The Effects of the Proton Pump Inhibitor Esomeprazole on the Bioavailability of Regorafenib

Regorafenib is a novel oral multi-kinase inhibitor which targets angiogenic, stromal and oncogenic receptor tyrosine kinases. It is currently registered for GIST and mCRC. When regorafenib is co-administered with an acid suppressive agent, the intra-gastric pH increases, and as a result the equilibrium of ionized/non-ionized regorafenib may shift to the less soluble non-ionized form which reduces regorafenib bioavailability and exposure. Since proton pump inhibitors (PPIs) are often used during regorafenib therapy, this drug-drug interaction (DDI) confronts pharmacists and oncologists with challenges in clinical practice. In this study the investigators will therefore evaluate the impact of PPI-induced intra-gastric pH elevation on regorafenib pharmacokinetics in patients with GIST and mCRC.