Pharmacokinetics and metabolism of TR-14035, a novel antagonist of a4ss1/a4ss7 integrin mediated cell adhesion, in rat and dog

The pharmacokinetics and disposition of N-(2,6-dichlorobenzoyl)-4-(2,6-dimethoxyphenyl)-L-phenylalanine (TR-14035), a novel a4ss1/a4ss7 antagonist, were investigated in the rat and dog. Results indicate extensive clearance of TR-14035 and low oral bioavailability, 17% and 13% in the rat and dog, respectively, at an oral dose of 10 mg/kg. At least 63% of the oral dose was absorbed from the gastrointestinal tract in the rat, and about one-third of the intravenous dose was excreted into bile as unchanged drug in the rat and dog. These data indicate that the oral bioavailability of TR-14035 was limited due to significant first-pass metabolism and biliary excretion in the liver. A species-dependent difference in metabolism was observed. The principal metabolite, O-desmethyl TR-14035, observed in rat, dog and probably human, was further conjugated with sulfate in the rat, but never in dog and human, based on in vitro metabolism and in vivo metabolite profile studies. Urinary excretion was a minor elimination route, but an interesting species difference was recognized. TR-14035 was reabsorbed from the rat renal proximal tubules, and by contrast, secreted into the tubules in the dog, probably via active transport systems.