to justify dropping either arm. The early analysis did not reach formal statistical significance, which Moleculin said was expected under the trial’s conservative group-sequential design.
The June and July percentages should not be compared as though the treatment effect declined. The June analysis separated the three randomized groups in 45 patients, while the July figures pool all treatment and control participants in a larger blinded population. A pooled rate will usually fall between the stronger and weaker treatment-arm results, and the patient mix also changed as more venetoclax-exposed participants entered the trial.
Across blinded analyses conducted after 30, 45 and 62 evaluable patients, the composite remission rate has remained between approximately 37% and 40%. During the same period, the proportion of patients previously treated with venetoclax increased from 31.1% in the 45-patient population to 48% in the current analysis. The stability of the pooled remission rate is encouraging, but it still cannot identify the contribution of either Annamycin dose.
The final Part A unblinding must determine whether the treatment-control separation remains consistent as the sample expands from 45 to 90 patients. It must also identify which dose offers the better combination of remission activity, safety and tolerability for advancement into Part B.
MIRACLE is selecting an Annamycin dose for the pivotal expansion
MIRACLE is a multicenter, randomized, double-blind, placebo-controlled and adaptive Phase 2/3 trial in adults with acute myeloid leukemia that is refractory to or has relapsed after induction therapy. Part A compares Annamycin at 190 mg/m² or 230 mg/m², each combined with high-dose cytarabine, against high-dose cytarabine plus placebo. All three groups receive one treatment cycle before the initial bone-marrow response assessment.
The primary endpoint is complete remission after one cycle. Overall survival is an important secondary measure, while duration of remission and other outcomes will help determine whether early bone-marrow responses lead to sustained clinical benefit. A higher remission rate is valuable only when responses last long enough to improve transplantation opportunities, survival or meaningful disease control.
Enrollment has reached 74 of the planned 90 Part A participants. Moleculin expects the 90th patient to be treated in September 2026, followed by comprehensive unblinded results between December 2026 and February 2027. The selected Annamycin dose is then expected to advance into Part B, where the trial will test whether the regimen produces a statistically reliable improvement over the randomized control.
The adaptive structure allows information from Part A to contribute to the broader pivotal analysis rather than functioning only as a separate dose-finding experiment. This can improve development efficiency, but it places considerable importance on prespecified statistical methods, consistent response assessment and the proper handling of patients whose treatment or follow-up is incomplete.
The 62-patient update does not provide detailed information on overall survival, remission duration, measurable residual disease, transplantation rates or adverse events. Those outcomes will be needed to determine whether the apparent remission advantage translates into a clinically meaningful treatment effect.
Cardiac safety remains promising but requires complete unblinded evidence
Annamycin is a liposomal anthracycline designed to avoid multidrug resistance and reduce the cardiac toxicity associated with conventional anthracyclines. Anthracycline-related heart injury can limit cumulative dosing and may restrict treatment choices in older patients or those with pre-existing cardiovascular disease.
Moleculin said the MIRACLE trial continues to show no evidence of cardiotoxicity based on reported ejection fractions and adverse events. This observation is important because more than three-quarters of the first 45 participants were older than 60, an age group in which cardiovascular comorbidities may complicate intensive AML treatment.
The company has not released complete patient-level cardiac measurements or detailed adverse-event rates from the 62-patient dataset. The statement should therefore be understood as a preliminary blinded safety observation rather than proof that Annamycin has no cardiac risk. Rare toxicity, cumulative injury or differences between the two dose levels may become apparent only after more patients and longer follow-up.
Other severe toxicities are also expected in this population because high-dose cytarabine and intensive leukemia treatment can cause profound suppression of blood-cell production, infection, bleeding and organ complications. The eventual safety analysis must separate events associated with Annamycin from those caused by cytarabine, active AML or the medical vulnerability of the study population.
Annamycin holds FDA Orphan Drug Designation for acute myeloid leukemia but is not approved for AML or any other indication. The MIRACLE results remain preliminary, and the July update does not replace the randomized unblinded analysis required to evaluate the experimental therapy.
The new data nevertheless answer one useful question: the pooled remission rate has remained near 37% to 40% even as the study enrolled a larger proportion of patients whose disease had already failed venetoclax. The next and more important question is whether the final unblinded results continue to show that one or both Annamycin regimens outperform cytarabine alone with acceptable safety.
