Johannes Waiser

Donor‐Specific HLA Antibodies in a Cohort Comparing Everolimus With Cyclosporine After Kidney Transplantation

Donor‐specific HLA antibodies (DSA) have a negative impact on kidney graft survival. Therefore, we analyzed the occurrence of DSA and antibody‐mediated rejection (AMR) in patients from two prospective randomized trials in our center. At 3–4.5 months posttransplant 127 patients were randomized to continue cyclosporine or converted to everolimus therapy. The presence of DSA was prospectively assessed using Luminex assays. AMR was defined according to the Banff 2009 classification. Antibody screening was available in 126 patients with a median follow‐up of 1059 days. Seven out of 65 (10.8%) patients on cyclosporine developed DSA after a median of 991 days. In comparison, 14/61 patients (23.0%) randomized to everolimus developed DSA after 551 days (log‐rank: p = 0.048). Eight patients on everolimus compared to two patients on cyclosporine developed AMR (log‐rank: p = 0.036). Four of 10 patients with AMR—all in the everolimus group—lost their graft. A multivariate regression model revealed everolimus, >3 mismatches and living donor as significant risk factors for DSA. Acute rejection within the first year, >3 mismatches, everolimus and living donor were independent risk factors for AMR. This single center analysis demonstrates for the first time that everolimus‐based immunosuppression is associated with an increased risk for the development of DSA and AMR.

Pre-transplant inosine monophosphate dehydrogenase activity is associated with clinical outcome after renal transplantation.

Mycophenolate mofetil (MMF), an inhibitor of inosine monophosphate dehydrogenase (IMPDH) activity, is usually administered as a standard dose of 1 g b.i.d. after renal transplantation. Because MMF dose reductions are associated with inferior outcome, we investigated pre‐transplant IMPDH activity, MMF dose reductions and outcome. IMPDH activity was determined in isolated peripheral mononuclear cells immediately prior to renal transplantation. We observed considerable inter‐individual variability in pre‐transplant IMPDH activity (9.35 ± 4.22 nmol/mg/h). Thirty of 48 patients (62.5%) with standard MMF dose (1 g b.i.d.) had dose reductions within 3 years post‐transplant; these patients also had significantly lower IMPDH activity. The area under the receiver‐operating characteristics curve (AUC‐ROC) for prediction of dose reduction within 6 months post‐transplant was 0.75 (95% CI, 0.61–0.89; p < 0.004). IMPDH activity above the cut‐off value, MMF dose reduction and age of recipient were significant contributors for the occurrence of acute rejection in the multivariate logistic regression. Patients with high IMPDH activity and MMF dose reduction had the highest rejection rate (81.8% vs. 36.4%; p < 0.01). Conclusion: Patients with low IMPDH activity experienced more complications of MMF therapy. High pre‐transplant IMPDH activity and MMF dose reductions were associated with rejection. Determination of IMPDH activity prior to transplantation may help to improve MMF therapy after renal transplantation.

Comparison between bortezomib and rituximab in the treatment of antibody-mediated renal allograft rejection

BACKGROUND Antibody-mediated rejection (ABMR) following kidney transplantation is associated with poor allograft survival. Conventional treatment based on plasmapheresis (PPH) and the administration of intravenous immunoglobulins (IVIG) is not satisfactory. Two compounds, more specifically targeting B cells and plasma cells, may help to improve the prognosis: rituximab, a B-cell-depleting monoclonal antibody, and bortezomib, a proteasome inhibitor causing apoptosis of plasma cells. METHODS Starting in February 2009, we treated 10 consecutive patients with ABMR according to current Banff criteria with one cycle of bortezomib [1.3 mg/m(2) intravenously (i.v.), Day 1, 4, 8, 11]. This group was compared to a historical control group of patients (n = 9) treated with a fixed single dose of rituximab (500 mg i.v.). All patients received PPH (6×) and IVIG (30 g). Patients with acute ABMR additionally received methylprednisolone (3 × 500 mg i.v.). RESULTS Patient survival in both groups was 100%. At 18 months after treatment, graft survival was 6/10 in the bortezomib group as compared to 1/9 functioning grafts in the rituximab group (P = 0.071). Renal function was superior in patients treated with bortezomib as compared to rituximab-treated patients (serum creatinine at 9 months: 2.5 ± 0.6 versus 5.1 ± 2.1 mg/dL, P = 0.008). Proteinuria was not different between both groups (9 months: 1.3 ± 1.0 versus 1.6 ± 1.6 g/day, P = n.s.). CONCLUSIONS Treatment of ABMR with bortezomib in addition to standard therapy was partially effective, whereas treatment with a fixed dose of rituximab in addition to standard therapy with PPH and IVIG did not result in sufficient long-term graft survival. In the future, new strategies including the combination of both substances and the application of higher doses must be discussed.

