Willem Weimar

Genetic polymorphisms of the CYP3A4, CYP3A5, and MDR‐1 genes and pharmacokinetics of the calcineurin inhibitors cyclosporine and tacrolimus

The calcineurin inhibitors cyclosporine (INN, ciclosporin) and tacrolimus have a narrow therapeutic index and show considerable interindividual variability in their pharmacokinetics. The low oral bioavailability of calcineurin inhibitors is thought to result from the actions of the metabolizing enzymes cytochrome P450 (CYP) 3A4 and CYP3A5 and the multidrug efflux pump P‐glycoprotein, encoded by MDR‐1.

Cyclosporine interacts with mycophenolic acid by inhibiting the multidrug resistance-associated protein 2

In mycophenolate mofetil (MMF)‐treated organ transplant recipients, lower mycophenolic acid (MPA) plasma concentrations have been found in cyclosporine (CsA) compared with tacrolimus (Tac)‐based immunosuppressive regimens. We previously demonstrated that CsA decreases exposure to MPA and increases exposure to its metabolite MPA‐glucuronide (MPAG), possibly by interfering with the biliary excretion of MPAG. To elucidate the role of the multidrug resistance‐associated protein (Mrp)‐2 in the interaction between MMF and CsA, we treated three groups of 10 Mrp2‐deficient rats (TR− rat) for 6 days with either vehicle, CsA (8 mg/kg) or Tac (4 mg/kg) by oral gavage. Hereafter, co‐administration with MMF (20 mg/kg) was started in all groups and continued through day 14. The 24‐h MPA/MPAG area under the concentration‐time curve (AUC) was determined after single (day 7) and multiple MMF doses (day 14). On both study days, there were no significant differences in the mean MPA and MPAG AUC between CsA and Tac‐treated animals. We conclude that the pharmacokinetics of MMF are comparable in Mrp2‐deficient rats receiving either CsA or Tac as co‐medication. This finding suggests that CsA‐mediated inhibition of the biliary excretion of MPAG by the Mrp2 transporter is the mechanism responsible for the interaction between CsA and MMF.

Differential effect of calcineurin inhibitors, anti-CD25 antibodies and rapamycin on the induction of FOXP3 in human T cells.

Background. The transcription factor FOXP3 has been identified as the molecule associated with the regulatory function of CD25+ T cells. Methods. To understand the biology of FOXP3+ T cells in allogeneic reactions, we measured FOXP3 mRNA expression levels in allostimulated CD25 bright+ cells and CD25 intermediate( int)/- cells and in peripheral blood mononuclear cells (PBMC). The effect of immunosuppressive drugs on FOXP3 expression was studied in mixed lymphocyte reactions (MLR) in the presence and absence of calcineurin inhibitors (CNI), &agr;CD25 mAb, and Rapamycin (Rapa), and analyzed in biopsies from cardiac allograft recipients during acute rejection by quantitative (Q)-PCR. Results. FOXP3 mRNA expression was restricted to the CD25 bright+ population that inhibited the proliferation of allostimulated CD25 int/- cells. In the MLR FOXP3 was readily induced after allostimulation. Kinetic examination of the MLR showed a 10–20-fold higher FOXP3 mRNA expression level after 5 days of culture. The CNI Cyclosporin and Tacrolimus, and &agr;CD25 mAb inhibited in vitro induced FOXP3 gene transcription (range 70%–90%), whereas Rapa did not inhibit the induction. After clinical heart transplantation the highest FOXP3 mRNA expression levels were measured in biopsies during acute rejection (P=0.03). Conclusions. The high FOXP3 mRNA levels during allogeneic responses in vivo and in vitro suggests that regulatory activities of CD25 bright+ T cells or the generation of these cells is an intrinsic part of activation. CNI and &agr;CD25 mAb in contrast to Rapa, did interfere with this immunosuppressive counter-mechanism and as a result might have an inhibitory effect to tolerance induction after transplantation.

Effect of One-HLA-DR-Antigen–Matched and Completely HLA-DR–Mismatched Blood Transfusions on Survival of Heart and Kidney Allografts

