Absorption, Distribution, Metabolism, and Excretion of [14C]BS1801, a Selenium-Containing Drug Candidate, in Rats.

BS1801 is a selenium-containing drug candidate with potential for treating liver and lung fibrosis. To fully elucidate the biotransformation of BS1801 in animals and provide sufficient preclinical drug metabolism data for human mass balance study, the metabolism of BS1801 in rats was investigated. We used radiolabeling techniques to investigate the mass balance, tissue distribution, and metabolite identification of BS1801 in Sprague-Dawley/Long-Evans rats after a single oral dose of 100 mg/kg (100 µCi/kg) [14C]BS1801: 1. The mean recovery of radioactive substances in urine and feces was 93.39% within 168 h postdose, and feces were the main excretion route. 2. Additionally, less than 1.00% of the dose was recovered from either urine or bile. 3. BS1801-related components were widely distributed throughout the body. 4. Fifteen metabolites were identified in rat plasma, urine, feces, and bile, and BS1801 was detected only in feces. 5. BS1801-M484, the methylation product obtained via a N-Se bond reduction in BS1801, was the most abundant drug-related component in plasma. The main metabolic pathways of BS1801 were reduction, amide hydrolysis, oxidation, and methylation. Overall, BS1801 was distributed throughout the body, and excreted mainly as an intact BS1801 form through feces. No differences were observed between male and female rats in distribution, metabolism, and excretion of BS1801.

Pharmacokinetic and metabolite profile of orally administered anemoside B4 in rats with an improved exposure in formulations of rectal suppository.

ETHNOPHARMACOLOGICAL RELEVANCE: Pulsatilla chinensis (Bunge) Regel is a traditional Chinese herbal medicine used to treat intestinal amebiasis, malaria, vaginal trichomoniasis, and bacterial infections. Anemoside B4 (AB4), a pentacyclic triterpenoid saponin, is one of the primary bioactive substances in Pulsatilla chinensis (Bunge) Regel, and gavage administration of AB4 to animals has been demonstrated to exhibit anticancer, anti-inflammatory, and antiviral actions. However, AB4 exposure in plasma is very low after oral administration, and the biotransformation of AB4 in vivo after oral administration remains unknown. AIM OF THE STUDY: The reason for conducting this research was to explore at the metabolite profile of AB4 in rats following oral administration. Additionally, we aimed to develop an appropriate extravascular formulation to increase the exposure and duration of AB4 in vivo. MATERIALS AND METHODS: A well-validated HPLC-QQQ-MS/MS method was used for the quantification of AB4 in plasma and was further applied to evaluate and compare the pharmacokinetic properties of AB4 dissolved in a saline solution and AB4 formulations in a rectal suppository or enteric capsule. Reliable UHPLC coupled to Q-Exactive Plus high-resolution MS was used to identify the metabolites in rat plasma, bile, urine, and faeces. RESULTS: AB4 was extensively metabolized, and a total of 29 metabolites were identified. The primary metabolic routes included deglycosylation, oxidation, dehydrogenation, reduction, sulfation, hydration, acetylation, and glucuronidation. The pharmacokinetic comparison showed that both the rectal suppository and enteric capsule increased the exposures of AB4 and one of its active metabolites, 23-hydroxybetulinic acid (23-HA). Notably, rectal suppositories increased systemic AB4 exposure (AUC0-∞) by approximately 49 and 28 times higher than that of the AB4 saline solution and enteric capsules, respectively. The t1/2 of AB4 was extended to approximately 7 h after rectal administration compared to 2 h after oral administration. CONCLUSION: Overall, our study demonstrated that the mismatched exposure-response relationship of AB4 could result from extensive metabolism in the gastrointestinal and circulatory systems. Thus, a rectal suppository could be an alternative formulation of AB4 to obtain both higher and longer exposure.