Cytochrome P450 inhibition potential and initial genotoxic evaluation of 14-O-[(4,6-diaminopyrimidine-2-yl)thioacetyl] mutilin

14-O-[(4,6-Diaminopyrimidine-2-yl)thioacetyl] mutilin (DPTM) is a promising drug candidate with excellent antibacterial activity against Gram-positive bacteria. The present study was designed to characterize its Cytochrome P450 (CYP) enzymes inhibition activities and the genotoxicity with the standard Ames test. We determined the inhibitory effects of DPTM on CYP1A2, CYP2D1/6, CYP2E1, CYP2C11/9 and CYP3A/4 in rat liver microsomes (RLMs) and in human liver microsomes (HLMs). The mRNA expressions of the above CYP isoforms and their transcriptional regulators were also evaluated using the Hep G2 cell model. The results showed DPTM exhibited a moderate inhibitory potential against CYP3A/4 (IC(50) values of 10 ± 2 and 8 ± 2 μM, respectively) and weak against the other CYP enzymes based on their IC(50) values. Compared to the control, CYP isoforms and their transcriptional regulators mRNA expressions significantly increased when the Hep G2 cells were treated with DPTM for a certain period of time. In the Ames test, Salmonella strains TA97, TA98, TA100, TA102 and TA1535 were treated with or without the metabolic activation (S9). Analysis showed the average number of revertant colonies per plate was less in double in the groups treated with DPTM than that in the negative control plate and showed no dose-related increase.