BACKGROUND: Most cutaneous squamous cell carcinomas (CSCCs) can be treated with surgical excision or radiation; however, approximately 1% of patients develop advanced disease. In 2018, the FDA approved cemiplimab-rwlc as the first programmed cell death-1 (PD-1) monoclonal antibody for the treatment of patients with metastatic CSCC or locally advanced CSCC who are not candidates for curative surgery or curative radiation. In June 2020, pembrolizumab, another PD-1 monoclonal antibody, was approved for the treatment of patients with recurrent or metastatic CSCC who are not candidates for curative surgery or radiation. We previously reported on the cost-effectiveness of cemiplimab vs historical standard of care for the treatment of advanced CSCC from a US perspective. OBJECTIVE: To estimate the cost-effectiveness of cemiplimab vs pembrolizumab for patients with advanced CSCC in the United States. METHODS: A "partitioned survival" framework was used to assess the cost-effectiveness of cemiplimab vs pembrolizumab. Clinical inputs were based on the most recent data cut of the phase 2 trials for cemiplimab (EMPOWER-CSCC-1; NCT02760498) and pembrolizumab (KEYNOTE-629). Progression-free survival and overall survival were extrapolated using parametric models until all patients had progressed or died. Health state utilities were derived from data collected in the EMPOWER-CSCC-1 trial. Costs included drug acquisition, drug administration, disease management, terminal care, and adverse events and were based on published 2020 US list prices. To assess model uncertainty, 1-way sensitivity and probabilistic sensitivity analyses (PSA) were conducted, alongside scenario analyses evaluating key modeling assumptions. RESULTS: In the base case, cemiplimab resulted in an incremental gain of 3.44 life-years (discounted) and incremental cost-effectiveness ratio (ICER) of $130,329 per quality-adjusted life-year (QALY) vs pembrolizumab. At a willingness-to-pay threshold of $150,000/QALY, PSA indicated a 71% probability that cemiplimab is cost-effective when compared with pembrolizumab. Scenario analysis resulted in ICERs ranging from $115,909 to $187,374. CONCLUSIONS: Findings suggest that cemiplimab is a cost-effective treatment for patients with advanced CSCC, compared with pembrolizumab. These results should be interpreted cautiously in the absence of head-to-head trials; however, in the absence of such data, these results can be used to inform health care decisions over resource allocation. DISCLOSURES: This study was supported by Regeneron Pharmaceuticals, Inc., and Sanofi. Paul, Cope, Keeping, Mojebi, and Ayers are employees of PRECISIONheor, which received funding to produce this work. Chen, Kuznik, and Xu are employees and stockholders of Regeneron Pharmaceuticals, Inc. Sasane is an employee and stockholder of Sanofi, Inc. Konidaris, Atsou, and Guyot are employees of Sanofi, Inc. The authors were responsible for all content and editorial decisions and received no honoraria related to the development of this publication.