This product is a first-in-class bispecific antibody that is designed to target CD20 on the surface of B cells and CD3 on the surface of T cells. This dual targeting activates and redirects a patient’s existing T cells to engage and eliminate target B cells by releasing cytotoxic proteins into the B cells, according to the manufacturer, Genentech.
Mosunetuzumab-axgb is administered as an intravenous infusion for a fixed duration, which allows for time off therapy, and can be infused in an outpatient setting, the company noted.
The drug was granted an accelerated approval on the basis of response rate data from the phase 2 GO29781 trial. Continued approval for this indication may be contingent upon verification and description of clinical benefit in a confirmatory trial, the company noted.
The GO29781 study was carried out in individuals with pretreated follicular lymphoma, including those who were at high risk for disease progression or whose disease was refractory to prior therapies.
A complete response was achieved in 60% of patients (54 of 90).
An objective response rate (a combination of complete and partial responses) was seen in 80% of patients who received the drug, with a majority maintaining responses for at least 18 months.
The median duration of response among those who responded was 22.8 months.
Safety data come from 218 patients with hematologic cancers who received mosunetuzumab-axgb at the recommended dose. The most common adverse event was cytokine release syndrome (39%), which can be severe and life-threatening. The median duration of cytokine release syndrome events was 3 days (range, 1-29 days). Other common adverse events (≥ 20%) included fatigue, rash, pyrexia, and headache.
“This approval is a significant milestone for people with relapsed or refractory follicular lymphoma, who have had limited treatment options until now,” said Elizabeth Budde, MD, PhD, from the City of Hope, Los Angeles, division of lymphoma, and clinical trial investigator.
Dr. Budde presented data on mosunetuzumab-axgb at the 2021 annual meeting of the American Society of Hematology, as reported by this news organization.
She noted that the 60% complete response rate seen with this new drug contrasts with the 14% that has been seen for historical controls.
“We have seen deep and durable responses in heavily pretreated, high-risk relapsed/refractory follicular lymphoma patients with fixed-duration treatment. We also observed a very favorable tolerability profile, with most cytokine release syndrome confined to cycle 1 and low grade, and treatment administration is without mandatory hospitalization,” she commented at the time.
A lymphoma specialist who was not involved in the study told this news organization at the time that he was favorably impressed by the findings.
“To me, the single-agent data looks really outstanding, with a response rate of 80%, a complete response rate of 60%, and a median duration of response of 23 months, and really very acceptable rates of cytokine release syndrome,” commented Brad S. Kahl, MD, from the Siteman Cancer Center and Washington University in St. Louis.
“I think as a single agent – if it does get approval – it will be a really valuable addition to the armamentarium in follicular lymphoma,” he added.
A version of this article first appeared on Medscape.com.