Torsten Böhler

FTY720 (fingolimod) in renal transplantation

Abstract:u2002 FTY720 (Fingolimod) is a novel immunomodulator with a mode of action that is completely different from classical immunosuppressants. FTY is a structural and functional analogue of the natural serum lipid, sphingosine, and is the first in a new class of drugs called sphingosine 1‐phosphate receptor (S1P‐R) modulators. This review discusses the recent findings on the mechanism of action, preclinical models and outlines the results of the ongoing clinical development program. FTY is highly effective in prolonging allograft survival in preclinical models of transplantation and in experimental models of autoimmune diseases. In clinical trials, this novel compound was investigated in de novo renal transplantation and in multiple sclerosis. Pharmacokinetics are characterized by a prolonged absorption phase, a large volume of distribution, and a long elimination half‐life. FTY induces a rapid and transient decrease in lymphocyte counts, which supports the modulatory effects of the drug on lymphocyte sequestration. The most common adverse event was asymptomatic transient bradycardia, a pharmacodynamic effect modulated by atrial S1 P‐R. FTY failed to show an improvement in efficacy for the prevention of renal allograft rejection in two large phase III studies. FTY treatment regimens were associated with impaired renal function and the development of macula edema. Consequently, the further development in renal transplantation was stopped. Because initial clinical studies strongly suggest that FTY is highly effective in multiple sclerosis FTY is now being explored in phase III studies for the treatment of demyelinating diseases, Ongoing studies in multiple sclerosis are eagerly awaited because they may provide novel therapeutic options for patients with autominnue diseases.

HLA Class I Antibodies Provoke Graft Arteriosclerosis in Human Arteries Transplanted into SCID/Beige Mice

Antibodies toward HLA class I and/or MICA are commonly observed in transplanted patients suffering from allograft arteriosclerosis, also called chronic vascular rejection (CVR). The relative importance of cellular versus humoral alloreactivity for CVR is still disputed. We demonstrate that antibodies toward HLA class I provoke lesions typical for CVR in human arteries in vivo in the absence of cellular immunity. To show this, we grafted segments of human mesenteric arteries from 8 deceased organ donors into 36 immunodeficient SCID/beige mice in the infrarenal aortic position. Three mice died postoperatively. The remaining 33 mice received weekly i.v. injections of either a monoclonal antibody toward HLA class I, toward MICA or an irrelevant monoclonal antibody. At sacrifice after 6 weeks, mice receiving the HLA antibody showed a significant neointimal thickening in the grafted artery due to smooth muscle cell (SMC) proliferation while control mice receiving anti‐MICA or irrelevant antibody showed little or no thickening. Whereas antibodies toward HLA class I were mitogenic to SMC in vitro, those directed toward MICA did not have any effect. Humoral alloreactivity toward HLA may thus play a causal role for the development of CVR and this opens new possibilities for the treatment of CVR.

Current perspectives on FTY720

The search for effective immunosuppressants with fewer side effects continues not only for transplantation, but also for autoimmune diseases. With a novel mechanism of action (sphingosine-1 receptor modulation), oral FTY720 (fingolimod) has the potential to address this need. FTY720 has been preclinically tested with promising results in transplantation and autoimmune disease models. Phase I studies explored the pharmacokinetics and pharmacodynamics of this novel therapeutic concept. Recently, the surprising results of two sister Phase III studies in de novo renal transplant patients, as well as a Phase II study in patients with relapsing multiple sclerosis, were published. This review discusses these findings as well as their implications for the future of sphingosine-1 receptor modulation.

Cytokines correlate with age in healthy volunteers, dialysis patients and kidney-transplant patients

