Regeneron Pharmaceuticals, Inc. reported a lower estimated death hazard with Libtayo (cemiplimab) in a 44-month follow-up of patients with high-risk skin cancer, though the confidence interval still included no difference. The company presented the update at the European Society for Medical Oncology Congress in Madrid on Oct. 25.
At a median follow-up of 44 months, the hazard ratio for death was 0.63 for patients given Libtayo after surgery and radiation, compared with placebo. Regeneron characterized the estimate as a 37% reduction in the risk of death. The 95% confidence interval ranged from 0.36 to 1.11, crossing 1.0; the update therefore did not establish a statistically significant overall-survival advantage.
Regeneron’s earlier overall-survival estimates were 0.78 at 30 months and 0.86 at 24 months. Their respective 95% confidence intervals were 0.39 to 1.56 and 0.39 to 1.90.
The randomized Phase 3 C-POST trial enrolled 415 patients with high-risk cutaneous squamous cell carcinoma (CSCC) after surgery and radiation. It assigned 209 patients to cemiplimab and 206 to placebo. Disease-free survival was the trial’s primary endpoint; overall survival was a secondary endpoint. At the earlier median follow-up of 24 months, the disease-free-survival hazard ratio was 0.32 (95% CI, 0.20 to 0.51), with estimated two-year disease-free survival of 87.1% for cemiplimab and 64.1% for placebo. The U.S. Food and Drug Administration approved cemiplimab for adults with high-risk CSCC after surgery and radiation on Oct. 8, 2025.
Of 69 patients assigned to placebo whose cancer recurred, 61, or 88%, later received Libtayo, Regeneron said. The company said the findings support giving eligible patients the drug after surgery and radiation rather than waiting for recurrence.
Regeneron reported grade 3 or higher treatment-emergent adverse events in 26% of patients in the Libtayo group and 17% in the placebo group. Adverse events led to treatment discontinuation in 10% and 3%, respectively. The company also reported adverse events leading to death in 2% of each group.
