Regeneron Pharmaceuticals has reported new long-term data showing that Libtayo (cemiplimab) may help reduce the risk of death in patients with high-risk cutaneous squamous cell carcinoma (CSCC), a type of skin cancer. The latest results from the Phase 3 C-POST trial show an increasing overall survival benefit after nearly four years of follow-up.
The findings were presented at the European Society for Medical Oncology (ESMO) Congress 2026. The study evaluated Libtayo as an additional treatment after surgery and radiation therapy in patients at high risk of their cancer returning.
After a median follow-up of 44 months, patients who received Libtayo had a 37% lower risk of death compared with those who received a placebo. This benefit increased over time, from a 14% reduction at 24 months to 22% at 30 months and 37% at 44 months.
The results are notable because many patients in the placebo group received Libtayo after their cancer returned. Of the 69 patients in that group whose cancer recurred, 61 later received the medicine. Despite this, the group initially treated with Libtayo continued to show a growing survival benefit.
The trial also showed that Libtayo continued to help patients remain free from cancer recurrence or progression. An additional analysis found that the benefit was seen in patients both with and without detectable minimal residual disease (MRD) at the start of the study. MRD refers to small amounts of cancer that may remain in the body after treatment but are difficult to detect using standard methods.
Libtayo is an immunotherapy that blocks the PD-1 protein, helping the immune system recognise and attack cancer cells. It is already approved in the United States and Europe as an additional treatment for adults with high-risk CSCC after surgery and radiation therapy.
The Phase 3 C-POST trial included 415 patients. Participants received either Libtayo or a placebo for up to 48 weeks. The study’s main goal was to assess disease-free survival, while overall survival was a secondary measure.
Safety findings remained consistent with earlier reports. Severe treatment-related adverse events were reported more often in patients receiving Libtayo than in those receiving a placebo. Treatment-related side effects led to treatment discontinuation in 10% of patients in the Libtayo group and 3% in the placebo group.
The longer-term findings add to the evidence supporting Libtayo as a treatment option for patients at high risk of skin cancer returning after surgery and radiation. However, the overall survival analysis remains an estimate, and its confidence interval includes the possibility of no effect. Further follow-up will help clarify the size and reliability of the survival benefit.