Background: In the phase 2 EMPOWER-CSCC-1 study (NCT02760498), cemiplimab demonstrated antitumor activity against metastatic cutaneous squamous cell carcinoma (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 every 2 weeks [groups 1 and 2]) or cemiplimab (350 mg intravenously [groups 3 and 6]) every 3 weeks. The primary end point 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: Nonrandomized study, nonsurvival primary end point., 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., Competing Interests: Conflicts of interest Dr Hughes reports consulting/advisory roles at AstraZeneca, Bristol-Myers Squibb, Eisai, Merck, Merck Sharp & Dohme, Pfizer, and Roche; and institutional research funding from Amgen. Dr Guminski reports personal fees and advisory board and travel support from Bristol-Myers Squibb and Sun Pharma; advisory board fees from Eisai, Merck KGaA, and Pfizer; travel support from Astellas; and clinical trial unit support from PPD Australia. Dr Bowyer reports advisory board roles for Eli Lilly Australia, Ipsen, Merck Sharp & Dohme, and Sanofi; virtual meeting sponsorship from Bristol-Myers Squibb and Merck Sharp & Dohme Australia; and travel support from Merck Sharp & Dohme and AstraZeneca. Michael Migden reports honoraria and travel expenses from Regeneron Pharmaceuticals, Inc, and Sanofi; consulting fees from Feldan Therapeutics, Replimune, Stamford Pharma, and Sun Pharma; and institutional research funding from Regeneron Pharmaceuticals, Inc, and Replimune. Dr Schmults reports steering committee membership for Castle Biosciences; steering committee membership and consultancy for Regeneron Pharmaceuticals, Inc; consultancy for Sanofi; research funding from Castle Biosciences, Genentech, Merck, Novartis, and Regeneron Pharmaceuticals, Inc; and serving as a chair for the National Comprehensive Cancer Network. Dr Khushalani reports grants and advisory board fees from Bristol-Myers Squibb, Merck, Novartis, and Regeneron Pharmaceuticals, Inc; advisory board fees from AstraZeneca (data safety monitoring committee), Castle Biosciences, Incyte (data safety monitoring committee), Instil Bio, Iovance, Jounce Therapeutics, Nektar, and Replimune; grants from Celgene, GlaxoSmithKline, HUYA, Modulation Therapeutics, and Replimune; honoraria from Genzyme, National Comprehensive Cancer Network (grant funding from general research support through Pfizer), and Nektar (study steering committee); common stock ownership of Amarin, Bellicum Pharmaceuticals, and Transenetrix; study steering committee membership for Bristol-Myers Squibb, Regeneron Pharmaceuticals, Inc, and Replimune; and travel support from Regeneron Pharmaceuticals, Inc. Dr Chang reports consulting and advisory roles with Merck, and Regeneron Pharmaceuticals, Inc; research funding from Galderma, Merck, Novartis, and Regeneron Pharmaceuticals, Inc, and consultancy for Castle Biosciences and Feldan. Dr Grob reports serving on an advisory board for Amgen, Bristol-Myers Squibb, Merck, Merck Sharp & Dohme, Novartis, Pierre-Fabre, Pfizer, Philogen, Roche, and Sanofi; and an advisory role for Bristol-Myers Squibb. Dr Lewis reports employment, stock, and other ownership interests at Regeneron Pharmaceuticals, Inc. At the time of this study, Dr Lewis was affiliated with the University of Colorado Denver Cancer Center and is now an employee of Regeneron Pharmaceuticals, Inc. Dr Day reports serving on an advisory board for Amgen, travel support from Merck; and clinical trial