Prolongation of canine liver allograft survival by a novel immunosuppressant, FTY720: effect of monotherapy and combined treatment with conventional drugs

A study of the mechanisms responsible for the action of new immunosuppressants and their effects on rat small intestinal transplantation

In a series of studies, using an identical rat intestinal transplantation model, we evaluated the effects of several drugs. FK-506 caused a significant attenuation in the proliferation of allogeneic CD4+ T cells and IFN-γ secreting effector functions. FYT720 resulted in a marked reduction in the numbers of lymphocytes, associated with a reduction of T cell recruitment, in grafts. An anti-MAdCAM antibody was next reported to significantly down-regulate CD4+ T cell infiltration in intestinal grafts by blocking the adhesion molecule, and could be useful as an induction therapy. Concerning TAK-779, this CCR5 and CXCR3 antagonist diminished the number of graft-infiltrating cells by suppressing the expression of their receptors in the graft. As a result, it reduced the total number of recipient T cells involved in graft rejection. As the next step, we focused on the participation of monocytes/ macrophages in this field. PQA-18 has been the focus of a novel immunosuppressant that attenuates not only the production of various cytokines, such as IL-2 & TNF-α, on T cells, but the differentiation of macrophages by inhibiting PAK2 as well. In this report, we summarize our previous studies not only regarding the above drugs, but on an anti-complement drug and a JAK inhibitor as well.

Development and Effects of FTY720 Ophthalmic Solution on Corneal Allograft Survival

Fingolimod (FTY720), a novel class of sphingosine 1-phosphate receptor modulators, has received special interest among ophthalmologists, particularly given that oral administration of FTY720 has proven to effectively treat corneal graft rejection in animal models. However, no studies have examined the performance of FTY720 as an ophthalmic solution in reducing corneal rejection in high-risk corneal rejection models, and the stability and ocular irritation profile of FTY720 ophthalmic solution are also unknown. Thus, we developed 0.1%, 0.2% and 0.5% FTY720 ophthalmic solutions and evaluated their chemical stabilities under various storage conditions with high- performance liquid chromatography. To investigate the ocular irritancy of the FTY720 ophthalmic solution, New Zealand albino rabbits were subjected to the Draize test. Furthermore, classic, well-established rat allogenic penetrating keratoplasty models were used to investigate the anti-rejection efficacy of the tested FTY720 ophthalmic solutions. We found that the non-irritating 0.5% FTY720 ophthalmic solution could prolong corneal allograft survival in rats with significant efficacy for about one month. Furthermore, no significant concentration changes occurred in any of the types of FTY720 ophthalmic solutions within three months. These results revealed crucial profiles of FTY720 ophthalmic solutions and warrant further investigation and optimization of FTY720 in the anti-rejection therapy after keratoplasty.

FTY720 improves functional recovery after spinal cord injury by primarily nonimmunomodulatory mechanisms

Spinal cord injury (SCI) is an incapacitating injury that can result in limited functional recovery. We have previously shown increases in the lysophospholipid mediator, sphingosine-1-phosphate (S1P), in the spinal cord after contusion injury. To apply S1P receptor modulation to the treatment of SCI, we examined the therapeutic effects of FTY720, an S1P receptor agonist, on locomotor recovery after SCI in mice. Oral administration of FTY720 shortly after contusion SCI significantly improved motor function recovery, as assessed by both Basso Mouse Scale scores and Rotarod Performance test results. FTY720 induced lymphopenia and reduced T-cell infiltration in the spinal cord after SCI but did not affect the early infiltration of neutrophils and the activation of microglia. In addition, plasma levels and mRNA expression of inflammatory cytokines in the spinal cord after SCI were not attenuated by FTY720. Vascular permeability and astrocyte accumulation were both decreased by FTY720 in the injured spinal cord. The therapeutic effects of FTY720 were not solely dependent on immune modulation, as confirmed by the demonstration that FTY720 also ameliorated motor function after SCI in mice with severe combined immunodeficiency. Finally, the S1P(1) receptor agonist, SEW2871, partly mimicked the therapeutic effect of FTY720. Our data highlight the importance of immune-independent functions of FTY720 in decreasing vascular permeability and astrogliosis in the injured spinal cord and promoting locomotor function recovery after SCI.

