Yttrium-90-labeled anti-CD20 monoclonal antibody therapy of recurrent B-cell lymphoma

A Phase I/II dose escalation study of ⁹⁰Y-murine anti-CD20 monoclonal antibody (mAb) in patients with recurrent B-cell lymphoma was performed. The primary objectives of the study were: (a) to determine the effect of the preinfusion of unlabeled anti-CD20 mAb on the biodistribution of ¹¹¹In-anti-CD20 mAb; (b) to determine the maximal tolerated dose of ⁹⁰Y-anti-CD20 mAb that does not require bone marrow transplantation; and (c) to evaluate the safety and antitumor effect of ⁹⁰Y-anti-CD20 mAb in patients with recurrent B-cell lymphoma. Eighteen patients with relapsed low- or intermediate-grade non-Hodgkin's lymphoma were treated. Biodistribution studies with ¹¹¹In-anti-CD20 mAb were performed prior to therapy. Groups of three or four patients were treated at dose levels of ~ 13.5, 20, 30, 40, and 50 mCi ⁹⁰Y-anti-CD20 mAb. Three patients were retreated at the 40-mCi dose level. The use of unlabeled antibody affected the biodistribution favorably. Nonhematological toxicity was minimal. The only significant toxicity was myelosuppression. The overall response rate following a single dose of ⁹⁰Y-anti-CD20 mAb therapy was 72%, with six complete responses and seven partial responses and freedom from progression of 3-29+ months following treatment, Radioimmunotherapy with ≤50 mCi ⁹⁰Y-anti-CD20 mAb resulted in minimal nonhematological toxicity and durable clinical responses in patients with recurrent B cell lymphoma. Doses of ≤40 mCi ⁹⁰Y-anti-CD20 mAb were not myeloablative.