Human mass balance, pharmacokinetics and metabolism of rovatirelin and identification of its metabolic enzymes in vitro

Abstract

1. The mass balance, pharmacokinetics and metabolism of rovatirelin were characterised in healthy male subjects after a single oral dose of [¹⁴C]rovatirelin. [¹⁴C]Rovatirelin was steadily absorbed, and the peak concentrations of radioactivity and rovatirelin were observed in plasma at 5–6 h after administration. The AUC_inf of radioactivity was 4.9-fold greater than that of rovatirelin. Rovatirelin and its metabolite (thiazoylalanyl)methylpyrrolidine (TAMP) circulated in plasma as the major components. The total radioactivity recovered in urine and faeces was 89.0% of the administered dose. The principal route of elimination was excretion into faeces (50.1% of the dose), and urinary excretion was the secondary route (36.8%). Rovatirelin was extensively metabolised to 20 metabolites, and TAMP was identified as the major metabolite in plasma and excreta among its metabolites.

2. To identify the metabolic enzymes responsible for TAMP formation, the in vitro activity was determined in human liver microsomes. The enzymatic activity depended on NADPH, and it was inhibited by ketoconazole. Furthermore, recombinant human cytochrome P450 (CYP) 3A4 and CYP3A5 displayed enzymatic activity in the assay. Therefore, CYP3A4/5 are the most important enzymes responsible for TAMP formation.

Keywords:

• Rovatirelin
• TRH analogue
• human mass balance study
• metabolic enzyme
• reaction phenotyping
• CYP3A4/5

Acknowledgements

The authors thank all members of Kissei Pharmaceutical Co., Ltd. who assisted with the human mass balance study and pre-clinical studies of rovatirelin.

Disclosure statement

The authors are employees of Kissei Pharmaceutical Co., Ltd.

Additional information

Funding

Funding for this research was provided by Kissei Pharmaceutical Co., Ltd.