Phase II confirmatory study of cemiplimab (350mg IV Q3W) in patients with locally advanced or metastatic cutaneous squamous cell carcinoma (CSCC): Study 1540 Group 6

While most patients (pts) diagnosed with CSCC are cured with local therapies, for the small percentage developing advanced CSCC the disease is life threatening with dismal prognosis. In a phase 1 (NCT02383212) and a pivotal phase 2 (NCT02760498) clinical trials, cemiplimab, an anti–programmed cell death receptor-1 [anti–PD-1], was the first systemic therapy to demonstrate significant antitumor activity in pts with advanced CSCC. Here, we report results from group 6 of the pivotal phase 2 trial, providing additional efficacy and safety data for cemiplimab monotherapy, 350 mg every 3 weeks (Q3W) up to 104 weeks, in patients with advanced CSCC. Patients with advanced CSCC (metastatic [nodal or distant] or locally advanced) were treated with cemiplimab 350 mg intravenous (IV) Q3W for up to 108 weeks. The primary endpoint was objective response rate (ORR; complete response + partial response) per independent central review (ICR). Secondary endpoints included duration of response (DOR), progression-free survival (PFS), and overall survival (OS) by central and investigator review as well as safety and tolerability of cemiplimab. At data cut-off date of Oct 25 2021, 167 pts were enrolled, of which 165 pts received at least one dose of cemiplimab and were followed-up for a median of 8.71 months (range: 0.0 - 19.5). 5 of 167 pts received prior systemic therapies. Per ICR, ORR was 44.3% (74/167, 95% CI: 36.6%, 52.2%) with complete response in 5.4% (9/167), partial response in 38.9% (65/167), and DOR was not reached (95% CI: 13.0 months, not evaluable [NE]). Among treated patients, median PFS was 14.7 months (95% CI: 10.4, NE) and median OS was not reached (95% CI: 17.6 months, NE). The most common treatment-emergent adverse events (TEAEs) by any grade were fatigue (26.1%), diarrhoea and pruritus (each 21.2%), and nausea (17.0%). The most common grade ≥3 TEAEs were hypertension and pneumonia (each 3.6%), and general physical health deterioration (3.0%). The group 6 primary analysis demonstrates a safety and efficacy profile that is consistent with that of the earlier groups of the study.