FDA Approves New Merkel Cell Carcinoma Drug Zynyz

The US Food and Drug Administration (FDA) has approved retifanlimab-dlwr (Zynyz), an intravenous programmed death receptor–1 (PD-1) inhibitor, for the treatment of adults with metastatic or recurrent locally advanced Merkel cell carcinoma (MCC), the agency announced.

This marks the first regulatory approval for the PD-1 inhibitor. The FDA granted accelerated approval for the drug on the basis of tumor response rate and duration of response from the POD1UM-201 trial. Drugmaker Incyte said that “continued approval of Zynyz for this indication may be contingent upon verification and description of clinical benefit in confirmatory trials.”

MCC is a rare and aggressive skin cancer with a high rate of metastatic disease and an estimated 5-year overall survival of just 14% among those who present with metastatic disease. Incidence is rapidly increasing in the US, particularly among adults older than 65 years, Incyte noted.

“More than a third of patients with MCC present with regional or distant metastases, which are associated with high rates of mortality,” principal author Shailender Bhatia, MD, of the University of Washington and Fred Hutchinson Cancer Center, said in a news release. “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.”

POD1UM-201 was an open-label, single-arm, phase 2 study that evaluated the agent in 65 systemic treatment–naive adults with metastatic or recurrent locally advanced MCC.

Overall, 52% of patients had an objective response rate. A complete response was observed in 12 patients (18%), and a partial response was observed in 22 patients (34%).

Duration of response ranged from 1.1 to 24.9 months; 76% of responders experienced responses of 6 months or longer, and 62% experienced responses of 12 months or longer.

Study participants received a 500-mg dose of retifanlimab every 4 weeks for up to 24 weeks or until disease progression or unacceptable toxicity. Serious adverse events occurred in 22% of patients and most often included fatigue, arrhythmia, and pneumonitis; 11% of patients discontinued treatment because of serious adverse events.

Retifanlimab may cause a severe or life-threatening immune response during treatment or after discontinuation. Patients should be advised to immediately report any new or worsening signs or symptoms to their healthcare provider. Side effects can also be reported to the FDA. 

Sharon Worcester, MA, is an award-winning medical journalist based in Birmingham, Alabama, writing for Medscape, MDedge and other affiliate sites. She currently covers oncology, but she has also written on a variety of other medical specialties and healthcare topics. She can be reached at [email protected] or on Twitter: @SW_MedReporter.

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