Pluronic ® block copolymers for overcoming drug resistance in cancer

Pluronic ® block copolymers have been used extensively in a variety of pharmaceutical formulations including delivery of low molecular mass drugs and polypeptides. This review describes novel applications of Pluronic ® block copolymers in the treatment of drug-resistant tumors. It has been discovered that Pluronic ® block copolymers interact with multidrug-resistant cancer (MDR) tumors resulting in drastic sensitization of these tumors with respect to various anticancer agents, particularly, anthracycline antibiotics. Furthermore, Pluronic ® affects several distinct drug resistance mechanisms including inhibition of drug efflux transporters, abolishing drug sequestration in acidic vesicles as well as inhibiting the glutathione/glutathione S-transferase detoxification system. All these mechanisms of drug resistance are energy-dependent and therefore ATP depletion induced by Pluronic ® block copolymers in MDR cells is considered as one potential reason for chemosensitization of these cells. Following validation using in vitro and in vivo models, a formulation containing doxorubicin and Pluronic ® mixture (L61 and F127), SP1049C, has been evaluated in phase I clinical trials. Further mechanistic studies and clinical evaluations of these systems are in progress.