Complete remissions observed in acute myeloid leukemia following prolonged exposure to lintuzumab: a phase 1 trial

A multi-institutional, phase 1 dose-escalation trial of lintuzumab (humanized anti-CD33 antibody; SGN-33, HuM195) was performed in patients with CD33-positive myeloid malignancies. In this study, higher doses than previously tested and prolonged duration of treatment for responding patients were evaluated. Over the dose range of 1.5-8 mg/kg/week, lintuzumab was well tolerated, and a maximum tolerated dose was not defined. The most common adverse event was transient chills with the initial lintuzumab infusion (39%). Responses were observed in 7 of 17 patients with acute myeloid leukemia: morphologic complete remission (n = 4), partial remission (n = 2), and morphologic leukemia-free state (n = 1). Of 14 patients with myelodysplastic syndrome or myeloproliferative diseases, 1 patient had major hematologic improvement and 9 patients had stable disease. In contrast to aggressive conventional chemotherapy, lintuzumab was administered in an ambulatory clinic setting with acceptable toxicity.