Abstract 5256: Tertiary Lymphoid Structures as Predictors of Immune Checkpoint Inhibitor Efficacy in NSCLC and the Development of an Ex Vivo Model for Precision Medicine

Background: Tertiary lymphoid structures (TLS) emerge as essential players in modulating anti-tumor immune responses and shaping the outcomes of immune checkpoint inhibitor (ICI) therapies. Here we explored, on the one hand, the impact of TLS maturity on clinical outcomes in non-small cell lung cancer (NSCLC), and introduce, on the other hand, a novel ex vivo tool model to investigate TLS-mediated immune synapses and test potential therapeutic strategies. Methods: In this study, 509 NSCLC patients from the BIP cohort (NCT02534649) - treated with ICI-based regimens - were retrospectively analyzed and assessed by multiplex IHC (Ventana Discovery, Roche) and digital pathology (PhenoImager HT, Akoya). TLS status and maturity were evaluated histologically in pre-treatment FFPE samples, with mature TLS (mTLS) defined by the presence of CD23+ follicular dendritic cells. Correlations with overall survival (OS), progression-free survival (PFS), and response rates were analyzed. Interestingly, an ex vivo model was developed using T follicular helper (Tfh) and memory B cells isolated from human tonsils. Tfh cells (CD4+/CXCR5+/PD1high/ICOShigh) and memory B cells (CD19+/CD27+) were co-cultured in the presence of staphylococcal enterotoxin B (SEB). Effects of ICIs (e.g., anti-PD1, anti-TIGIT, anti-CTLA4), anti-CD40, and kynurenine (IDO metabolite) were evaluated on IgG produced levels - quantified by ELISA - as a surrogate of synapse function. Results: TLS were detected in 49.5% of cases, of which 28.7% were classified as mTLS. mTLS were significantly associated with improved OS and PFS, independent of PD-L1 expression and molecular status. Long-term survivors (≥24 months) had a higher frequency of mTLS (41.3% vs. 22.9%; p < 0.001). Response rates to ICIs were notably higher in mTLS-positive patients than in mTLS-negative patients (56.8% vs. 33.6%; p < 0.001). On the other hand, the ex vivo model demonstrated robust IgG production in Tfh-B cell co-cultures, modulated positively by ICIs (Nivolumab, Atezolizumab, Tiragolumab, Ipilimumab) and negatively by anti-CD40 and kynurenine. Conclusions: This study highlights the critical role of TLS maturity in predicting response to ICIs and improving survival outcomes in NSCLC. The ex vivo Tfh-B cell model provides a novel platform to evaluate therapies targeting TLS function. Combining TLS stratification via histology with Tfh-B cell synapse-enhancing agents represents a promising approach in precision medicine. Citation Format: Jean-Philippe Guegan, Imane NAFIA, Florent PEYRAUD, Lucile VANHERSECKE, Christophe Rey, Lucie Lefevre, Assia CHAIBI, Alban Bessede, Antoine ITALIANO. Tertiary Lymphoid Structures as Predictors of Immune Checkpoint Inhibitor Efficacy in NSCLC and the Development of an Ex Vivo Model for Precision Medicine [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 5256.