628 CD40 agonist-based triplet therapy engages intra-tumoral T cells to drive tumor control independent of lymph node trafficking in triple negative breast cancers

作者：Xinyi Qi, Preetesh L. Mylabathula, Riyasat Ali, Anas Alkhani, Skanda Hebbale, James Zhu, Vivek Mathesh, Isaac S. Chan, Sangeetha M. Reddy · 发表于：Regular and Young Investigator Award Abstracts · 年份：2025 · DOI：10.1136/jitc-2025-sitc2025.0628 · 研究领域：Cancer Immunotherapy and Biomarkers、T-cell and B-cell Immunology、Immunotherapy and Immune Responses

Background Anti-tumor immunity is deficient in aggressive triple-negative breast cancers (TNBC). Impaired antigen presentation, driven by reduced number and function of cross-presenting dendritic cells (cDC1s), is a major barrier to effective T cell-mediated immunity. Flt3 ligand (Flt3L) expands cDC1s, CD40 agonists (CD40a) activate antigen-presenting cells, and anthracycline chemotherapy promotes immunogenic tumor cell death. We hypothesized that combining these agents would enhance anti-tumor immunity.Methods EO771, AT3, or 4T1 TNBC cells were implanted orthotopically in female mice. Triplet therapy consisted of Doxil D1, Flt3L D1-5, and CD40a D11, 14, 17 after tumors reached 50 mm 3. Tumor growth and survival were recorded thrice weekly. Immune profiling was performed with flow cytometry, single-cell RNA sequencing (scRNA-seq), and bulk TCR sequencing (TCR-seq). Mechanistic dependence was tested by depleting CD8+, CD4+, and Foxp3+ regulatory T cells (Tregs) as well as by blocking lymphocyte egress with FTY720.Results Triplet therapy significantly delayed tumor progression and extended median survival compared to chemotherapy alone or doublet combinations. Compared to chemotherapy alone or doublet combinations, triplet therapy markedly increased intra-tumoral CD8+ T cell infiltration. Enhanced CD8 infiltration was accompanied by reduced expression of exhaustion markers (LAG-3 and TIM-3) and elevated activation, as evidenced by increased PD-1 single-positive T cells. scRNA-s...