FDA OKs Another PD-1 Inhibitor for Merkel Cell Carcinoma

The second time proved to be the charm for the PD-1 inhibitor retifanlimab (Zynyz), as the FDA approved the drug for Merkel cell carcinoma (MCC).

The agency had previously rejected an application from Incyte for approval of retifanlimab for locally advanced squamous carcinoma of the anal canal, following a negative review from the Oncologic Drugs Advisory Committee.

The accelerated approval in MCC stipulates use of the drug for metastatic or recurrent locally advanced forms of the aggressive skin cancer. Full approval may require additional studies to support the drug's safety and efficacy.

"More than a third of patients with MCC present with regional or distant metastases, which are associated with high rates of mortality," said Shailender Bhatia, MD, of the University of Washington and Fred Hutchinson Cancer Center in Seattle, in a statement from Incyte. "The approval of Zynyz offers healthcare providers another first-line treatment option against MCC that can result in durable responses in patients with metastatic disease, and I look forward to having Zynyz in our treatment portfolio for these difficult-to-treat patients."

Principal support for the accelerated approval came from the single-arm, open-label PODIUM-201 trial, which involved 65 patients with metastatic or recurrent locally advanced MCC and no prior chemotherapy for advanced disease. The trial had a primary endpoint of objective response, and the results showed a 52% response rate, including 12 complete responses (18%). Duration of response ranged from 1.1 to 24.9 months, and 62% of the responses lasted 12 months or longer.

Serious adverse events (AEs) occurred in 22% of patients, the most common being fatigue, arrhythmia, and pneumonitis. The most common AEs (≥10% of patients regardless of grade) were fatigue, musculoskeletal pain, pruritus, diarrhea, rash, pyrexia, and nausea.

The recommended dose of intravenous retifanlimab is 500 mg, administered every 4 weeks for up to 2 years, or until disease progression or unacceptable toxicity.

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