Actinium Pharmaceuticals, Inc. announced that initial patient enrollment in the second dose cohort in the Phase 1 portion of the Actimab-A venetoclax Phase 1/2 combination trial in fit and unfit patients with relapsed or refractory Acute Myeloid Leukemia (r/r AML) has been completed. The Phase 1 portion of the trial is a 3 + 3 dose escalation study to determine the maximum tolerable dose of Actimab-A that is to be studied in the Phase 2 portion of the study. Based on the progress of enrollment, Actinium expects to complete the Phase 1 portion and present further proof-of-concept data in the second half of 2021. First-in-human data from the first dose cohort of 0.5 µCi/kg of Actimab-A and Venetoclax were presented at the 62ndAmerican Society of Hematology annual meeting in December 2020. Patients enrolled in the first dose cohort had a median of 2 prior therapies (range 2-3) and a median bone marrow blast percentage of 30% (range 20 - >60). All 3 patients had poor risk disease with adverse cytogenetics, and each patient had an additional high-risk marker (FLT3-ITD+, antecedent JAK2+ myelofibrosis, or TP53 mutation). One patient who had multiple genetic mutations including IDH2, RUNX1, TP53 and others, achieved a complete remission with incomplete blood count recovery (CRi) after the first cycle of Actimab-A and venetoclax. Next generation sequencing at the end of the first cycle showed that the patient was negative for the known IDH2 and RUNX1 mutations. In addition, another patient achieved a partial response after one cycle of Actimab-A and venetoclax. There were no Actimab-A related dose limiting toxicities or nonhematologic Grade 3 or greater related AEs reported in the first cohort.