Randomized Phase II Trial Comparing Obinutuzumab (GA101) With Rituximab in Patients With Relapsed CD20+ Indolent B-Cell Non-Hodgkin Lymphoma: Final Analysis of the GAUSS Study

Purpose Obinutuzumab (GA101), a novel glycoengineered type II anti-CD20 monoclonal antibody, demonstrated responses in single-arm studies of patients with relapsed/refractory non-Hodgkin lymphoma. This is the first prospective, randomized study comparing safety and efficacy of obinutuzumab with rituximab in relapsed indolent lymphoma. The primary end point of this study was the overall response rate (ORR) in patients with follicular lymphoma after induction and safety in patients with indolent lymphoma. Patients and Methods A total of 175 patients with relapsed CD20+ indolent lymphoma requiring therapy and with previous response to a rituximab-containing regimen were randomly assigned (1:1) to four once-per-week infusions of either obinutuzumab (1,000 mg) or rituximab (375 mg/m2). Patients without evidence of disease progression after induction therapy received obinutuzumab or rituximab maintenance therapy every 2 months for up to 2 years. Results Among patients with follicular lymphoma (n = 149), ORR seemed higher for obinutuzumab than rituximab (44.6% v 33.3%; P = .08). This observation was also demonstrated by a blinded independent review panel that measured a higher ORR for obinutuzumab (44.6% v 26.7%; P = .01). However, this difference did not translate into an improvement in progression-free survival. No new safety signals were observed for obinutuzumab, and the incidence of adverse events was balanced between arms, with the exception of infusion-related reactions and cough, which were higher in the obinutuzumab arm. Conclusion Obinutuzumab demonstrated a higher ORR without appreciable differences in safety compared with rituximab. However, the clinical benefit of obinutuzumab in this setting remains unclear and should be evaluated within phase III trials.