Key Highlights

  • Preliminary blinded complete remission rate stood at 24 percent and composite remission rate at 37 percent across 62 evaluable subjects.
  • Among the 30 subjects who had failed prior venetoclax therapy, CRc remained essentially identical at 37 percent.
  • Published salvage remission rates following venetoclax failure are approximately 13 percent, with median survival near 2.4 months.
  • Enrollment reached 74 of 90 subjects, with final Part A treatment expected in September 2026.

Remission Rates Hold Steady Despite a Harder-to-Treat Population

Moleculin Biotech ( Nasdaq :MBRX) announced updated preliminary blinded results from Part A of its pivotal Phase 2/3 MIRACLE trial evaluating Annamycin in combination with cytarabine for relapsed or refractory acute myeloid leukemia. With 62 subjects evaluable to date, the preliminary blinded complete remission rate was 24 percent and the composite complete remission rate was 37 percent, figures that included both investigational and control arm patients given the trial remains blinded.

Of those 62 subjects, 30, or 48 percent, had previously received a venetoclax-based regimen, a patient population for which published salvage remission rates are approximately 13 percent and median survival is approximately 2.4 months. Within that subgroup, the preliminary blinded CR and CRc rates were 23 percent and 37 percent respectively, essentially identical to the evaluable population as a whole, suggesting prior venetoclax failure has not diminished the remissions observed in the trial.

Consistency Across Successive Analyses Builds Confidence Ahead of Part A Completion

Chairman and CEO Walter Klemp noted that because the current analysis remains blinded and includes control-arm subjects, the company would expect it to sit below the unblinded Annamycin-arm results reported in June, when CRc reached 50 percent and 57 percent in the two Annamycin arms versus 29 percent for control. Klemp said the fact that the blinded composite rate has held in a narrow band even as the population became measurably harder to treat gives the company added confidence as it approaches completion of Part A.

Across three successive blinded analyses at 30, 45, and 62 evaluable subjects, the blinded CRc has remained within a narrow range of approximately 37 percent to 40 percent, even as the proportion of subjects entering the trial after failing a first-line venetoclax-based regimen rose from 31.1 percent in the 45-subject population to 48 percent today. Klemp also highlighted that, based on reported ejection fractions and adverse events, the trial continues to show no evidence of cardiotoxicity, a defining characteristic the company believes differentiates Annamycin from conventional anthracyclines. Enrollment currently stands at 74 of 90 subjects, with the company expecting to treat the 90th subject in September 2026 and anticipating unblinding of the comprehensive Part A data in the December 2026 to February 2027 timeframe.

Balancing Encouraging Interim Signals Against Trial Design Limitations

The company cautioned that remission rates across all three trial arms, including control, reflect outcomes after only a single cycle of therapy as specified by the MIRACLE protocol, whereas historical benchmark studies such as MIRROS, CLASSIC I, and Moleculin's own earlier MB-106 study permitted multiple treatment cycles. As a result, absolute remission rates in this single-cycle interim analysis were expected to run lower than those seen in multi-cycle datasets, meaning the most meaningful comparison for regulatory purposes will be the final optimum-dose Annamycin arm measured against the concurrent randomized control arm on the same single-cycle basis.

Since the current data remain blinded and include control-arm patients, the reported 37 percent composite rate cannot be directly compared to the unblinded Annamycin-specific results from June, and the final locked efficacy and safety results may still differ from these preliminary figures once full unblinding occurs. Additionally, enrollment has been weighted more heavily toward European sites to date, with the company noting it is focused on improving recruitment in the United States as it works toward a target of at least 45 sites for the subsequent Part B phase of the trial.

Conclusion

Moleculin's latest MIRACLE trial update shows a composite remission rate holding steady even as the patient population has grown more difficult to treat, a pattern the company views as supportive of Annamycin's potential efficacy ahead of full Part A completion. Whether this consistency translates into a statistically meaningful advantage over the control arm may become clearer once comprehensive unblinded Part A results are available in the December 2026 to February 2027 timeframe. The continued absence of observed cardiotoxicity remains a key differentiating Factor the company is emphasizing as it advances toward the trial's next phase.