Effect of a novel immunosuppressant, FTY720, on allograft survival after renal transplant in rats

FTY720 was developed by chemical modification of ISP-1 which was purified from culture filtrates of an ascomycete, Isaria sinclairii. We evaluated the effect of FTY720 on allograft survival using a rat renal transplantation model in which Wistar King Aptekman Hokkaido rats (WKAH, RT1(K)) served as the organ donor and Lewis rats (LEW, RT1(l)) as the recipient. WKAH renal allografts were acutely rejected by the untreated LEW recipients at a mean graft survival +/- SD of 7.2 +/- 0.4 days (n = 5). Consecutive oral administration of FTY720 following transplantation significantly prolonged allograft survival in a dose-dependent manner over the range of 0. 05-3 mg/kg/day. The mean allograft survival of the recipients treated with FTY720 at a doses of 0.05, 0.1, 0.5, 1, and 3 mg/kg/day was 12.2 +/- 3.3 (n = 5, p < 0.05, vs. untreated host), 11.2 +/- 2.4 (n = 5, p < 0.05, vs. untreated host), 13.6 +/- 0.9 (n = 5, p < 0.01, vs. untreated host), 14.6 +/- 1.7 (n = 5, p < 0.01, vs. untreated host) and 20.2 +/- 0.8 days (n = 5, p < 0.01, vs. untreated host). In the recipients treated with FTY720 (3 mg/kg/day), the number of peripheral blood lymphocytes significantly decreased. From the results of the flow cytometric study, FTY720 significantly diminished the percentage of interleukin-2 receptor (IL-2R)-positive cells in the allografts (6.34 +/- 0.81% in the untreated recipients vs. 3.10 +/- 0.86% in the recipients treated with FTY720, p < 0.05). As to the CD4/CD8 ratio of splenic cells and graft infiltrate, there was no significant difference between the untreated hosts and the recipients treated with FTY720. In conclusion, FTY720 significantly extended rat renal allograft survival and the immunosuppressive effects of FTY720 may be due to a reduction in not only the number of peripheral lymphocytes but also the percentage of IL-2R-positive cells in the allografts.     

A new immunosuppressant, FTY720, in canine kidney transplantation: effect of single-drug, induction and combination treatments

Three different types of treatment were conducted to clarify the properties of a novel immunomodulator, FTY720, in canine kidney allograft models. Survival, biochemical and hematological tests, pharmacokinetics, and histopathology of grafts and extra-renal organs were analyzed. Accompanying a remarkable reduction in circulating lymphocytes, single-drug treatment of FTY720, ranging from 0.05 to 10 mg/kg, exhibited significant prolongation of graft survival without a dose-dependent effect. Short-course induction with FTY720 at 5 mg/kg per day exhibited similar anti-rejection effects as did single-drug treatment but no advantage in rescuing ongoing rejection. In combination with cyclosporine (CsA; 5 mg/kg) or tacrolimus (FK; 0.5 mg/kg), FTY720 had an additive effect. Trough blood concentrations of FTY720 were linearly correlated with dose. No animal showed critical adverse effects at any point. FTY720 holds promise as a candidate in a new category of drugs that can be combined with conventional agents for induction and maintenance immunosuppression in clinical organ transplantation.     

Long-term effect of FTY720 on lymphocyte count and islet allograft survival in mice

This study was performed to observe the long-term effect of FTY720 on lymphocyte count change and islet allograft survival. Diabetic C57BL/6 mice were given FTY720 (group 1, 0.5 mg/kg/day; group 2, 1.0 mg/kg/day) or its vehicle (group 3, controls) after transplantation. Median graft survival time was prolonged in a dose-dependent manner (group 1, 84.5 days; group 2, >100 days, and group 3, 10 days, P < 0.01). Peripheral blood lymphocytes in groups 1 and 2 decreased to 23.81% and 12.59% compared with control group after FTY720 treatment. Lymphocytes from mesenteric lymph nodes and axillary nodes in groups 1 and 2 significantly increased on day 5, but decreased on day 14. Lymphocyte infiltration to the graft site was attenuated in groups 1 and 2. In conclusion, continuous FTY720 administration can induce and maintain lymphopenia, and inhibit lymphocytes from infiltrating the graft site so as to prolong islet allograft survival in mice.     

Islet allograft survival in nonhuman primates immunosuppressed with basiliximab, RAD, and FTY720

