FDA Approves Bispecific Antibody Mosunetuzumab for R/R Follicular Lymphoma


The approval makes mosunetuzumab the first in its class approved to treat follicular lymphoma and comes shortly after data from a phase 2 trial was presented at the annual meeting of the American Society of Hematology.

The FDA has approved mosunetuzumab-axgb (Lunsumio; Genentech), a bispecific antibody for the treatment of adults with relapsed or refractory follicular lymphoma (R/R FL) after 2 or more prior lines of systemic therapy. In July 2022, FDA had granted priority review to mosunetuzumab for R/R FL.

The decision was supported by data from the phase 2 GO29781 study (NCT02500407), which demonstrated high and durable response rates. As this is an accelerated approval, continued approval may be contingent on the verification of clinical benefit in a confirmatory trial.

Mosunetuzumab is the first of its class approved to treat FL. Bispecific antibodies aim at 2 targets, increasing their potency against cancer. These are off-the-shelf products, as opposed to chimeric antigen receptor (CAR) T-cell therapies, which are personalized.

“This approval is a significant milestone for people with relapsed or refractory follicular lymphoma, who have had limited treatment options until now,” Elizabeth Budde, MD, PhD, hematologic oncologist and associate professor, City of Hope Division of Lymphoma, Department of Hematology & Hematopoietic Cell Transplantation, and Lunsumio clinical trial investigator, said in a statement. “As a first-in-class T-cell engaging bispecific antibody that can be initiated in an outpatient setting, Lunsumio’s high response rates and fixed-duration could change the way advanced follicular lymphoma is treated.”

Data presented1 at the annual meeting of the American Society of Hematology (ASH), held earlier this month in New Orleans, Louisiana, showed that after a median of 28.3 months of follow-up, 60% of patients with 2 or more prior therapies experienced a complete response (CR) (95% CI, 49.1%-70.2%) and 77.8% achieved an objective response, which includes CR plus partial responses (95% CI, 67.8%-85.9%).

Furthermore, 62.7% of patients who achieved CR were still in remission after 24 months (95% CI, 37.7%-87.7%). Nearly half (48.3%) of patients remained progression free (95% CI, 36.2%-60.5%).

The most common adverse event (AE) was cytokine release syndrome (CRS), which occurred in 38% of patients for a median duration of 3 days. CRS can be severe and life-threatening and is also a common AE of CAR T-cell therapies. Other common AEs that occurred in 20% or more of patients were fatigue, rash, pyrexia, and headache.

Prior to the approval, Nancy L. Barlett, MD, of the Siteman Cancer Center of Washington University School of Medicine in St Louis, Missouri, wrote in an editorial2 in New England Journal of Medicine that “bispecific agents will be an excellent option for the 60% of patients in whom second-line CAR T-cell therapy fails.” Bartlett also presented the phase 2 data on mosunetuzumab at the ASH annual meeting.

Mosunetuzumab is delivered as an intravenous infusion for a fixed duration and can be infused in the outpatient setting. Hospitalization for select AEs may be necessary and hospitalization is recommended for infusions after a grade 3 CRS event or should be considered after a grade 2 CRS event.

“This additional treatment option is good news for people whose blood cancer has not responded to multiple lines of treatment because it can become more difficult to treat each time it returns,” said Lee Greenberger, PhD, chief scientific officer of the Leukemia & Lymphoma Society. “This bispecific antibody is an off-the-shelf, accessible treatment option that has the potential to help those with relapsed or refractory follicular lymphoma achieve remission.”


1. Bartlett NL, Sehn LH, Matasar MJ, et al. Mosunetuzumab monotherapy demonstrates durable efficacy with a manageable safety profile in patients with relapsed/refractory follicular lymphoma who received ≥2 prior therapies: updated results from a pivotal phase II study. Presented at: 64th American Society of Hematology Annual Meeting & Exposition; December 9-13, 2022; New Orleans, Louisiana. Abstract 610.

2. Bartlett NL. Bispecific antibodies in lymphoma - another win for T cells. N Engl J Med. 2022;387(24):2285-2286. doi:10.1056/NEJMe2212732

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