Actinium Presents Mutation Data and Linker Tech for Solid Tumor Radioconjugates at 2024 SNMMI Annual Meeting

Actinium Pharmaceuticals, Inc., a leader in the development of Antibody Radiation Conjugates (ARCs) and targeted radiotherapies, recently presented promising data from various abstracts at the 2024 Society of Nuclear Medicine & Molecular Imaging (SNMMI) Annual Meeting in Toronto. The focus was on Iomab-B, a CD45 targeting ARC used for conditioning patients with relapsed or refractory acute myeloid leukemia (r/r AML) before a potentially curative bone marrow transplant (BMT).

The Phase 3 SIERRA trial, which included 153 r/r AML patients, demonstrated the efficacy of Iomab-B. The primary endpoint of durable Complete Remission (dCR) was achieved with high statistical significance (p<0.0001). Importantly, Iomab-B showed improved survival rates in patients with high-risk relapsed or refractory AML, including those with TP53 mutations.

In the trial, 37 patients (24%) had TP53 mutations. Among these, 27 patients received Iomab-B, showing a median overall survival (OS) of 5.49 months, compared to just 1.66 months for those who did not receive the treatment (HR=0.23; 95% CI [0.10, 0.52]). This data supports the unique mechanism of Iomab-B in overcoming the negative prognosis typically associated with TP53 mutations.

For the delivery of radiation, Iomab-B safely administered high doses of myeloablative targeted radiation to the diseased bone marrow. A median of 16Gy of radiation was delivered to the bone marrow while sparing healthy organs, which only received significantly lower doses, such as the heart (2.6 Gy), lungs (2.5 Gy), small intestine (2.4 Gy), stomach (3.6 Gy), kidneys (4.1 Gy), and the whole body (3.3 Gy). This highlights the precision and safety of Iomab-B in targeting the bone marrow while minimizing exposure to healthy tissues.

Patients in the SIERRA trial received up to 1,030 mCi of Iodine-131 through Iomab-B, administered as a single infusion 12 days prior to the BMT. The median time for patients to meet the release criteria was 5 days, even for those receiving doses greater than 800 mCi.

Actinium Pharmaceuticals also introduced their novel linker technology aimed at improving targeted radiotherapy delivery for solid tumors. This technology showed significantly lower kidney and liver uptake compared to standard DOTA linkers, with high tumor uptake and in vivo stability in preclinical models. Actinium’s proprietary linker technology is supported by two U.S. patents with terms extending into 2043, and a pending international patent application.

Sandesh Seth, Actinium's Chairman and CEO, expressed pride in the company's advancements. He emphasized Actinium's focus on addressing high-risk relapsed or refractory AML, especially in patients with TP53 mutations or extensive prior treatments, including Venetoclax. Seth also highlighted the company's novel linker technology's potential in treating solid tumors and their proprietary Actinium-225 cyclotron-based manufacturing technology that ensures a highly pure medical grade Actinium-225 supply.

The SNMMI Annual Meeting, a premier event in nuclear medicine and molecular imaging, provided a platform for Actinium Pharmaceuticals to showcase their latest developments. The event draws professionals across various fields to explore the latest research and applications in nuclear medicine.

Actinium Pharmaceuticals, Inc. is dedicated to developing targeted radiotherapies to significantly improve survival outcomes for patients who have failed existing oncology therapies. Their advanced pipeline, including Iomab-B and Actimab-A, aims to extend survival for those with relapsed and refractory acute myeloid leukemia, with plans to expand Iomab-B to other blood cancers and develop next-generation conditioning agents to enhance cell and gene therapy outcomes. Actinium holds an extensive portfolio of over 230 patents and applications, including innovations related to the cyclotron-based manufacture of Ac-225.