Adjuvant Cemiplimab Significantly Improves Disease-Free Survival in High-Risk Skin Cancer

Adjuvant treatment with cemiplimab (Libtayo) significantly improves disease-free survival (DFS) in patients with high-risk cutaneous squamous cell carcinoma (CSCC) after surgery, according to new phase 3 trial results shared by Regeneron Pharmaceuticals.¹

According to the Regeneron news release, the latest findings mark the first time an immunotherapy has demonstrated a clear benefit in preventing recurrence in this high-risk population. Although surgery is a curative option for most patients with CSCC, many of them are still at a higher risk of recurrence, emphasized Danny Rischin, MD, MBBS, research lead in the department of medical oncology at the Peter MacCallum Cancer Centre in Melbourne, Australia.

In the ongoing C-POST trial, cemiplimab reduced the risk of CSCC recurrence or death by 68% compared with placebo. According to the researchers, this milestone outcome highlights cemiplimab’s potential as the first approved adjuvant therapy for high-risk CSCC, addressing a major gap in treatment options.

“At the first prespecified interim analysis, [cemiplimab] achieved a remarkably high bar in improving disease-free survival in high-risk cutaneous squamous cell carcinoma,” Rischin said. “With no currently approved options in the adjuvant setting, these landmark results demonstrate [cemiplimab] could represent a major advance in delaying recurrence in these vulnerable patients.”

The trial included 415 patients with features associated with a high likelihood of recurrence, such as extracapsular extension or multiple lymph nodes affected. Patients were randomized to receive cemiplimab or placebo for up to 48 weeks, with DFS as the primary end point. At a median follow-up of 24 months, the hazard ratio for recurrence or death was 0.32 (95% CI, 0.20-0.51; P < .0001) for those taking the medication compared with placebo.

Adverse events (AEs) were monitored in both treatment arms, with AEs of any grade occurring in 91% of patients in the treatment arm and 89% in the placebo arm. Patients on cemiplimab were also more likely to experience grade 3 or higher AEs (24%) than patients on placebo (14%) and more likely to discontinue treatment due to AEs (10% vs 1.5%). Additionally, 2 patients in each arm experienced AEs that led to death.

The trial will continue with extended follow-up to evaluate overall survival, a key secondary endpoint. Regeneron plans to submit the data to the FDA in the first half of 2025, with further details to be presented at an upcoming medical meeting.

This development comes as other immunotherapies, such as pembrolizumab (Keytruda), have not demonstrated success in the adjuvant treatment of high-risk CSCC.² Cemiplimab’s promising results highlight the potential of PD-1 inhibitors to address unmet needs in oncology and improve outcomes for patients with aggressive, high-risk cancers.

References

1. 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 17, 2025. https://investor.regeneron.com/news-releases/news-release-details/adjuvant-libtayor-cemiplimab-significantly-improves-disease-free
2. Manalac T. Where Keytruda failed, Regeneron touts phase III skin cancer win for Libtayo. BioSpace. January 14, 2025. Accessed January 17, 2025. https://www.biospace.com/drug-development/where-keytruda-failed-regeneron-touts-phase-iii-skin-cancer-win-for-libtayo