Results of inotuzumab ozogamicin, a CD22 monoclonal antibody, in refractory and relapsed acute lymphocytic leukemia

BACKGROUND CD22 expression occurs in >90% of patients with acute lymphocytic leukemia (ALL). Inotuzumab ozogamicin, a CD22 monoclonal antibody bound to calicheamicin, is active in ALL. METHODS Patients with refractory-relapsed ALL received treatment with inotuzumab. The first 49 patients received single-dose, intravenous inotuzumab at doses of 1.3 to 1.8 mg/m2 every 3 to 4 weeks. In the next 41 patients, the schedule was modified to inotuzumab weekly at a dose of 0.8 mg/m2 on day 1 and at a dose of 0.5 mg/m2 on days 8 and 15, every 3 to 4 weeks, based on higher in vitro efficacy with more frequent exposure. RESULTS Ninety patients were treated; 68% were in salvage 2 or beyond. Overall, 17 patients (19%) achieved a complete response (CR), 27 (30%) had a CR with no platelet recovery (CRp), and 8 (9%) had a bone marrow CR (no recovery of counts), for an overall response rate of 58%. Response rates were similar for single-dose and weekly dose inotuzumab (57% vs 59%, respectively). The median survival was 6.2 months overall, 5.0 months with the single-dose schedule, and 7.3 months with the weekly dose schedule. The median survival was 9.2 months for patients in salvage 1 (37% at 1 year), 4.3 months for patients in salvage 2, and 6.6 months for patients in salvage 3 or later. The median remission duration was 7 months. Reversible bilirubin elevation, fever, and hypotension were observed less frequently on the weekly dose. In total, 36 of 90 patients (40%) underwent allogeneic stem cell transplantation. Veno-occlusive disease was noted in 6 of 36 patients after stem cell transplantation (17%), was less frequent after the weekly schedule (7%), and with less alkylators in the preparative regimen. CONCLUSIONS Inotuzumab single-agent therapy was highly active, safe, and convenient in patients with refractory-relapsed ALL. A weekly dose schedule appeared to be equally effective and less toxic than a single-dose schedule. Cancer 2013;119:2728–2736. © 2013 American Cancer Society.