On October 8, 2025, the U.S. Food and Drug Administration (FDA) approved Libtayo (cemiplimab-rwlc) as an adjuvant treatment for adults with cutaneous squamous cell carcinoma (CSCC) at high risk of recurrence following surgery and radiation therapy. This approval marks an important advancement for patients with high-risk CSCC, offering a new option to help reduce disease recurrence after standard treatment.
The approval was based on results from the C-POST (NCT03969004) trial, a randomized, double-blind, placebo-controlled, multicenter study involving 415 patients with high-risk CSCC after surgery and radiation. Eligible participants were required to complete adjuvant radiation therapy within two to ten weeks before randomization and were assigned to receive either cemiplimab-rwlc or placebo. Patients with autoimmune disease requiring immunosuppressive therapy, a history of organ or stem cell transplantation, or uncontrolled viral infections such as HIV, hepatitis B, or hepatitis C were excluded.
The primary endpoint was disease-free survival (DFS), defined as the time from randomization to recurrence or death from any cause. Results showed a significant improvement in DFS with Libtayo: median DFS was not reached in the cemiplimab group compared to 49.4 months in the placebo group (Hazard ratio 0.32; 95% CI: 0.20–0.51; p < 0.0001), indicating a 68% reduction in the risk of recurrence or death.
Libtayo’s safety profile was consistent with that of other immune checkpoint inhibitors. Key warnings and precautions include immune-mediated adverse reactions, infusion-related reactions, complications after stem cell transplantation, and embryo-fetal toxicity. The most common side effects reported were fatigue, rash, itching, and diarrhea. Healthcare professionals should monitor patients closely and manage immune-related side effects promptly.
The recommended dosage is 350 mg intravenously every three weeks for 12 weeks, followed by 700 mg every six weeks, or continued 350 mg every three weeks until recurrence, unacceptable toxicity, or for up to 48 weeks.
This approval utilized the FDA’s Real-Time Oncology Review (RTOR) pilot program, allowing earlier data submission to expedite the review process, and the Assessment Aid tool to support evaluation. The application also received priority review for addressing an unmet medical need in this high-risk population.
Healthcare professionals are encouraged to report any serious or unexpected adverse events related to Libtayo to the FDA MedWatch Reporting System.
