Abstract

Hepatic metabolism of low-clearance compound TAK-041 was studied in two different in vitro model systems using rat, dog, monkey, and human suspended cryopreserved hepatocytes and HepatoPac micropatterned coculture model primary hepatocytes. The aim of this work was to investigate the most appropriate system to assess the biotransformation of TAK-041, determine any notable species difference in the rate and in the extent of its metabolic pathways, and establish correlation with in vivo metabolism. TAK-041 exhibited very low turnover in suspended cryopreserved hepatocyte suspensions for all species, with no metabolites observed in human hepatocytes. However, incubations conducted for up to 14 days in the HepatoPac model resulted in more robust metabolic turnover. The major biotransformation pathways of TAK-041 proceed via hydroxylation on the benzene ring fused to the oxotriazine moiety and subsequent sulfate, glucuronide, and glutathione conjugation reactions. The glutathione conjugate of TAK-041 undergoes further downstream metabolism to produce the cysteine S-conjugate, which then undergoes N-acetylation to mercapturic acid and/or conversion to β-lyase–derived thiol metabolites. The minor biotransformation pathways include novel ring closure and hydrolysis, hydroxylation, oxidative N-dealkylation, and subsequent reduction. The HepatoPac model shows a notable species difference in the rate and in the extent of metabolic pathways of TAK-041, with dogs having the fastest metabolic clearance and humans the slowest. Furthermore, the model shows its suitability for establishing correlation with in vivo metabolism of low-turnover and extensively metabolized compounds such as TAK-041, displaying an extensive and unusual downstream sequential β-lyase–derived thiol metabolism in preclinical species and human.