Regeneron posts 44‑month Libtayo survival data

Regeneron Pharmaceuticals has announced longer-term data from the Phase 3 C-POST trial of Libtayo (cemiplimab) as adjuvant therapy for patients with high-risk cutaneous squamous cell carcinoma (CSCC) after surgery and radiation. With nearly four years of follow-up, Libtayo demonstrated sustained disease-free survival benefits versus placebo and an increasing overall survival advantage over time in this high-risk population.

At a median follow-up of 44 months, treatment with Libtayo reduced the risk of death by 37% compared with placebo, with a hazard ratio of 0.63 and a 95% confidence interval of 0.36 to 1.11. This survival effect represents an increase from a 22% reduction at 30 months and a 14% reduction at 24 months, indicating a progressively strengthening survival benefit as follow-up lengthened.

C-POST is a randomized, placebo-controlled, double-blind, multicenter global Phase 3 trial evaluating Libtayo versus placebo as adjuvant treatment in patients with features associated with a high risk of CSCC recurrence who had completed surgery and post-operative radiation therapy. The study enrolled 415 patients, who were assigned to receive Libtayo (209 patients) or placebo (206 patients) for up to 48 weeks.

Participants received intravenous Libtayo 350 mg or placebo every three weeks for the first 12 weeks, followed by Libtayo 700 mg or placebo every six weeks for an additional 36 weeks. Patients in the placebo arm whose disease recurred were eligible to cross over to Libtayo, while those initially treated with Libtayo could be retreated upon recurrence occurring at least three months after their last adjuvant dose.

The longer-term analysis showed that Libtayo’s disease-free survival benefit over placebo was sustained through the 44‑month median follow-up. Regeneron reported that, alongside the overall survival advantage, these findings support the long-term durability of adjuvant Libtayo in this setting of high-risk CSCC after surgery and radiation.

An exploratory analysis in patients with baseline circulating tumour DNA data found that adjuvant Libtayo improved disease-free survival compared with placebo regardless of minimal residual disease (MRD) status. Among MRD-negative patients at baseline, who were considered at lower risk of recurrence, Libtayo achieved a hazard ratio for disease-free survival of 0.45 with a 95% confidence interval of 0.22 to 0.95. In MRD-positive patients, who were at higher risk of recurrence, the hazard ratio was 0.24 with a 95% confidence interval of 0.07 to 0.86.

The safety profile for adjuvant Libtayo in C-POST remained consistent with previously reported findings. Treatment-emergent adverse events of any grade occurred in 94% of patients receiving Libtayo and 91% of those receiving placebo, underscoring that adverse events were common in both treatment arms.

Grade 3 or higher treatment-emergent adverse events were reported in 26% of patients in the Libtayo group and 17% in the placebo group. Treatment discontinuations due to such events occurred in 10% of Libtayo-treated patients and 3% of placebo-treated patients. Events resulting in death were reported in 2% of patients in each arm, indicating a similar incidence of fatal adverse events between the groups.

The updated C-POST data come alongside solid recent financial performance for Regeneron. In the second quarter of 2026, the company reported revenue of USD 4.29 billion, representing year-over-year growth of 16.70 percent. Net income attributable to common shareholders for the quarter was USD 1.30 billion, and diluted earnings per share reached USD 12.23.

Libtayo, a fully human anti-PD-1 monoclonal antibody developed using Regeneron’s VelocImmune technology, has been approved in more than 30 countries for a range of advanced cancer indications, including advanced or recurrent high-risk CSCC. The long-term C-POST results further characterize its role as adjuvant treatment for patients with high-risk CSCC following surgery and radiation.