Blood transfusions can influence the survival of organ allografts favorably, in spite of the danger of sensitization. We investigated the influence of HLA compatibility between blood donors and transfusion recipients on the production of HLA antibodies and on graft survival. Among recipients of transfusions who shared one HLA-DR antigen with their respective donors, antibodies developed in 6 of 28 who had received one transfusion, in 2 of 16 who had received three transfusions, and in 4 of 24 who had undergone renal transplantation. Among recipients who were mismatched with their donors for both HLA-DR antigens, the rate of sensitization was significantly higher in all three of these groups (18 of 30, P = 0.02; 12 of 16, P = 0.0007; and 12 of 22, P = 0.001). The survival of kidney allografts among graft recipients who were given transfusions and shared one HLA-DR antigen with their blood donors (81 percent at five years) was significantly higher than among recipients who were given transfusions and were mismatched for both HLA-DR antigens (57 percent; P = 0.02) or among recipients who were not given transfusions (45 percent; P = 0.001). There was no difference in graft survival between patients who received transfusions mismatched for two HLA-DR antigens and those who were not given transfusions. We conclude that allograft survival can be improved by pretransplantation blood transfusion when the transfusion recipients share at least one HLA-DR antigen with their donors. In view of the increased rate of sensitization and the lack of improvement in graft survival, the transfusion of blood mismatched for two HLA-DR antigens appears to be contraindicated in candidates for transplantation.

Three‐Year Efficacy and Safety Results from a Study of Everolimus Versus Mycophenolate Mofetil in de novo Renal Transplant Patients

Everolimus 1.5 or 3 mg/day was compared with mycophenolate mofetil (MMF) 2 g/day in a randomized, multicenter 36‐month trial in de novo renal allograft recipients (n = 588) receiving cyclosporine microemulsion (CsA) and corticosteroids. The study was double‐blind until all patients had completed 12 months, then open‐label. By 36 months, graft loss occurred in 7.2, 16.7 and 10.7% of patients in the everolimus 1.5, 3 mg/day, and MMF groups, respectively (p = 0.0048 for everolimus 1.5 mg/day vs. 3 mg/day); efficacy failure (biopsy‐proven acute rejection (BPAR), graft loss, death or lost to follow‐up) occurred in 33.0, 38.9 and 37.2% of patients (p = 0.455 overall), respectively. Mortality and incidence of BPAR were comparable in all groups. Creatinine values were higher in everolimus groups, requiring a protocol amendment that recommended lower CsA exposure. Diarrhea, lymphocele, peripheral edema and hyperlipidemia were more common among everolimus‐treated patients, whereas viral infections, particularly cytomegalovirus infection, increased in the MMF group. Overall safety and tolerability were better with MMF and everolimus 1.5 mg/day than with everolimus 3 mg/day. In conclusion, at 36 months, an immunosuppressive regimen containing everolimus 1.5 mg/day had equivalent patient, and graft survival and rejection rates compared with MMF in de novo renal transplant recipients, whereas everolimus 3 mg/day had inferior graft survival. Renal dysfunction in everolimus cohorts necessitates close monitoring.

Comparison of laparoscopic and mini incision open donor nephrectomy: single blind, randomised controlled clinical trial.

Abstract Objectives To determine the best approach for live donor nephrectomy to minimise discomfort to the donor and to provide good graft function. Design Single blind, randomised controlled trial. Setting Two university medical centres, the Netherlands. Participants 100 living kidney donors. Interventions Participants were randomly assigned to either laparoscopic donor nephrectomy or to mini incision muscle splitting open donor nephrectomy. Main outcome measures The primary outcome was physical fatigue using the multidimensional fatigue inventory 20 (MFI-20). Secondary outcomes were physical function using the SF-36, hospital stay after surgery, pain, operating times, recipient graft function, and graft survival. Results Conversions did not occur. Compared with mini incision open donor nephrectomy, laparoscopic donor nephrectomy resulted in longer skin to skin time (median 221 v 164 minutes, P < 0.001), longer warm ischaemia time (6 v 3 minutes, P < 0.001), less blood loss (100 v 240 ml, P < 0.001), and a similar number of complications (intraoperatively 12% v 6%, P = 0.49, postoperatively both 6%). After laparoscopic nephrectomy, donors required less morphine (16 v 25 mg, P = 0.005) and shorter hospital stay (3 v 4 days, P = 0.003). During one years follow-up mean physical fatigue was less (difference - 1.3, 95% confidence interval - 2.4 to - 0.1) and physical function was better (difference 6.2, 2.0 to 10.3) after laparoscopic nephrectomy. Function of the graft and graft survival rate of the recipient at one year censored for death did not differ (100% after laparoscopic nephrectomy and 98% after open nephrectomy). Conclusions Laparoscopic donor nephrectomy results in a better quality of life compared with mini incision open donor nephrectomy but equal safety and graft function.

Population pharmacokinetics of cyclosporine in kidney and heart transplant recipients and the influence of ethnicity and genetic polymorphisms in the MDR-1, CYP3A4, and CYP3A5 genes

Our objective was to determine the relationship between single nucleotide polymorphisms (SNPs) in the multidrug resistance 1 (MDR‐1) gene and the cytochrome P450 (CYP) genes CYP3A4 and CYP3A5 and the pharmacokinetics of cyclosporine (INN, ciclosporin).

