Comparative study on reversal efficacy of SDZ PSC 833, cyclosporin A and verapamil on multidrug resistance in vitro and in vivo

Acta Oncol. 1995;34(2):235-41. doi: 10.3109/02841869509093961.


A non-immunosuppressive cyclosporin, SDZ PSC 833 (PSC833), shows a reversal effect on multidrug resistance (MDR) by functional modulation of MDR1 gene product, P-glycoprotein. The objective of the present study was to compare the reversal efficacy of three multidrug resistance modulators, PSC833, cyclosporin A (CsA) and verapamil (Vp). PSC833 has approximately 3-10-fold greater potency than CsA and Vp with respect to the restoring effect on reduced accumulation of doxorubicin (ADM) and vincristine (VCR) in ADM-resistant K562 myelogenous leukemia cells (K562/ADM) in vitro and also on the sensitivity of K562/ADM to ADM and VCR in in vitro growth inhibition. The in vivo efficacy of a combination of modifiers (PSC833 and CsA: 50 mg/kg, Vp 100 mg/kg administered p.o. 4 h before the administration of anticancer drugs) with anticancer drugs (ADM 2.5 mg/kg i.p., Q4D days 1, 5 and 9, VCR 0.05 mg/kg i.p., QD days 1-5) was tested in ADM-resistant P388-bearing mice. PSC833 significantly enhanced the increase in life span by more than 80%, whereas CsA and Vp enhanced by less than 50%. This reversal potency, which exceeded that of CsA and Vp, was confirmed by therapeutic experiments using colon adenocarcinoma 26-bearing mice. These results demonstrated that PSC833 has significant potency to reverse MDR in vitro and in vivo, suggesting that PSC833 is a good candidate for reversing multidrug resistance in clinical situations.

Publication types

  • Comparative Study

MeSH terms

  • Animals
  • Antineoplastic Agents / pharmacokinetics
  • Cyclosporine / pharmacology*
  • Cyclosporins / pharmacology*
  • Doxorubicin / pharmacokinetics
  • Drug Resistance, Multiple*
  • Humans
  • Leukemia, Myeloid / drug therapy
  • Mice
  • Mice, Inbred BALB C
  • Mice, Inbred Strains
  • Tumor Cells, Cultured / drug effects
  • Tumor Cells, Cultured / metabolism
  • Verapamil / pharmacology*
  • Vincristine / pharmacokinetics


  • Antineoplastic Agents
  • Cyclosporins
  • Vincristine
  • Doxorubicin
  • Cyclosporine
  • Verapamil
  • valspodar