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.
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.
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.
- 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.