Additional Relevant Details The study is a phase 1, open-label, multicenter, dose-escalation clinical trial. It will initially evaluate the maximum tolerated dose of SGN-CD123A, followed by an expansion cohort to further define safety and estimate anti-leukemic activity. In addition, the trial will assess pharmacokinetics, remission rate, duration of complete remission and overall survival. The study is designed to evaluate SGN-CD123A administered every three weeks and will enroll up to approximately 100 relapsed or refractory patients at multiple centers in the United States.