TY - JOUR T1 - Disposition and Metabolism of [<sup>14</sup>C]Lemborexant in Healthy Human Subjects and Characterization of Its Circulating Metabolites JF - Drug Metabolism and Disposition JO - Drug Metab Dispos DO - 10.1124/dmd.120.000229 SP - DMD-AR-2020-000229 AU - Takashi Ueno AU - Tomomi Ishida AU - Jagadeesh Aluri AU - Michiyuki Suzuki AU - Carsten Theodor Beuckmann AU - Takaaki Kameyama AU - Shoji Asakura AU - Kazutomi Kusano Y1 - 2020/01/01 UR - http://dmd.aspetjournals.org/content/early/2020/11/03/dmd.120.000229.abstract N2 - Lemborexant is a novel dual orexin receptor antagonist recently approved for the treatment of insomnia in the U.S. and Japan. Here, disposition and metabolic profiles were investigated in healthy human subjects. Following single oral administration of 10 mg [14C]lemborexant (100 μCi), plasma concentrations of lemborexant and radioactivity peaked at 1 hour postdose and decreased biphasically. Cumulative recovery of the administered radioactivity within 480 hours was 86.5% of the dose, with 29.1% in urine and 57.4% in feces. Unchanged lemborexant was not detected in urine but accounted for 13.0% of the dose in feces, suggesting that the main elimination pathway of lemborexant was metabolism. Metabolite analyses revealed that the major metabolic pathways of lemborexant are oxidation of the dimethylpyrimidine moiety and subsequent further oxidation and/or glucuronidation. In plasma, lemborexant was the dominant component accounting for 26.5% of total drug-related exposure. M4, M9, M10, and M18 were detected as the major radioactive components; M10 was the only metabolite exceeding 10% of total drug-related exposure. Although M4, M9, and M10 showed binding affinity for orexin receptors comparable to that of lemborexant, their contributions to the sleep-promoting effects of lemborexant are likely low due to limited brain penetration by P-glycoprotein. Exposure comparison between humans and nonclinical toxicology species confirmed that plasma exposure of M10 was higher in at least one animal species compared with that in humans, indicating that there is no disproportionate metabolite in humans, as defined by ICH M3(R2) and FDA MIST guidances, and therefore no additional toxicology studies are needed. Significance Statement This study provides detailed data of the disposition and metabolism of lemborexant, a novel therapeutic drug for insomnia, in humans, as well as a characterization of the circulating metabolites and assessment of their contributions to efficacy and safety. The information presented herein furthers our understanding of the pharmacokinetic profiles of lemborexant and its metabolites and will promote the safe and effective use of lemborexant in the clinic. ER -