T-cell functions are currently used as biomarkers for the pharmacodynamic monitoring of immunosuppressive drugs or as disease biomarkers of inflammation/sepsis and organ rejection. In order to evaluate co-factors potentially influencing the expression of the immunological biomarkers, we explored T-cell proliferation, T-cell activation (CD25 and CD71 expressions) and intra-lymphocyte cytokine production (interleukin (IL)-2 and tumor necrosis factor (TNF)-alpha) in healthy volunteers, dialysis patients and stable kidney-transplant patients treated with standard immunosuppressive therapy, i.e. tacrolimus, mycophenolic acid with or without steroids. Age was positively correlated with TNF-alpha expression in all three patient populations, and with IL-2 expression in healthy volunteers and kidney-transplant patients. Further age was correlated with inhibition of lymphocyte proliferation in healthy volunteers and with the T-cell activation marker CD25 in kidney-transplant patients. In healthy volunteers lymphocyte proliferation was higher in woman as compared to men. Other biomarkers of T-cell function were independent of the gender. In the kidney-transplant patient group a significantly lower expression of all biomarkers of T-cell functions compared to healthy volunteers and dialysis patients. In dialysis patients we found significant increased IL-2 expression compared to healthy volunteers, while the other T-cell functions were not significantly different. Further time on dialysis had no effect on the level of biomarker expression. In conclusion we found decreased T-cell functions in kidney-transplant patients compared to healthy volunteers and dialysis patients, increased IL-2 expression in dialysis patients compared to healthy volunteers and in all three populations we found a correlation of age and intra-T-lymphocyte TNF-alpha expression.

Pharmacodynamic monitoring of the conversion from mycophenolate mofetil to enteric-coated mycophenolate sodium in stable kidney-allograft recipients

BACKGROUNDnThe formulations of mycophenolic acid, i.e., mycophenolate mofetil (MMF) and enteric-coated mycophenolate sodium (EC-MPS), seem to have different pharmacokinetic profiles. The aim of this study was to compare the effects MMF and EC-MPS on T-cell proliferation, T-cell activation, T-cell function, and lymphocyte subsets. CLINICAL STUDY AND METHODS: Ten stable kidney-transplant patients on standard maintenance therapy of tacrolimus and MMF (1 g/d), with or without steroids, were converted from MMF to EC-MPS at equivalent dose (720 mg/d). Tacrolimus and steroid doses remained unchanged before, and at 1, 2, 3, and 6 months (M) after conversion. Intra T-lymphocyte cytokines IL-2 and TNF-alpha, lymphocyte-activation surface markers (CD25 and CD71), T-cell proliferation (PCNA+ PI(high)), total lymphocyte count, as well as lymphocytes subsets (CD2, CD3, CD4, CD8, CD19, NK cells) were measured by flow cytometry before conversion and at M1, M2, M3, and M6.nnnRESULTSnWe found no significant differences of MMF versus EC-MPS on lymphocyte function. T-cell proliferation and T-cell activation (CD25 and CD71 expression), but not cytokine expression (TNF-alpha and IL-2), showed a trend to increase after conversion from MMF to EC-MPS. Total lymphocyte, CD2, CD3, CD4, CD8, and NK cells counts were not significantly modified.nnnCONCLUSIONnThis study revealed a trend to a lower immunosuppression with EC-MPS as compared to MMF in stable renal transplant patients.

Polyoma BK virus-associated nephropathy in kidney-transplant patients: effects of leflunomide on T-cell functions and disease outcome.

BACKGROUNDnIn kidney-transplant recipients, leflunomide has been shown to be efficient for treating polyomavirus BK virus-associated-nephropathy (PVAN). However, it is unknown whether the beneficial effect of leflunomide is related to it having a lower immunosuppressive effect than mycophenolate mofetil (MMF), or to its anti-viral activity. The aim of this study was to assess i) T-cell functions before and after conversion from MMF to leflunomide in kidney-transplant patients with PVAN, and ii) effects of leflunomide on PVAN outcome.nnnPATIENTS AND METHODSnTwelve patients were enrolled in this study. At PVAN diagnosis, MMF was replaced by leflunomide. Other immunosuppressive drug doses and levels were maintained unchanged. T-cell functions, i.e., intralymphocyte cytokine expression (IL-2 and TNF-alpha), T-cell activation [i.e., transferrin receptor (CD71) and interleukin (IL)-2 alpha-chain (CD25) expression], and T-cell proliferation were measured using a flow-cytometry whole-blood assay before and at one month after conversion.nnnRESULTSnDespite a slight decrease in tacrolimus trough levels, no significant change in T-cell-function biomarkers was observed after conversion. After a follow-up of 6 (4-30) months, five patients were cleared of the virus, and decreased viral load was observed in four patients. Only one patient suffered a graft loss. No difference in immunological parameters was observed between patients who were cleared or not of BKV.nnnCONCLUSIONnResults of this pilot study suggest that the potential benefits of leflunomide to treat PVAN in kidney-transplant patients is not related to reduced immunosuppression induced by replacing MMF by leflunomide. Virological studies are required to determine the anti-BKV effect of leflunomide.