Fertility after homologous prepubertal testis transplantation in the dog

Canine models of hereditary human diseases are widely used throughout the biomedical community, particularly when no suitable rodent model exists. In several models, the homozygote dogs die prior to puberty, or have substantially reduced fertility. Prepubertal transplantation of the testes was used to propagate the genotype of a mutant dog that would not otherwise have survived until puberty. The transplant recipient remained fertile 7 years postoperatively. To begin determining the factors necessary for successful function in testis transplants, prepubertal dogs that were dog leukocyte antigen (DLA) identical and disparate were examined for fertility and compared to the original transplant recipient as well as unoperated and sham-operated dogs. Immunosuppression was maintained with cyclosporine (CyA) and prednisone in the immediate postoperative period and CyA alone thereafter. The DLA-identical dogs demonstrated initial acceptance of the transplant, whereas one of two underwent chronic rejection. Both DLA-disparate dogs had subacute rejection prior to sexual maturity. These results demonstrate that homologous transplantation of prepubertal testes can be an effective method to preserve genotype in DLA-identical dogs. This model may also be useful for studying testis development and immunobiology.

The thymus is required for the ability of FTY720 to prolong skin allograft survival across different histocompatibility MHC barriers

The immunosuppressive effect of FTY720 is associated with the reversible sequestration of lymphocytes from the blood and the spleen into secondary lymphoid organs and reduced egress of mature thymocytes from the thymus. This work was designed to dissect the differential effect of FTY720 on CD4 and CD8 T cell-mediated mechanisms of skin graft rejection in the presence (euthymic) or absence (thymectomized) of thymic output. To that end, untreated and FTY720-treated euthymic (Euthy) and thymectomized (ATX) mice received skin allografts across a full, class II or class I major histocompatibility complex (MHC) mismatched (MM) barriers and graft survival was monitored. We demonstrate that a short course of FTY720 treatment significantly augments the survival of full, class I and class II MHC MM skin grafts compared to the nontreated controls. Interestingly, FTY720-treated Euthy recipients showed a significantly prolonged skin allograft survival compared to FTY720-treated ATX mice. These results together show that FTY720 impairs both CD4 and CD8 T cell-mediated mechanisms of rejection and, more importantly, the presence of the thymus is necessary for the ability of FTY720 to modulate skin allograft rejection across different histocompatibility MHC barriers.

Advances in the understanding of acute graft-versus-host disease

Allogeneic stem cell transplantation (SCT) remains the definitive immunotherapy for malignancy. However, morbidity and mortality due to graft-vs.-host disease (GVHD) remains the major barrier to its advancement. Emerging experimental data highlights the immuno-modulatory roles of diverse cell populations in GVHD, including regulatory T cells, natural killer (NK) cells, NK T cells, gammadelta T cells, and antigen presenting cells (APC). Knowledge of the pathophysiology of GVHD has driven the investigation of new rational strategies to both prevent severe GVHD and treat steroid-refractory GVHD. Novel cytokine inhibitors, immune-suppressant agents known to preserve or even promote regulatory T-cell function and the depletion of specific alloreactive T-cell sub-populations all promise significant advances in the near future. As our knowledge and therapeutic options expand, the ability to limit GVHD whilst preserving anti-microbial and tumour responses becomes a realistic prospect.

Protection of Mouse Small Bowel Allografts by FTY720 and Costimulation Blockade

BACKGROUND

The clinical application of small bowel transplantation (SBTx) is hampered by its pronounced immunogenicity. We aimed to test the hypothesis that prolonged sequestration of lymphocytes in secondary lymphoid organs may enhance the alloprotective effect of costimulation blockade.

METHODS

For this purpose, recipients of intestinal allografts were treated with MR1, FTY720, combined FTY720 plus MR1, or were left untreated. Grafts were examined 6 and 14 days after transplantation by applying a histologic rejection score, multiparameter-immunofluorescent staining, and flow cytometry.

RESULTS

FTY720 or MR1 monotherapy did not prevent the rejection of mouse intestinal allografts, whereas combined therapy with FTY720 plus MR1 profoundly inhibited rejection at day 6 and day 14 after transplantation. In FTY720-treated mice infiltration of host lymphocytes in graft mesenteric lymph nodes, Peyer's patches, intraepithelial lymphocytes, and lamina propria lymphocytes (LPLs) was reduced on day 6. Anti-CD40L antibody improved the rejection score at day 14 but had no effect at day 6. Importantly, host CD8 T-cell infiltration in graft LPLs was significantly reduced compared with all other groups.

CONCLUSION

FTY720 plus MR1 effectively inhibited intestinal allograft rejection in mice, possibly by enhancing the alloprotective effects of costimulation blockade by prolonged sequestration of lymphocytes in secondary lymphoid organs.

