Exploring new immunosuppressive strategies inducing donor-specific hyporesponsiveness is an important challenge in transplantation. For this purpose, a careful immune monitoring and graft histology assessment is mandatory. Here, we report the results of a pilot study conducted in twenty renal transplant recipients, analyzing the immunomodulatory effects of a protocol based on induction therapy with rabbit anti-thymocyte globulin low doses, sirolimus, and mofetil mycophenolate. Evolution of donor-specific cellular and humoral alloimmune response, peripheral blood lymphocyte subsets and apoptosis was evaluated. Six-month protocol biopsies were performed to assess histological lesions and presence of FOXP3+ regulatory T cells (Tregs) in interstitial infiltrates. After transplantation, there was an early and transient apoptotic effect, mainly within the CD8+HLADR+ T cells, combined with a sustained enhancement of CD4+CD25+high lymphocytes in peripheral blood. The incidence of acute rejection was 35%, all steroid sensitive. Importantly, only pretransplant donor-specific cellular alloreactivity could discriminate patients at risk to develop acute rejection. Two thirds of the patients became donor-specific hyporesponders at 6 and 24 mo, and the achievement of this immunologic state was not abrogated by prior acute rejection episodes. Remarkably, donor-specific hyporesponders had the better renal function and less chronic renal damage. Donor-specific hyporesponsiveness was inhibited by depleting CD4+CD25+high T cells, which showed donor-Ag specificity. FOXP3+CD4+CD25+high Tregs both in peripheral blood and in renal infiltrates were higher in donor-specific hyporesponders than in nonhyporesponders, suggesting that the recruitment of Tregs in the allograft plays an important role for renal acceptance. In conclusion, reaching donor-specific hyporesponsiveness is feasible after renal transplantation and associated with Treg recruitment in the graft.

A population pharmacokinetics analysis was performed after intravenous ganciclovir and oral valganciclovir in solid organ transplant patients with cytomegalovirus. Patients received ganciclovir at 5 mg/kg of body weight (5 days) and then 900 mg of valganciclovir (16 days), both twice daily with dose adjustment for renal function. A total of 382 serum concentrations from days 5 and 15 were analyzed with NONMEM VI. Renal function given by creatinine clearance (CL CR ) was the most influential covariate in CL. The final pharmacokinetic parameters were as follows: ganciclovir clearance (CL) was 7.49 ⅐ (CL CR /57) liter/h (57 was the mean population value of CL CR ); the central and peripheral distribution volumes were 31.9 liters and 32.0 liters, respectively; intercompartmental clearance was 10.2 liter/h; the first-order absorption rate constant was 0.895 h ؊1 ; bioavailability was 0.825; and lag time was 0.382 h. The CL CR was the best predictor of CL, making dose adjustment by this covariate important to achieve the most efficacious ganciclovir exposure.

Treatment of solid-organ transplant (SOT) patients with ganciclovir (GCV)-valganciclovir (VGCV

Several factors contribute to mycophenolic acid (MPA) between-patient variability. Here we characterize the metabolic pathways of MPA and quantify the effect of combining genetic polymorphism of multidrug-resistant-associated protein-2, demographics, biochemical covariates, co-medication (cyclosporine (CsA) vs. macrolides), and renal function on MPA, 7-O-MPA-glucuronide (MPAG), and acyl-glucuronide (AcMPAG) disposition, in renal transplant recipients, after mycophenolate mofetil. Complete pharmacokinetic profiles from 56 patients (five occasions) were analyzed. Enterohepatic circulation was modeled by transport of MPAG to the absorption site. This transport significantly decreased with increasing CsA trough concentrations (CtroughCsA). MPAG and AcMPAG plasma clearances significantly decreased with renal function. No significant influence of multidrug-resistant-associated protein-2 C24T single-nucleotide polymorphism was found. The model adequately predicted the increase in MPAG/AcMPAG exposures in CsA and macrolide patients with decreased renal function. This resulted in higher MPA exposures in macrolide patients versus CsA patients, and increased MPA exposures with renal function from 25 to 10 ml/min, in macrolide patients, owing to enhanced MPAG enterohepatic circulation. Lower-percentage enterohepatic circulation occurred with higher CtroughCsA and renal function values. The lack of MPA protein-binding modeling did not permit evaluation of the impact of renal function and CtroughCsA on MPA exposures in CsA patients. Thus, dose tailoring of covariates is recommended for target MPA exposure.

