# Why Cemiplimab? Defining a Unique Therapeutic Niche in First-Line Non-Small-Cell Lung Cancer with Ultra-High PD-L1 Expression and Squamous Histology

## TL;DR

Cemiplimab is a new anti-PD-1 antibody that shows strong results in treating non-small-cell lung cancer, especially in patients with ultra-high PD-L1 expression and squamous histology.

## Contribution

Cemiplimab's unique structural design reduces anti-drug antibody risks and improves efficacy in high PD-L1 and squamous NSCLC patients.

## Key findings

- Cemiplimab monotherapy shows exceptional survival benefits in patients with ultra-high PD-L1 expression (≥90%).
- Cemiplimab is effective in squamous NSCLC, both as monotherapy and in combination with chemotherapy.

## Abstract

This review evaluates the role of cemiplimab, an anti-PD-1 antibody, analyzing data from the pivotal EMPOWER-Lung1 and EMPOWER-Lung3 trials. The findings highlight cemiplimab’s robust efficacy across difficult-to-treat subgroups, including those with squamous histology and brain metastases. A key distinction is its exceptional performance in patients with “ultra-high” PD-L1 expression (≥90%). We discuss the plausible biological mechanism linking cemiplimab’s unique structural stability to reduced anti-drug antibody risks, potentially enhancing efficacy in these highly immunogenic tumors. Additionally, the combination of cemiplimab and chemotherapy offers a strong alternative for lower PD-L1 expression levels. In conclusion, cemiplimab represents a critical therapeutic option, potentially establishing a unique niche for specific, high-need Non-Small Cell Lung Cancer populations.

The landscape of first-line treatment for metastatic non-small cell lung cancer (NSCLC) without actionable driver mutations is rapidly evolving, currently dominated by pembrolizumab-based regimens. This review discusses the unique molecular characteristics of cemiplimab, a newer anti-PD-1 antibody, and defines its optimal positioning against established standards. Cemiplimab is a fully human IgG4 monoclonal antibody distinguished by two key features: an engineered hinge-region mutation that prevents Fab-arm exchange, ensuring exceptional molecular stability which minimizes anti-drug antibody (ADA) risks associated with unstable molecules; and a unique interaction with PD-1 glycosylation sites, potentially enhancing binding efficacy. These structural advantages may be particularly relevant in histologies like squamous NSCLC, where accumulating somatic mutations drive high neoantigen loads and heightened immune responses, creating an environment historically prone to ADA formation. Based on data from the pivotal EMPOWER-Lung program, we highlight cemiplimab’s exceptional promise in specific populations. Firstly, in the EMPOWER-Lung 1 trial, cemiplimab monotherapy demonstrated extraordinary survival benefits in a pre-specified analysis of the distinct “ultra-high” PD-L1 expression subgroup (TPS ≥90%), potentially surpassing historical benchmarks. Secondly, cemiplimab displays consistent, robust efficacy in challenging-to-treat squamous histology, both as monotherapy for patients with high PD-L1 expression and in combination with chemotherapy for patients with PD-L1 < 50%. In conclusion, cemiplimab establishes a unique therapeutic niche for patients with squamous histology and ultra-high PD-L1 expression, likely driven by its distinct structural stability and reduced immunogenicity.