Actinium’s Targeted Radiotherapy for AML Called “Practice-Changing”

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Actinium Pharmaceuticals’ Iomab-B met the primary endpoint in the Phase III SIERRA trial, demonstrating durable Complete Remission (dCR) at six months in patients with elapsed or refractory acute myeloid leukemia (r/r AML).

Among patients treated with the targeted radiotherapy candidate, 75% showed initial remission following bone marrow transplant (BMT), as opposed to 6.3% in the control group.

Complete remission persisted through six months in 22% of patients in the Iomab-B cohort, an effect Actinium deemed highly statistically significant. Those who reached six-month dCR had a survival rate of 90% at one year and 60% at two years. Median overall survival has not yet been reached in these patients.

None of the patients in the control arm achieved a six-month dCR.

SIERRA, a pivotal, randomized and controlled trial, sought to evaluate the potential of Iomab-B in 153 patients with r/r AML aged 55 years and older, comparing it against a physician’s choice of salvage therapy.

Aside from six-month dCR, SIERRA assessed the therapy’s efficacy through the secondary endpoints of event-free and overall survival. Compared with the control arm, treatment with Iomab-B cut the probability of an event occurring by 78%. Events included death, relapse and not receiving BMT.

In addition, Iomab-B doubled one-year and median overall survival relative to controls. The radiotherapy also allowed 100% of its recipients to undergo BMT engraftment, while 18% of control comparators could undergo the procedure.

Actinium documented lower rates of treatment-related adverse events in favor of Iomab-B, including febrile neutropenia, mucositis and acute graft-versus-host disease.

Sergio Giralt, M.D., deputy head, division of hematologic malignancies, attending physician, Adult BMT Service, Memorial Sloan Kettering Cancer Center, called these dCR and two-year survival data “practice changing.”

Along with significantly better overall and event-free survival, and a good safety profile, Iomab-B can become “a new standard of care for active, r/r AML,” Giralt said.

Iomab-B is designed to improve access to potentially curative BMT by rapidly and substantially depleting a patient’s immune, blood cancer and bone marrow cells. In previous studies, treatment with Iomab-B has resulted in near-universal access to BMT, leading to better survival outcomes, Actinium reported.

Actinium is preparing to submit a Biologics License Application for Iomab-B in 2023.

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