Nonclinical and Clinical Assessments of an Optimized Tablet Formulation of the Novel HER2-Selective Tyrosine Kinase Inhibitor Zongertinib: Focus on Relative Bioavailability and Impact of Variation of Gastric pH

Zongertinib (BI 1810631), a novel orally administered HER2-specific tyrosine kinase inhibitor, has recently received accelerated approval in the United States and China for patients with advanced, previously treated <i>HER2</i> mutant NSCLC. This multifaceted analysis assessed the influence of gastric pH variation on the pharmacokinetics of conventional and spray-dried dispersion (SDD) formulations of zongertinib. The influence of gastric pH on zongertinib pharmacokinetics was evaluated in male beagles. Increased gastric pH substantially reduced absorption of zongertinib as a Natrosol suspension. At low gastric pH, the SDD formulation provided improved exposure and reduced variability compared with a conventional formulation. We then evaluated the <i>in vitro</i> release and bioaccessibility of conventional and SDD tablet formulations of zongertinib with the tiny-TIM gastrointestinal system. Bioaccessibility was similar between the two formulations under simulated fasted conditions; however, under simulated fasted conditions with a proton pump inhibitor, the conventional formulation showed reduced bioaccessibility versus SDD. In a randomized, open-label crossover study, fasted healthy human male participants received 30 mg zongertinib as a conventional tablet formulation, an SDD tablet formulation, and as an SDD tablet formulation after multiple doses of rabeprazole 40 mg. The primary pharmacokinetic end points were area under the plasma concentration-time curve from time 0 to the last quantifiable point (AUC_0-tz) and maximum plasma concentration (<i>C</i>_max) of zongertinib. <i>C</i>_max and AUC_0-tz were ∼39% and ∼35% higher, respectively, with the SDD versus the conventional formulation. Geometric mean <i>C</i>_max and AUC_0-tz were similar after treatment with zongertinib SDD with and without rabeprazole. Zongertinib SDD formulation showed good bioavailability irrespective of pH, supporting further clinical development.