IN-VITRO METABOLISM OF A POTENT HIV-PROTEASE INHIBITOR (141W94) USINGRAT, MONKEY AND HUMAN LIVER S9

Compound 141W94 (Vertex VX478) (3S)-tetrahydro-3-furyl butylbenzenesul fonamido)-1-benzyl-2-hydroxypropyl] carbamate, is a potent HIV-proteas e inhibitor and is currently undergoing clinical trials. The purpose o f this study was the rapid identification of the phase I and II in vit ro metabolite of 141W94 using mass spectrometry. Four different source s of liver S9 fractions were used for studying comparative in vitro me tabolism of 141W94. They were obtained from Arochlor-induced rat, norm al (untreated) rat, cynomolgus monkey and human livers. Selected incub ations were supplemented with uridine diphosphate glucuronic acid and the reduced form of glutathione. The predominant species seen in the i ncubation mixture was the parent compound 141W94. Metabolites arising from ring opening to form the diol and carboxylic acid and oxidation o f the tetrahydrofurran ring (formation of dihydrofuran) were identifie d. In addition, of the two monohydroxylated products identified, one r esulted from hydroxylation on the aniline ring and the other from hydr oxylation at the benzylic position. Two different glucuronides were al so observed. Comparing the three species, very little metabolism was s een in the normal (non-induced) rat. The metabolic profile and extent of metabolism with induced rat, monkey and human S9 was similar. Induc ed rat S9 incubation showed the formation of two unique metabolites th at were not seen in non-induced rat, monkey and human S9 fractions. Th ey were the monohydroxylated glucuronide and a carbamate cleavage prod uct. The metabolites were identified using mass spectrometry based on their molecular masses and fragmentation patterns.