Document resource
Background Adoptive transfer of tumor-infiltrating lymphocytes (TIL) has demonstrated durable benefit in melanoma, but its role in pancreatic ductal adenocarcinoma (PDAC) remains unexplored. PDAC features low TMB, dense stroma, and marked heterogeneity, hindering effective immunotherapy.Methods We describe a 39-year-old male with metastatic PDAC unresponsive to FOLFIRINOX who underwent three sequential TIL infusions. TILs were generated from a lung metastasis and expanded ex vivo in the presence of IL-2/IL-15/IL-21. Each infusion was preceded by cyclophosphamide lymphodepletion and followed by IL-2 support. Clinical responses were monitored radiographically and by serum CA19-9. Biopsies were collected from regressing, stable and progressing metastatic lesions post-TIL infusions. Multi-omic profiling incorporated whole-exome sequencing, RNA-seq, T-cell receptor (TCR) sequencing, flow cytometry, and peptide reactivity assays to characterize tumor evolution and TIL function.Results The first infusion (0.5×10 9 TILs) induced stable disease, while a second infusion (1.9×109 TILs) achieved a partial response with declining CA19-9 levels. A third infusion (1.2×109 TILs) given after intensified lymphodepletion and high-dose IL-2 produced no further benefit, and disease progression followed. Treatment was well tolerated with only transient fever and lymphopenia.Genomic profiling confirmed low TMB and extensive inter-lesional heterogeneity. While TP53, CDKN2A, BRCA1/2, and ATM mutations were shared across lesions, most nonsynonymous variants were private. The regressing lesion harbored multiple TP53 mutations, potentially enhancing antigenicity, whereas the progressing lesion displayed unique alterations linked to immune escape and stromal remodeling.Transcriptomic analysis revealed CD4+ memory and CD8+ T-cell enrichment and TCR signaling in regressing and stable lesions, but dominance of non-immune pathways in the progressing lesion.TCR repertoire mapping showed persistence of infused clonotypes in regressing and stable lesions, contrasted with restricted diversity in the progressing lesion. TRBV12-4+CD4+ clonotypes dominated in the regressing lesion, while TRBV12-4+CD8+ clonotypes dominated in the stable lesion, both with high PD-1 expression consistent with sustained antigen engagement. TCR overlap analysis demonstrated preferential infiltration of CD8+ TIL-derived clonotypes, which mediated tumor regression.Functional assays confirmed polyclonal recognition of 18 peptide pools by the infused TILs, with maintained reactivity in TILs expanded from the regressing lesion. Individual tumor-specific TCR clonotypes were identified and mapped across lesions. Regressing and stable lesions contained abundant tumor-specific CD8+ TCR clonotypes, whereas the progressing lesion showed only limited clonotype presence.Conclusions This case highlights the feasibility, safety, and immunological activity of IL-2/IL-15/IL-21-expanded TIL therapy in metastatic PDAC. Clinical benefit correlated with clonal persistence, tumor-specific T-cell responses, and immune-enriched microenvironments, while progression reflected restricted TCR diversity and immunosuppression.Ethics Approval Ethics approval was not required, as single-patient compassionate use in Germany is not subject to ethics committee oversight.Consent Study participant provided informed consent before taking part, including consent for publication.