ABSTRACT
Multidrug resistance [MDR] was circumvented by a large number of compounds including verapamil and a newly synthesized triazinoaminopiperidine derivative S9788 [Servier 9788]. S9788 was found to overcome multidrug resistance both in vitro and in vivo. The mode of action of these chemosensitizers is thought to involve interaction on P-glycoprotein, a membrane-bound efflux transport protein for cytotoxic drugs. On the other hand, verapamil binds strongly to alpha 1-acid glycoprotein [AGP] in serum or solutions and AGP can modulate the chemosensitizing action of verapamil in MDR in vitro. The interaction of S9788 with [3H] vincristine was measured at binding sites on alpha 1-acid glycoprotein in vitro using equilibrium dialysis [Dianorm] and clinically relevant concentrations of ligands and protein