BACKGROUND: In the phase 2 EMPOWER-CSCC-1 study (NCT02760498), cemiplimab demonstrated antitumor activity against metastatic (mCSCC) and locally advanced cutaneous squamous cell carcinoma (laCSCC).

OBJECTIVES: To report final analysis of weight-based cemiplimab in mCSCC and laCSCC (Groups 1 and 2), fixed-dose cemiplimab in mCSCC (Group 3), and primary analysis of fixed-dose cemiplimab in mCSCC/laCSCC (Group 6).

METHODS: Patients received cemiplimab (3 mg/kg intravenously [IV] every 2 weeks [Groups 1 and 2]) or cemiplimab (350 mg IV [Groups 3 and 6]) every 3 weeks. The primary endpoint was objective response rate (ORR). Duration of response (DOR) and progression-free survival (PFS) are presented per protocol, according to post-hoc sensitivity analyses that only include the period of protocol-mandated imaging assessments.

RESULTS: At 42.5 months, ORR for Groups 1-3 (n=193) was 47.2%, estimated 12-month DOR was 88.3%, and median PFS was 26.0 months. At 8.7 months, ORR for Group 6 (n=165 patients) was 44.8%; median DOR and median PFS were not reached. Serious treatment-emergent adverse event rates (grade ≥3) were Groups 1-3: 31.1% and Group 6: 34.5%.

LIMITATIONS: Non-randomized study, non-survival primary endpoint.

CONCLUSION: EMPOWER-CSCC-1 provides the largest prospective data on long-term efficacy and safety for anti-programmed cell death-1 therapy in advanced CSCC.