Cemiplimab (Libtayo®): A Comprehensive Monograph on a PD-1 Checkpoint Inhibitor in Modern Oncology

Executive Summary

Cemiplimab, marketed under the brand name Libtayo®, is a fully human IgG4 monoclonal antibody that functions as a programmed death receptor-1 (PD-1) immune checkpoint inhibitor. By binding to the PD-1 receptor on T-cells, Cemiplimab blocks its interaction with ligands PD-L1 and PD-L2, thereby releasing the brakes on the immune system and restoring T-cell-mediated anti-tumor activity. This mechanism has demonstrated broad and durable efficacy across a range of malignancies.

Developed by Regeneron Pharmaceuticals, Inc., Cemiplimab has achieved landmark regulatory approvals from both the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA). It was the first systemic therapy approved for advanced cutaneous squamous cell carcinoma (CSCC), establishing a new standard of care in a setting with a significant unmet need. Subsequent approvals were secured for advanced basal cell carcinoma (BCC) in patients who have progressed on or are intolerant to hedgehog pathway inhibitors, another niche population with limited options.

In the highly competitive landscape of non-small cell lung cancer (NSCLC), Cemiplimab is approved both as a monotherapy for first-line treatment of patients whose tumors exhibit high PD-L1 expression (Tumor Proportion Score ≥ 50%) and in combination with platinum-based chemotherapy for a broader first-line population without EGFR, ALK, or ROS1 aberrations. The pivotal EMPOWER-Lung 1 trial demonstrated a remarkable and durable overall survival benefit for Cemiplimab monotherapy over chemotherapy.