PBPK Modeling of Esomeprazole to Support Adolescent Pharmacokinetic Extrapolation and Label Extension in Chinese Patients With Gastroesophageal Reflux Disease (GERD).

Esomeprazole, a proton pump inhibitor (PPI), is widely approved for gastroesophageal reflux disease (GERD) in adults and pediatrics globally, but prior to December 2022, its oral tablets (20 and 40 mg) were approved only for adults in China. To address unmet needs in Chinese adolescents aged 12-17 years, physiologically based pharmacokinetic (PBPK) modeling was employed to extrapolate data and support label extension, leveraging similarities in GERD pathophysiology and PK/PD relationships across ages and ethnicities. A PBPK model was developed for esomeprazole to capture the enteric-coated formulation's pharmacokinetics. The model was validated against clinical PK studies in Caucasian, Japanese, and Chinese adults and/or adolescents, demonstrating good predictions of concentration-time profiles and area under the curve (AUC) for CYP2C19-specific genotypes as well as overall populations across these ethnic groups. All predicted-to-observed ratios for AUC fell within 0.5- to 2.0-fold, with 14 out of 18 predictions within the 0.67- to 1.5-fold. This robust validation enabled the model's application to predict PK in Chinese adolescents. PBPK predictions for Chinese adolescents indicated that steady-state AUC for 20- and 40-mg doses was comparable to that in Japanese adolescents and slightly higher than in Caucasian adolescents. By integrating an established PK/PD relationship between AUC and the percentage of time with intragastric pH >4, once-daily doses of 20 or 40 mg were justified, achieving adequate acid suppression with a favorable safety profile. This PBPK-informed extrapolation was accepted by China's National Medical Products Administration (NMPA), enabling GERD indication extension to adolescents.