Treatment of Cholangiocarcinoma with a Humanized Anti-Claudin-1 Monoclonal Antibody

Background: Cholangiocarcinoma (CCA) is an adenocarcinoma of the hepatobiliary system showing an alarming rise in incidence and mortality with unsatisfactory treatment options. Claudin-1 (CLDN1) is a transmembrane protein involved in epithelial tight junctions and is also expressed non-junctionally mediating cell plasticity and signaling. However, its functional role in CCA pathogenesis and progression is unknown. We have previously developed a highly specific monoclonal antibody (mAb) targeting exposed non-junctional CLDN1 exhibiting an excellent safety profile in non-human primates. Here, we aimed to explore the role of CLDN1 as an oncogenic driver and therapeutic target in intra- and extrahepatic CCA. Material and methods: Comprehensive CLDN1 expression analyses were performed to evaluate CLDN1 as a target for treatment of CCA. Proof-of-concept studies using CLDN1 mAbs were performed in state-of-the-art cell line-derived and patient-derived xenograft mouse models, as well as in human CCA cell lines. Single-cell and bulk RNA sequencing, and proteomics were applied to investigate tumor cell fate and signaling in vivo. Results: Comprehensive analyses of CLDN1 protein and RNA expression in CCA patient tissues revealed a marked and significant upregulation of CLDN1. Single-cell RNA sequencing of the CCA microenvironment revealed strong expression in tumor cells showing EMT, cell cycle and interferon response signature, uncovering CLDN1 as a therapeutic target. Targeting exposed non-junctional CLDN1 by highly specific mAbs resulted in a significant and robust antitumoral effect in vivo across cell line-derived and patient-derived xenograft models for intra- and extrahepatic CCA. Functional studies in cell-based models of CCA showed that CLDN1 mAbs markedly and significantly suppressed migration and invasion of tumor cells. Mechanistically, treatment with CLDN1 mAb suppressed Notch1, Src, and Hippo-YAP signaling - key signal transduction pathways implicated in CCA development and progression. Conclusions: Collectively, these results provide robust pre-clinical proof-of-concept for CLDN1-specific mAbs to treat CCA and set the stage for its clinical development. No conflict of interest.