Lintuzumab-Ac225 in Older Acute Myeloid Leukemia (AML) Patients

The study is a multicenter, open label Phase I/II trial. 1. Establish the MTD of fractionated doses of Lintuzumab-Ac225 in combination with low dose cytosine arabinoside (Low Dose Ara-C, LDAC) (Phase 1 portion) 2. Determine the response rate (CR + CRp + CRi) to fractionated doses of Lintuzumab-Ac225 alone (Phase 2 portion)

The study is a multicenter, open label Phase I/II trial. Phase I, dose-escalation: This portion of the overall study uses a 3+3 design to estimate the maximum tolerated dose (MTD). The starting dose level will be 1.0 μCi/Kg of Lintuzumab-Ac225 and 15 μg/Kg unlabeled HuM195 divided into 2 equal fractionated doses (0.5 μCi/Kg and 7.5 μg /Kg + 0.5 μCi/Kg and 7.5 μg /Kg) with the first fraction administered approximately 4 - 7 days after 1 cycle of LDAC (20 mg subQ every 12 h x 10 days administered for cytoreduction) and the second fraction administered 4-7 days after the first fraction. Subjects will then go on to receive up to 11 additional cycles of LDAC or until progression of disease. Three to six patients will be treated at each dose level, and dose escalation will proceed if less than 33% of patients in a cohort experience dose-limiting toxicity. Phase II, efficacy component. The study was designed as a 2- stage minimax design. Patients will be given two infusions of Lintuzumab-Ac225, 4-8 days apart (Day 5-Day 9), initially at the dose level determined to be the MTD in the Phase I portion. The second dose of Lintuzumab-Ac225 may be delayed up to 14 days after the first dose for clinical or scheduling reasons. Response will be initially assessed on or around days 28-42 after the final study drug administration. The primary endpoint (CR+CRp + CRi) will be determined on day 42. Best response will be evaluated from Day 1, Dose 1 until the end of the study.