Granzyme B PET Imaging Reveals Lgmn+ Macrophage-Mediated Immune Evasion and Guides Immunotherapy in EGFR-TKI-Resistant NSCLC.

Determining optimal therapies for EGFR-mutant NSCLC after tyrosine kinase inhibitor (TKI) resistance remains challenging. Immune checkpoint inhibitors (ICIs) show limited efficacy, but some patients regain immunotherapy sensitivity post-TKI. Non-invasive monitoring to identify responders and understand persistent immune tolerance is needed. In this study, we prospectively evaluated a novel granzyme B-targeted PET radiotracer, 68Ga-GZB, in a clinical cohort of NSCLC patients. 68Ga-GZB PET/CT accurately visualized early immune responses and stratified patients likely to benefit from immunotherapy. In preclinical models of acquired EGFR-TKI resistance, we tracked dynamic immune reactivity via 68Ga-GZB PET/CT. Single-cell transcriptomics and functional validation identified Lgmn+ macrophages as a highly immunosuppressive subset driving persistent immunotherapy tolerance. Mechanistically, Lgmn+ macrophages secrete extracellular vesicles (EVs) that deliver Lgmn directly into CD8+ T cells. Internalized Lgmn recruits the E3 ubiquitin ligase Chip, initiating the ubiquitination and proteasomal degradation of the glycolytic enzyme Eno1. This cascade severely impairs CD8+ T cell glycolysis, ultimately leading to CD8+ T cell exhaustion. Furthermore, we demonstrate that targeting of Lgmn synergizes with PD-1 blockade to reactivate anti-tumor immunity in TKI-resistant models. Thus, 68Ga-GZB PET/CT provides a non-invasive platform to stratify immunotherapy responses, and targeting Lgmn represents a novel combination strategy for EGFR-TKI-resistant NSCLC.