Received for publication April 4, 2007.
Revised September 25, 2007.
Accepted for publication September 26, 2007.

Disposition and Metabolism of [¹⁴C]Brasofensine in Rats, Monkeys and Humans

Abstract

Brasofensine is an inhibitor of the synaptic dopamine transporter. It is a geometric isomer of the E-form; the Z-isomer is denoted as BMS-205912. These studies were conducted to characterize the pharmacokinetics, absolute bioavailability, disposition, and metabolism of brasofensine after intravenous (iv) and oral (po) administrations of [¹⁴C]brasofensine in rats (1.5 mg/kg, iv; 4 mg/kg, po) and monkeys (4 mg, iv; 12 mg, po), and humans (50 mg, po). Brasofensine was rapidly absorbed after oral administration in rats and monkeys, with peak plasma concentrations occurring 0.5-1 hr, but 3-8 hr for brasofensine in humans. Plasma terminal elimination half-lives were ~2 hr in rats, ~4 hr in monkeys, but ~24 hr in humans. Total body clearance and steady-state volume of distribution values were 199 mL/min/kg and 24 L/kg, respectively, in the rat and 32 mL/min/kg and 46 L/kg, respectively, in the monkey. Absolute bioavailability was 7% in rats and 0.8% in monkeys. After a single oral dose, urinary excretion of radioactivity accounted for 20% of the administered dose in rats, 70% in monkeys, and 86% in humans, with the remainder excreted into the feces. Brasofensine had extensive first-pass metabolism following oral administration in humans, monkeys, and rats. It primarily underwent O- and N-demethylation and isomerization. Some of the desmethyl metabolites were further converted to glucuronides. These primary metabolites and glucuronides of demethyl brasofensine (M1 and M2) were major circulating metabolites in humans, and were also observed in rat and monkey plasma.

Key words: drug disposition, HPLC, human pharmacokinetics, mass spectrometry, metabolite identification, pharmacokinetics, structure elucidation