Actinium Pharmaceuticals, Inc. announced that it has completed enrollment of the pivotal Phase 3 SIERRA trial for Iomab-B, an Antibody Radiation Conjugate (ARC) comprised of apamistamab, a CD45 targeting antibody, and the radioisotope iodine-131. The SIERRA trial is a 150-patient, randomized and controlled study conducted at 24 leading bone marrow transplant centers in the United States and Canada. SIERRA is the only randomized Phase 3 trial to offer bone marrow transplant (BMT) to patients with active, relapsed or refractory acute myeloid leukemia (AML) age 55 and above, which is the only curative treatment option for this patient population.
Actinium expects to present data updates from the SIERRA trial in the fourth quarter of 2021 and to announce topline data for the primary endpoint of six-month durable Complete Remission (dCR) in mid-2022. These data are expected to support registration of a Biologics License Application (BLA) for Iomab-B.
The SIERRA trial is a 150-patient, randomized clinical trial, studying Iomab-B compared to physician's choice of salvage therapy in patients with active, relapsed or refractory acute myeloid leukemia (r/r AML) age 55 and above. In SIERRA, patients receiving Iomab-B, those achieving a remission after salvage therapy or those patients not achieving remission after salvage therapy that crossed over to receive Iomab-B were offered a bone marrow transplant (BMT), which is the only treatment option with curative potential for patients with active r/r AML. The SIERRA trial is the only randomized Phase 3 trial to offer BMT to this patient population. The control arm of SIERRA included over 20 single agents or combination treatment options based on physician's choice which include salvage chemotherapy and recently approved targeted agents including Bcl-2 inhibitor (Venetoclax), FLT3 inhibitors and IDH 1/2 inhibitors as there is no standard of care for this patient population. The SIERRA trial was conducted at 24 sites in the United States and Canada.
Iomab-B (I-131 apamistamab) via the monoclonal antibody apamistamab, targets CD45, an antigen widely expressed on leukemia and lymphoma cancer cells, immune cells and bone marrow stem cells. Apamistamab is linked to the radioisotope iodine-131 (I-131) and once attached to its target cells emits energy that travels about 100 cell lengths, destroying a patient's cancer cells and ablating their bone marrow. By carrying iodine-131 directly to the bone marrow in a targeted manner, Actinium believes Iomab-B may avoid the side effects of radiation on most healthy tissues while effectively killing the patient's cancer (induction) and marrow cells (myeloablation) including those in bone marrow niches due to the "crossfire" effect enabled by the I-131 radioisotope. Iomab-B was licensed from the Fred Hutchinson Cancer Research Center where it was studied in nearly 300 patients, in multiple clinical trials in 6 blood cancer indications. Iomab-B is being studied in the pivotal Phase 3 SIERRA (Study of Iomab-B in Relapsed or Refractory AML) trial, a 150-patient, randomized controlled clinical trial in patients with relapsed or refractory Acute Myeloid Leukemia (AML) who are age 55 and above. The SIERRA trial was conducted at 24 preeminent transplant centers in the U.S. and Canada. The primary endpoint of durable Complete Remission (dCR) at six months and a secondary endpoint of overall survival. Upon approval, Iomab-B is intended to prepare and condition patients for a bone marrow transplant, also referred to as a hematopoietic stem cell transplant, in a potentially safer and more efficacious manner than the non-targeted intensive chemotherapy conditioning that is the current standard of care in bone marrow transplant conditioning. A bone marrow transplant is often considered the only potential cure for patients with certain blood-borne cancers and blood disorders.