On December 22, 2022, the Food and Drug Administration (FDA) granted accelerated approval to mosunetuzumab-axgb (Lunsumio, Genentech, Inc.), a bispecific CD20-directed CD3 T-cell engager for adult patients with relapsed or refractory follicular lymphoma (FL) after two or more lines of systemic therapy.

Mosunetuzumab-axgb was evaluated in GO29781 (NCT02500407), an open-label, multicenter, multi-cohort study. The efficacy population consisted of 90 patients with relapsed or refractory FL who had received at least two prior lines of systemic therapy, including an anti-CD20 monoclonal antibody and an alkylating agent.

The main efficacy outcome measure was objective response rate (ORR) assessed by an independent review facility according to standard criteria for non-Hodgkin’s lymphoma (Cheson 2007). The ORR was 80% (95% CI: 70, 88), with 60% achieving complete responses. With a median follow-up of 14.9 months among responders, the estimated median duration of response (DOR) was 22.8 months (95% CI: 10, not reached) and the estimated DOR rate at 12 months and 18 months was 62% and 57%, respectively.

The prescribing information has a Boxed Warning for serious or life-threatening cytokine release syndrome (CRS). Warnings and precautions include neurologic toxicity, infections, cytopenias, and tumor flare. Among 218 patients with hematologic malignancies who received mosunetuzumab-axgb at the recommended dose, CRS occurred in 39% of patients, neurologic toxicity in 39% (including ICANS in 1%), serious infections in 17%, and tumor flare in 4%. For CRS, Grade 2 occurred in 15%, Grade 3 in 2%, and Grade 4 in 0.5%.

In the pooled safety population of 218 patients, the most common adverse reactions (≥20%) were cytokine release syndrome, fatigue, rash, pyrexia, and headache. The most common Grade 3 to 4 laboratory abnormalities (≥10%) were decreased lymphocyte count, decreased phosphate, increased glucose, decreased neutrophil count, increased uric acid, decreased white blood cell count, decreased hemoglobin, and decreased platelets.

The recommended mosunetuzumab-axgb dose is 1 mg on Cycle 1 Day 1, 2 mg on Cycle 1 Day 8, 60 mg on Cycle 1 Day 15, 60 mg on Cycle 2 Day 1, and 30 mg on Day 1 in subsequent cycles. A treatment cycle is 21 days. Mosunetuzumab-axgb should be administered for 8 cycles unless patients experience unacceptable toxicity or disease progression. After 8 cycles, patients with a complete response should discontinue therapy. Patients with a partial response or stable disease should continue treatment up to 17 cycles unless they experience progressive disease or unacceptable toxicity.

View full prescribing information for Lunsumio.

This review used the Assessment Aid, a voluntary submission from the applicant to facilitate the FDA’s assessment.

This application was granted priority review and breakthrough designation. A description of FDA expedited programs is in the Guidance for Industry: Expedited Programs for Serious Conditions-Drugs and Biologics. The application also was granted orphan drug designation.

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