(856) Exploring the Role of Natural Anti-PD-L1 antibodies in Shaping the Anti-Tumor Immune Response to Neoadjuvant Chemo-Immunotherapy in NSCLC

Introduction/Rationale: Non-small-cell lung cancer (NSCLC) is a major contributor to cancer-related deaths worldwide. Although the introduction of immune checkpoint inhibitors, such as anti-PD-1, has improved patient survival, treatment responses remain heterogeneous, and the complete mechanisms of action are not yet fully understood. Our group previously described naturally immune checkpoint blockade mediated by endogenous antibodies that functionally mimic the effects of therapeutic checkpoint inhibitors, without autoimmune symptoms in non-previously treated NSCLC patients (Frozza et al., 2025, under review). Now we are investigating the immune profile of NSCLC patients undergoing neoadjuvant anti-PD-1 therapy combined with chemotherapy, with the hypothesis that the presence and dynamic modulation of circulating anti-PD-L1 autoantibodies influence the tumor immune microenvironment, thereby impacting treatment response, immune activation, and therapeutic efficacy.

Methods: To achieve this, transcriptomic profiling through single-cell RNA sequencing (scRNAseq) of immune cells from blood, tumor and draining lymph node are being performed pre and post treatment, following by the validation with flow cytometry and immunohistochemistry. The quantification of autoantibodies anti-PD-L1 are being performed by ELISA.

Results: Preliminary analyses demonstrate the presence of circulating anti–PD-L1 autoantibodies both before and after chemo-immunotherapy. Post-treatment antibody levels exhibited marked variability, suggesting heterogeneous immune modulation in response to treatment. scRNAseq showed an increase in the frequency of the CD8⁺ T and B cell infiltrating the tumor and draining lymph nodes post treatment.

Conclusion: In conclusion, this study seeks to elucidate mechanisms of immunotherapy resistance in NSCLC by linking tumor immune profiles and the presence of anti–PD-L1 autoantibodies to responses to neoadjuvant chemo-immunotherapy, with the goal of identifying predictive biomarkers and improving treatment strategies.