On December 22, 2022, the FDA accelerated the approval of mosunetuzumab-axgb (Lunsumio; Genentech), a bispecific CD20-directed CD3 T-cell engager, for adults with relapsed or refractory follicular lymphoma after ≥2 lines of systemic therapy. The FDA granted this indication breakthrough therapy and orphan drug designations.
This approval was based on results of the GO29781 study, an open-label, multicenter, multicohort clinical trial of 90 patients with relapsed or refractory follicular lymphoma who received ≥2 lines of systemic therapy.
The main efficacy measure was objective response rate (ORR). The ORR was 80% (95% confidence interval [CI], 70-88), with 60% of the patients achieving a complete response. At a median follow-up of 14.9 months, the estimated median duration of response (DOR) was 22.8 months (95% CI, 10-not reached). At 12 months, the estimated DOR was 62%, and at 18 months, 57%.
The prescribing information for mosunetuzumab includes a boxed warning for cytokine release syndrome (CRS). Among 218 patients with hematologic malignancies who received this drug, 39% had CRS, 17% had serious infections, and 4% had tumor flare. Grade 2 CRS was reported in 15% of patients, grade 3 in 2%, and grade 4 in 0.5%.
The most common (≥10%) grade 3 or 4 laboratory abnormalities were decreased lymphocyte count, decreased phosphate, increased glucose, decreased neutrophil count, increased uric acid, decreased white blood cell count, decreased hemoglobin, and decreased platelets.