The Food and Drug Administration (FDA) has accepted for Priority Review the Biologics License Application (BLA) for mosunetuzumab for the treatment of adults with relapsed or refractory (R/R) follicular lymphoma (FL) who have received at least 2 prior systemic therapies.

Mosunetuzumab is a potential first-in-class CD20xCD3 T-cell engaging bispecific antibody that targets CD20 on the surface of B cells and CD3 on the surface of T cells. The application is supported by data from an open-label, dose-escalation and expansion phase 1/2 study (GO29781; Identifier: NCT02500407), which evaluated the efficacy, safety and pharmacokinetics of mosunetuzumab in adults with R/R B-cell non-Hodgkin lymphoma.

Results showed mosunetuzumab induced high and durable complete response rates in patients with follicular lymphoma who received 2 or more prior therapies, with 57% (95% CI, 49-70) of patients maintaining responses for at least 18 months. At a median follow-up of 18.3 months, the complete response (CR) rate was 60% (n=54/90) and the objective response rate was 80% (n=72/90). Among responders, the median duration of response was 22.8 months (95% CI, 9.7-not estimable).

The most common adverse event associated with mosunetuzumab treatment was cytokine release syndrome (39%; n=86/218). Other adverse events included fatigue, headache, neutropenia, fever, and hypophosphatemia.

“Clinical trial results have demonstrated durable responses with mosunetuzumab in advanced follicular lymphoma, representing a step toward shifting the treatment paradigm,” said Levi Garraway, MD, PhD, chief medical officer and head of Global Product Development, Genentech. “Since mosunetuzumab does not require the collection or genetic modification of patient cells, it could become an effective, fixed-duration outpatient option without the barriers of travelling to a major academic center.”

The FDA previously granted Breakthrough Therapy and Orphan Drug designations to mosunetuzumab for the treatment of adults with R/R FL who have received at least 2 prior systemic therapies. The FDA is expected to make a decision on approval by December 29, 2022.

The Company is also investigating mosunetuzumab in combination with lenalidomide in patients with R/R FL after at least 1 prior systemic therapy in the phase 2 CELESTIMO study ( Identifier: NCT04712097), and in combination with polatuzumab vedotin (Polivy) in patients with diffuse large B-cell lymphoma after at least 1 prior systemic therapy in the phase 2 SUNMO study ( Identifier: NCT05171647).


FDA grants Priority Review to Genentech’s mosunetuzumab for people with relapsed or refractory follicular lymphoma. News release. Genentech. Accessed July 6, 2022.