XR9051 is as a potent modulator of P-glycoprotein (P-gp)-mediated multidrug resistance (MDR) following a synthetic chemistry programme based on a natural product lead compound. XR9051 was shown to be a potent inhibitor of the binding of the cytotoxic to P-glycoprotein (EC50 = 1.4 +/- 0.5 nM). XR9051 reverses the MDR phenotype through direct interaction with P-glycoprotein.
