NEW YORK—Actinium Pharmaceuticals Inc. presented encouraging initial patient outcomes from the ongoing multicenter Phase 1/2 clinical trial of Actimab-A, a targeted payload immunotherapeutic for the treatment of newly diagnosed acute myeloid leukemia (AML) in patients over age 60.
Actimab-A is a radiolabeled antibody co-developed with Memorial Sloan Kettering Cancer Center that is based on Actinium’s proprietary alpha-particle immunotherapy platform. The compound consists of the CD33 antibody lintuzumab linked to the actinium-225 payload. The U.S. Food and Drug Administration has granted Orphan Drug Designation for Actimab-A based on positive interim data from the trial that showed a significant increase in median overall survival among secondary AML patients in the study, according to a news release issued by Actinium.
Dr. Joseph Jurcic of Columbia University Medical Center, Actinium’s Clinical Advisory Board chairman, presented a poster and abstract of the ongoing trial at the 51st Annual Meeting of the American Society of Clinical Oncology in Chicago this May.
According to a news release summarizing the presentation, among the first 12 patients treated with Actimab-A at increasing dose levels, two achieved complete remission with some degree of hematological recovery, and one achieved complete remission with incomplete platelet count recovery. The combined overall response rate was 25 percent among all patients and 67 percent among patients treated at the highest dose level administered through the first three cohorts in the trial.
The enrolled patients had high pretreatment leukemia burdens of up to 88 percent in the bone marrow, and half demonstrated blast reductions greater than 50 percent after treatment with Actimab-A. Dose-limiting toxicities occurred in one patient with prolonged myelosuppression; no extra medullary dose-limiting toxicities were observed.
“These results generated significant interest and were well received by the oncology experts,” said Jurcic in a media statement about the initial data. “Oncologists were particularly excited to see objective responses in patients who already received best available therapy for their prior blood cancer.”
Actimab-A reportedly has attracted support from leading experts at prestigious cancer treatment hospitals due to its promising safety and efficacy profile, potential potency, specificity and ease of use.
AML is an aggressive cancer of the blood and bone marrow characterized by an uncontrolled proliferation of immature blast cells in the bone marrow. Actimab candidates also are in early development for other cancers.
Actinium’s product pipeline includes at least eight drugs at different stages of development and testing, according to an investor report published by Caprock Research on June 2, 2015. The pipeline contains treatments focused on antiangiogenesis, bone marrow ablation, metastatic colorectal cancer and prostate cancer.
Actinium has one other clinical-stage product: its lead radiopharmaceutical product candidate, Iomab-B, designed for bone marrow conditioning to be used in preparing patients for hematopoietic stem cell transplant. The company plans to conduct a single, pivotal, multicenter Phase 3 clinical study of Iomab-B in refractory and relapsed AML patients over age 55, with a primary endpoint of durable complete remission. In earlier Phase 1 and Phase 2 trials, Iomab-B led to effective cures in patients that had no other treatment options, according to a Small Cap IR investor report about Actinium.