A New Checkpoint Inhibitor Targeting PD-1 

The FDA has approved the monoclonal antibody retifanlimab-dlwr for some patients with Merkel cell carcinoma. 

The U.S. Food and Drug Administration (FDA) has granted accelerated approval to retifanlimab-dlwr (Zynyz) for the treatment of adult patients with metastatic or recurrent locally advanced Merkel cell carcinoma (MCC). 

Retifanlimab-dlwr is an immune checkpoint inhibitor, a type of immunotherapy that boosts the ability of T cells to kill cancer cells by turning off the T cells’ natural brakes. Retifanlimab-dlwr targets the protein PD-1 on the surface of T cells, preventing the cells from receiving signals that deactivate them.  

This is the first FDA approval for retifanlimab-dlwr.  

The approval is based on results from POD1UM-201, a phase II, open-label, multiregional, single-arm study in which 65 patients with metastatic or recurrent locally advanced MCC received retifanlimab-dlwr. The patients had not been previously treated with a systemic therapy. 

The objective response rate was 52% with a complete response rate of 18%. Among responders, 76% and 62% had responses that lasted for at least six and 12 months, respectively.  

Merkel cell carcinoma is a rare but aggressive type of skin cancer that forms in the top layer of the skin, often in areas of the body that are exposed to the sun.  According to federal statistics, Merkel cell carcinomas were diagnosed in 2.1 per 100,000 individuals each year between 2006 and 2015. The five-year relative survival rate was approximately 60% between 2005 and 2014. 

The FDA rendered its decision on March 22, 2023. Accelerated approval means that continued approval may be contingent upon a confirmatory trial.