Cancer multidrug resistance: a review of recent drug discovery research.

Conventional cancer chemotherapy is seriously limited by tumor cells exhibiting multidrug resistance (MDR), caused by changes in the level or activity of membrane transporters that mediate energy-dependent drug efflux and of other proteins that affect drug metabolism and/or drug action. Many inhibitors of MDR transporters have been identified and some are undergoing clinical trials, but currently none are in clinical use. Here we briefly review the status of MDR drugs, outline novel approaches designed to suppress or circumvent MDR mechanisms and discuss the future of MDR therapy in oncology.