On March 11, 2021 Actinium Pharmaceuticals, Inc. (NYSE AMERICAN: ATNM) ("Actinium" or the "Company") reported that preclinical feasibility data supporting an Actinium-225-based CD45-targeted Next-Generation conditioning agent has been accepted for poster presentation at the American Association of Cancer Research (AACR 2021) annual meeting being held virtually April 10th – 15th, 2021 (Press release, Actinium Pharmaceuticals, MAR 11, 2021, View Source [SID1234576525]). The data to be presented includes initial dose escalation, safety, tolerability, and conditioning experiments of an Ac-225-based CD45 ARC or antibody radiation conjugate. Dosimetry results with this Ac-225-based alpha emitting ARC showed selective accumulation in immune cell target organs such as bone marrow, spleen, and liver with the potential for lower exposure to non-target tissues from longer path length beta emitter radioisotopes like Iodine-131 and Lutetium-177. The data to be presented demonstrate that conditioning with this Ac-225-based CD45-targeting agent result in depletion of peripheral immune cells and hematopoietic progenitor cells, thereby enabling engraftment of donor cells. A dose dependent response was observed with low doses depleting white blood without effecting hematopoietic progenitor cells, representing a lymphodepletive dose that is relevant for adoptive cell therapies such as CAR-T, while higher doses eliminated peripheral immune cells and hematopoietic progenitor cells, which is applicable to ex vivo gene therapies and BMT or bone marrow transplant.
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This program further augments Actinium’s targeted conditioning portfolio that is led by Iomab-B, an ARC consisting or the radioisotope Iodine-131 and the CD45 targeting antibody apamistamab. In total, apamistamab has been studied in several hundred patients. Iomab-B is currently being studied in the pivotal Phase 3 SIERRA trial for BMT conditioning in patients with active relapsed or refractory acute myeloid leukemia age 55 and above that is expected to complete enrollment in 2021.
Details of the poster presentation at AACR (Free AACR Whitepaper) are as follows:
Dr. Dale Ludwig, Actinium’s Chief Scientific and Technology Officer said, "We are excited to present this data supporting an Ac-225 antibody radiation-conjugate at AACR (Free AACR Whitepaper) and to have the opportunity to develop potentially safer and better targeted chemotherapy-free conditioning agents. Recent cases of secondary malignancies potentially tied to toxic chemotherapy regimens highlight the urgent need for improved conditioning to enable the very promising cell and gene therapy strategies to treat diseases such as Sickle Cell Disease and Beta-Thalassemia. As advances in cell and gene therapies address more disease indications and thus a larger overall patient population, our commitment to developing targeted conditioning agents to improve patient access to the these potentially curative therapies and patient outcomes grows stronger. We look forward to further optimizing this construct to enable advancement into the clinic."
Actinium is developing the only multi-target, multi-indication, clinical-stage pipeline for targeted conditioning and the only ARC based targeted conditioning regimens in development. This Ac-225-CD45 construct to be highlighted at AACR (Free AACR Whitepaper) resulted from Actinium’s AWE or Antibody Warhead Enabling technology platform. AWE encompasses Actinium’s intellectual property of over 140 patents, know-how, and clinical experience including nearly 150 patients treated with alpha emitters like Ac-225 for which Actinium is an industry leader. Specific to Ac-225, Actinium has gold-standard linker technology with a strong stability and safety profile and patents covering composition of matter, formulations, methods of use and methods of manufacturing the radioisotope Actinium-225 in a cyclotron. In addition to fueling Actinium’s R&D efforts, AWE is being utilized in collaborative research partnership with Astellas Pharma, Inc. who is focused on the development of theranostics for solid tumors.
Sandesh Seth, Actinium’s CEO, said "This new program and initial data is yet another example of the potential of Actinium’s AWE platform technology and our team’s ability to create disruptive agents for oncology therapeutics and cell and gene-based therapies. It also exemplifies Actinium’s strong commitment to advancing and increasing access to life-changing and potentially curative therapies. With 2021 expected to be a transformational year for Actinium marked with key clinical milestones including completion of the SIERRA trial it is also exciting to see our R&D efforts delivering tangible results that will position us for continued future success."