Potent and non-specific inhibition of cytochrome P450 by JM216, a new oral platinum agent

Bis-acetato-ammine-dichloro-cyclohexylamine-platinum (IV), JM216, is the first antineoplastic platinum compound that can be given to patients orally. Several phase II clinical trials of JM216 monotherapy have already been reported. However, no information on the potential drug interactions caused by JM216 is available. In this study, the capacity of JM216 to inhibit cytochrome P450 (CYP) in human liver microsomes was investigated by measuring the inhibition potential (IC50 and K-i) on prototype reactions. Specific substrates of CYP included testosterone (catalysed by CYP3A4), paclitaxel (CYP2C8), 7-ethoxyresorufin (CYP1A1, CYP1A2), coumarin (CYP2A6), aniline (CYP2E1) and (+/-)-bufuralol (CYP2D6). JM216 inhibited the catalytic activities of CYP isozymes. The IC50 values were between 0.3 mu M and 10 mu M, indicating strong and non-specific inhibitory effects of JM216. The inhibition occurred in a non-competitive manner, and the K-i value was 1.0 and 0.9 mu M for metabolite formation of testosterone and paclitaxel respectively. Therefore, some in vivo studies should be conducted to determine whether or not there is a correlation between in vivo and in vitro results.