Actinium Pharmaceuticals is a biopharmaceutical company focused on developing radioimmunotherapy drugs for the oncology market. Actinium’s drugs are monoclonal antibodies labeled with radioisotopes. The radiopharmaceutical components of the company’s drug candidates include both alpha-particle and beta-particle emitters. Alpha-particle emitters release high energy particles that travel only short distances thus sparing non-target tissues from the effects of irradiation. Beta-particle emitters have a longer particle range with varying ability to penetrate tissue that is suitable for tumors of varying diameters. Actinium’s most advanced products are Iomab-B, an antibody-drug construct containing the beta-emitter iodine-131 (I-131), used in myeloablative conditioning for hematopoietic stem cells transplantation (HSCT) in various indications, and Actimab-A, an antibody-drug construct containing the alpha-emitter actinium-225 (Ac-225), currently in clinical trials for acute myeloid leukemia (AML).
All of its product candidates are in development, the company does not currently market any products. Actinium does not have the technology and operational capabilities to develop and manufacture monoclonal antibodies and it relies on collaboration with third parties to gain access to such monoclonal antibodies.
Iomab-B is potentially transformative in AML in older patients. Currently there is no standard of care for refractory and relapsed AML while the majority of older AML patients end up in this category. Iomab-B is a combination of the in-licensed monoclonal antibody BC8 and the beta-emitting radioisotope I-131. This construct has been extensively tested in Phase I and Phase II clinical trials in approximately 250 patients with different blood cancer indications who were in need of HSCT. Iomab-B is used to condition the bone marrow of these patients by destroying blood cancer cells in their bone marrow and elsewhere thus allowing for a subsequent transplant containing healthy donor bone marrow stem cells. The company is initially focusing on the patients over 55 years old with active AML in relapse and/or refractory to existing treatments. In both Phase I and Phase II trials Iomab-B has led to effective cures in patients with no options left. In Phase I/II trials, all patients achieved Complete Response and one year survival was 30% in advanced AML patients with active disease at all does levels. Historic survival in advanced active AML is 10%. The company is currently in talks with the FDA to discuss the design of a pivotal Phase III study in HSCT. We believe the potential addressable HSCT market in AML for Iomab-B in the U.S. is about $500 million and the total worldwide market is about $800 million – $1 billion. We model that the Phase III trial will begin in 2014. Iomab-B has demonstrated utility in other groups of patients and other indications as well, including Acute Lymphoblastic Leukemia (ALL), Hodgkin’s Disease (HD) and Non-Hodgkin Lymphoma (NHL). Actinium could potentially also develop another BC8 antibody based radioimmunoconjugate for the treatment of Multiple Myeloma. We believe the market potential for these indications could be over $4 billion.
The Phase I dose escalation trial for Actimab-A to determine the safety pharmacology, and biological activity of Actimab-A in AML showed no acute toxicities and that it has anti-leukemic activity. Bone marrow blast reductions of over 33% were seen in 7 of 11 evaluable patients at 4 weeks. Data shows elimination of leukemia cells from blood in 67% of all evaluable patients who received a full dose and in 83% of those treated at higher levels, and eradication of leukemia cells in both blood and bone marrow in 20% of all evaluable patients. Actinium has commenced a Phase I/II multi-center AML trial with fractionated doses of Actimab-A. This will be an event driven trial that will look at overall survival. We believe data from this trial will be available in mid-2014. A Phase III trial could potentially start in 2015. We believe Actinium could file a BLA with the FDA for Actimab-A in 2018. A launch could occur in 2019. We forecast the potential U.S. market for Actimab-A is about $450 million and the total worldwide market is $900 million – $1 billion.