Phase II study of cemiplimab in patients (pts) with advanced cutaneous squamous cell carcinoma (CSCC): Longer follow-up

10018 Background: Cemiplimab monotherapy achieves clinically meaningful activity in pts with advanced CSCC (metastatic [mCSCC] or locally advanced [laCSCC] not amenable to curative surgery or curative radiation) and has a safety profile consistent with other anti–PD-1 agents. Based on initial data (median follow-up of 9.4 months in the pivotal study, NCT02760498), cemiplimab (cemiplimab-rwlc in the US) was approved for the treatment of pts with advanced CSCC. Historical data shows median overall survival (OS) of approximately 15 months with conventional chemotherapy or EGFR inhibitors (ASCO 2019, e21033). We present ~1-year additional follow-up from the largest prospective data set in advanced CSCC. Methods: Pts received cemiplimab 3 mg/kg Q2W (Group [Gp] 1; mCSCC; Gp 2, laCSCC) or cemiplimab 350 mg Q3W (Gp 3, mCSCC). The primary endpoint was objective response rate (ORR; complete response + partial response) per independent central review (ICR). Data presented here are per investigator review (INV); ICR data will be available at the meeting. Results: 193 pts were enrolled (Gp 1, n = 59; Gp 2, n = 78; Gp 3, n = 56). 128 pts had received no prior anti-cancer systemic therapy, 65 pts were previously treated. As of Oct 11, 2019 (data cut-off), median duration of follow-up was 15.7 months (range: 0.6–36.1) among all pts; 18.5 months (range: 1.1–36.1) for Gp 1, 15.5 months (range: 0.8–35.0) for Gp 2, and 17.3 months (range: 0.6–26.3) for Gp 3. ORR per INV was 54.4% (95% CI: 47.1–61.6) for all pts; 50.8% (95% CI: 37.5–64.1) for Gp 1, 56.4% (95% CI: 44.7–67.6) for Gp 2, and 55.4% (95% CI: 41.5–68.7) for Gp 3. ORR per INV was 57.8% (95% CI: 48.8–66.5) among treatment-naïve pts and 47.7% (95% CI: 35.1–60.5) among previously treated pts. Median duration of response (DOR) has not been reached (observed DOR range: 1.8–34.2 months). In responding pts, estimated proportion of pts with ongoing response at 24 months was 76.0% (95% CI: 64.1–84.4). Median OS has not been reached. Estimated OS at 24 months was 73.3% (95% CI: 66.1–79.2). The most common treatment-emergent adverse events (TEAEs) by any grade were fatigue (34.7%), diarrhea (27.5%), and nausea (23.8%). The most common grade ≥3 TEAEs were hypertension (4.7%) and anemia and cellulitis (each 4.1%). Conclusions: For pts with advanced CSCC, cemiplimab achieves ORRs, DOR and survival superior to what has been reported with other agents. Clinical trial information: NCT02760498.