support (investigational medical product provision, no financial support) from AstraZeneca and Bristol-Myers Squibb. Dr Ladwa reports honoraria from AstraZeneca, Bristol-Myers Squibb, and Merck Sharp & Dohme; consulting or advisory roles for AstraZeneca, and Roche; and travel, accommodation, and expenses from Merck Sharp & Dohme. Dr Stein reports ownership of stocks/shares in Icon Group. Dr Muñoz Couselo reports serving on an advisory board for Amgen, Bristol-Myers Squibb, Merck Sharp & Dohme, Novartis, Pierre Fabre, Roche, and Sanofi; honoraria from Amgen, Bristol-Myers Squibb, Merck Sharp & Dohme, Novartis, Pierre Fabre, and Roche; and clinical trial participation (principal investigator) for Amgen, Bristol-Myers Squibb, GlaxoSmithKline, Merck Sharp & Dohme, Novartis, Pierre Fabre, Roche, and Sanofi. Dr Meier reports travel support, speaker’s fees, or advisor’s honoraria from Bristol-Myers Squibb, Merck Sharp & Dohme, Novartis, Pierre Fabre, Roche, and Sanofi; and research funding from Novartis and Roche. Dr Hauschild reports institutional grants, speaker’s honoraria, and consultancy fees from Amgen, Bristol-Myers Squibb, Merck, Merck Sharp & Dohme, Pierre Fabre, Provectus, Roche, and Novartis; institutional grants and consultancy fees from Merck Serono, Philogen, and Regeneron Pharmaceuticals, Inc; and consultancy fees from OncoSec. Dr Schadendorf reports honoraria from 4SC AG, Array BioPharma, Bristol-Myers Squibb, Immunocore, InflarxGmbH, Merck, Merck Sharp & Dohme, NeraCare GmbH, Novartis, Pierre Fabre, Pfizer, Philogen, Regeneron Pharmaceuticals, Inc, Sandoz, Sanofi, Serono, Sun Pharma, Roche/Genentech, and Ultimovacs; advisory board and consulting fees from 4SC AG, Bristol-Myers Squibb, Merck Serono, Merck Sharp & Dohme, Novartis, Pierre Fabre, Regeneron Pharmaceuticals, Inc, Roche/Genentech, Sanofi, and Nektar; speaker fees from Bristol-Myers Squibb, Merck KgaA, Merck Sharp & Dohme, Novartis, Pierre Fabre, Regeneron Pharmaceuticals, Inc, and Sanofi; institutional research funding from Array BioPharma/Pfizer, Bristol-Myers Squibb, Merck Sharp & Dohme, Novartis, and Roche; and travel/accommodation expenses from Bristol-Myers Squibb, Merck Serono, Merck Sharp & Dohme, Novartis, Pierre Fabre, Regeneron Pharmaceuticals, Inc, Roche/Genentech, and Sanofi. Dr Basset-Seguin reports serving as an invited speaker, advisory board member, and consultant for Galderma, Regeneron Pharmaceuticals, Inc, Sanofi, and Sun Pharma. Dr Modi reports consulting/advisory board participation for Merck, Regeneron Pharmaceuticals, Inc, and Sanofi Genzyme; and speaker bureau participation for Regeneron Pharmaceuticals, Inc, and Sanofi Genzyme. Dr Dalac-Rat reports honoraria from Bristol Myers Squibb, Merck Sharpe & Dohme, Novartis, and Sun Pharma. Dr Dunn reports advisory board participation for Merck and Regeneron Pharmaceuticals, Inc; and research support from CUE-101, Regeneron Pharmaceuticals, Inc, Replimune Pharmaceuticals, and Seagen. Dr Flatz reports research funding from Hookipa Pharma; and advisory board fees from Bristol-Myers Squibb, Novartis, Philogen, and Sanofi. Dr Mortier reports personal fees and nonfinancial support from Bristol-Myers Squibb, and Merck Sharp & Dohme, Novartis, and Roche. Dr Guégan reports consulting fees from Bristol-Myers Squibb, Janssen, and Pierre Fabre; and technical support for congress attendance from Bristol-Myers Squibb, Janssen, Merck Sharp & Dohme, and Sanofi. Dr Heinzerling reports consulting fees from