Abstract

Compound A (3-{2-oxo-3-[3-(5,6,7,8-tetrahydro-[1,8]naphthyrindin-2-yl)propyl]-imidazolidin-1-yl}-3(S)-(6-methoxy-pyridin-3-yl)-propionic acid), a potent and selective antagonist of integrin α_vβ₃ receptor, is under development for treatment of osteoporosis. This study describes metabolism and excretion of A in vivo in rats, dogs, and monkeys, and metabolism of A in vitro in primary hepatocytes from rats, dogs, monkeys, and humans. In all three animal species studied, A was primarily excreted as unchanged drug and, to a lesser degree, as phase I and phase II metabolites. Major biotransformation pathways of A included glucuronidation/glucosylation on the carboxylic group to form acyl-linked glucuronides/glucosides; and oxidation on the tetrahydronaphthyridine moiety to generate a carbinolamine and its further metabolized products. Minor pathways involved O-demethylation and hydroxylations on the alkyl chain. Only in rats, a glutathione adduct of A was also observed, and its formation is proposed to be via an iminium intermediate on the tetrahydronaphthyridine ring. Similar metabolic pathways were observed in the incubates of hepatocytes from the corresponding animals as well as from humans. CYP 3A and 2D subfamilies were capable of metabolizing A to its oxidative products. Overall, these in vitro and in vivo findings should provide useful insight on possible biotransformation pathways of A in humans.