Neoadjuvant modified FOLFIRINOX plus nivolumab in borderline-resectable pancreatic ductal adenocarcinoma: a pilot phase 1 trial

Chemotherapy and immune checkpoint inhibitor combinations have failed to improve survival in pancreatic ductal adenocarcinoma (PDAC), except in rare microsatellite instability-high cases; most studies focused on advanced disease. Here, we present clinical and translational results from a single-arm, prospective phase 1b/2 investigator-initiated study (NCT03970252) evaluating neoadjuvant modified FOLFIRINOX (mFFX) plus nivolumab in patients with borderline-resectable PDAC. The co-primary endpoints of safety and pathological response rate were met, with 22 (79%) of 28 patients proceeding to surgery and no grade ≥3 immune-related adverse events. All grade 3-4 treatment-related adverse events were chemotherapy-related. By CAP scoring, 9% of patients achieved a complete pathologic response, 9% a near-complete response, and 72% a partial response. Secondary endpoints included CA 19-9 response rate, R0 resection rate, objective response rate, and disease-free survival (median 19.7 months, 95% CI: 7.3-30.8). In post-hoc analyses, median progression-free survival was 26 months (95% CI: 14.7-34.3), and median overall survival was 38 months (95% CI: 27.9-not reached). Exploratory gene expression, immunohistochemistry and spatial transcriptomics showed increased intratumoral plasma cells and CD8 T cells in treated patients versus mFFX-only controls, and lymphoid aggregates with high plasma-cell-to-B cell ratios enriched for terminally exhausted CD8 T cells with fewer progenitor exhausted CD8 T cells and central memory CD4 T cells.