The approval was supported by data from the phase 1/2 GO29781 trial (NCT02500407), which compared SC mosunetuzumab with intravenous (IV) administration of the agent in patients with relapsed/refractory follicular lymphoma.2 Findings from the primary analysis of GO29781 demonstrated that SC mosunetuzumab displayed pharmacokinetic noninferiority compared with the IV formulation.1 The overall response rate (ORR) among patients who received the fixed-duration, SC formulation was 74.5% (95% CI, 64.4%-82.9%); the complete response (CR) rate was 58.5% (95% CI, 46.9%-68.6%). The median duration of CR was 20.8 months (95% CI, 18.8-not evaluable [NE]).
“Building on the benefits of its fixed-duration dosing schedule, [mosunetuzumab] can now be administered with a one-minute subcutaneous injection, providing people with relapsed or refractory follicular lymphoma an additional treatment option to help meet their individual clinical requirements and lifestyle preferences,” Levi Garraway, MD, PhD, chief medical officer and head of global product development at Roche, stated in a news release. “Developing new formulations of our medicines is part of our commitment to offering greater flexibility and a better treatment experience for patients.”
What were the key design characteristics of the GO29781 study?
GO29781 was an open-label, multicenter study that enrolled patients with histologically confirmed grade 1 to 3a follicular lymphoma.2 Patients were required to have relapsed/refractory disease following treatment with at least 2 systemic therapies, including a prior anti-CD20 agent and an alkylator therapy. An ECOG performance status of 0 or 1 was also necessary for enrollment.
Patients received IV or SC mosunetuzumab. In the IV arm (n = 90), patients received the agent on days 1, 8, and 16 of cycle 1 at respective doses of 1 mg, 2 mg, and 60 mg; on day 1 of cycle 2 at 60 mg; on day 1 of cycle 3 through 8 at 30 mg. In the SC arm (n = 94), mosunetuzumab was administered at 5 mg, 45 mg, and 45 mg on days 1, 8, and 15 of cycle 1, respectively, as well as at 45 mg on day 1 of cycles 2 through 8. In both arms, patients with a partial response or stable disease after cycle 8 continued treatment for up to cycle 17, using the same dosing schedule given in cycle 8.
The coprimary end points were observed C3 serum trough concentration and model-predicted cumulative serum area under the time curve over days 0 through 84. Key secondary end points included ORR, CR rate, duration of response (DOR), duration of CR, progression-free survival (PFS), overall survival (OS), and safety.
What were the safety and additional efficacy data that were reported with SC mosunetuzumab?
Additional findings from the primary analysis of GO29781 presented during the 2025 SOHO Annual Meeting showed that the median DOR in the SC arm was 22.8 months (95% CI, 18.8-NE). The median PFS was 23.7 months (95% CI, 14.6-NE) and the median OS was not reached (95% CI, NE-NE). All of the prespecified efficacy measures in the SC arm were similar with those in the IV arm.
In terms of safety, any-grade adverse effects (AEs) were reported at a rate of 98.9% in the SC arm. Patients in this arm also experienced grade 3 to 4 AEs (48.9%), serious AEs (39.4%), grade 5 AEs (5.3%), and AEs leading to discontinuation of mosunetuzumab. Any-grade cytokine release syndrome (CRS) occurred in 29.8% of patients. The median duration of CRS was 2 days (range, 1-15) and all instances of CRS were resolved in both arms.
Findings from GO29781 have been submitted to other global health care authorities, including the FDA, according to Roche.1 Long-term data from the study will be presented during the 2025 ASH Annual Meeting and Exposition in December.
References
- European Commission approves Roche’s Lunsumio subcutaneous for relapsed or refractory follicular lymphoma. News release. Roche. November 18, 2025. Accessed November 19, 2025. https://www.roche.com/media/releases/med-cor-2025-11-19
- Bartlett NL, Sehn LH, Assouline S, et al. Fixed-duration subcutaneous mosunetuzumab (Mosun SC) leads to high rates of durable responses, low rates of cytokine release syndrome (CRS), and non-inferior exposure compared with intravenous administration in patients with relapsed/refractory (R/R) follicular lymphoma (FL): primary analysis of a pivotal phase 2 study. Clin Lymphoma Myeloma Leuk. 2025;25(suppl 1):S821. doi:10.1016/S2152-2650(25)02418-8
