Proton pump inhibitors and potassium competitive acid blockers decrease pembrolizumab efficacy in patients with metastatic urothelial carcinoma.

We elucidated the efficacy of gut microbiome-altering drugs on pembrolizumab efficacy in patients with metastatic urothelial carcinoma (mUC). Clinical data were analyzed retrospectively from 133 patients with mUC who received second-line pembrolizumab therapy between January 2018 and January 2021, following failed platinum-based chemotherapy. We evaluated the effects of gut microbiome-altering drugs (proton pump inhibitors [PPI]/potassium-competitive acid blockers [P-CAB], H2 blockers, antibiotics, non-steroidal anti-inflammatory drugs [NSAIDs], metformin, antipsychotics, steroids, and opioids), taken by patients within 30 days before/after pembrolizumab treatment, on progression-free survival (PFS) and overall survival (OS). Fifty-one patients received PPI/P-CAB (37/14, respectively); H2 blockers, 7; antibiotics, 35; NSAIDs, 22; antipsychotics, 8; metformin, 3; steroids, 11; and opioids, 29. Kaplan-Meier curves revealed PPI or P-CAB users showed shorter PFS than non-PPI-P-CAB users (p = 0.001, p = 0.005, respectively). Multivariate analysis highlighted PPI/P-CAB use as the only independent prognostic factor for disease progression (hazards ratio: 1.71, 95% confidence interval: 1.14-2.07, p = 0.010) but not death (p = 0.177). Proton pump inhibitors/potassium-competitive acid blockers may decrease the efficacy of pembrolizumab therapy for mUC, possibly via gut microbiome modulation.