Annamycin Demonstrates Encouraging Overall Survival in Refractory AML

Overall survival (OS) data from the completed phase 1b/2 clinical trial MB-106 (NCT05319587) evaluating the investigational anthracycline annamycin in combination with cytarabine has shown positive results for the treatment of relapsed or refractory acute myeloid leukemia (AML).¹

The findings, which show OS rates significantly exceeding historical benchmarks for this patient population, underscore the drug's potential to address a persistent and critical unmet need in hematologic oncology. The company is now advancing annamycin into a pivotal phase 3 trial based on these encouraging findings.

Relapsed or refractory AML represents one of the most challenging clinical scenarios in oncology. Despite initial treatment responses, many patients experience disease recurrence, at which point therapeutic options are limited and prognosis is poor, with median OS typically ranging from 4 to 6 months. Standard chemotherapy regimens, often involving anthracyclines, are limited by dose-dependent cardiotoxicity, which can preclude retreatment and worsen long-term outcomes. Annamycin is a next-generation anthracycline designed to overcome the multidrug resistance mechanisms that often lead to treatment failure and, critically, to avoid the cardiotoxicity that limits the use of currently prescribed anthracyclines.

The completed phase 1b/2 study enrolled a total of 22 patients with relapsed or refractory AML who had received between 1 and 7 prior lines of therapy.² The updated data show a median OS of 9 months for the entire intent-to-treat population, which spans a wide range of prior treatments. For the subgroup of patients who achieved complete remission (CR) on the study, the median OS extended to an encouraging 15 months. In the second-line patient cohort, the median OS was 12 months. These survival rates stand in stark contrast to the historical OS data for relapsed AML, highlighting the potential clinical impact of this therapeutic approach.¹

“We are glad to finally be in a position to close out our last phase 2 AML trial, MB-106, by having completed follow-up on all subjects—some with durable CRs continuing—with database lock expected by the end of next month. While still technically preliminary, we are extremely pleased with the results of the MB-106 trial and look forward to the final CSR. These 2L data formed the basis for the design of the phase 2B/3 pivotal MIRACLE trial with which we aim to gain eventual approval of annamycin to serve the unmet need in 2L AML,” said Walter Klemp, chairman and CEO of Moleculin Biotech, in a press release.

The favorable safety profile of annamycin is also a significant finding. Unlike traditional anthracyclines, which are often limited by cumulative cardiotoxicity, clinical trials to date have shown no signs of cardiotoxicity associated with annamycin. This tolerability allows for the potential for repeat dosing and prolonged treatment, which may be essential for achieving durable remissions.

Annamycin has also been granted fast track status and orphan drug designation by the FDA for the treatment of relapsed or refractory AML, in addition to orphan drug designation for soft tissue sarcoma, acknowledging the high unmet need in these indications.

Based on the compelling data from the phase 1B/2 trial, the company has begun a pivotal phase 3 trial, known as the MIRACLE (Moleculin R/R AML AnnAraC Clinical Evaluation) Trial (NCT06788756).³ This adaptive-design trial will further evaluate annamycin in combination with cytarabine for patients with relapsed or refractory AML. The progression to a pivotal study underscores the confidence in the drug’s potential to earn eventual regulatory approval and address a significant therapeutic gap for patients with this difficult-to-treat cancer.

A clinical study report for the completed phase 1b/2 trial is anticipated to be published in the first quarter of 2026.

REFERENCES:

1. Moleculin Issues New Positive AML Overall Survival Data. News release. Moleculin Biotech. August 27, 2025. Accessed August 29, 2025. https://tinyurl.com/bddpb9ur

2. Study of Liposomal Annamycin in Combination with Cytarabine for the Treatment of Subjects with Acute Myeloid Leukemia (AML). ClinicalTrials.gov. Updated December 20, 2025. Accessed August 29, 2025. https://clinicaltrials.gov/study/NCT05319587

3. L-Annamycin for Injection in Combination With Cytarabine Injection as Second Line Therapy for Remission Induction in Adult Subjects With Refractory/​Relapsed AML. ClinicalTrials.gov. Updated August 8, 2025. Accessed August 29, 2025. https://clinicaltrials.gov/study/NCT06788756