Cemiplimab (REGN2810): A fully human anti-PD-1 monoclonal antibody for patients with unresectable locally advanced or metastatic cutaneous squamous cell carcinoma (CSCC)—Initial safety and efficacy from expansion cohorts (ECs) of phase I study.

195Background: There is no established standard of care for unresectable locally advanced or metastatic CSCC. UV-induced DNA damage causes hypermutation in most CSCCs. Therefore, these tumors may be responsive to PD-1 checkpoint blockade. In the dose escalation portion of the phase 1 study of cemiplimab (REGN2810), a durable (19 + months) radiologic complete response was observed in a patient (pt) with metastatic CSCC (ASCO 2015, #3024). Methods: ECs enrolled pts with distantly metastatic (EC 7) and locally advanced (EC 8) CSCC. All patients received cemiplimab 3 mg/kg by intravenous infusion over 30 minutes every 2 weeks for up to 48 weeks. Research biopsies were performed at baseline and Day 29 (and at progression, if possible). Tumor measurements were performed every 8 weeks according to RECIST 1.1 to determine overall response rate (ORR). Data cutoff date was 31 Jan 2017. Results: 26 pts were enrolled (10 in EC 7 and 16 in EC 8): median age, 72.5 y (range, 56–88y); median PS 1 (range, 0–1); 21M:5F; me...