Metabolism of DHED In Vitro and In Vivo to Support Drug Optimization

Authors

• Y Zhao
• IS Lee
• Q Yu
• M Rose-McCandlish
• D Mischkowski
• J Avery
• JE Ingeholm
• LY Atlas

Abstract

DHED (10β,17β-dihydroxyestra-1,4-dien-3-one) is a prodrug of 17β-estradiol which selectively releases 17β-estradiol within the central nervous system. DHED has been demonstrated to have neuroprotective and antidepressant effects in animal models, without peripheral estrogenic effects. However, when the pharmacokinetics of DHED were examined in mice, a high clearance was observed and the vast majority of the prodrug was metabolized into unknown non-17β-estradiol products. This study aims to investigate the cause of the observed high clearance of DHED in PK studies. Studies using liver microsomal fractions, hepatocytes, and in vivo analysis of PK samples were used to fil the knowledge gaps in the metabolism of DHED. The metabolite profiles of the compound in these different systems were analyzed using LC-UV-HRMS on a Synapt G2 TOF system. We found that although minimal turnover occurred in liver microsomes, clearance was extensive in human and mouse hepatocytes, resulting in a major metabolite in human hepatocytes, the dehydrogenated metabolite M286. The formation of M286 is likely attributed to the olefination of the steroid's B-ring or the oxidation of the 23C-hydroxyl group to a ketone. In mouse PK samples, the metabolite M286 was confirmed as the main metabolite. In conclusion, hepatocytes but not microsomes or cytosols, replicated the DHED rapid in vivo clearance in PK studies and produced the major plasma circulating metabolite. Therefore, to prevent the rapid clearance of DHED in humans, structural modifications should be considered to inhibit the formation of M286 identified in this study.

Scientific Focus Area: Chemical Biology

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