Regeneron's Libtayo (cemiplimab) has shown a statistically significant and clinically meaningful improvement in disease-free survival (DFS) as an adjuvant treatment for patients with high-risk cutaneous squamous cell carcinoma (CSCC) following surgery. The Phase 3 C-POST trial (NCT03969004) demonstrated a 68% reduction in the risk of disease recurrence or death compared to placebo (HR: 0.32; 95% CI: 0.20-0.51; p<0.0001). This advancement could redefine post-surgical treatment strategies for CSCC. The results were announced by Regeneron Pharmaceuticals.
C-POST Trial Details
The C-POST trial, a Phase 3 study, evaluated Libtayo as an adjuvant therapy in patients with high-risk CSCC after surgery. At the first prespecified interim analysis for DFS, with a median follow-up of 24 months (range: 2-64 months), Libtayo demonstrated a substantial improvement in DFS. The trial included 415 patients. Detailed results are slated for presentation at an upcoming medical meeting, and Regeneron intends to submit the data to the U.S. Food and Drug Administration (FDA) in the first half of 2025.
Clinical Significance
CSCC is a common form of skin cancer, and patients with high-risk features face a significant risk of recurrence after surgery. The current treatment landscape lacks effective adjuvant therapies to reduce this risk. Libtayo's demonstrated efficacy in the C-POST trial addresses this unmet need, offering a potential new standard of care for these patients. The 68% reduction in the risk of recurrence or death represents a clinically meaningful benefit that could significantly improve patient outcomes.
Cemiplimab's Expanding Role
Libtayo (cemiplimab) is a PD-1 inhibitor that has already established its role in treating various cancers. Regeneron reported that Libtayo sales exceeded $1 billion in 2024, underscoring its importance in the company's oncology portfolio. Beyond CSCC, cemiplimab is being investigated in other cancers, including cervical cancer, where it has shown survival benefits compared to chemotherapy in recurrent cases after progression on first-line platinum therapy. Furthermore, cemiplimab is being explored in combination with other agents, such as fianlimab (anti-LAG-3), in melanoma, with Phase 3 results expected in the second half of 2025.
Ongoing Research and Future Directions
Several ongoing trials are evaluating cemiplimab in different settings and combinations. A Phase 2 trial (NCT06571708) is assessing gemcitabine/cisplatin plus cemiplimab with or without fianlimab for organ preservation in localized muscle-invasive bladder cancer. Additionally, a Phase 1/2 study (NCT03972657) is investigating nezastomig (anti-PSMAxCD28) with or without cemiplimab in metastatic castration-resistant prostate cancer and clear cell renal cell carcinoma. These studies aim to further expand the clinical utility of cemiplimab and improve outcomes for patients with various cancers.
Another trial (clinicaltrials.gov) is testing cemiplimab plus surgery versus surgery alone for treating advanced skin cancer, with an initiation date in September 2025.
