On March 22, 2023, the anti–PD-1 antibody retifanlimab-dlwr was granted accelerated approval for adults with metastatic or recurrent locally advanced Merkel cell carcinoma.1
Supporting Efficacy Data
Approval was based on findings in POD1UM-201 (ClinicalTrials.gov identifier NCT03599713), a multicenter trial evaluating 65 patients who had not received prior systemic therapy for advanced disease. Patients received retifanlimab at 500 mg via intravenous (IV) infusion every 4 weeks until disease progression, unacceptable toxicity, or up to 24 months. An objective response on independent central review committee assessment occurred in 34 patients (52%, 95% confidence interval = 40%–65%), with a complete response in 12 (18%). Response durations ranged from 1.1 to more than 24.9 months.
How It Is Used
The recommended retifanlimab dose is 500 mg via IV infusion every 4 weeks until disease progression, unacceptable toxicity, or up to 24 months. No dose reductions are recommended. In general, retifanlimab should be withheld for grade 3 immune-mediated adverse reactions and permanently discontinued for grade 4 immune-mediated adverse reactions, recurrent grade 3 immune-mediated reactions requiring systemic immunosuppressive treatment, or an inability to reduce corticosteroid dose to ≤ 10 mg prednisone or equivalent per day within 12 weeks of initiating steroids.
The safety population consisted of 105 patients with Merkel cell carcinoma treated with retifanlimab in POD1UM-201. The most common adverse events of any grade were fatigue, musculoskeletal pain, pruritus, diarrhea, rash, pyrexia, and nausea. Serious adverse events occurred in 22% of patients. Retifanlimab has warnings/precautions for immune-mediated adverse reactions, infusion-related reactions, complications of allogeneic hematopoietic stem cell transplantation, and embryofetal toxicity. Patients should be advised not to breastfeed while receiving retifanlimab.
1. Zynyz (retifanlimab-dlwr) injection, for intravenous use, prescribing information, Incyte Corporation, March 2023. Available at https://www.accessdata.fda.gov/drugsatfda_docs/label/2023/761334s000lbl.pdf. Accessed April 4, 2023.