title: Immunosuppressive effects of defibrotide.
abstract: The effect of defibrotide (DF) alone or in combination with CsA was examined using in vitro proliferation assays with human PBLs and in vivo heterotopic heart allografts in rats. DF alone (12.5-50 mg/ml) inhibited in vitro PBL proliferation more effectively after PHA (50-56%) or OKT3 (50-95%), than after alloantigenic (25-30%), stimulation. Furthermore, the combination of DF (1-4 mg/ml) with CsA (10-40 ng/ml) caused an 85.2-86.8% reduction in proliferative responses after OKT3 stimulation. Median-effect analysis documented that the combination index for DF and CsA was consistently lower than 0.3 at various concentration ratios of the 2 agents. Combination index values below 1.0 reflect drug synergism; those equal to 1.0 show additive, and above 1.0, antagonistic, interactions. Daily intraperitoneal injections of DF (150 mg/kg) failed to prolong the survival of Buffalo (RT-1b) heart allografts in Wistar-Furth (RT-1u) recipients, namely mean survival times of 7.0 +/- 0.7 days with, vs. 6.5 +/- 0.5 days without, DF treatment. Similarly, intravenous or intra-arterial infusion of DF (280 mg/kg) delivered directly into the heart allograft by a 7-day osmotic pump was ineffective. However, a course of local, but not systemic, DF (280 mg/kg) combined with a 14-day i.v. administration of a subtherapeutic dose of CsA (1 mg/kg) significantly prolonged heart allograft survival to 22.8 +/- 5.0 days (P < 0.001). Thus, in vitro DF is immunosuppressive alone at high concentrations, and in combination with CsA at low concentrations. Continuous infusion of DF into the graft combined with systemic administration of CsA prolonged transplant survival in vivo. These findings suggest that high tissue levels of DF potentiate the immunosuppressive effects of CsA.
authors.affiliation: Department of Surgery, University of Texas Medical School, Houston 77030.
authors.forename: M
authors.initials: M
authors.lastname: Ferraresso
authors.forename: P
authors.initials: P
authors.lastname: Rigotti
authors.forename: S M
authors.initials: SM
authors.lastname: Stepkowski
authors.forename: T C
authors.initials: TC
authors.lastname: Chou
authors.forename: B D
authors.initials: BD
authors.lastname: Kahan
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D016572:Cyclosporine / Q000494:pharmacology / Q000627:therapeutic use; D004347:Drug Interactions; D005343:Fibrinolytic Agents / Q000494:pharmacology*; D006085:Graft Survival / Q000187:drug effects / Q000276:immunology; D016027:Heart Transplantation / Q000276:immunology*; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D008213:Lymphocyte Activation / Q000187:drug effects*; D007959:Lymphocyte Culture Test, Mixed; D008214:Lymphocytes / Q000187:drug effects / Q000276:immunology*; D008297:Male; D016853:Muromonab-CD3 / Q000494:pharmacology; D011089:Polydeoxyribonucleotides / Q000494:pharmacology* / Q000627:therapeutic use; D051381:Rats; D011915:Rats, Inbred BUF; D011920:Rats, Inbred WF; D014184:Transplantation, Homologous / Q000276:immunology
chemical_list: D005343:Fibrinolytic Agents; D007166:Immunosuppressive Agents; D016853:Muromonab-CD3; D011089:Polydeoxyribonucleotides; C036901:defibrotide; D016572:Cyclosporine