Targeting intratumoral heterogeneity in pancreatic cancer with sequential TIL infusions.

Adoptive transfer of tumor-infiltrating lymphocytes (TIL) is effective in melanoma and selected solid tumors, but its potential in pancreatic ductal adenocarcinoma (PDAC) remains largely unexplored. We report a 39-year-old male with metastatic PDAC involving lung, peritoneal, liver, and lymph node who received three sequential infusions of TIL expanded ex vivo with IL-2/IL-15/IL-21 from a lung metastasis. Each infusion followed low-dose lymphodepletion and IL-2 support. The patient achieved stable disease after the first infusion and a partial response after the second along with reductions in serum CA19-9. Genome sequencing revealed substantial inter-tumoral heterogeneity, with mutations in ITGB2, C1QTNF3, CDK9, TMEM200C, FHOD1 and ZZZ3 impacting TIL infiltration and clinical response. RNA-seq showed that responding lesions were enriched for inflammatory and tumor-specific programs, displayed enrichment of T-cell activation transcripts and had reduced infiltration of cancer-associated fibroblasts. TCR sequencing confirmed the robust infiltration of TIL-derived CD8+ clonotypes, while functional assays demonstrated a polyclonal recognition of patient-derived somatic mutations and cytotoxicity against autologous tumor lines. Single-cell TCR mapping further validated the dominance of tumor-specific CD8+ clonotypes in responding lesions. This case demonstrates the feasibility and immunological activity of TIL therapy in PDAC, while underscoring the impact of spatial tumor heterogeneity on therapeutic outcomes.