Dose‐dependent pharmacokinetics and tentative identification of urine metabolites from an isosteviol derivative with anti‐hepatitis B activity in rats

Compound 1 ( ent ‐16‐oxobeyeran‐19‐ N ‐methylureido) is a semisynthetic isosteviol derivative that shows anti‐hepatitis B virus activity in Huh7 cells by affecting viral DNA transcription and the Toll‐like receptor 2/nuclear factor‐ κ B signaling pathway. Thus, the pharmacokinetics and metabolite identification were studied as part of the discovery and development process of compound 1 . The pharmacokinetics was evaluated after administration to rats at an intravenous dose of 2 mg/kg, and oral doses of 2, 5 and 10 mg/kg. Plasma concentrations were determined using LC–MS/MS. Moreover, urine samples from rats dosed at 10 mg/kg were scanned for metabolites using UPLC‐QTOF‐MS/MS. Results for the intravenously administered dose of 2 mg/kg showed that the area under the concentration–time curve was 65,223.31 ± 4269.80 ng min/mL, and the systemic clearance was 0.031 ± 0.0021 L/min. Oral pharmacokinetic parameters were dose‐dependent, showing nonproportional increases in the oral AUCs with respective values of 4371.62 ± 3084.81, 22,472.75 ± 9103.33 and 135,141.83 ± 38,934.03 ng min/mL for 2, 5 and 10 mg/kg. The bioavailability was low at 1.5% for 2 mg/kg dose, and at 1.1% for both 5 and 10 mg/kg doses. Metabolites excreted in the urine indicate possible N ‐oxidation and glucuronide conjugation.