Activation of carboplatin by chloride ions: a theoretical investigation

We carried out a theoretical study to investigate the thermodynamics and the kinetics of the reaction of the anticancer drug carboplatin with chloride ions, of potential interest to clarify the in vivo mechanism of action of this compound. The reaction consists of two consecutive substitution steps that lead to the removal of the malonate moiety and the formation of cisplatin. Because the acidity of the solution seems to play an important role on the actual outcome and rate of the reaction, different pH conditions (corresponding to neutral, weakly acidic, and strongly acidic environments) have been investigated, by considering differently protonated species. Our results are in good agreement with the few experimental evidences, indicating that the process is very unlikely to occur in neutral or weak acidic media, whereas a concentrated acidic environment leads to the fast and irreversible conversion of carboplatin to cisplatin.