D’Angelo SP, et al. - Avelumab, an anti–programmed cell death ligand 1 (PD-L1) antibody, was shown to be efficacious in second-line or later treatment of patients with metastatic Merkel cell carcinoma (mMCC) in part A of the JAVELIN Merkel 200 trial (avelumab in patients with Merkel cell carcinoma). In JAVELIN Merkel 200 part B trial, first-line avelumab therapy for distant mMCC elicited high rates of response. This finding builds on previously reported antitumor activity after second-line or later treatment. Moreover, the durability of responses was suggested by maturing progression-free survival data. Avelumab’s approval in the United States and European Union and use as a standard-of-care treatment for mMCC was further supported.

• Researchers carried out an international, multicenter, single-arm, open-label clinical trial of first-line avelumab monotherapy, the JAVELIN Merkel 200 part B trial, including adults with mMCC who had not received prior systemic treatment for metastatic disease.
• Patients were not selected for PD-L1 expression or Merkel cell polyomavirus status.
• They gathered data from April 15, 2016, to March 24, 2017, and enrollment is ongoing.
• Administration of avelumab, 10 mg/kg, by 1-hour intravenous infusion every 2 weeks was continued until confirmed disease progression, unacceptable toxic effects, or withdrawal occurred.
• Researchers assessed tumor status every 6 weeks and evaluated it using independent review committee per Response Evaluation Criteria in Solid Tumors version 1.1.
• Durable response, defined as an objective response with a duration of at least 6 months, was the primary end point and secondary end points included best overall response, duration of response, progression-free survival, safety, and tolerability.

• As of March 24, 2017, enrollment of a total of 39 patients (30 men and 9 women; median age, 75 years [range, 47-88 years]) was carried out, with a median follow-up of 5.1 months (range, 0.3-11.3 months).
• A preplanned analysis assessing efficacy in 29 patients with at least 3 months of follow-up revealed the confirmed objective response rate to be 62.1% (95% CI, 42.3%-79.3%), with 14 of 18 responses (77.8%) ongoing at the time of analysis.
• In responding patients, with duration of response of at least 3 months and at least 6 months, the estimated proportion was noted to be 93% (95% CI, 61%-99%) and 83% (95% CI, 46%-96%), respectively.
• A general good tolerability of first-line avelumab treatment was shown, and no treatment-related deaths or grade 4 adverse events were reported.