LY335979 (Zosuquidar 3HCL)

LY335979 is a selective inhibitor of P-Gp with IC50 value of 1.2 nM [1, 2].

P-gp (P-glycoprotein) is a member of ATP-binding cassette (ABC) transporters and plays a pivotal role in pumping many foreign substances out of cells. It has been reported that abnormal expression of P-Gp is correlated with the multidrug resistance of tumor cells [3].

LY335979 is a potent P-Gp inhibitor and has a different selectivity with the reported P-Gp inhibitor cyclosporin A or verapamil. In drug-resistant cell line HL60/VCR with highly expression of P-Gp, LY335979 exhibited highly restore ability of P-Gp than cyclosporin A or verapamil and the IC 50 value of 1.2 nM [1]. When tested with a panel of cell lines over-expressed P-Gp (CEM/VLB100, MCF-7/ADR, 2780AD, P388/ADR, and UCLA-P3.003VLB), administration of LY335979 reversed the cells resistance to Vinblastine, Doxorubicin, Btoposide and Taxol by inhibiting P-Gp activity [2].

In female nude mice model with UCLA-P3.003VLB MDR tumor cells subcutaneous xenograft, pre-treated with LY335979 (30mg/kg) restored tumor cells sensitivity to Taxol (20 mg/kg) which combination markedly suppressed solid tumor growth compared with control group [2].

References:
1.  Green, L.J., P. Marder, and C.A. Slapak, Modulation by LY335979 of P-glycoprotein function in multidrug-resistant cell lines and human natural killer cells. Biochem Pharmacol, 2001. 61(11): p. 1393-9.
2.  Dantzig, A.H., et al., Reversal of P-glycoprotein-mediated multidrug resistance by a potent cyclopropyldibenzosuberane modulator, LY335979. Cancer Res, 1996. 56(18): p. 4171-9.
3.   Hu, T., et al., Reversal of P-glycoprotein (P-gp) mediated multidrug resistance in colon cancer cells by cryptotanshinone and dihydrotanshinone of Salvia miltiorrhiza. Phytomedicine, 2014. 21(11): p. 1264-72.

Phase I/II trial of a P-glycoprotein inhibitor, Zosuquidar.3HCl trihydrochloride (LY335979), given orally in combination with the CHOP regimen in patients with non-Hodgkin's lymphoma.[Pubmed:17454628]

Leuk Lymphoma. 2007 Apr;48(4):708-15.

A phase I/II trial was performed to investigate the safety and tolerance of zosuquidar.3HCL, a potent inhibitor of P-glycoprotein (P-gp), when administered orally alone and in combination with the CHOP regimen in patients with untreated non-Hodgkin's lymphoma and to determine whether zosuquidar.3HCL affects pharmacokinetics of doxorubicin and vincristine. Doses of CHOP remained constant and the doses of zosuquidar.3HCL were increased from 200 to 500 mg per dose. A total of 15 patients were treated at three dose levels. A target dose providing peak and trough levels compatible with prolonged modulation of P-gp function was obtained in patients receiving three doses of 500 mg of zosuquidar.3HCL p.o. At this dose level, toxicity was minimal and no enhancement of CHOP-related toxicity was observed. Zosuquidar.3HCL did not significantly affect the pharmacokinetics of doxorubicin and had moderate effects on the pharmacokinetics of vincristine. Zosuquidar.3HCL can be safely administered with CHOP therapy using a 24-h schedule.

A phase I trial of a potent P-glycoprotein inhibitor, Zosuquidar.3HCl trihydrochloride (LY335979), administered orally in combination with doxorubicin in patients with advanced malignancies.[Pubmed:12473580]

Clin Cancer Res. 2002 Dec;8(12):3710-7.

PURPOSE: The purpose of this study was to investigate the safety and tolerability of Zosuquidar.3HCl, a potent inhibitor of P-glycoprotein (Pgp), when administered p.o. alone and in combination with doxorubicin and to determine whether Zosuquidar.3HCl affects doxorubicin pharmacokinetics and inhibits Pgp function in peripheral blood natural killer lymphocytes. EXPERIMENTAL DESIGN: Patients with advanced nonhematological malignancies were eligible for this Phase I trial. Zosuquidar.3HCl and doxorubicin were administered separately during the first cycle of therapy and then administered concurrently. Zosuquidar.3HCl was administered over 4 days, with doses escalated until the occurrence of dose-limiting toxicity. Subsequently, doxorubicin doses were increased from 45 to 75 mg/m(2). Zosuquidar.3HCl, doxorubicin, and doxorubicinol pharmacokinetics were analyzed, and dual fluorescence cytometry was used to determine the effects of Zosuquidar.3HCl on Pgp function in natural killer cells. RESULTS: A total of 38 patients were treated at nine dose levels. Neurotoxicity was dose-limiting for oral Zosuquidar.3HCl, characterized by cerebellar dysfunction, hallucinations, and palinopsia. The maximum-tolerated dose for oral Zosuquidar.3HCl administered every 12 h for 4 days is 300 mg/m(2). Zosuquidar.3HCl did not affect doxorubicin myelosuppression or pharmacokinetics, and Zosuquidar.3HCl pharmacokinetics were similar in the absence and presence of doxorubicin. Higher plasma concentrations of Zosuquidar.3HCl were associated with greater Pgp inhibition in natural killer cells. CONCLUSION: Zosuquidar.3HCl can be coadministered with doxorubicin using a 4-day oral dosing schedule, with little effect on doxorubicin toxicity or pharmacokinetics. Further refinement in Zosuquidar.3HCl dosing and scheduling should be explored to optimize Pgp inhibition while minimizing cerebellar toxicity.