OBJECTIVE: In a preclinical, nonhuman primate islet allotransplant model, the authors evaluated a novel immunosuppressive combination of basiliximab for induction and of RAD and FTY720 for maintenance. METHODS: Five ABO-compatible and mixed lymphocyte reactivity-mismatched streptozotocin-induced diabetic juvenile cynomolgus monkeys underwent transplantation intraportally with 48-hr cultured 10,000 islet equivalents per kilogram. Induction immunosuppression was with intravenous basiliximab (10 mg on postoperative days 0 and 4). Maintenance immunosuppression was with RAD (everolimus) (0.075 mg/kg per day administered subcutaneously) and FTY720 (0.3 mg/kg per day administered orally), both administered on day -2 through day 180 posttransplant. RESULTS: All five recipients tolerated their transplants and immunosuppressive therapy well, without adverse events or infectious complications. Insulin requirements pretransplant were 2.6 to 4.0 U/kg per day. All recipients became normoglycemic and insulin-independent posttransplant. Posttransplant serum C-peptide levels averaged 2.7 ng/mL (range, 0.6-6.2 ng/mL). Morning blood glucose levels ranged from less than 100 mg/dL to 150 mg/dL. Posttransplant acute C-peptide response to intravenous arginine averaged 1.3 ng/mL (range, 0.23-2.72 ng/mL). In one recipient with subtherapeutic RAD blood levels on day 7 posttransplant, exogenous insulin was resumed 100 days posttransplant; basal C-peptide levels remained positive in this recipient and averaged 2.6 ng/mL. The other four recipients remained insulin-independent for more than 6 months. CONCLUSIONS: This study provides preliminary evidence of the safety and efficacy of corticosteroid- and calcineurin inhibitor-free immunosuppression in a relevant preclinical transplant model. These findings provide a strong rationale for evaluating this nondiabetogenic regimen in a clinical trial of islet transplants in type 1 diabetic recipients.     

Prolongation of experimental cardiac allograft survival with thromboxane-related drugs

A novel receptor antagonist, 3-hydroxymethyl-dibenzo (b,f) thiepin 5,5-dioxide (L-640,035) and the thromboxane synthase inhibitor, sodium (E) -3-(4-[3-pyridylmethyl phenyl]) -2-methyl-acrylate (OKY 1581) were evaluated for their effect in promoting the survival of cardiac allografts in Lewis rats that received cardiac allografts from Lewis x Brown-Norway F1 rats. Neither of these drugs or azathioprine alone significantly prolonged graft survival. However a combination of azathioprine with either of the two drugs significantly increased graft survival. Because L-640,035 inhibits platelet and smooth muscle responses to thromboxane-mimics, and because OKY 1581 is a specific thromboxane synthase inhibitor, we conclude that thromboxane may have a causal role in experimental cardiac allograft rejection in rats.     

Prevention of graft rejection and graft-versus-host reaction by a novel immunosuppressant, FTY 720, in rat small bowel transplantation

In the present study, we examined the immunosuppressive effect of a new drug, FTY 720, on small bowel transplantation (SBT) in rats. Grafts from (LEW × BN) F 1-to-LEW rats treated with FTY 720 at 0.5 mg/kg from day 0 to 14 post-SBT survived significantly longer than untreated grafts. In addition, the administration of FTY 720 combined with cyclosporin (CyA; 5 mg/kg per day) had a synergistic effect on allograft survival. The graft-versus-host reaction (GVHR) that occurred in the LEW-to-F 1 rats was markedly reduced after the administration of FTY 720. FTY 720 combined with a low dose of CyA completely abrogated GVHR without any adverse reaction. FTY 720 treatment resulted in a significant decrease in the number of lymphocytes in the peripheral blood and the spleen, but the number of peripheral neutrophils was unchanged. Thus, FTY 720 would appear to be an ideal drug to combine with CyA in order to control the immune reaction after SBT. Received: 19 February 1997 Received after revision: 23 May 1997 Accepted: 9 June 1997     

Effect of a new immunosuppressant, FTY720, on joint allografts.

The immunosuppressive effects of a new agent, FTY720, on joint allografts were studied histologically in a rat model. Favorable results without side effects were obtained at a dose of 3.0 mg/kg/day. The authors believe that this agent is one of the most useful immunosuppressants in the reported experimental model.     

Immunosuppressive activity of FTY720, sphingosine 1-phosphate receptor agonist: I. Prevention of allograft rejection in rats and dogs by FTY720 and FTY720-phosphate

FTY720, a new class of immunomodulator, induces lymphopenia by sequestration of circulating lymphocytes into secondary lymphoid tissues. FTY720 at 0.1 to 1 mg/kg significantly prolonged the allograft survival in a dose-dependent manner and showed a marked synergistic effect in combination with cyclosporine (CsA) in rat skin and cardiac allograft models. In addition, the canine renal allograft survival was significantly prolonged by combination therapy with FTY720 at 0.03 to 1 mg/kg and CsA at 10 mg/kg as compared with monotherapy of FTY720 or CsA. By contrast, the combination therapy with CsA and azathioprine or CsA and mycophenolate mofetil resulted in only an additive effect in rat skin allograft. When FTY720 was administered to rats, FTY720 was metabolized by omega-oxidation of the octyl side chain, and beta-oxidation subsequently, or phosphorylated by sphingosine kinase. Omega- and beta-oxidized 4 metabolities of FTY720 at 10 mg/kg i.v. showed neither lymphopenia nor immunosuppressive activity in rat skin allograft. On the other hand, (S)-enantiomer of FTY720-phosphate at 0.1 and 1 mg/kg intravenously induced a marked lymphopenia and significantly prolonged the allograft survival in the rat allotransplantation. From these results, it is suggested the lymphopenia and the immunosuppression induced by FTY720 administration is due to the agonistic activity against SIP receptors of the active metabolite, (S)-FTY720-phosphate.