Everolimus (certican) 12-month safety and efficacy versus mycophenolate mofetil in de novo renal transplant recipients

Background. Everolimus is a proliferation inhibitor designed to target chronic rejection, including prevention of acute rejection. Everolimus blocks growth factor-mediated transduction signals, preventing organ rejection by a mechanism different than that of calcineurin inhibitors and of mycophenolate mofetil (MMF). Methods. Everolimus (1.5 mg or 3 mg daily) was compared with MMF (2 g daily) in a randomized, multicenter, multinational, 12-month double-blind, double-dummy and 2-year open-label, phase 3 trial in de novo renal allograft recipients (n=588) who also received cyclosporine and corticosteroids as part of a triple immunosuppressive regimen. Results. At 12 months, there were no statistically significant differences between doses of 1.5 and 3 mg/day everolimus and MMF (2 g/day) in incidence of biopsy-proven acute rejection (23.2%, 19.7%, and 24.0%, respectively), graft loss (4.6%, 10.6%, and 9.2%), or death (5.2%, 4.0%, and 2.6%), respectively. Everolimus 1.5 mg/day and MMF were generally equally well tolerated. Both were better tolerated than everolimus 3 mg/day. The incidence of cytomegalovirus infection was significantly lower in patients receiving either 1.5 or 3 mg/day everolimus than in those receiving MMF (5.2% and 7.6% vs. 19.4%, respectively) (P=.001). Conclusions. Everolimus is effective in preventing acute rejection and graft loss in de novo renal allograft recipients receiving a triple immunosuppressive regimen. Prevention of acute rejection, along with reduction in cytomegalovirus infection, addresses two factors known to contribute to chronic rejection in such patients.

Withdrawal of Cyclosporine or Prednisone Six Months after Kidney Transplantation in Patients on Triple Drug Therapy: A Randomized, Prospective, Multicenter Study

Uncertainty exists regarding the necessity of continuing triple therapy consisting of mycophenolate mofetil (MMF), cyclosporine (CsA), and prednisone (Pred) after kidney transplantation (RTx). At 6 mo after RTx, 212 patients were randomized to stop CsA (n = 63), stop Pred (n = 76), or continue triple drug therapy (n = 73). The MMF dose was 1000 mg twice daily, target CsA trough levels were 150 ng/ml, and Pred dose was 0.10 mg/kg per d. Follow-up was until 24 mo after RTx. Biopsy-proven acute rejection occurred in 14 (22%) of 63 patients after CsA withdrawal compared with 3 (4%) of 76 in the Pred withdrawal group (P = 0.001) and 1 (1.4%) of 73 in the control group (P = 0.0001). Biopsy-proven chronic rejection was present in one patient in the control group, in nine patients after CsA withdrawal (P = 0.006 versus control group); and in four patients after discontinuation of Pred (NS). Graft loss occurred in two versus one patient after CsA or Pred withdrawal, respectively, and in two patients in the control group (NS). Patients who successfully withdrew CsA had a significantly lower serum creatinine during follow-up. Pred withdrawal resulted in a reduction in mean arterial pressure, and the total cholesterol/HDL ratio increased. In conclusion, rapid CsA withdrawal at 6 mo after RTx results in a significantly increased incidence of biopsy-proven acute and chronic rejection. Pred withdrawal was safe and resulted in a reduction in mean arterial pressure. However, patient and graft survival and renal function 2 yr after RTx were not different among groups.

The Dutch national living donor kidney exchange program

The wait time for deceased‐donor kidney transplantation has increased to 4–5 years in the Netherlands. Strategies to expand the donor pool include a living donor kidney exchange program. This makes it possible that patients who cannot directly receive a kidney from their intended living donor, due to ABO blood type incompatibility or a positive cross match, exchange donors in order to receive a compatible kidney. All Dutch kidney transplantation centers agreed on a common protocol. An independent organization is responsible for the allocation, cross matches are centrally performed and exchange takes place on an anonymous basis. Donors travel to the recipient centers. Surgical procedures are scheduled simultaneously. Sixty pairs participated within 1 year. For 9 of 29 ABO blood type incompatible and 17 of 31 cross match positive combinations, a compatible pair was found. Five times a cross match positive couple was matched to a blood type incompatible one, where the recipients were of blood type O. The living donor kidney exchange program is a successful approach that does not harm any of the candidates on the deceased donor kidney waitlist. For optimal results, both ABO blood type incompatible and cross match positive pairs should participate.