Moleculin Biotech, Inc. announced the following topline results from its MB-105 European Phase 1 clinical trial assessing the safety and efficacy of Annamycin as a single agent for the treatment of adults with relapsed or refractory acute myeloid leukemia (AML). The final MB-105 results align with the overall safety profile of Annamycin and observations made in previously completed and ongoing clinical studies evaluating Annamycin. Additionally in the last cohort where all subjects were at least 60 years of age, Annamycin demonstrated an overall response rate (ORR) of 80%.

Topline results in MB-105, an open label, single arm clinical trial conducted in Europe showed one CRi (complete response with incomplete recovery of peripheral blood count) and three PRs (Partial Response) for an 80% overall response rate (ORR) in the last cohort. In this cohort, the age range at time of treatment of the 5 subjects was 62-73. The subject who achieved the CRi was 65 years of age at time of treatment.

For purposes of this clinical trial, a CR means that the subject's bone marrow blasts reduced to 5% or less (with CRi meaning a CR where there was incomplete recovery of white blood cell and/or platelet counts), and a PR means the subject's bone marrow blasts reduced by 50% and resulted in a blast count of 25% or less. 20 subjects were enrolled in the trial with the age range of 24-76 years with a median age of 64.5. The median number of prior therapies for all subjects was 4 (range 1-18). Of the 20 subjects enrolled, 17 received the full 3 consecutive days of dosing per protocol.

PRs (3) and CRi (1) were noted in 4 (80%) of the 5 subjects dosed according to protocol in the last cohort (240 mg/m2).  In earlier cohorts receiving lower doses, 2 subjects (1 at 120 mg/m2 and 1 at 180 mg/m2) although qualified to receive a second cycle (they exhibited a =50% decrease in marrow blasts and marrow blasts < 25%), did not meet what the protocol defined as a PR at that time. Per protocol at that time to achieve a PR, these subjects were required to have normalization of blood counts/hematologic values in addition to bone marrow blast reduction to qualify as a PR which did not occur. The final version of the protocol required just a >50% reduction in marrow blasts to qualify as a PR.

Despite these subjects qualifying to receive a second cycle of treatment, the two subjects were recorded as having a best overall response of "treatment failure" as they did not mean the definition of PR as defined by the protocol at that time. All subjects have been included in the evaluation for cardiotoxicity by an independent expert, with none noted. The most frequently reported adverse events (occurring in >10 % of subjects) were hematologic in nature, being neutropenia, thrombocytopenia and anemia.  The clinical study report for MB-105 has been finalized, internally published and reviewed and the Company expects to share detailed data in a paper and/or publication in the near future.

Annamycin currently has Fast Track Status and Orphan Drug Designation from the U.S. Food and Drug Administration (FDA) for the treatment of STS lung metastases and the treatment of relapsed or refractory AML.