SDZ PSC 833, a non-immunosuppressive cyclosporine: its potency in overcoming P-glycoprotein-mediated multidrug resistance of murine leukemia

Int J Cancer. 1992 Feb 20;50(4):593-7. doi: 10.1002/ijc.2910500418.


Cyclosporin A (CsA, Sandimmune) is known to reverse P-glycoprotein (P-gp170)-mediated multidrug resistance as efficiently as other prototype compounds of resistance modifiers. The immunosuppressive activity and nephrotoxicity of CsA, however, may limit its clinical use. PSC-833, a new cyclosporine, exerts a similar resistance-modifying activity but lacks toxicity or immunosuppressive activity. We have tested its potency in vitro and in vivo on the L1210 leukemia cell line transfected with a full-length cDNA copy of the human mdr I gene, which showed a stable 30-fold resistance towards adriamycin as compared to the parental cell line. In vitro growth of the transfected cell was unchanged. In vivo growth was less aggressive; the survival time of inoculated mice was prolonged. In vitro, PSC-833 was at least as potent as CsA or verapamil in reversing multidrug resistance. In vivo, the drug-resistant L1210 leukemia was completely unresponsive to i.v. monotherapy with adriamycin at its maximum tolerated dose (MTD). PSC-833 enhanced the activity and toxicity of adriamycin. The MTD of adriamycin was about 3 times lower than when given alone. On this basis, the MTD of i.v. adriamycin in combination with oral PSC-833 successfully overcame refractoriness to treatment. Survival times of the mice were considerably prolonged and even some cures of leukemic mice occurred.

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B, Member 1
  • Animals
  • Cell Division
  • Cyclosporins / pharmacology*
  • Doxorubicin / pharmacology
  • Drug Resistance*
  • Immunity / drug effects
  • In Vitro Techniques
  • Leukemia L1210 / drug therapy*
  • Membrane Glycoproteins / physiology*
  • Mice
  • Peptides, Cyclic / pharmacology
  • Survival Analysis


  • ATP Binding Cassette Transporter, Subfamily B, Member 1
  • Cyclosporins
  • Membrane Glycoproteins
  • Peptides, Cyclic
  • Doxorubicin
  • valspodar