Bristol-Myers Squibb, Highlight Therapeutics, Novartis, Pierre Fabre, Roche, and Sanofi; lecture fees from Astellas, Bristol-Myers Squibb, Merck Sharp & Dohme, Novartis, Pierre Fabre, Pfizer, Roche, and Sanofi; and travel grants from Bristol-Myers Squibb, Ipsen, Merck Sharp & Dohme, Novartis, Pfizer, Pierre Fabre, and Roche. Dr Mehnert reports advisory board fees from Bristol-Myers Squibb, Eisai, Novartis, Pliant Therapeutics, Regeneron Pharmaceuticals, Inc, and Seagen; and consultancy fees from Merck. Dr Soria-Rivas reports speaker’s honoraria from Bristol-Myers Squibb, Immunocore, Merck Serono, Merck Sharp & Dohme, Novartis, Pierre Fabre, Roche Pharma, and Sanofi Aventis; and advisory board fees from Bristol-Myers Squibb, Immunocore, Merck Serono, Merck Sharp & Dohme, Novartis, Pierre Fabre, Regeneron Pharmaceuticals Inc, and Sanofi Aventis. Dr Stratigos reports advisory board or steering committee roles for Janssen, Regeneron Pharmaceuticals Inc, Roche, and Sanofi; and research support from AbbVie, Bristol Myers Squibb, Genesis Pharma, LEO Pharma, Novartis, and Pfizer. Dr Ulrich reports advisory board and speaker roles for Regeneron Pharmaceuticals Inc, Roche, Sanofi, and Sun Pharma. Dr Wong reports grant funding to institution from AstraZeneca, Bristol-Myers Squibb, Eli Lilly, F-Star Therapeutics, Genentech, Gilead, Kura Oncology, Merck Sharp & Dohme, Pfizer, Regeneron Pharmaceuticals Inc, and TopAlliance Biosciences, and consulting fees from Blueprint Medicines, Genzyme/Sanofi, and Regeneron Pharmaceuticals Inc. Dr Beylot-Barry reports institutional research funding from Roche and speaker honoraria from Sun Pharma. Dr Bossi reports advisory board or conference honoraria for Merck, Merck Sharp & Dohme, Sanofi-Regeneron, and Sun Pharma. Dr Bugés Sánchez reports personal fees from Amgen, Merck, Novartis, and Sanofi. Dr Chandra reports honoraria from Array BioPharma, Bristol Myers Squibb, EMD Serono, Exicure, Novartis, Pfizer, Regeneron Pharmaceuticals Inc, and Sanofi; consulting/advisory roles for Array BioPharma, Bristol Myers Squibb, EMD Serono, Exicure, Novartis, Pfizer, Regeneron Pharmaceuticals Inc, and Sanofi; and institutional research funding from Bristol Myers Squibb, EMD Serono, Exicure, Novartis, Pfizer, Regeneron Pharmaceuticals Inc, and Sanofi. Dr Robert reports grants, personal fees, and advisory board roles for Amgen, Biothera, Bristol Myers Squibb, Merck, Merck Sharp & Dohme, Novartis, Pierre Fabre, Roche, Sanofi, and Ultimovacs. Dr Silk reports institutional research grant and funding from Biohaven Pharmaceuticals, Merck, Morphogenesis, Regeneron Pharmaceuticals, Inc, Replimune, and Shattuck Laboratories; advisory board fees from Natera, Merck and Regeneron Pharmaceuticals, Inc; consulting fees from Leerink, and royalties from UpToDate, Inc. Ms Booth and Drs, Yoo, Seebach, Lowy, and Fury report employment, stock, and other ownership interests at Regeneron Pharmaceuticals, Inc. Dr Rischin reports institutional research grant and funding from ALX Oncology, Bristol-Myers Squibb, GlaxoSmithKline, Kura Oncology, Merck Sharp & Dohme, Regeneron Pharmaceuticals, Inc, Roche, and Sanofi; and uncompensated scientific committee and advisory board roles for Eisai, Bicara, GlaxoSmithKline, Merck Sharp & Dohme, Regeneron Pharmaceuticals, Inc, and Sanofi. Drs Ansstas, Trabelsi, and Russell have no conflicts of interest to declare., (Copyright © 2024 American Academy of Dermatology, Inc. Published by Elsevier Inc. All rights reserved.)