Dr. Nghiem on Pembrolizumab for Advanced Merkel Cell Carcinoma

Paul Nghiem, MD, PhD, Michael Piepkorn Endowed Chair in Dermatology Research, professor of Dermatology/Medicine at Fred Hutchinson Cancer Research Center, University of Washington Medicine, discusses a phase II trial investigating PD-1 blockade with pembrolizumab as first systemic therapy in patients with advanced Merkel cell carcinoma (MCC).

Adults with advanced, unresectable MCC, good performance status, and those who were not immune suppressed or did not have autoimmune disease were eligible for the trial. Pembrolizumab was administered at 2 mg/kg every 3 weeks. At the time of analysis, which was performed after 12-weeks of treatment, 24 patients had received pembrolizumab and 14 patients had been scanned for signs of disease, explains Nghiem.

Of the 14 evaluable patients, 10 responded to pembrolizumab; representing a 71% response rate, according to Nghiem. These responses consisted of 1 complete response (CR), 1 unconfirmed CR, 4 partial responses (PR), 2 unconfirmed PRs, and 2 progressions. While this data is still early, these results are very promising, especially in such a rare and difficult-to-treat disease, says Nghiem.

Although analysis of PD-L1 expression is still ongoing, Merkel polyomavirus-specific T cells, which are often found in patients with MCC, commonly express inhibitory coreceptors, such as PD-1. Additionally, MCC often expresses PD-L1, suggesting that this rare disease could be highly vulnerable to PD-1 inhibition.

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