Clinical and molecular dissection of CAR T cell resistance in pancreatic cancer

Patients with advanced pancreatic ductal adenocarcinoma (PDAC) have a median survival of less than a year, highlighting the urgent need for treatment advancements. We report on a phase 1 clinical trial assessing the safety and feasibility of intravenous and local administration of anti-mesothelin CAR T cells in patients with advanced PDAC. While therapy is well tolerated, it demonstrates limited clinical efficacy. Analyses of patient samples provide insights into mechanisms of treatment resistance. Single-cell genomic approaches reveal that post-infusion CAR T cells express exhaustion signatures, including previously identified transcription factors ID3 and SOX4, and display enrichment for a GZMK+ phenotype. Single knockout of ID3 or SOX4 enhances efficacy in xenograft models, though with donor-dependent variability. However, single-knockout cells eventually fail. Conversely, ID3 and SOX4 double-knockout CAR T cells exhibit prolonged relapse-free survival, demonstrating a sustained therapeutic effect and a potential avenue for engineering more potent CAR T cells in PDAC. This study was registered at ClinicalTrials.gov (NCT03323944).