Retifanlimab: A PD-1 Inhibitor for Rare and Difficult Cancers
Retifanlimab is a modern immunotherapy drug. Doctors know it better by its brand name, Zynyz. Incyte Corporation developed this medication.
It belongs to the class of PD-1 inhibitors. These drugs help the immune system fight cancer more effectively.
How Retifanlimab Works
Cancer cells often hide from the immune system. They use proteins called PD-L1 and PD-L2 to switch off T-cells.
Retifanlimab blocks the PD-1 receptor on T-cells. As a result, it prevents this shutdown signal. The immune system can then recognize and attack the cancer cells more actively.
Approved Uses
The U.S. Food and Drug Administration first approved retifanlimab in March 2023. Regulators cleared it for adults with metastatic or recurrent locally advanced Merkel cell carcinoma. This rare and aggressive skin cancer had limited treatment options before.
In May 2025, the FDA expanded its approval. Doctors can now use retifanlimab in two ways for squamous cell carcinoma of the anal canal.
First, they combine it with carboplatin and paclitaxel as an initial treatment for patients with inoperable locally recurrent or metastatic disease. Second, they prescribe it alone when the cancer returns or spreads after platinum-based chemotherapy, or when patients cannot tolerate that chemotherapy.
How Patients Receive the Drug
Healthcare providers give retifanlimab as an intravenous infusion. The typical dose is 500 mg every four weeks. Each infusion usually lasts about 30 minutes.
Clinical Importance
Retifanlimab offers a new option for two challenging cancers. Merkel cell carcinoma and advanced anal canal cancer often respond poorly to older treatments.
By releasing the brakes on the immune system, this PD-1 inhibitor has shown meaningful tumor responses in clinical studies. Researchers continue to explore its potential in other cancer types.
Overall, retifanlimab expands the growing list of immune checkpoint inhibitors. It provides targeted hope for patients with rare or hard-to-treat malignancies.