Phase II Study: Mosunetuzumab Shows ‘Highly Encouraging Efficacy’ in Follicular Lymphoma

Subcutaneous mosunetuzumab treatment attained a promising safety and efficacy profile in patients with untreated, high-burden follicular lymphoma (FL), according to a phase II study.

Led by Lorenzo Falchi, MD, of the Memorial Sloan Kettering Cancer Center in New York, the multicenter study included 43 patients with stage II to IV FL. Subcutaneous mosunetuzumab was administered at 5 mg on day one, 45 mg on days eight, and 15 of cycle one, and 45 mg on day one of each subsequent 21-day cycle. Before each dose of mosunetuzumab, patients were premedicated with dexamethasone, diphenhydramine, and acetaminophen during cycle one and on day one of cycle two if cytokine release syndrome (CRS) was observed.

Treatment continued for eight cycles in patients who achieved complete response, and up to 17 cycles in patients who achieved partial response. Among 26 response-evaluable patients, the best overall response rate was 96% and the complete response rate was 81%. Two patients experienced disease progression at a median follow-up of six months.

Among 39 safety-evaluable patients, the most common treatment-emergent adverse events (AEs) included injection site reaction (72%), CRS (51%), fatigue (33%), dry skin (33%), skin rash (26%), ALT elevation (23%), and AST elevation (21%). CRS occurred most often after day one of cycle one.

Overall, Dr. Falchi and colleagues concluded that mosunetuzumab treatment presents a manageable safety profile and “highly encouraging efficacy,” though a follow-up assessment of durability of response is needed.

Reference

Falchi L, Okwali M, Ghione P, et al. Subcutaneous (SC) mosunetuzumab (mosun) as first-line therapy for patients (pts) with high tumor-burden follicular lymphoma (FL): first results of a multicenter phase 2 study. Blood. 2023. doi.org/10.1182/blood-2023-179906