Pharmacokinetic/pharmacodynamic relationships of FTY720 in kidney transplant recipients

FTY720 is a new and effective immunosuppressive agent, which produces peripheral blood lymphopenia through a lymphocyte homing effect. We investigated the relationship between the dose of FTY720 or blood concentration (pharmacokinetics, PK) and peripheral lymphopenia (pharmacodynamics, PD) in 23 kidney transplant recipients randomized to receive FTY720 (0.25-2.5 mg/day) or mofetil mycophenolate (2 mg/day) in combination with cyclosporine and steroids. FTY720 dose, blood concentrations and lymphocyte counts were determined weekly before and 4 to 12 weeks after transplantation. The effect of PD was calculated as the absolute lymphocyte count or its reductions. PK/PD modeling was used to find the best-fit model. Mean FTY720 concentrations were 0.36 +/- 0.05 (0.25 mg), 0.73 +/- 0.12 (0.5 mg), 3.26 +/- 0.51 (1 mg), and 7.15 +/- 1.41 ng/ml (2.5 mg) between 4 and 12 weeks after transplantation. FTY720 PK was linear with dose (r(2) = 0.98) and showed low inter- and intra-individual variability. FTY720 produced a dose-dependent increase in mean percent reduction of peripheral lymphocyte counts (38 vs 42 vs 56 vs 77, P < 0.01, respectively). The simple Emax model [E = (Emax * C)/(C + EC50)] was the best-fit PK/PD modeling for FTY720 dose (Emax = 87.8 +/- 5.3% and ED50 = 0.48 +/- 0.08 mg, r(2) = 0.94) or concentration (Emax = 78.3 +/- 2.9% and EC50 = 0.59 +/- 0.09 ng/ml, r(2) = 0.89) vs effect (% reduction in peripheral lymphocytes). FTY720 PK/PD is dose dependent and follows an Emax model (EC50 = 0.5 mg or 0.6 ng/ml). Using lymphopenia as an FTY720 PD surrogate marker, high % reductions (~80%) in peripheral lymphocytes are required to achieve best efficacy to prevent acute allograft rejection.

FTY720: early clinical experience

FTY720 is the first in a new class of immunomodulators--sphingosine 1-phosphate receptor (S1P-R) agonists. It is highly effective in prolonging allograft survival in preclinical models of transplantation. Furthermore, FTY720 acts synergistically with calcineurin inhibitors and proliferation inhibitors in these models, suggesting that use of FTY720 in combination with classical immunosuppressants may be a promising new option for transplant patients. Phase I studies conducted in stable renal transplant patients maintained on a cyclosporine (CsA)-based regimen have revealed a tolerable profile of FTY720 for transplant pharmacotherapy. The pharmacokinetics of FTY720 is characterized by linear dose-proportional exposure over a wide range of doses, only moderate interpatient variability, and a prolonged elimination half-life (t(1/2) 89 to 157 hours). These factors suggest that FTY720 can be administered according to a simple once-daily schedule, without the need for blood-level monitoring or dose titration. The pharmacodynamics of FTY720 in humans are characterized by a significant reduction in peripheral blood count by up to 85%. In contrast to the nonspecific myelosuppressive effects of other immunosuppressants, this effect of FTY720 is specific for lymphocytes, with no effect observed on monocytes or granulocytes. In combination with CsA, FTY720 was well tolerated following single or multiple dosing, without any evidence of additional toxicities, indicating that FTY720 may be useful in the future design of more effective and less toxic regimens for prevention of graft rejection.

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.

Protective effects of FTY720 on chronic allograft nephropathy by reducing late lymphocytic infiltration

BACKGROUND

Lymphocytic infiltration is obvious throughout early and late stages of chronic allograft nephropathy. Early infiltrating lymphocytes are involved in initial insults to kidney allografts, but the contribution of late infiltration to long-term allograft attrition is still controversial. Early application of FTY720 reduced the number of graft infiltrating lymphocytes, and inhibited acute rejection. The present study investigated the potential of FTY720 to reduce the number of infiltrating lymphocytes even at a late stage, and, thus, slow the pace of chronic allograft nephropathy.

METHODS

Fisher (F344) rat kidneys were orthotopically transplanted into Lewis recipients with an initial 10-day course of cyclosporine A (1.5 mg/kg/day). FTY720, at a dose of 0.5 mg/kg/day, or vehicle was administered to recipients either from weeks 12 to 24 or from 20 to 24 after transplantation. Animals were harvested 24 weeks after transplantation for histologic, immunohistologic, and molecular analysis.

RESULTS

FTY720, either initiated at 12 or 20 weeks after transplantation, reduced urinary protein excretion, and significantly ameliorated glomerulosclerosis, interstitial fibrosis, tubular atrophy, and intimal proliferation of graft arteries at 24 weeks after transplantation. Furthermore FTY720 markedly suppressed lymphocyte infiltration and decreased mRNA levels of interleukin-10 (IL-10), transforming growth factor-beta (TGF-beta), and platelet-derived growth factor-B (PDGF-B) but enhanced the number of apoptotic cells in grafts.

