Moleculin Biotech has announced completion of its Phase 1B/2 clinical trial (MB-106) evaluating Annamycin in combination with cytarabine for acute myeloid leukemia (AML), reporting overall survival data that significantly exceeds industry expectations for relapsed disease. The Houston-based pharmaceutical company enrolled 22 subjects in the trial, with database lock expected by the end of September 2025 and final clinical study report projected for early Q1 2026.
Survival Outcomes Exceed Industry Standards
The updated overall survival data revealed median survival of 15 months for the eight subjects who achieved complete remission, with four subjects still alive at study closure. For the intent-to-treat population of 22 subjects across first through seventh-line treatments, median overall survival reached 9 months, while the second-line efficacy evaluable population demonstrated median survival of 12 months.
"Industry publications note that the typical OS for relapsed AML patients is roughly 4-6 months, these results highlight a remarkable improvement, exceeding expectations by 30% or more," said Walter Klemp, Chairman and CEO of Moleculin Biotech.
Complete Remission Rates and Durability
Among the 22 subjects in the intent-to-treat population, 8 patients (36%) achieved complete remission following treatment with the Annamycin-cytarabine combination, referred to as AnnAraC. The complete remission rate was particularly notable in the second-line setting, where 50% of the 10 treated subjects achieved complete remission - the same primary efficacy endpoint used in the ongoing Phase 3 MIRACLE trial.
Median durability for subjects achieving complete remission was 10 months and continuing at study end, with durability ranging from 2 to 22 months. Complete remissions were achieved across subjects with various prior treatments, including traditional 7+3 and venetoclax regimens.
Safety Profile and Clinical Outcomes
The trial demonstrated a favorable safety profile, with no clinically significant signs of cardiotoxicity observed during or after treatment in any enrolled subjects. The combination was well tolerated, with myelosuppression and infections representing the main adverse events. Two subjects discontinued early due to allergic reactions.
Notably, 50% of subjects achieving complete remission proceeded to curative bone marrow transplant, which Klemp described as "the most sought-after goal of any induction therapy in AML." The CEO emphasized that "the results we have seen in 2L patients are better than any drug ever approved for second line AML and more than double the average for the last five drugs approved for 2L use."
Case Study and Compassionate Use
The trial included a remarkable case of an 80-year-old subject who achieved complete remission with one cycle of Annamycin, received two maintenance cycles, and finally relapsed after more than 600 days. The patient subsequently received a fourth round of Annamycin under compassionate use and returned to remission, highlighting the drug's potential for durable responses.
Study Population and Design
The median age of subjects in MB-106 was 68 years, with 18 subjects having relapsed/refractory AML and 4 subjects receiving first-line treatment. All subjects who completed treatment underwent post-therapy disease response assessments through bone marrow evaluation and/or peripheral blood assessment at day 15 or later.
Regulatory Status and Ongoing Development
Annamycin, also known by its non-proprietary name naxtarubicin, currently holds Fast Track Status and Orphan Drug Designation from the FDA for relapsed or refractory acute myeloid leukemia treatment. The drug also has Orphan Drug Designation for soft tissue sarcoma from the FDA and Orphan Drug Designation for relapsed or refractory AML from the European Medicines Agency.
Phase 3 MIRACLE Trial Progress
The company continues executing Part A of its pivotal Phase 3 MIRACLE trial (Moleculin R/R AML AnnAraC Clinical Evaluation), a global adaptive design study evaluating AnnAraC for relapsed or refractory AML patients. The trial includes sites across the United States, Europe, and the Middle East, with plans to recruit the first 45 enrolled patients before year-end 2025 for safety and efficacy unblinding.
"The final data from MB-106, coupled with the expected data from the MIRACLE trial will be invaluable as we continue to unlock the full potential of Annamycin for the treatment of AML," concluded Klemp.
