The U.S. Food and Drug Administration (FDA) has approved the PD-1 inhibitor cemiplimab-rwlc (Libtayo, Regeneron Pharmaceuticals, Inc.) as an adjuvant treatment for adult patients with cutaneous squamous cell carcinoma (cSCC) at high risk of recurrence after surgery and radiation.

Cemiplimab-rwlc is a fully human monoclonal antibody targeting the immune checkpoint receptor PD-1 on T cells and was invented using Regeneron’s VelocImmune technology. By binding to PD-1, cemiplimab-rwlc helps block cancer cells from using the PD-1 pathway to suppress T-cell activation.

The FDA evaluated cemiplimab-rwlc under Priority Review, which is reserved for medicines that represent potentially significant improvements in efficacy or safety in the treatment of serious conditions. An additional regulatory application is also under review in the European Union, with a decision expected by the first half of 2026.

A New Option

“Patients whose cSCC is at a high risk of recurrence following surgery and radiation often have the poorest outcomes. Until now, we lacked options to help prevent a devastating recurrence, and immunotherapy was only available for patients with advanced cSCC who were no longer candidates for curative surgery or curative radiation,” said Vishal A. Patel, MD, Associate Professor of Dermatology and of Medicine (Hematology/Oncology), George Washington University School of Medicine & Health Sciences and Director, Cutaneous Oncology Program, GW Cancer Center, in a news release. “Many patients who undergo surgical resection of their cSCC are later found, on full pathological evaluation, to be at high risk of recurrence. As the first and only immunotherapy approved in the adjuvant setting, cemiplimab-rwlc represents a practice-changing opportunity for this patient population, backed by compelling data showcasing its ability to significantly improve disease-free survival.”

The FDA approval is based on data from the Phase 3 C-POST trial investigating adjuvant cemiplimab-rwlc versus placebo in patients with cSCC at high risk of recurrence after surgery and radiation. Results from the study, which were published in the New England Journal of Medicine and presented at the American Society of Clinical Oncology (ASCO) 2025 Annual Meeting earlier this year, showed that cemiplimab-rwlc demonstrated a 68% reduction in the risk of disease recurrence or death compared to placebo in patients with cSCC at high risk of recurrence after surgery and radiation (hazard ratio [HR]: 0.32; 95% confidence interval [CI]: 0.20-0.51; p<0.0001).

The safety profile of cemiplimab-rwlc as adjuvant treatment of patients with cSCC at high risk of recurrence after surgery and radiation is consistent with the known safety profile for cemiplimab-rwlc monotherapy in advanced cancers. The most common adverse reactions as a single agent in adjuvant cSCC at high risk of recurrence (≥10%, with a difference between arms of ≥3% compared to placebo) were rash, pruritus, and hypothyroidism. Serious adverse reactions occurred in 18% of patients, and those that occurred in ≥1% of patients in the cemiplimab-rwlc arm were pneumonia (1.5%), rash (1.5%), diarrhea (1.5%), adrenal insufficiency (1%), and arrhythmia (1%).

Experts React

“This approval provides patients with cSCC at high risk of disease recurrence following surgery and radiation a much-needed option, as Libtayo is the only immunotherapy to demonstrate efficacy in this setting,” said George D. Yancopoulos, MD, PhD, Board co-Chair, President, and Chief Scientific Officer of Regeneron, in the news release. “Now with five FDA-approved indications, Libtayo is firmly established as a strong and versatile PD-1 inhibitor option for patients with a variety of cancers.”

“cSCC is one of the most common skin cancers in the world, with an estimated 1.8 million cases diagnosed each year in the US alone. While it can often be treated successfully with surgery and radiation, many patients face serious risk of advanced disease recurrences,” said Samantha R. Guild, President, AIM at Skin Cancer Foundation. “This approval is wonderful news for people living with cSCC, and we commend Regeneron for its long-standing commitment to addressing needs in non-melanoma skin cancer through its pioneering research.”