CONCLUSIONS

FTY720 ameliorated chronic allograft nephropathy even at advanced stages. Furthermore, our data suggest that this effect was achieved by a reduction of graft infiltrating lymphocytes.

Crossing the bridge: large animal models in translational transplantation research

Many methods for reducing the immunosuppressive requirements of allotransplantation have been proposed based on a growing understanding of physiological and allospecific immunity. As these regimens are developed for clinical application, they require validation in models that are reasonably predictive of their performance in humans. This article provides an overview of the large animal models commonly used to test immunomodulatory organ transplant protocols. The rationale for the use of large animals and the effects of common immunosuppressants in the dog, pig, and non-human primate are reviewed. Promising methods for the induction of allospecific tolerance are surveyed with references to early human trials where appropriate.

FTY720 immunomodulation: optimism for improved transplant regimens

FTY720, a sphingosine 1-phosphate receptor (S1P-R) agonist, is the first in a new class of immunomodulators. FTY720 has been shown to be highly effective for preventing graft rejection in preclinical models of cardiac, renal, and hepatic transplantation. To date, phase I single and multiple dosing studies conducted in stable renal transplant patients have revealed a favorable efficacy and tolerability profile. Following these preliminary clinical evaluations, phase II studies have determined optimal dosing for prevention of acute rejection and the efficacy and tolerability of FTY720 in combination with reduced and full-dose cyclosporine (CsA). Data available for these studies demonstrate that FTY720 5 mg combined with reduced-dose CsA provides equivalent freedom from acute rejection to a standard mycophenolate mofetil (MMF)/CsA regimen. Moreover, rejection prophylaxis with a 5-mg dose of FTY720 appears to allow for a 50% reduction in the dose of calcineurin inhibitors while effectively preventing graft rejection. These studies have also shown that FTY720 has no overlapping toxicity with classical immunosuppressive agents; FTY720 can be used safely in combination with CsA and everolimus. Overall, these synergistic effects suggest that FTY720 has the potential to provide a real improvement in the efficacy and tolerability of future immunosuppressive regimens.

FTY720: A new kid on the block for transplant immunosuppression

FTY720, a synthetic analogue of myriocin (ISP-1), is derived from culture filtrates of the fungus Isaria sinclairii. As a sphingosine analogue, FTY720 appears to undergo phosphorylation and thereby interact with specific G-protein-linked receptors. In vivo, FTY720 causes emigration of lymphocytes from peripheral blood to secondary lymphoid structures. Thus, the drug is the archetype of a new class of agents that alter cellular homing patterns: the adhesion-migration paradigm. Since FTY720 seems to spare nonspecific elements of host resistance, it may address the not infrequent complications of infections associated with existing therapies. In experimental rodent, canine and non-human primate models, FTY720 produces lymphopenia and immunosuppression, prolonging the survival of allografts. Because of synergistic interactions, it promotes the immunosuppressive effects not only of calcineurin antagonists, but also of proliferation signal inhibitors. These interactions proffer the possibility of large reductions in exposure to and mitigated toxicity of existing drugs. In humans, FTY720 causes dose-dependent peripheral blood lymphopenia, a reduced incidence of acute rejection episodes and only one apparent adverse reaction - a negative chronotropic effect - particularly after the loading dose. While the clinical utility of FTY720 is difficult to predict before completion of Phase III studies that elucidate its benefits versus unanticipated side effects, the initial data suggest several potential advantages: it does not produce hyperlipidaemia, diabetes mellitus, nephrotoxicity, neurotoxicity or myelosuppression, which are characteristic of other immunosuppressants. Furthermore, it displays high oral bioavailability and a low interindividual coefficient of variation. Clearly, structural analogues, as well as other agents that alter the balance of chemokines or affect cellular adhesion to activated endothelium, will represent important components of future regimens.

Pharmacodynamics of single doses of the novel immunosuppressant FTY720 in stable renal transplant patients

FTY720, a new and potent immunosuppressant, causes in animal models a rapid, reversible reduction of all subsets of peripheral blood lymphocytes, inducing their migration to secondary lymphoid organs. In this human phase I trial, the pharmacodynamics of single oral doses of FTY720 were evaluated. A randomized, double-blind, placebo-controlled, time-lagged study of six different single ascending oral doses of FTY720 ranging from 0.25 to 3.5 mg was conducted in stable renal transplant patients receiving a cyclosporine-based regimen. Absolute and subset lymphocyte counts, as well as absolute differential leukocyte counts, were determined by differential blood counts and flow cytometry at screening and multiple intervals thereafter. A pharmacodynamic model was established. Twenty-four single doses of FTY720 that were administered caused a transient, reversible pan-lymphopenia within 4 h. Lymphocyte subgroup analysis revealed that almost all subsets declined, with CD4- and CD45RA-positive cells being affected the most. Natural killer cells, granulocytes and monocytes were not influenced by FTY720. The lymphocyte count returned to baseline within 72 h in all dosing cohorts except the highest. Pharmacokinetik/pharmacodynamic modelling revealed a nonlinear dose effect and resulted in a good fit with observed values. These data show that FTY720 is highly effective in humans, with single oral doses of FTY720 ranging from 0.25 to 3.5 mg causing a reversible selective panlymphopenia.

