A Phase 2 Study of Actinium-225 (225Ac)-Lintuzumab in Older Patients with Untreated Acute Myeloid Leukemia (AML) - Interim Analysis of 1.5 Μci/kg/dose

Background: Older patients (pts) with AML unfit for intense induction chemotherapy have a poor prognosis with a 5 year survival of <10%. 225Ac-lintuzumab is composed of 225Ac linked to a humanized anti-CD33 monoclonal antibody. Data were previously presented on the initial 13 pts who received 2.0 µCi/kg/dose on Days 1 and 8 (ASH, 2017, Abstract 616). Although that dose resulted in a high response rate of 69%, there were 6 pts with Grade 4 thrombocytopenia lasting >6 weeks and 5 CRi patients did not reach an ANC of ≥ 500/µL. Therefore, the activity level was reduced to 1.5 µCi/kg/dose for further evaluation.