Population pharmacokinetic model for daunorubicin and daunorubicinol coadministered with zosuquidar.3HCl (LY335979).[Pubmed:15045528]

Cancer Chemother Pharmacol. 2004 Jul;54(1):39-48.

PURPOSE: The impact of zosuquidar.3HCl, an inhibitor of P-glycoprotein, on the pharmacokinetics of daunorubicin and daunorubicinol was examined in a phase I trial using a population approach. Pharmacokinetic and pharmacodynamic properties of zosuquidar.3HCl were also determined. METHODS: The pharmacokinetics of daunorubicin and daunorubicinol were studied following daunorubicin administration on day 1 (50 mg/m2 i.v. infusion over 10 min) alone and on day 3 concomitantly with zosuquidar.3HCl (i.v. 200 or 300 mg/m2 over 6 h or 400 mg over 3 h). Of a total of 18 patients entered, 16 with acute leukemia completed the study. RESULTS: A three-compartment pharmacokinetic model adequately described daunorubicin concentration-time profiles. Five- and four-compartment models adequately described the daunorubicin-daunorubicinol pharmacokinetics in the absence and presence of zosuquidar.3HCl, respectively. The impact of zosuquidar.3HCl on coadministered daunorubicin was minimal, with a 10% reduction in daunorubicin clearance. The model predicted a 50% decrease in daunorubicinol apparent clearance in the presence of zosuquidar.3HCl. A direct concentration-effect relationship between zosuquidar.3HCl concentrations and inhibition of rhodamine 123 (Rh123) efflux in CD56 lymphocytes was defined by a sigmoid E(max) model. The IC(50) was 31.7 microg/l. The zosuquidar.3HCl dosing regimen led to concentrations in excess of the IC(90) (169.6 microg/l) and provided maximal P-glycoprotein inhibition during the distribution phases of daunorubicin. CONCLUSIONS: The decrease in daunorubicin and daunorubicinol clearance in the presence of zosuquidar.3HCl likely reflects inhibition of P-glycoprotein in the bile canaliculi impeding their biliary excretion. The results need to be interpreted carefully due to the sequential nature of daunorubicin administration and analysis.

Selectivity of the multidrug resistance modulator, LY335979, for P-glycoprotein and effect on cytochrome P-450 activities.[Pubmed:10411602]

J Pharmacol Exp Ther. 1999 Aug;290(2):854-62.

Overexpression of ATP-dependent drug efflux pumps, P-glycoprotein (Pgp) or multidrug resistance-associated protein (MRP), confers multidrug resistance to tumor cells. Modulators of multidrug resistance block the action of these pumps, thereby sensitizing cells to oncolytics. A potent Pgp modulator is LY335979, which fully sensitizes Pgp-expressing cells at 0.1 microM in cytotoxicity assays and for which Pgp has an affinity of 59 nM. The present study examines its effect on MRP1-mediated drug resistance and cytochrome P-450 (CYP) activity and its ability to serve as a Pgp substrate. Drug resistance was examined with HL60/ADR and MRP1-transfected HeLa-T5 cells. Drug cytotoxicity was unaffected by 1 microM LY335979; leukotriene C4 uptake into HeLa-T5 membrane vesicles was unaffected. Because the substrate specificity of Pgp and CYP3A overlap, the effect of LY335979 on the 1'-hydroxylation of midazolam by CYP3A in human liver microsomes was examined. The apparent K(i) was 3.8 microM, approximately 60-fold higher than the affinity of Pgp for LY335979. The modulator's effect on Pgp was evaluated with Pgp-overexpressing CEM/vinblastine (VLB)(100) and parental CCRF-CEM cells. Both cell lines accumulated [(3)H]LY335979 equally well and did not efflux [(3)H]LY335979 during a 3-h incubation, indicating that it is not a substrate of Pgp. Equilibrium-binding studies with CEM/VLB(100) plasma membranes and [(3)H]LY335979 showed that Pgp had a K(d) of 73 nM, which is in good agreement with the previously determined K(i) value. Thus, LY335979 is an extremely potent Pgp, and not MRP1 or MRP2, modulator and has a significantly lower affinity for CYP3A than for Pgp.

Reversal of P-glycoprotein-mediated multidrug resistance by a potent cyclopropyldibenzosuberane modulator, LY335979.[Pubmed:8797588]

Cancer Res. 1996 Sep 15;56(18):4171-9.

Overexpression of P-glycoprotein (Pgp) by tumors results in multidrug resistance (MDR) to structurally unrelated oncolytics. MDR cells may be sensitized to these oncolytics when treated with a Pgp modulator. The present study evaluates LY335979 as a modulator both in vitro and in vivo. LY335979 (0.1 microM) fully restored sensitivity to vinblastine, doxorubicin (Dox), etoposide, and Taxol in CEM/VLB100 cells. LY335979 modulated Dox cytotoxicity even when LY335979 (0.5 microM) was removed 24 h prior to the cytotoxicity assay. LY335979 blocked [3H]azidopine photoaffinity labeling of the M(r) approximately 170,000 Pgp in CEM/VLB100 plasma membranes and competitively inhibited equilibrium binding of [3H]vinblastine to Pgp (Ki of approximately 0.06 microM). Treatment of mice bearing P388/ADR murine leukemia cells with LY335979 in combination with Dox or etoposide gave a significant increase in life span with no apparent alteration of pharmacokinetics. LY335979 also enhanced the antitumor activity of Taxol in a MDR human non-small cell lung carcinoma nude mouse xenograft model. Thus, LY335979 is an extremely potent, efficacious modulator that apparently lacks pharmacokinetic interactions with coadministered anticancer drugs and is, therefore, an exciting new agent for clinical evaluation for reversal of Pgp-associated MDR.