FTY720 reduces T-cell recruitment into murine intestinal allograft and prevents activation of graft-infiltrating cells

BACKGROUND

Effective immunosuppression is a critical determinant of graft survival in small-bowel transplantation (SBTx). The present study was designed to determine the potency of FTY720, a newly synthesized immunosuppressant, in rat SBTx and examine the phenotype of graft-infiltrating cells to evaluate its effect on intestinal allografts.

MATERIALS AND METHODS

A segment of intestine of Dark Agouti rats was transplanted heterotopically into Lewis rats. The recipients were treated with or without oral FTY720 at a dose of 1 mg/kg per day. Six days after surgery, peripheral blood lymphocytes and lymphocytes from the mesenteric lymph nodes, Peyer's patches, intraepithelial site, and lamina propria of the intestinal allograft were isolated. After the number of lymphocytes in each site was counted, the lymphocyte subpopulations in the intestinal allograft were evaluated by means of a FACScan flow cytometer using several monoclonal antibodies.

RESULTS

FTY720 treatment significantly prolonged recipient survival and strongly inhibited rejection histologically in comparison with control rats. FTY720 immunosuppression resulted in a marked reduction of lymphocyte number in the graft epithelium and lamina propria and the proportion of CD8+ and CD25+ cells. FTY720 also significantly decreased T-cell receptors and increased B cells in the graft Peyer's patches.

CONCLUSION

FTY720 promoted long-term SBTx recipient survival and maintained the architecture of intestinal allografts. FTY720 immunosuppression may be associated with a reduction of T-cell recruitment subsequent to the redistribution of lymphocyte subpopulations to control the proliferation and activation of graft-infiltrating cells in intestinal allografts.

Sphingosine-1-phosphate receptor agonism impairs the efficiency of the local immune response by altering trafficking of naive and antigen-activated CD4+ T cells

FTY720 (2-amino-[2-(4-octylphenyl) ethyl]-1,3-propanediol hydrochloride) is an immunosuppressive agent that inhibits allograft rejection. We recently demonstrated that FTY-phosphate, the active metabolite of FTY720, acts as a full agonist for sphingosine-1-phosphate (S1P) receptors. Furthermore, activation of S1P receptors with their natural ligand, S1P, as well as pharmacological ligands leads to lymphopenia, probably due to sequestration of lymphocytes in secondary lymphoid organs. In the present study we used a local Ag-challenged mouse model to examine the effects of FTY720 on T cell activation in the draining lymph node (DLN) and on the release of activated T cells to the peripheral blood compartment. We showed that the number of Ag-activated CD4(+) T cells in the DLN after injection of Ag and CFA into a footpad was dramatically reduced after FTY720 treatment. However, T cell proliferation, both in vitro and in vivo, was not impaired by FTY720. Our results suggest that the reduced efficiency of T cell responses in the DLN in response to a local Ag is probably due to a defective recirculation of naive T cells caused by FTY720 treatment. Furthermore, we found that the numbers of naive and Ag-activated CD4(+) T cells in the peripheral blood of Ag-challenged mice were equally reduced with FTY720 treatment, suggesting that both T cell subsets are sequestered in the DLNs. Thus, FTY720 induces immunosuppression through inhibition of both the recirculation of naive T cells and the release of Ag-activated T cells from the DLN to lymph and to the blood compartment.

Elimination of cell-cycle regulators during caspase-3-dependent apoptosis caused by an immunosuppressant, FTY720

The immunosuppressant, FTY720 causes apoptosis of lymphocytes, reduces numbers of lymphocytes in peripheral blood, and prevents infiltration of lymphocytes into allografts, which may be one of the mechanisms involved in its effects. Here we compared caspase activation and expression of cell-cycle regulators during apoptosis caused by FTY720, and Fas-stimulation in a mouse lymphoma transfected with human Fas antigen. FTY720 activated caspases-3, -8, and -9 as rapidly as did Fas-mediated apoptosis. The activation was blocked by a peptide inhibitor for caspase-3, DEVD-CHO. Fas-induced activation of caspases-8 and -9 was unaffected by the inhibitor. FTY720 eliminated proliferating cell nuclear antigen, retinoblastoma family members, differentiation regulated transcription factor polypetide-1, and cyclin H. These cell-cycle regulators were not eliminated when the peptide inhibitor was used. Dysfunction of cell-cycle regulators may play a critical role in the signal transduction pathway for activation of FTY720-mediated apoptosis.