Pharmacodynamic effects of everolimus on anti-CD3 antibody-stimulated T-lymphocyte proliferation and interleukin-10 synthesis in stable kidney-transplant patients

Everolimus (rapamycin derivative, RAD) is a new immunosuppressive drug that prevents allograft rejection. Herein, the pharmacodynamics of everolimus in human renal-allograft recipients is evaluated. Single doses of everolimus (0.75-10mg), combined with a maintenance immunosuppressive therapy based on CyA, decreased lymphocyte proliferation. In addition, the effect of multiple doses of everolimus (0.75-10mg) given daily for 21 days, to stable renal-allograft patients (n=11), was investigated. Everolimus treatment resulted in immediate inhibition (25-55%) of lymphocyte proliferation in renal-allograft recipients; values returning to baseline by 14 days after cessation of everolimus treatment. Placebo-treated patients showed no decrease in lymphocyte proliferation. Interestingly, everolimus reduced IL-10 synthesis by 20-60% in renal-allograft recipients. Phagocytosis rates were not changed by everolimus. In vitro, everolimus inhibited lymphocyte proliferation and IL-10 synthesis dose dependently in anti-CD3 mAb and LPS stimulated peripheral blood mononuclear cell cultures derived from human volunteers.

In vitro mitogen-stimulated T-cell from hepatitis C virus-positive liver transplantation candidates, increases T-cell activation markers and T-cell proliferation.

The incidence of acute rejection is significantly higher in hepatitis C virus (HCV) liver-transplant patients than in patients who have received a graft for other liver diseases, i.e., mainly alcoholic cirrhosis. The aim of this study was to assess T-cell function, i.e., intralymphocyte cytokine expression (IL-2 and TNF-alpha), T-cell activation [i.e., transferrin receptor (CD71) and interleukin (IL)-2 alpha-chain (CD25) expression], and T-cell proliferation using a flow-cytometry whole-blood assay in patients waiting for a liver transplantation (n=49). Our data suggest that, in mitogen-stimulated T-cells, (i) intra-lymphocyte cytokine expression is significantly higher in patients with liver disease than in healthy volunteers (n=25); (ii) the expression of T-cell activation markers is decreased in patients with liver cirrhosis compared to healthy volunteers, and (iii) the expression of T-cell activation markers and T-cell proliferation are increased in patients with HCV infection (n=15) compared to those without HCV infection (n=34), particularly compared to patients with alcoholic liver disease (n=19). Circulating CD19-positive cells count was also significantly higher in HCV-positive patients. In conclusion, in vitro, mitogen-stimulated T-cell seem to induce a higher immune response in the blood from patients waiting for a liver transplant for HCV-related liver disease than those without HCV infection, and particularly those with alcoholic liver disease.

T-cell function in maintenance renal transplant patients receiving mycophenolate mofetil and steroids with or without tacrolimus.

Nephrotoxicity-sparing protocols, using mycophenolate mofetil (MMF) and steroids without calcineurin inhibitors (CNIs) or mammalian target rapamycin (mTOR), could be used to treat maintenance renal transplant patients. However, the risk for acute rejection seems to be high. The aim of this pharmacodynamic study was to analyze T-cell function, T-cell activation, and T-cell proliferation among patients receiving MMF and steroids (n = 15) compared with patients receiving immunosuppression with CNI-based therapy including tacrolimus, MMF, and steroids. Our data suggested that among stable maintenance patients, dual therapy with MMF and steroids might provide a similar reduction in T-cell proliferation and T-cell activation as that observed among patients on standard immunosuppressive therapy. As expected, intralymphocytic interleukin-2 (IL-2) and tumor necrosis factor-alpha (TNF-alpha) expressions were higher in patients not receiving CNIs.

Long-term results of a calcineurin inhibitor-free immunosuppression based on Thymoglobulin® and mycophenolate mofetil in elderly kidney transplant recipients

storage disorders such as Fabry disease, standardized screening for particular biomarkers is beginning to be considered a useful tool for diagnostics [6]. Future screening studies may help to identify Fabry patients that would gain immediate benefit from diagnosis. Screening for this disease is particularly timely in Canada, where a comparative clinical trial of currently approved ERT drugs is ongoing.