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

The FDA approval is based on data from the pivotal Phase 3 C-POST trial investigating adjuvant Libtayo 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 Libtayo 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 Libtayo as adjuvant treatment of patients with CSCC at high risk of recurrence after surgery and radiation is consistent with the known safety profile for Libtayo 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 Libtayo arm were pneumonia (1.5%), rash (1.5%), diarrhea (1.5%), adrenal insufficiency (1%), and arrhythmia (1%).