T cell selective apoptosis by a novel immunosuppressant, FTY720, is closely regulated with Bcl-2

1. A novel immunosuppressant FTY720 caused a significant decrease in peripheral T lymphocytes, but not in B lymphocytes upon oral administration. This decrease was mainly a result of FTY720-induced apoptosis. In this study, we confirmed FTY720-induced T cell selective apoptosis using lymphoma cell lines in vitro. 2. Viability loss, DNA fragmentation, Annexin V binding, and caspases activation (caspase-3, -8, and -9) were observed in Jurkat cells (T lymphoma cells), but not significantly in BALL-1 cells (B lymphoma cells). These results indicated that FTY720 selectively induced apoptosis in T cell lymphoma to a greater extent than in B cell lymphoma, a finding that is similar to the result observed when FTY720 was treated with T lymphocytes and B lymphocytes in vitro. 3. FTY720 released cytochrome c from mitochondria in Jurkat intact cells as well as from isolated Jurkat mitochondria directly, but not from mitochondria in BALL-1 cells nor from isolated BALL-1 mitochondria. 4. BALL-1 cells and B cells had more abundant mitochondria-localized anti-apoptotic protein Bcl-2 than did Jurkat cells and T cells. 5. FTY720-induced apoptosis is inhibited by the overexpression of Bcl-2, suggesting that the cellular Bcl-2 level regulates the sensitivity to FTY720.

Combination treatment with FTY720 and CTLA4IgG preserves the respiratory epithelium and prevents obliterative disease in a murine airway model

BACKGROUND

Mouse heterotopic tracheal transplantation offers a reproducible model of obliterative bronchiolitis after lung transplantation. CTLA4IgG inhibits signaling of the CD28/B7 pathway and induces antigen-specific T-cell unresponsiveness. FTY720 induces T-cell apoptosis and sequestration of circulating mature lymphocytes. We previously found that CTLA4IgG could prevent the development of obliterative airway disease but could not preserve the respiratory epithelium of grafted tracheae. We evaluated whether treatment with either FTY720 or CTLA4IgG, or with combination FTY720 and CTLA4IgG could preserve the respiratory epithelium and inhibit the development of obliterative airway disease.

METHODS

Tracheae with main bronchi from C3H/He mice were transplanted heterotopically into BALB/C mice and harvested on Day 35. Recipient mice received either no treatment or treatment with intraperitoneal FTY720, CTLA4IgG, or the combination of the 2.

RESULTS

Either FTY720 or CTLA4IgG alone significantly inhibited the development of obliterative airway disease. However, normal ciliated columnar respiratory epithelial cells were lost in the allografts. In contrast, combination therapy preserved the respiratory epithelium of the allografted tracheae. FTY720 concentration in the tissue was very high; treatment with FTY720 inhibited mixed lymphocyte reactions and augmented T-cell apoptosis.

CONCLUSION

Combination treatment with FTY720 and CTLA4IgG may prevent obliterative airway disease.

First human trial of FTY720, a novel immunomodulator, in stable renal transplant patients

FTY720 is a novel immunomodulator to be developed for use in organ transplantation. The primary objective of this study was to measure safety, single-dose pharmacokinetics, and pharmacodynamics in stable renal transplant patients-the first human use of FTY720. This study used a randomized, double-blind, placebo-controlled design that explored single oral doses of FTY720 from 0.25 to 3.5 mg in 20 stable renal transplant patients on a cyclosporine-based regimen. Safety assessments and blood samples were taken predose and at multiple time points during a 96-h period postdose. Standard pharmacokinetic parameters were derived from the FTY720 whole blood concentrations, measured by HPLC/MS/MS. FTY720 was well tolerated, with no serious adverse events. Transient, asymptomatic bradycardia occurred after administration in 10 of 24 doses of FTY720. Pharmacokinetics are characterized by a prolonged absorption phase; the terminal elimination phase started 36 h after the administration, with elimination half-life (t(1/2)) ranging from 89 to 157 h independent of dose. Maximum plasma concentration and AUC were proportional to dose with low intersubject variability, the apparent volume of distribution (V(d)/F) ranged from 1116 to 1737 L. FTY pharmacodynamics were characterized by a reversible transient lymphopenia within 6 h, the nadir being 42% of baseline. The lymphocyte count returned to baseline within 72 h in all dosing cohorts except the highest. Single oral doses of FTY720 ranging from 0.25 to 3.5 mg were well tolerated and caused a reversible selective lymphopenia. Transient, but asymptomatic bradycardia was the most common adverse event. The long t(1/2) suggests less frequent dosing intervals. The size of V(d)/F is in excess of blood volume, consistent with widespread tissue distribution

Advantages of Celsior solution in graft preservation from non-heart-beating donors in a canine liver transplantation model

BACKGROUND

The optimal method for preserving livers from non-heart-beating donors (NHBD) is still unknown. We compared the Celsior solution, a new extracellular-type, low-potassium, low-viscosity preservation solution, with the University of Wisconsin (UW) solution in a canine orthotopic liver transplantation from NHBD.

