Obinutuzumab monotherapy at a dose of 1,000 mg as well as 2,000 mg has significant efficacy in untreated patients with chronic lymphocytic leukemia (CLL) with acceptable toxicity, a new study published online ahead of print in the journal Blood has shown.1

Because obinutuzumab, a glycoengineered, type 2 anti-CD20 humanized monoclonal antibody, has single-agent activity in relapsed CLL, and dose-response relationships have been observed with other CD20 antibodies, researchers sought to evaluate whether an obinutuzumab dose response exists in symptomatic, previously untreated patients with CLL.

For the phase 2 study, 80 participants were randomly assigned to receive obinutuzumab at a dose of 1,000 mg (100 mg IV day 1; 900 mg day 2; 1,000 mg days 8 and 15 of cycle 1; 1,000 mg day 1 of cycles 2-8) or 2,000 mg (100 mg IV day 1; 900 mg day 2; 1,000 mg day 3; 2,000 mg days 8 and 15 of cycle 1; 2,000 mg day 1 of cycles 2-8). Of the 80 patients, 41% had high-risk Rai disease and 10% had del(17p)(13.1) mutations.

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Results showed that overall response rate was 67% in the 2,000 mg group compared with 49% in the 1,000 mg group (P=.08) and complete response or complete response with incomplete cytopenia response was higher in the 2,000 mg treatment arm.

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In regard to safety, therapy was well tolerated overall and infusion reactions were manageable.

“Although exploratory, a dose response relationship may exist but its relevance to improving progression-free survival is uncertain and will require further follow-up,” the authors concluded.


  1. Byrd JC, Flynn J, Kipps, TJ, et al. Randomized phase II study of obinutuzumab monotherapy in symptomatic, previously untreated chronic lymphocytic leukemia (CLL) [published online ahead of print October 15, 2015]. Blood. doi: 10.1182/blood-2015-03-634394.