Mosunetuzumab Showed Durable Responses for Relapsed or Refractory Follicular Lymphoma

Updated data from a pivotal phase II study of the bispecific antibody mosunetuzumab in relapsed or refractory follicular lymphoma demonstrated that the durable responses previously seen with the drug continued to be observed with longer follow-up.

Loretta Nastoupil, MD, of the University of Texas MD Anderson Cancer Center, and colleagues presented data with a 28.3-month median follow-up as a poster presentation during the Eleventh Society of Hematologic Oncology Annual Meeting.¹

The single-arm, multicenter study included 90 patients with grade 1-3a follicular lymphoma who had received two or more prior lines of therapy. Intravenous mosunetuzumab was given using step-up dosing in cycle one, with patients receiving eight cycles if they achieved a complete response (CR) by cycle eight, or 17 cycles if they achieved partial response or stable disease by cycle eight.

In December 2022, mosunetuzumab received US Food and Drug Administration (FDA) accelerated approval for relapsed or refractory follicular lymphoma after two or more lines of therapy. The approval was based on initial results of this study, with an objective response rate of 80% and a complete response rate of 60%. With a median follow-up of 14.9 months among responders, the estimated median duration of response was 22.8 months.²

As of July 8, 2022, the investigator based objective response rate was 78% with a CR rate of 60%. Median progression-free survival (PFS) was 24 months with mosunetuzumab compared with 12 months with the last prior therapy. The 24-month PFS was 48% with mosunetuzumab.

Median duration of response, median duration of CR, and time-to-next therapy with mosunetuzumab were not reached.

Cytokine release syndrome (CRS) occurred in 44% of patients but was mostly grade 1/2. No new CRS events or other fatal, serious, or grade 3 or worse adverse events were reported since the previous analysis.

References

1. Barlett NL, Sehn LH, Matasar M, 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. IBCL-458. Presented at the Eleventh Society of Hematologic Oncology Annual Meeting; September 6-9, 2023; Houston, Texas.

2. US Food and Drug Administration. FDA grants accelerated approval to mosunetuzumab-axgb for relapsed or refractory follicular lymphoma. December 22, 2022. https://www.fda.gov/drugs/resources-information-approved-drugs/fda-grants-accelerated-approval-mosunetuzumab-axgb-relapsed-or-refractory-follicular-lymphoma