In vitro antitumor activity, intracellular accumulation, and DNA adduct formation of cis-[((1R,2R)-1,2-cyclohexanediamine-N,N′)bis(myristato)] platinum (II) suspended in lipiodol

SM-11355, cis-[((1R,2R)-1,2-cyclohexanediamine-N,N')bis(myristato)] platinum (II), is a lipophilic platinum complex under clinical development that targets primary hepatocellular carcinoma using Lipiodol as a carrier, SM-11355 was compared with cisplatin (CDDP) using an in vitro evaluation system capable of examining the release characteristics and the cytotoxicity of drugs suspended in Lipiodol, SM-11355 suspended in Lipiodol (SM-11355/Lipiodol) and CDDP suspended in Lipiodol (CDDP/Lipiodol) showed cytotoxic activity against rat ascites hepatoma AH-109A cells in a dose-dependent manner. Their IC50 values following 7-day exposure were 22.3 and 0.40 mu g/ml, respectively, Following the subsequent 7-day exposure, from day 7 to day 14 after preparation of the suspension, SM-11355/Lipiodol showed an almost equivalent activity, but CDDP/Lipiodol did not show any activity at all, SM-11355/Lipiodol showed a sustained release into the culture medium over the course of a 14-day exposure. Following the exposure to CDDP/Lipiodol, the platinum concentration in the medium was at its maximum on the first day and remained constant thereafter, Intracellular platinum uptake and formation of platinum-DNA adducts were dependent on the release characteristics of each drug suspension, For SM-11355/Lipiodol, the drug release, intracellular drug uptake, and formation of platinum-DNA adducts over the course of the subsequent 7-day exposure were similar to those observed during the first 7 days, DPC, one of the compounds released from SM-11355/Lipiodol,,vas taken up by cells and showed formation of platinum-DNA adducts, Thus, this study suggests that SM-11355/Lipiodol may release active platinum compound(s) that bind to nuclear DNA and mediate the cytotoxic activity of SM-11355/Lipiodol.