Best Practices in Physiologically Based Pharmacokinetic (PBPK) Modeling

Physiologically based pharmacokinetic (PBPK) modeling is a mechanistic cornerstone of model-informed drug development (MIDD), providing evidence for regulatory decisions. PBPK models integrate physiological and pharmacological data and have been applied across a plethora of contexts of use, including assessing drug-drug interactions (DDIs), optimizing dosing for special populations (e.g., pediatrics and those with organ impairment), and supporting clinical study waivers. However, despite the established history of PBPK modeling, a significant gap persists between the quality of submitted PBPK analyses and regulatory expectations. Recent reviews by the European Medicines Agency (EMA) and other regulatory bodies indicate that many PBPK models are not deemed adequately qualified for their intended application. This discrepancy highlights the need for consolidated guidance on model development, evaluation, and application, particularly to harmonize terminology and expectations with the ICH M15 guideline. To address this challenge, this paper provides comprehensive best-practice guidance for the development, verification, validation, and applicability assessment of PBPK models. We delineate strategies for defining explicit technical criteria to ensure models are appropriately qualified and demonstrably fit-for-purpose for a specific context of use. This guidance aims to enhance the quality, consistency, and regulatory acceptance of PBPK analyses, thereby strengthening the reliability of MIDD evidence supporting drug development and approval.