The pH factor: unraveling drug-drug interactions in protein kinase inhibitors through the regulatory lens

Drug-drug interactions (DDIs) are a significant concern in clinical practice, DDIs might be relevant when drugs with pH-dependent solubility are co-administered with gastric acid-reducing agents (ARAs) such as histamine, H2-receptor antagonists and proton pump inhibitors. One class prone to such DDI at the absorption phase are the weakly basic protein kinase inhibitors (PKIs). The aim of this work is to review recent Food & Drug Administration (FDA) and European Medicines Agency (EMA) submissions for PKIs and evaluate the various approaches by drug developers to characterize pH-dependent DDI liability potentially affecting efficacy in this class of drugs and assess how this impacts the labelling. For this purpose, 32 FDA New Drug Applications (NDAs) and 25 EMA Market Authorization Applications of PKIs in the last 5 years (2019 through 2024) were reviewed More than two-thirds of the submissions included a dedicated clinical DDI studies with an ARA, which remains the most frequent approach to evaluating gastric pH-dependent DDIs among the PKIs investigated, albeit model-informed drug development approaches are also attempted by applicants in about 20% of the submissions. In cases where no clinical DDI study was submitted and alternative approaches taken, this was accepted by the approving agencies. Only the complete absence of data on the DDI potential triggered the request to provide the information post-marketing. A risk-based approach, considering the drug’s properties and patient population, is crucial for determining the need for a clinical DDI study and should be discussed with the agencies during drug development.