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

Abstract 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 [ 14 C]‐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.