Absorption, Metabolism, and Excretion of [14C]-Labeled Anaprazole: A New Proton Pump Inhibitor, After a Single Oral Administration in Healthy Chinese Male Subjects

Anaprazole is a proton pump inhibitor. This study aims to elucidate absorption, metabolism, and excretion pathways of anaprazole sodium in the human body. A total of 4 healthy Chinese male subjects were administered a single oral dose of 20 mg/100 µCi of [¹⁴C]-anaprazole sodium enteric-coated capsules. The whole blood, plasma, and excreta were analyzed for a total radioactivity (TRA) and metabolite profile. The cumulative radioactivity excretion rate was 93.2%, with 53.3% and 39.9% of the radioactive dose excreted in urine and feces, respectively, and 91.6% of dose recovered within 96 hours after dosing. The parent drug, anaprazole, showed good absorption and was extensively metabolized majorly to thioether M8-1 via nonenzymatic metabolism. Overall, 35 metabolites were identified in plasma, urine, and fecal samples. Anaprazole was the most abundant component in plasma followed by the thioether M8-1, accounting for 28.3% and 16.6%, respectively, of the plasma TRA. Thioether carboxylic acid XZP-3409 (26.3% of urine TRA) and XZP-3409 oxidation and dehydrogenation product M417a (15.1% of fecal TRA) were the major metabolites present in urine and feces, respectively. Anaprazole was undetectable in urine, while fecal samples showed traces (0.07% dose). Blood/plasma ratios of the radioactivity (approximately 0.60) remained consistent over time. Anaprazole showed good absorption and was extensively metabolized majorly to thioether M8-1 via nonenzymatic metabolism, and cytochrome P450 3A4 also contributed to its metabolism in healthy individuals.