MATERIALS AND METHODS

Fourteen adult mongrel dogs, weighing 9 to 17 kg, were divided into two groups: the Celsior or the UW group (n = 7 each). The thoracic descending aorta and supradiaphragmatic inferior vena cava were cross-clamped for 20 min to induce warm ischemia as a NHBD model. The liver was flushed with the respective cold preservation solution and then stored at 4 degrees C for 4 h. The grafts were transplanted using the piggy-back technique under portal decompression by leaving the native right lobe as a temporary shunt.

RESULTS

The duration of liver flushing out (min) was shorter (P < 0.05), and the serum glutamic oxaloacetic transaminase, glutamic pyruvic transaminase, lactate dehydrogenase, lactate, and alpha-glutathione S-transferase concentrations 2 and 6 h after reperfusion of the graft (RPF) were lower (P < 0.05) in the Celsior group than in the UW group. Hepatic tissue blood flow (HTBF) did not deteriorate as much (P < 0.05) in the Celsior group. The serum endothelin-1 level was lower (P < 0.05) in the Celsior group 2 h after RPF. Histopathology of liver specimens revealed portal congestion and hepatocyte necrosis with neutrophil infiltration in the UW group, while these findings were mild in the Celsior group.

CONCLUSIONS

The Celsior solution improves vascular endothelial injury in livers from NHBDs and may have advantages in graft flush and preservation of grafts from NHBDs.

Trends in expenditures for Medicare liver transplant recipients

Liver transplantation, a resource-intensive medical procedure, is under particular scrutiny in the current era of cost containment. There have been significant changes in treatment protocols over the past decade; however, information is limited on how these changes have affected the economics of liver transplantation. This study examines a time series from 1993 to 1999 in Medicare expenditures for liver transplantation. We estimated total first- and second-year expenditures, as well as expenditures 90 days pretransplantation. These expenditures included inpatient, outpatient, physician, home health, and hospice care; immunosuppression expenditures were not estimated. Average first-year expenditures (in year 2000 dollars) for liver transplantation, excluding immunosuppressives, decreased from 201,677 dollars in 1993 to 143,363 dollars in 1998. Inpatient costs accounted for the majority of total expenditures, decreasing from 179,306 dollars in 1993 to 120,445 dollars in 1998. Total days of hospitalization decreased from 56.7 days in 1993 to 42.2 days in 1998. The majority of hospitalization occurred during the first 90 days posttransplantation, but decreased from 44.4 days in 1993 to 29.4 days in 1999. Substantial cost reductions over this period were a result of reduced hospitalization and occurred while survival rates gradually improved.

New immunosuppressive drugs: an update

An increasing number of immunosuppressive drugs became available for clinical use over the past few decades. These include substances with recently recognized immunosuppressive properties, which needed careful evaluation in various trials before they could be approved for use in different diseases. The effectiveness of other agents was already established, but knowledge about their modes of action or the mechanisms that lead to side effects was acquired much later. This understanding also contributed to the development of new drugs that display synergistic effects or lack certain adverse effects. The greater choice afforded by such research endeavours allows us to select the best therapeutic strategy for an individual patient; however, this requires a comprehensive knowledge of the available options. The present review provides an update of current knowledge of the most important substances (including calcineurin and target of rapamycin inhibitors, regulators of gene expression, and inhibitors of purine and pyrimidine synthesis) and surveys some of the novel agents that are expected to play an important role in the future.

Combined FTY720/cyclosporine A treatment promotes graft survival and lowers the peripheral lymphocyte count in DA to lewis heart and skin transplantation models

OBJECTIVE

The immunomodulator, FTY720, lowers the peripheral lymphocyte count (PLC) by inducing migration of circulating lymphocytes to secondary lymphoid organs. We investigated the efficacy of mono- vs. combined-FTY720/CsA therapy on graft survival (GS) and on lowering the PLC in a solid organ and a skin graft model, using strains with strong MHC disparity.

