Abstract
Immune checkpoint inhibitors (ICI) have demonstrated clinical efficacy in non–small cell lung cancer (NSCLC), and extensive research has been conducted to explore biomarkers predictive of ICI response. However, the impact of ICI on the tumor and tumor microenvironment at primary and acquired resistance states is understudied due to the difficulty of collecting tissue biopsies at disease progression. In this study, we leveraged clinical and real-world data to study ICI resistance. Data used in this work consist of treatment outcome information and tissue RNA sequencing data from advanced-stage NSCLC cohorts from three sources: the Tempus real-world evidence database; CANOPY-1 (NCT03631199), a phase III clinical trial in first-line NSCLC; and Stand Up To Cancer (SU2C) publication. Our results indicate higher IFNγ and T-cell exhaustion in patients’ tumors at acquired resistance and low levels of B-cell and dendritic cell expression at primary resistance. The lower B-cell and dendritic cell levels may be primarily driven by prior treatment with a platinum-based chemotherapy regimen. Baseline transcriptomics data additionally suggest that innate immune cells may play an antitumor role in PD-L1<1% patients, whereas IFNγ and T-cell inflammation are more predictive of ICI treatment outcomes in PD-L1≥1% patients. Our study suggests a clear divergence of the tumor microenvironment in patients with primary versus acquired resistance and a potential role of myeloid cells in the PD-L1<1% population. These findings shed light on potential next-generation therapies to overcome ICI resistance.

Significance
ICI benefits patients with NSCLC, but resistance remains common. Our research highlights differences in tumor environments between primary and acquired resistance after ICI treatment, emphasizing distinct post-therapy approaches. Findings also suggest myeloid cells as key players in PD-L1–negative cases, guiding future treatment strategies to overcome resistance and improve outcomes.

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