Vonoprazan is associated with a phenotype-specific increase in cholangitis reporting in immune checkpoint inhibitor-treated patients: a VigiBase pharmacovigilance study

BACKGROUND: Immune checkpoint inhibitors (ICIs) can cause immune-related adverse events (irAEs), including cholangitis, a rare but clinically severe hepatobiliary phenotype. Whether potassium-competitive acid blockers (PCABs) such as vonoprazan are associated with hepatobiliary adverse-event reporting among ICI-treated patients remains unclear. METHODS: We performed a READUS-PV-compliant case-noncase disproportionality analysis using VigiBase, the WHO global individual case safety report database (inception through December 1, 2025; MedDRA v27.1). Adjusted reporting odds ratios (aRORs) were estimated for composite liver injury and a custom cholangitis-related endpoint for vonoprazan, proton pump inhibitors (PPIs), and histamine-2 receptor antagonists (H2RAs). The primary analysis was restricted to ICI-exposed reports and adjusted for age, sex, region, hepatotoxic co-medications, and ICI class. Sensitivity analyses addressed treatment intensity, microbiome-modifying co-medications, regional restriction, endpoint definition, sparse-data bias, and ICI subgroup. Six additional irAE categories were analyzed as comparator outcomes. RESULTS: Among 295,671 ICI-exposed reports, 1098 co-reported vonoprazan and 1186 reports met the cholangitis-related endpoint. Cholangitis was reported in 35 of 1098 vonoprazan-exposed reports (3.19%) versus 0.39% of ICI reports without vonoprazan. Vonoprazan was associated with increased cholangitis reporting (aROR 2.79; 95% CI 1.93-4.02; P < 0.001; E-value 5.02), whereas PPIs and H2RAs showed no significant association. The association persisted across sensitivity analyses, including Western Pacific restriction, microbiome- and treatment-intensity adjustment, and PD-1/PD-L1 monotherapy. Comparator irAE associations were modest and heterogeneous. CONCLUSIONS: Vonoprazan was associated with a phenotype-specific increase in cholangitis reporting among ICI-treated patients, a pattern absent with PPIs or H2RAs and unmatched across comparator irAEs. Prospective clinical validation is warranted.