METHODS

Heterotopic cardiac or tail skin grafting was performed using the DA (RT1a) to Lewis (RT1(1)) rat strain combination. FTY720 was administered as a single daily dose by gavage alone or in combination with subcutaneously delivered CsA. PLC, body weight and drug concentrations were determined on day 7, 28, or the day of rejection.

MAIN FINDINGS

In placebo-treated animals the heart and skin allografts rejected after 6 and 8 days. FTY720 delayed rejection of both the solid organ and skin grafts. The maximal effect was achieved at 1 mg x kg(-l) x day(-1) FTY720, resulting in a median survival time (MST) of 14 days for both allotransplants comparable to the effect achieved by 1 mg x kg x day(-1) CsA in both models. In the cardiac graft experiment with CsA co-administration, doses of 0.3 and 1 mg/kg were used. Under these conditions very small doses of FTY720 were effective in maintaining grafts throughout the treatment period. Adding higher FTY720 doses to the 1 mg x kg(-1) x day(-1) CsA was needed to effectively extend the skin GS, e.g. 0.3 mg x kg(-l) x day(-1) FTY720 prolonged GS from 13 to 47.5 days MST, i.e. well beyond the 28 day-treatment period. CsA did not influence the PLC at clinically relevant doses. FTY720 lowered the PLC significantly and dose-dependently, at doses lower than those needed for the prolongation of both cardiac and skin GS with FTY720 monotherapy. In rats with skin grafts the PLC was markedly lowered up to 1 mg x kg(-1) x day(-1) FTY720, whereas, in the heart model, it was lowered up to 0.1 mg x kg(-1) x day(-1). Independently of the graft type, within the combination regimens 0.3 mg x kg(-1) x day(-1) FTY720 achieved a maximal PLC depletion.

CONCLUSIONS

Combining FTY720 and CsA was very well tolerated with respect to weight gain and lack of any clinically detectable infections. In the strain combination used FTY720 monotherapy was less effective than previously reported in maintaining grafts. The two-drug regimens extended strikingly the GS for both models. However, the prolongation of the heart GS was smoothly dose-related with FTY720 doses ranging from 0.01 to 1 mg x kg(-1) x day(-1) , whereas, the skin graft prolongation was modest at doses up to 0.1 mg x kg(-1) x day(-1) and remarkably enhanced at 0.3 and 1 mg x kg(-1) x day(-1) FTY720.

Obliterative airway disease and graft stenting in pig-to-dog tracheal xenotransplantation

OBJECTIVE

Obliterative airway disease occurring in concordant tracheal xenografts in rodent models is histologically similar to obliterative bronchiolitis in human lung allografts. We studied whether obliterative airway disease would occur in a large animal-discordant model.

METHODS

Pig and dog tracheas were cryopreserved for 7 to 14 days, and 18 recipient dogs given splenectomy 7 days before transplantation, then seven tracheal rings were removed and a corresponding five-ring donor tracheal segment was transplanted to the excised site. Grafts were wrapped with pedicled omentum and inmmunosuppression was conducted with tacrolimus or deoxyspergualin. Graft status was observed by bronchoscopy. Dogs were classified into three groups. Group 1 consisted of dog-to-dog allotransplantation animals (control group, n = 5), Group 2 of pig-to-dog xenotransplantation animals (n = 8), and Group 3 of pig-dog xenotransplantation animals who also underwent graft stenting immediately after transplantation (n = 5).

RESULTS

Grafts healed well in 4 of 5 Group 1 dogs. Tracheal stricture began on day 5 post transplantation and the lumen was obstructed by fibrosis by days 8 to 14 in all Group 2 dogs. All Group 3 dogs remained in good respiratory status until death.

CONCLUSION

Obliterative airway disease developed quickly in pig-to-dog discordant tracheal xenografts. Graft stenting is a feasible treatment for managing of tracheal obstruction.

Current treatment practice in immunosuppression

New drugs have recently been added that may eventually replace the two-decade dominance of cyclosporin in solid organ transplantation. This cornerstone of immunosuppression was introduced by Borel [1] and Calne [2] in the mid-70s. In 1989, Starzl et al., after 2 years of preclinical experimentation, introduced tacrolimus (originally designated as FK506 by the Fujisawa Pharmaceutical Company of Japan) as a potent immunosuppressant for liver transplants [3]. Also, in recent years, a variety of novel purine and pyrimidine biosynthesis inhibitors have been tested for transplantation therapy. The leading agent which appears to be replacing the 35-year position occupied by azathioprine is the semi-synthetic morpholinoethyl ester of mycophenolic acid (MPA), mycophenolate mofetil (MMF), introduced by Allison [4] and Sollinger [5], and developed by the Syntex Corporation (now Roche Pharmaceuticals). Others, affecting different intra- or intercellular messages amplifying immunity, are in the pipeline.