FTY720 (fingolimod) in renal transplantation

Abstract:  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.

Pharmacodynamic monitoring of mycophenolate mofetil.

Abstract The immunosuppressive activity of Mycophenolate Mofetil (MMF) is based on the reversible inhibition of inosine-5′-monophosphate dehydrogenase (IMPDH) by mycophenolic acid. Pharmacodynamic monitoring by measurement of IMPDH activity reflects directly the biological response to MMF. For measurement of IMPDH activity in peripheral mononuclear cells we established a modified non-radioactive procedure, based on the incubation of cell lysates with inosine-5′-monophosphate and the chromatographic quantification of produced xanthosine-5′-monophosphate by isocratic ion-pair reversed phase HPLC. The between-run precision and within-run precision were 7% and 5%, respectively. We determined the time course of IMPDH activity in five patients after 1g MMF and in five healthy subjects without administration of MMF. Additionally, IMPDH activity was determined in a population study of 40 healthy volunteers. In healthy volunteers, we observed a wide range of IMPDH activity (4.7–32.9 nmol/h/mg) with only weak diurnal variation. All patients receiving MMF had a significant reduction of IMPDH activity (65–100%) after administration of the drug. Inhibition persisted for up to 6 hours, and after 11 hours IMPDH activity returned to predose activities. The interindividual variability of IMPDH activity may account for pharmacodynamic differences in MMF-treated patients. Based on pharmacodynamic monitoring better dosing strategies for MMF-treated patients may evolve.

Treatment of acute c-ANCA-positive vasculitis with mycophenolate mofetil.

Acute cytoplasmic antineutrophil cytoplasmic antibody (c-ANCA)-positive vasculitis is usually treated with cyclophosphamide and corticosteroids. The incidence of cyclophosphamide-induced lung injury, a potentially life-threatening event, is about 1%. We report on a patient with a history of cyclophosphamide-induced lung injury 2 months after initial treatment of systemic c-ANCA-positive vasculitis. Six months later, the patient presented with acute renal failure caused by an acute relapse of vasculitis. Mycophenolate mofetil (MMF) is a potent immunosuppressive drug that recently has been shown to be effective in the maintenance therapy of c-ANCA-positive systemic vasculitis. With the patients informed consent, we started treatment with MMF in combination with corticosteroids. Subsequently, anti-proteinase-3-titer (anti-Pr3-titer) returned to normal and renal function improved. In conclusion, MMF in combination with corticosteroids may be useful in the treatment of acute c-ANCA-positive vasculitis.

An evaluation of sirolimus in renal transplantation

Introduction: Sirolimus is a powerful antiproliferative immunosuppressive drug approved for the prevention of kidney allograft rejection. By its unique mechanism of action, sirolimus provides a multitude of clinical potential and has been used effectively in different drug combinations. Extensive experience has been gained regarding the best timing of its application, side effect profile and potential benefits and limitations compared with other immunosuppressive drugs. Areas covered: The authors evaluate the recent experience with sirolimus in kidney transplantation. Pivotal randomized controlled trials were used to provide an overview with special attention to pharmacokinetic and dynamic aspects of sirolimus, its current clinical use as well as perspectives for its future role. Expert opinion: Sirolimus enriches the possibilities of immunosuppressive therapies after renal transplantation. Beneficial effects toward kidney function by allowing CNI sparing, lower incidence of malignancies and less viral infections have been suggested. Sirolimus should be used cautiously in de novo patients for reasons of wound healing. An early conversion to a sirolimus-based CNI-free regimen has shown promising results, whereas late conversion is more challenging. Finally, sirolimus-associated side effects are causing tolerability concerns and frequent discontinuations. Future research should aim to better define the therapeutic window and those patients most likely to benefit.