Kidney grafts from suboptimal donors are more likely to suffer the nephrotoxic side‐effects of cyclosporine than kidneys from standard donors. In an attempt to avoid the use of cyclosporine, we carried out a prospective study in low‐immunological risk recipients of suboptimal kidneys, using an immunosuppressive protocol combining Thymoglobuline in induction with a bi‐therapy of mycophenolate mofetil (MMF) and steroids. Patients with panel reactive antibodies (PRA) <50% receiving a frist renal transplant from a suboptimal donor (age, 50, non heart beating, arterial hypertension, or actue renal failure) or a kidney at risk of delayed graft function (DGF) because of a prolonged cold ischaemia time (CIT) of 24 h or more, were eligible for this trial. Between September 1996 and December 1999, 30 patients were enrolled for the trial and treated with MMF 2 g orally, pre‐operatively, and 3 g daily, post‐operatively; Thymoglobuline 2 mg/kg IV preoperatively, 1.5 mg/kg IV the next day, and for doses of 1 mg/kg IV given on alternate days; and prednisolone 0.25 mg/kg per day, reduced progressively from the end of the first month to 0.1 mg/kg per day by 3 months post‐transplant. Cyclosporine was added only if rejection grade II or higher, or a reduction in MMF below 1 g daily, occurred. Ten patients (30%) suffered from DGF, and one kidney suffered primary non function. Seven patients (24%) suffered acute rejection (six were biopsy proven, 3 grade 1 and 3 grade II). MMF dosage was reduced in 28 patients because of adverse events, and calcineurin inhibitors were introduced in 16 patients. There were 14 episodes of opportunistic infection (cytomegalovirus (CMV 10), Herpes zoster 2, Listeria mono‐cytogenes 1, Pseudomonas aeuruginosa 1), and 7 malifnancies (skin 2, thyroid 1, lung 1, Kaposi's sarcoma 2, post‐transplantation lymphoproliferative disorder 1). Mean serum creatinine was 178, 199, 213, and 218 μmol/1 at 1, 2, 3 and 5 years after transplantation, respectively. Actuarial patient and graft (after censoring for death) survival was 94% and 83% after 1 year and 79% and 65% after 5 years, respectively. These results show that with the combination of MMF, Thymoglobuline and steroids the use of cyclosporine can be delayed, and in a few cases completely avoided with good efficacy in terms of prevention of rejection and recovery of renal function. Regardless of acceptable patient and graft survival, side‐effects of MMF at the doses used in this protocol were common and led to overimmunosuppression in the long‐term. Starting MMF at low dose, MPA monitoring and probably CMV prophylaxis may improve the results of this regimen.

One strategy to minimize nephrotoxicity in maintenance immunosuppression in renal transplantation is reduction of cyclosporine (CsA) with addition of mycophenolate mofetil (MMF). This approach seems safe, but concern exists about whether it yields adequate immunosuppression in the long term. Thus, we investigated the pharmacodynamic response to CsA in stable renal allografts treated with standard CsA (n = 17, CsA-C0h> or = 125 ng/mL) and low CsA plus MMF (n = 18 CsA-C0h <100 ng/mL). Patients treated with MMF without CsA (n = 13) and healthy subjects (n = 7) were used as controls. We observed that inhibition of calcineurin (CN) activity in peripheral blood mononuclear cells (PBMC), as well as interleukin (IL)-2 and interferon (IFN)-gamma production were similar in Standard-CsA and Low-CsA+MMF groups. Moreover, addition of MMF to a low CsA dose regime improved the correlation between CsA-C2h and both CN activity and IL-2 production. Thus, our results suggest that MMF could be synergistic with the pharmacodynamic effect of low CsA in maintenance immunosuppression.

SummaryThe function of the efflux pump P-glycoprotein (Pgp) and ABCB1 single nucleotide polymorphisms (SNPs) should be considered as important tools to deepen knowledge of drug nephrotoxicity and disposition mechanisms. The aim of this study is to investigate the association of C3435T, G2677T, C1236T, and T129C ABCB1 SNPs with Pgp activity and exposure to different immunosuppressive drugs in renal transplant patients. Patients included in the Symphony Pharmacogenomic substudy were genotyped for ABCB1 SNPs. According to the design, patients were randomized into four immunosuppressive regimens: low and standard dose of cyclosporine (n = 30), tacrolimus (n = 13), and sirolimus (n = 23) concomitantly with mycophenolate and steroids. Pgp activity was evaluated in PBMC using the Rhodamine 123 efflux assay. TT carrier patients on C3435T, G2677T, and C1236T SNPs (Pgp-low pumpers) showed lower Pgp activity than noncarriers. Pgp-high pumpers treated with cyclosporine showed lower values of Pgp function than macrolides. There was a negative correlation between cyclosporine AUC and Pgp activity at 3 months. Results did not show any correlation between tacrolimus and sirolimus AUC and Pgp activity at 3 months. We found an important role of the ABCB1 SNPs Pgp function in CD3 + peripheral blood lymphocytes from renal transplant recipients. Pgp activity was influenced by cyclosporine but not macrolides exposure.

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