Buthionine sulfoximine (BSO) is under investigation as a drug to deplete glutathione and make alkylating drugs such as melphalan or platinum derivatives more effective.
L-leucovorin and dipyridamole (persantine) are used to enhance the actions of 5-fluorouracil. Leucovorin's role as an enhancer is somewhat paradoxical, since it was initially introduced as a rescue agent for methotrexate .
Cyclosporin A analogues that do not suppress the immune system will undergo testing to reverse multi-drug resistance . We have improved our ability to identify tumors that have become resistant by expression of the gene named MDR. Many drugs of various kinds are being tested to counteract this resistance, but the restoration of drug effectiveness has yet to be shown convincingly.
