Actinium Pharmaceuticals, Inc. highlighted new data from a Phase 1 trial studying Actimab-A in combination with the salvage chemotherapy regimen CLAG-M that was presented in a poster presentation at the 61st American Society of Hematology (ASH) Annual Meeting. The poster reported results from the ongoing Phase 1 combination trial that is being conducted at the Medical College of Wisconsin (MCW). Patients receiving Actimab-A at a dose of 0.50 uCi/kg in the second dose cohort in addition to CLAG-M had an 86% overall response rate (ORR), which is a 56% higher response rate and is substantially greater than what has been observed with CLAG-M and MEC and more than double that of CLAG in a similar patient population that was treated at MCW. Notably, 71% of patients (5/7) achieved negative minimal residual disease (MRD) status in the second dose cohort. In addition to response rates, the poster reported that three patients on the study proceeded to a bone marrow transplant after receiving Actimab-A and CLAG-M. The addition of Actimab-A to CLAG-M appears to have a clinically acceptable safety profile with no patient deaths reported. A table below compares the ORR of patients receiving Actimab-A and CLAG-M to that of the CLAG-M, MEC and CLAG salvage regimens. Actimab-A is an Antibody Radiation-Conjugate (ARC) that delivers the potent alpha-emitting radioisotope Actinium-225 (Ac-225) via the antibody lintuzumab to cells that express CD33. CD33 is an antigen that is expressed on the vast majority of cancer cells in patients with acute myeloid leukemia (AML). CLAG-M is a salvage chemotherapy comprised of cytarabine, cladribine, G-CSF (granulocyte-colony stimulating factor) and mitoxantrone. The Phase 1 Actimab-A CLAG-M combination study is enrolling patients age 18 and older who have relapsed or refractory AML and are medically fit. The median age of patients enrolled in the trial to date is 62 and all patients had either intermediate risk or poor risk cytogenetics. Three patients had received three or more prior therapies and three patients had received a prior allogeneic bone marrow transplant. This patient population is similar to the study conducted at MCW that enrolled 146 patients, of which, 74 received CLAG-M, 57 received MEC and 15 received CLAG. MRD status was not reported in that study, however 71% of patients receiving 0.50 uCi/kg of Actimab-A and CLAG-M achieved MRD negative status. The Actimab-A CLAG-M Phase 1 trial is expected to be completed in mid-2020. Actinium is also conducting a Phase 1 clinical trial studying Actimab-A in combination with the Bcl-2 inhibitor venetoclax in patients with relapsed or refractory AML to evaluate the safety of the combination and determine if the addition of Actimab-A to venetoclax can increase patient responses and outcomes. In preclinical studies, it was observed that Actimab-A can deplete Mcl-1, a protein that has been implicated in mediating resistance to Bcl-2 inhibitors like Venetoclax and provides a potentiating effect.