FDA Approves Cemiplimab as Adjuvant Immunotherapy for High-Risk CSCC

Last week, Regeneron announced the U.S. Food and Drug Administration (FDA) approval of cemiplimab-rwlc (Libtayo) as an adjuvant treatment for adult patients with cutaneous squamous cell carcinoma (CSCC), particularly in those with a high risk of recurrence after surgery and radiation.¹ The PD-1 inhibitor was evaluated under priority review.

"The FDA approval of Libtayo as the first and only immunotherapy for adjuvant treatment of CSCC with a high risk of recurrence after surgery and radiation is a pivotal moment for patients battling this disease,” Israel Lowy, MD, PhD, Clinical Development Unit Head of Oncology at Regeneron, told Dermatology Times. “This approval not only reaffirms Libtayo’s position as a versatile PD-1 inhibitor with 5 approved indications in the US but offers a truly practice-changing advancement. At Regeneron, we remain steadfast in our commitment to advancing research and creating new innovative possibilities for patients.”

Supporting Phase 3 Research

The approval is supported by data from the phase 3 C-POST trial, which was published in the New England Journal of Medicine and presented at the American Society of Clinical Oncology Annual Meeting earlier this year.² In the global, randomized, double-blind, placebo-controlled study, 415 patients were assigned in a 1:1 ratio to receive adjuvant cemiplimab (350 mg) or placebo, administered intravenously every 3 weeks for 12 weeks, followed by a dose increase to 700 mg administered every 6 weeks.

Compared to placebo, cemiplimab significantly reduced the risk of disease recurrence or death by 68% (HR: 0.32; 95% CI: 0.20-0.51; p < 0.0001). The estimated 24-month disease-free survival was 87.1% (95% CI, 80.3 to 91.6) with cemiplimab and 64.1% (95% CI, 55.9 to 71.1) with placebo. Additionally, participants treated with cemiplimab showed an 80% reduction in the risk of locoregional recurrence and a 65% reduction in the risk of distant recurrence versus placebo.

“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,” Samantha R. Guild, President of AIM at Melanoma Foundation, said in a statement. “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.”¹

Confirmed Safety Profile

The safety profile also aligned with the known safety profile of cemiplimab for other advanced skin cancers, including basal cell carcinoma. The most commonly reported adverse events were rash, pruritus, and hypothyroidism. Serious adverse reactions occurred in 18% of patients and those that occurred in ≥1% of patients in the cemiplimab arm were pneumonia (1.5%), rash (1.5%), diarrhea (1.5%), adrenal insufficiency (1%), and arrhythmia (1%).

“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, President and Chief Scientific Officer of Regeneron. “Now with 5 FDA-approved indications, Libtayo is firmly established as a strong and versatile PD-1 inhibitor option for patients with a variety of cancers.”¹

Next Steps and Final Thoughts

Cemiplimab is a fully human monoclonal antibody targeting the immune checkpoint receptor PD-1 on T cells. It uses Regeneron's proprietary VelocImmunetechnology to bind to PD-1 and block cancer cells from using the PD-1 pathway to suppress T-cell activation. The drug is currently being investigated for use as a monotherapy as well as in combination with other approaches for other solid tumors and blood cancers. In this vulnerable patient population, an additional regulatory application is under review in the European Union, with a decision expected in early 2026.

"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 at the George Washington University School of Medicine & Health Sciences. “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, Libtayo represents a practice-changing opportunity for this patient population, backed by compelling data showcasing its ability to significantly improve disease-free survival.”¹

References

1. Libtayo® (cemiplimab-rwlc) Approved in the U.S. as First and Only Immunotherapy for Adjuvant Treatment of Cutaneous Squamous Cell Carcinoma (CSCC) with a High Risk of Recurrence After Surgery and Radiation. News release. Regeneron. Published October 8, 2025. Accessed October 13, 2025. https://investor.regeneron.com/news-releases/news-release-details/libtayor-cemiplimab-rwlc-approved-us-first-and-only

2. Rischin D, Porceddu S, Day F, et al. Adjuvant Cemiplimab or Placebo in High-Risk Cutaneous Squamous-Cell Carcinoma. N Engl J Med. 2025;393(8):774-785. doi:10.1056/NEJMoa2502449