Avelumab (Bavencio) is the first drug to receive approval from the Food and Drug Administration for Merkel cell carcinoma, and new findings show that it elicited durable responses in this hard-to-treat population.
The majority of responses were durable beyond 1 year, with an objective response rate of 33%.
“Merkel cell carcinoma is rare, aggressive skin cancer with a poor prognosis,” said lead author Howard L. Kaufman, MD, a surgical oncologist at the Rutgers Cancer Institute of New Jersey in New Brunswick, who discussed the findings during a presscast held at the annual meeting of the American Association for Cancer Research.
Even though Merkel cell carcinoma is a chemosensitive disease, long-term survival beyond 6 months has not been reported with chemotherapy, explained Dr. Kaufman.
In this phase II trial, Dr. Kaufman and his colleagues assessed the use of avelumab, a fully human anti–PD-L1 monoclonal antibody, in 88 patients with metastatic Merkel cell carcinoma that had progressed after treatment with chemotherapy.
All patients received 10 mg/kg avelumab as an intravenous infusion over one hour every 2 weeks. The primary endpoint was the best objective response and secondary endpoints included progression-free and overall survival.
At a median follow-up of 10.4 months, the response rate was 31.8% (28 responses), and this included 8 complete responses and 20 partial responses.
The estimated proportion of patients with duration of response of 6 months or longer was 92%, and the 6-month progression-free survival rate was 40%.
“The purpose of the presentation now is to report on longer 1-year follow-up data,” said Dr. Kaufman.
In the updated results, the objective response rate was 33.0% (95% confidence interval, 23.3%-43.8%) as two more patients moved into a total response. There were now a total of 10 (11.4%) complete responses and 19 (21.6%) partial responses.
The 6-month durable response rate was 30.6% (95% CI, 20.9%-40.3%), and the median duration of response has not yet been reached (range, 2.8–23.3-plus months; 95% CI, 18.0–not estimable). Responses were ongoing in 21 patients at the time of this analysis.
The estimated proportion of patients with a duration of response lasting 1 year or longer was 74% (95% CI, 53%-87%), and estimated 1-year progression-free survival was 30% (95% CI, 21%-41%). The 1-year overall survival rate was 52% (95% CI, 41%-62%) and median overall survival was 12.9 months (95% CI, 7.5–not estimable).
The maturing survival data suggest that there may be a long-term benefit for a proportion of patients.
“The findings of long-term responses and well-tolerated safety profile suggest that avelumab could be an important new agent for patients with Merkel cell carcinoma who have failed prior chemotherapy,” said Dr. Kaufman. “Given these results, it will be interesting to determine whether response rates could be increased by giving avelumab prior to chemotherapy or in combination with other treatments.”