Potential drug interactions between pazopanib and proton pump inhibitors/potassium-competitive acid blockers in patients with soft tissue sarcoma

Because absorption of the oral drug pazopanib depends on gastric pH, concomitant use of proton pump inhibitors (PPIs)/potassium-competitive acid blockers (P-CABs) may inhibit pazopanib absorption by elevating the gastric pH. This study investigated to what extent the concomitant use of PPIs/P-CABs affects treatment with pazopanib in patients with soft tissue sarcoma. We retrospectively reviewed the medical records of patients with soft tissue sarcoma who had received at least one dose of pazopanib at our institution, among which those who had received concomitant PPIs/P-CABs were included in this analysis. Using paired sample t tests, the frequency of dose reduction or interruption of pazopanib and the major adverse events (AEs) were compared in each patient between periods with and without PPIs/P-CABs. Between January 2018 and December 2022, eight patients were eligible. The median time to treatment failure (TTF) was 3.9 months (2.1–38.2 months). Two patients received concomitant PPIs/P-CABs throughout their treatment with pazopanib. Among the other six patients, dose reduction or interruption of pazopanib occurred less frequently (P = 0.021), and neutropenia tended to be milder (P = 0.155) with the concomitant use of PPIs/P-CABs. Although the concomitant use of PPIs/P-CABs had no apparent effect on TTF in patients undergoing pazopanib treatment, dose reduction or interruption of pazopanib occurred less frequently, and neutropenia was milder, suggesting that concomitant use of PPIs/P-CABs might decrease the pharmacological activity of pazopanib.