Rapid Reduction of Peripheral Blasts in Older Patients with Refractory Acute Myeloid Leukemia (AML) Using Re-Induction with Single Agent Anti-CD45 Targeted Iodine (131I) Apamistamab [Iomab-B] Radioimmunotherapy in the Phase III SIERRA Trial

Abstract

blasts by 98% by day 3 in chemotherapy refractory AML. • Iomab-B conditioning leads to myeloablation in older patients with active disease (up to a median of 45% blasts in the marrow) as demonstrated by engraftment in all patients. • Successful engraftment after Iomab-B and HCT benefits patients who had prolonged neutropenia due to active and refractory disease prior to transplant. • While efficacy data is not yet available for these patients, rapid peripheral blast reduction is encouraging as prior studies utilizing cytotoxic chemotherapy suggest a relationship between the rate of disease reduction and disease response. The SIERRA trial is a prospective, randomized, phase 3, open-label, ongoing multicenter trial for patients aged ≥55 years with active, relapsed/refractory (R/R) AML evaluating allogeneic hematopoietic cell transplantation (HCT) versus conventional care (CC). Recent preliminary data demonstrated robust donor engraftment in all patients treated with Iomab-B (Agura et al, Blood 2018 132:1017) despite active disease. Rapid peripheral blast clearance is predictive of CR and RFS after cytotoxic chemotherapy for AML (Elliot et al, Blood 2007 110:4172; Gianfaldoni et al, BJH 2006 134:54). In the present study we characterize the anti-leukemic effect and rate of peripheral disease reduction by single-agent Iomab-B. Rapid reduction of peripheral blasts in older patients with refractory acute myeloid leukemia (AML) using reinduction with single agent anti-CD45 targeted iodine (131I) apamistamab [Iomab-B] radioimmunotherapy in the phase III SIERRA trial. Benjamin Tomlinson1, Vijay Reddy2, Mark S. Berger2, Jennifer Spross2, Renee Lichtenstein2, Boglarka Gyurkocza3 1 University Hospitals Case Medical Center, Cleveland, OH, 2Actinium Pharmaceuticals, New York, NY, 3 Memorial Sloan Kettering Cancer Center, New York, NY