Received for publication January 5, 2007.
Revised March 27, 2007.
Accepted for publication March 28, 2007.

Biotransformation of BPR0L075, A Novel Antimicrotubule Agent, By Mouse, Rat, Dog And Human Liver Microsomes

Abstract

6-Methoxy-3- (3',4',5'-trimethoxy- benzoyl)-1H-indole (BPR0L075) is a novel synthetic indole compound with microtubule binding activity. Incubation of BPR0L075 with mouse, rat, dog and human liver microsomes in the presence of NADPH resulted in the formation of six metabolites. LC-MS/MS and comparison with the synthetic reference standards identified two metabolites (M1 and M5) as the products derived from hydroxylation on the indole moiety of the molecule. M3 was also identified as a product derived from hydroxylation, but the structure of this metabolite was not identified due to lack of reference standard. M2, M4 and M6 were identified as the products derived from O-demethylation. M2, 6-desmethyl-BPR0L075, was the major metabolite formed by the liver microsomes of the four species. No qualitative species-difference on the metabolism of BPR0L075 was observed. There was quantitative species-difference on the metabolism of BPR0L075 among the four species. While mouse and rat liver microsomes metabolized BPR0L075 predominantly via O-demethylation, dog liver microsomes metabolized BPR0L075 by O-demethylation and hydroxylation to about the same extent. The rank order of intrinsic clearance rates for the conversion of BPR0L075 to 6-desmethyl-BPR0L075 was mouse > rat > human > dog. Incubation of BPR0L075 with baculovirus-insect cell-expressed human CYP isozymes showed that CYP 1A2, 2C9, 2C19, 2D6, 2E1 and 3A4 all catalyzed the O-demethylation and hydroxylation of BPR0L075 but to a different degree. Among the six CYP isozymes tested, CYP 1A2 and 2D6 were most active on catalyzing the metabolism of BPR0L075. CYP 1A2 catalyzed mainly the formation of M1, M2 and M3. M2 was the predominant metabolite formed by CYP 2D6.

Key words: anticancer agents, cytochrome P450, drug discovery, liver microsomes, mass spectrometry