Doubt on a dogma: aquation of equatorial ligands of Pt(IV) complexes under physiological conditions.

Due to their higher kinetic inertness and consequently reduced side reactions with biomolecules, Pt(IV) complexes are considered as the future of anticancer platinum drugs. We investigated the aqueous stability of a series of biscarboxylato Pt(IV) complexes under physiologically relevant conditions. Unexpectedly and in contrast to the current chemical understanding, especially oxaliplatin and satraplatin complexes revealed fast hydrolysis in equatorial position (even in cell culture medium and serum). Notably, the formed hydrolysis products strongly differ in their reduction kinetics, a crucial parameter for activation of Pt(IV) drugs also changing the anticancer potential of the compounds in cell culture. The discovery that intact Pt(IV) complexes can hydrolyze at equatorial position, contradicts the dogma on the general kinetic inertness of Pt(IV) compounds and needs to be considered in the screening and design for novel anticancer drugs.