Limited Immune-Mediated Efficacy of Anti-PD-L1/VEGF in EGFR-TKI-Naïve Egfr-Mutant Lung Cancer with Non-Inflamed Tumor Microenvironment.

Immune checkpoint inhibitors (ICIs) show limited efficacy in epidermal growth factor receptor (EGFR)-mutant lung adenocarcinoma due to its non-inflamed tumor microenvironment (TME). While quadruple therapy combining chemotherapy, anti-programmed death-ligand 1 (PD-L1), and anti-vascular endothelial growth factor (VEGF) antibodies has shown inconsistent results in EGFR-tyrosine kinase inhibitor (TKI)-pretreated patients, whether anti-VEGF therapy can modulate the intrinsic non-inflamed TME remains unknown. We employed an EGFR-TKI-naïve syngeneic Egfr-mutant mouse model and evaluated effects of anti-VEGF, anti-PD-L1, carboplatin, and paclitaxel as monotherapies and combinations, with TME analysis via immunohistochemistry (IHC), flow cytometry, and RNA sequencing. Anti-PD-L1 showed no antitumor effect, and adding anti-VEGF failed to convert the TME to an inflamed status. Although paclitaxel-but not carboplatin-combined with low-dose anti-VEGF inhibited tumor growth, adding anti-PD-L1 provided no benefit, indicating the anti-VEGF-A antibody evaluated here has a limited role in sensitizing tumors to anti-PD-L1 regardless of chemotherapy. CD8+ T-cell depletion did not attenuate the effect of paclitaxel plus low-dose anti-VEGF, and IHC and RNA sequencing revealed increased natural killer cell infiltration, suggesting a CD8+ T-cell-independent, innate immune mechanism. These findings provide preclinical evidence that the evaluated anti-VEGF has limited immunomodulatory activity in EGFR-TKI-naïve Egfr-mutant tumors with a non-inflamed TME, and suggest immunotherapeutic strategies beyond CD8+ T-cell-mediated immunity warrant investigation.