ARTICLE ABSTRACTPurpose: To evaluate the safety, preliminary efficacy, and pharmacokinetics of inotuzumab ozogamicin, an anti-CD22 antibody conjugated to calicheamicin, in combination with the immunochemotherapeutic regimen, rituximab, cyclophosphamide, vincristine, and prednisone (R-CVP), in patients with relapsed/refractory CD22+ B-cell non-Hodgkin lymphoma (NHL).Experimental Design: In part 1 (n = 16), patients received inotuzumab ozogamicin plus R-CVP on a 21-day cycle with escalating doses of cyclophosphamide first then inotuzumab ozogamicin. Part 2 (n = 10) confirmed the safety and tolerability of the maximum tolerated dose (MTD), which required a dose-limiting toxicity rate of <33% in cycle 1 and <33% of patients discontinuing before cycle 3 due to treatment-related adverse events (AEs). Part 3 (n = 22) evaluated the preliminary efficacy of inotuzumab ozogamicin plus R-CVP.Results: The MTD was determined to be standard-dose R-CVP plus inotuzumab ozogamicin 0.8 mg/m2. The most common treatment-related grade ≥3 AEs in the MTD cohort (n = 38) were hematologic: neutropenia (74%), thrombocytopenia (50%), lymphopenia (42%), and leukopenia (47%). Among the 48 patients treated in the study, 13 discontinued due to AEs, most commonly thrombocytopenia (n = 10). Overall, 13 patients died, including one death due to treatment-related pneumonia secondary to neutropenia. Among patients receiving the MTD (n = 38), the overall response rate (ORR) was 84% (n = 32), including 24% (n = 9) with complete response; the ORR was 100% for patients with indolent lymphoma (n = 27) and 57% for those with aggressive histology lymphoma (n = 21).Conclusions: Inotuzumab ozogamicin at 0.8 mg/m2 plus full dose R-CVP was associated with manageable toxicities and demonstrated a high rate of response in patients with relapsed/refractory CD22+ B-cell NHL. The study is registered at ClinicalTrials.gov (NCT01055496). Clin Cancer Res; 22(19); 4807–16. ©2016 AACR.