Volume matters: CT‐based renal cortex volume measurement in the evaluation of living kidney donors

Currently, no international standard for the pre‐transplant evaluation of living donor renal function exists. Following a standardized questionnaire on current practice in all Eurotransplant (ET) centers, we compared a new CT‐based technique to measure renal cortex volume with our standard of DTPA‐clearance combined with MAG3‐scintigraphy (DTPA × MAG3) and with creatinine‐based methods in 167 consecutive living kidney donors. Most ET centers use creatinine‐clearance (64%) to measure total renal function and radioistopic methods (82%) to assess split renal function. Before transplantation, CT‐measured total cortex volume (r = 0.67; P < 0.001) and estimated GFR using the Cockcroft‐Gault formula [eGFR(CG)] (r = 0.55; P < 0.001) showed the strongest correlation with DTPA‐clearance. In contrast, the correlation between DTPA‐clearance and creatinine clearance was weak (r = 0.21; P = 0.02). A strong correlation was observed between CT‐measured split cortex volume and MAG3‐measured split renal function (r = 0.93; P < 0.001). A strong correlation was also found between pre‐transplant split renal function assessed by eGFR(CG) together with cortex volume measurement and post‐transplant eGFR(CG) of both, the donor (r = 0.83; P < 0.001) and the recipient (r = 0.75; P < 0.001). In conclusion CT‐based assessment of renal cortex volume bears the potential to substitute existing methods to assess pre‐transplant living donor split renal function.

Pretransplant virtual PRA and long-term outcomes of kidney transplant recipients

Virtual panel‐reactive antibodies (vPRA) have been implemented to gauge sensitization worldwide. It is unclear how it associates with long‐term outcomes, and its correlation with peak (pPRA) or actual (aPRA) has not been studied. We retrospectively reviewed data from 18‐ to 65‐year‐old kidney‐only transplant patients during 1.1.1996–31.7.2011 in our center. PRAs were calculated based on solid‐phase techniques. Of the 726 qualified cases, regardless of the PRA type, sensitized patients (PRA > 5%) had more females and previous transplant. Highly sensitized (HS, PRA > 50%) had longer waiting time, lower transplant rate, less living donor, more delayed graft function, and acute rejection. The conformity between vPRA and pPRA in HS was 75%, 57% between pPRA and aPRA. Forty‐three percent (61/142) patients whose pPRA was >5% had no detectable aPRA and maintained similar outcomes as sensitized patients. Multivariate analysis showed consistently lower death‐censored graft survival in HS defined by vPRA [HR 2.086 (95% CI 1.078–4.037), P < 0.05] and pPRA [HR 2.139 (95% CI 1.024–4.487), P < 0.05]. Both vPRA and pPRA provided reliable way estimating sensitization and predicting long‐term graft survival, while aPRA might underestimate true sensitization. vPRA might be the most objective parameter to gauge sensitization.

Dynamics and epitope specificity of anti-human leukocyte antibodies following renal allograft nephrectomy

BACKGROUND A considerable proportion of patients awaiting kidney transplantation is immunized by previous transplantation(s). We investigated how allograft nephrectomy (Nx) and withdrawal of maintenance immunosuppression (WD-MIS) in patients with a failed renal allograft contribute to allosensitization. METHODS HLA antibodies (HLAabs) were analyzed before and after Nx and/or WD-MIS using a single antigen bead assay. Patients were grouped as follows: (A) Nx and concomitant WD-MIS (n = 28), (B) Nx (n = 14) and (C) WD-MIS (n = 12). In a subgroup of patients, the epitope specificity of HLAabs was determined by adsorption and elution of sera with recombinant single HLA allele-expressing cell lines. RESULTS Following Nx and/or WD-MIS, HLAabs were detectable in 100, 100 and 92% of patients in Groups A, B and C, respectively. In patients of all groups, de novo donor-specific HLAabs (DSAs) were found. After Nx, an increase in the breadth [percent panel reactive antibody (%PRA)] and mean fluorescence intensity of class I HLAabs was predominant. In contrast, an increase of class II HLAabs prevailed following WD-MIS. Experimental analysis of the epitope specificities revealed that 64% of the class I HLAabs classically denoted as non-DSA were donor epitope-specific HLAabs (DESA). CONCLUSIONS Both Nx and WD-MIS contribute to alloimmunization with differing patterns concerning class I and II HLAabs. Nx preferentially increased class I HLAabs and most of the observed class I HLAabs were DESA. Considering that class I, but not class II, HLA molecules are constitutively expressed, our results support the hypothesis that the increase of HLAabs following Nx might have been caused by removal of the adsorbing donor tissue (sponge hypothesis).