Zosuquidar (LY335979) is a potent negative modulator of P-glycoprotein-mediated multi-drug resistance with Ki of 60 nM. IC50 value: 60 nM (Ki) Target: P-glycoprotein Zosuquidar (LY335979) is a potent modulator of P-glycoprotein-mediated multidrug resistance with Ki of 60 nM. Zosuquidar binds with high affinity to P-glycoprotein and inhibits P-glycoprotein-mediated multidrug resistance (MDR). P-glycoprotein, encoded by the MDR-1 gene, is a member of the ATP-binding cassette superfamily of transmembrane transporters and prevents the intracellular accumulation of many natural product-derived cytotoxic agents. Zosuquidar is a compound of antineoplastic drug candidates currently under development.