On September 7, 2023 Actinium Pharmaceuticals, Inc. (NYSE AMERICAN: ATNM) (Actinium or the Company), a leader in the development of targeted radiotherapies, reported updated survival data from its Phase 1b trial evaluating Actimab-A in combination with the salvage chemotherapy CLAG-M in patients with high-risk relapsed or refractory acute myeloid leukemia (r/r AML) and new preclinical data with Actimab-A in combination with FLT3 inhibitors at the Society of Hematologic Oncology (SOHO) 2023 Annual Meeting (Press release, Actinium Pharmaceuticals, SEP 7, 2023, View Source;clag-m-trial-and-preclinical-data-supporting-program-expansion-with-flt3-inhibitor-combinations-at-soho-301920692.html [SID1234635004]). In addition, results of the completed and positive Phase 3 SIERRA trial of Iomab-B were presented.

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SOHO Data Highlights:

Updated Actimab-A + CLAG-M Phase 1b Study Results:

– 30-month median Overall Survival (OS) in patients with prior venetoclax treatment who proceeded to bone marrow transplant (BMT) following Actimab-A + CLAG-M
– 24-month median OS in all patients who proceeded to BMT following Actimab-A + CLAG-M
– 100% measurable residual disease (MRD) negativity in patients with prior venetoclax treatment and 75% MRD negativity in all patients
– 83% of patients (19/23) had high-risk r/r AML; 57% of patients (13/23) received prior treatment with venetoclax
– Patients who relapse after venetoclax treatment have poor survival outcomes with a limited percentage of patients proceeding to BMT

Poster Title: Sequential Salvage Chemotherapy and Lintuzumab-Ac225 in Relapsed/Refractory AML Results in Deep Responses and Prolonged Survival in Adverse Risk Acute Myeloid Leukemia (AML) and in AML Patients that Received Prior Venetoclax Therapy

"These data continue to demonstrate the broad potential and applicability of targeted radiotherapeutics as well as Actinium’s leadership position in their development for r/r AML and other blood cancers," said Sandesh Seth, Actinium Chairman and CEO. "As we progress Actimab-A + CLAG-M to a pivotal trial, we are highly encouraged by this new follow-up data showing 100% MRD negativity and median survival of 30 months in patients proceeding to transplant who had prior venetoclax treatment. Given the significant number of patients with AML who receive venetoclax treatment and, unfortunately, have disease relapse, better therapeutic options are needed for this growing patient segment. We are excited by the potential of Actimab-A to meet this high unmet need given its differentiated mechanism of action and clinical profile thus far."

Actimab-A Program Expansion into FLT3 Mutant AML:

– Actimab-A shown to have single-agent cytotoxic activity against FLT3 mutant AML cell lines
– The addition of Actimab-A enhances the anti-leukemic activity of FLT3 inhibition of approved FLT3 inhibitors gilteritinib (Xospata, Astellas) and midostaurin (Rydapt, Novartis) in vitro
– FLT3 mutations are associated with aggressive disease with poor outcomes and occur in approximately 30% of patients, making it one of the most commonly mutated genes in AML
– Combinations of Actimab-A with FLT3 inhibitors can potentially be explored under Actinium’s CRADA with the NCI

Poster Title: Antileukemic Activity of Lintuzumab-Ac225 in Preclinical Model of FLT3 Mutant AML

Mr. Seth added, "The mutation agnostic mechanism of action, potent cell killing ability and synergistic potential of Actimab-A provides multiple avenues for development as evidenced by this new preclinical data supporting combinations with FLT3 inhibitors. With FLT3 gene mutations being the most common in AML, we are excited to further Actimab-A’s backbone potential by continuing to explore this novel combination that could address approximately 30% of the AML patient population."