LY335979

LY335979 (Zosuquidar trihydrochloride) is a selective Pgp (P-glycoprotein) inhibitor with a Ki of 59 nM. LY335979 displays the following characteristics of an 'ideal modulator' of Pgp-mediated multidrug resistance: high affinity binding to Pgp, high potency for in vitro reversal of drug resistance, high therapeutic index (activity was demonstrated at doses ranging from 1-30 mg/kg) observed in in vivo antitumor efficacy experiments, and a lack of pharmacokinetic interactions that alter the plasma concentration of coadministered oncolytic agents. These desirable features strongly suggest that LY335979 is an exciting new clinical agent to test the hypothesis that inhibition of P-glycoprotein activity will result in reversal of multidrug resistance in human tumors. LY335979 was without significant effect on the pharmacokinetics of these anticancer agents.