Chemotherapy is the key choice of treatment in many malignancies including leukaemia and therapy outcome is significantly affected by primary and secondary drug resistance observed in many cases. Failure to respond to chemotherapy is a significant obstacle in the treatment of these diseases. A host of drug efflux pumps such as multidrug resistance-associated protein 1 (MRP1) is implicated as a causative agent for drug resistance. The accurate delineation and classification of these resistance mechanisms and their ultimate inhibition is a key goal in drug resistance research.