Iomab-B: Pivotal Phase 3 SIERRA Trial

100% BMT Access and Engraftment with Iomab-B and Safety Data Through 100% Patient Enrollment in SIERRA

Gyurkocza et al. TCT 2022 Presentation. High Rates of Transplantation in the Phase III SIERRA Trial Utilizing Anti-CD45 Apamistamab with 131-Iodine (Iomab-B) Conditioning with Successful Engraftment and Tolerability in Relapsed/Refractory Acute Myeloid Leukemia Patients after Lack of Response to Conventional Care and Targeted Therapies

Iomab-B is currently being studied in the pivotal Phase 3 SIERRA (Study of Iomab-B in Elderly 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. Patient enrollment in the SIERRA trial was completed in the third quarter of 2021 and the last patient on SIERRA was transplanted in the fourth quarter of 2021.

The SIERRA trial enrolled patients at 24 preeminent transplant centers in the U.S. and Canada. The primary endpoint of the study is 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 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.

Iomab-B via the monoclonal antibody apamistamab, targets CD45, an antigen widely expressed on all types of blood cancer cells and immune cells including bone marrow progenitor stems cells. Iomab-B links apamistamab to the radioisotope iodine-131 and once attached to its target cells emits energy that travels a relatively long distance, 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 will avoid side effects of non-targeted chemotherapy and/or external beam radiation on most healthy tissues while effectively killing the patient's cancer and marrow cells.

Iomab-B was developed at the Fred Hutchinson Cancer Research Center where it was studied in several Phase 1 and Phase 2 trials in almost 300 patients in multiple blood cancer indications, including acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), chronic myeloid leukemia (CML), acute lymphoblastic leukemia (ALL), chronic lymphocytic leukemia (CLL), Hodgkin's disease (HD), Non-Hodgkin lymphomas (NHL) and multiple myeloma (MM) and is currently being studied in several ongoing physician trials. Iomab-B has been granted Orphan Drug Designation for relapsed or refractory AML in patients 55 and above by the U.S. Food and Drug Administration and the European Medicines Agency.

In a Phase 2 clinical study in 58 patients with advanced AML or high-risk myelodysplastic syndrome (MDS) age 50 and older, Iomab-B produced complete remissions in 100% of patients and these patients experienced transplant engraftment at day 28. The overall survival rate of the 36 relapsed or refractory AML patients in the proof of concept study was 30% at one year and approximately 20% at two years. See Iomab-B study results here.