MBRX · Moleculin Biotech, Inc.

This disclosure represents a HIGH-materiality regulatory update centered on clinical validation of Annamycin’s cardiac safety — a critical differentiator for an anthracycline-class drug in relapsed/refractory AML. The Cleveland Clinic’s independent cardio-oncology review analyzed comprehensive cardiac monitoring data from 90 subjects across five trials, with source-verified pre- and post-treatment ejection fraction assessments in 78 patients — none of whom met criteria for clinically significant left ventricular dysfunction. Mean ejection fraction remained stable, and no dose–response relationship was observed, directly confronting the principal limitation of traditional anthracyclines: cumulative cardiotoxicity. This finding is especially consequential for R/R AML, where patients are often heavily pretreated with prior anthracyclines and have limited salvage options after venetoclax failure. Management explicitly ties these data to de-risking the development pathway for Annamycin, citing FDA input following the MB-106 study and positioning the ongoing pivotal MIRACLE trial (MB-108) — evaluating Annamycin plus cytarabine — as the near-term catalyst for potential approval. While forward-looking statements caution that financing is required and long-term follow-up remains ongoing, the disclosure provides objective, third-party–validated evidence supporting Annamycin’s mechanistic advantage and expands its potential clinical utility beyond R/R AML into other oncology indications constrained by cardiotoxicity.