Phase 3 Trial Demonstrates Significant Benefits of Libtayo in High-Risk Cutaneous Squamous Cell Carcinoma

Regeneron Pharmaceuticals has announced promising interim results from the Phase 3 C-POST trial, evaluating the PD-1 inhibitor Libtayo (cemiplimab) as an adjuvant treatment for patients with high-risk cutaneous squamous cell carcinoma (CSCC) after surgery and postoperative radiation. The findings demonstrate a statistically significant and clinically meaningful improvement in disease-free survival, marking a potential breakthrough for this patient population. 

The randomized, placebo-controlled, double-blind trial enrolled 415 patients with high-risk CSCC, defined by poor prognostic features such as extracapsular lymph node extension or locally recurrent tumors. Patients received either Libtayo or placebo for up to 48 weeks. At a median follow-up of 24 months, Libtayo reduced the risk of disease recurrence or death by 68% compared to placebo (hazard ratio: 0.32; 95% CI: 0.20–0.51; P<0.0001). 

“While surgery is curative for most people living with cutaneous squamous cell carcinoma, many face a high risk of recurrence that can lead to death or disfigurement,” said Dr Danny Rischin, lead investigator and head of the department of medical oncology at the Peter MacCallum Cancer Centre in Melbourne, Australia. “At the first prespecified interim analysis, Libtayo achieved a remarkably high bar in improving disease-free survival. These landmark results demonstrate Libtayo could represent a major advance in delaying recurrence in these vulnerable patients.” 

Safety was evaluated in 409 patients, with adverse events (AEs) occurring in 91% of the Libtayo group and 89% of the placebo group. Grade ≥3 AEs were reported in 24% of the Libtayo group and 14% of the placebo group, with treatment discontinuations due to AEs occurring in 10% and 1.5%, respectively. 

Dr Israel Lowy, Regeneron’s clinical development unit head for oncology, stated, “These results highlight the potential for Libtayo to transform the treatment landscape for high-risk resectable CSCC. This trial underscores our commitment to advancing treatment options in areas of unmet need.” 

The C-POST trial will continue to collect additional data on overall survival and other secondary endpoints. Detailed results will be shared at an upcoming medical meeting, with plans for a US Food and Drug Administration submission in 2025. 

Reference
Adjuvant Libtayo (cemiplimab) significantly improves disease-free survival (DFS) after surgery in high-risk cutaneous squamous cell carcinoma CSCC) in phase 3 trial. News Release. Regeneron. January 13, 2025. Accessed January 14, 2025. https://investor.regeneron.com/news-releases/news-release-details/adjuvant-libtayor-cemiplimab-significantly-improves-disease-free