Opas Traitanon

Pharmacokinetics of mycophenolic acid in severe lupus nephritis

Mycophenolic acid (MPA) is an effective treatment for active lupus nephritis despite its variable efficacy in different ethnic groups. Here we tested whether pharmacokinetic monitoring may help to optimize dosing of MPA in an Asian population. Patients with biopsy-proven class III or IV lupus nephritis (ISN/RPS category) were treated with mycophenolate mofetil or enteric-coated mycophenolate sodium. One month after initiating treatment we measured plasma MPA levels in eight samples taken over a 12-h period after drug administration. The mean area under the time-dependent curve for MPA of responding patients was significantly higher than those not responding. Successful treatment was seen in patients with areas >45 mg h/l. The dosage of the drug was not related to MPA pharmacokinetics. In the mycophenolate mofetil group, however, MPA-area under the curve was positively, and significantly, correlated with trough or 1 h after dose concentrations and associated with a therapeutic response. Thus, our study shows that MPA pharmacokinetics were positively correlated with therapeutic responses of mycophenolate, suggesting that controlling the concentrations may improve its therapeutic efficacy in lupus nephritis. As the absorption and pharmacokinetic peak of enteric-coated tablets is slower, it is important to take different formulations into account when determining optimal MPA concentrations.

Differential Effects of Calcineurin and Mammalian Target of Rapamycin Inhibitors on Alloreactive Th1, Th17, and Regulatory T Cells.

Background Previously, we had reported the role of tacrolimus (TAC) versus sirolimus (SRL) on the generation of regulatory T cells (Tregs) in primary MLR assays with SRL, demonstrating a uniquely supportive effect. However, the mechanisms associated with their actions on alloreactive human T cells are not fully understood. Therefore, we tested whether TAC and SRL differentially affect already alloactivated human CD4+ T-cell subsets. Methods Alloreactive CD4+CD45RA−/CD45RO+ T cells generated in 9-day MLR were cocultured with anti-CD3 and autologous antigen presenting cells plus interleukin (IL)-2 in presence of TAC, SRL, or both, and the Tregs generated after another 5 to 6 days were phenotypically, molecularly, and functionally characterized. Results Tacrolimus significantly and SRL modestly inhibited interferon (IFN)-&ggr; (Th1) and IL-17 (Th17)–producing cells. At clinical therapeutic concentrations, SRL, however, significantly increased forkhead/winged helix transcription factor P3 (FOXP3+) Tregs, whereas TAC inhibited this T-cell population dose dependently and significantly. When used in combination, TAC and SRL had additive effects on inhibition of IFN-&ggr;– and IL-17–producing cells. This was in contrast to the ability of SRL to reverse TAC-mediated inhibition of FOXP3-expressing cells. Proinflammatory cytokines (IL-1&bgr;, IL-6, and tumor necrosis factor-&agr;) added to cultures caused significant decrease in FOXP3+ Tregs that was again reversed by SRL. Sirolimus-derived Tregs were phenotypically normal, anergic to allostimulation, and suppressed proliferation of allogeneic effector T-cells. Conclusions Thus, although TAC inhibits all alloreactive T cells, SRL promotes the differentiation and expansion of donor-specific Tregs without secondary reprogramming to IFN-&ggr;+FOXP3+ and IL-17+FOXP3+ Treg subsets. These results, although performed in an artificial in vitro model, add clinically applicable information on how these agents affect T-cell subpopulations.

Cellular and molecular immune profiles in renal transplant recipients after conversion from tacrolimus to sirolimus

Tacrolimus and Sirolimus are commonly used maintenance immunesuppressants in kidney transplantation. Since their effects on immune cells and allograft molecular profiles have not been elucidated, we characterized the effects of Tacrolimus to Sirolimus conversion on frequency and function of T cells, and on graft molecular profiles. Samples from renal transplant patients in a randomized trial of 18 patients with late Sirolimus conversion and 12 on Tacrolimus maintenance were utilized. Peripheral blood was collected at 0, 6, 12 and 24-months post-randomization with T cell subpopulations analyzed by flow cytometry and T cell alloreactivity tested by IFN-γ ELISPOT. Graft biopsy samples obtained 24-months post-randomization were used for gene expression analysis. Sirolimus conversion led to an increase in CD4+25+++Foxp3+ regulatory T cells. While Tacrolimus-maintained patients showed a decrease in indirect alloreactivity over time post-transplant, Sirolimus conversion increased indirect alloreactive T cell frequencies compared to Tacrolimus-maintained patients. No histological differences were found in graft biopsies, but molecular profiles showed activation of the antigen presentation, IL-12 signaling, oxidative stress, macrophage-derived production pathways, and increased inflammatory and immune response in Sirolimus-converted patients. Thus, chronic immune alterations are induced after Sirolimus conversion. Despite the molecular profile being favorable to calcineurin inhibitor-based regimen, there was no impact in renal function over 30 months of follow-up.

Differential Effects of Tacrolimus versus Sirolimus on the Proliferation, Activation and Differentiation of Human B Cells

The direct effect of immunosuppressive drugs calcineurin inhibitor (Tacrolimus, TAC) and mTOR inhibitor (Sirolimus, SRL) on B cell activation, differentiation and proliferation is not well documented. Purified human B cells from healthy volunteers were stimulated through the B Cell Receptor with Anti-IgM + anti-CD40 + IL21 in the absence / presence of TAC or SRL. A variety of parameters of B cell activity including activation, differentiation, cytokine productions and proliferation were monitored by flow cytometry. SRL at clinically relevant concentrations (6 ng/ml) profoundly inhibited CD19+ B cell proliferation compared to controls whereas TAC at similar concentrations had a minimal effect. CD27+ memory B cells were affected more by SRL than naïve CD27- B cells. SRL effectively blocked B cell differentiation into plasma cells (CD19+CD138+ and Blimp1+/Pax5low cells) even at low dose (2 ng/ml), and totally eliminated them at 6 ng/ml. SRL decreased absolute B cell counts, but the residual responding cells acquired an activated phenotype (CD25+/CD69+) and increased the expression of HLA-DR. SRL-treated stimulated B cells on a per cell basis were able to enhance the proliferation of allogeneic CD4+CD25− T cells and induce a shift toward the Th1 phenotype. Thus, SRL and TAC have different effects on B lymphocytes. These data may provide insights into the clinical use of these two agents in recipients of solid organ transplants.

A multicentre, randomised controlled study of enteric-coated mycophenolate sodium for the treatment of relapsed or resistant proliferative lupus nephritis: an Asian experience

Objective The optimal treatment of relapse or resistant lupus nephritis (LN) is still unclear. Mycophenolate might be an alternative therapy to avoid toxicities of cyclophosphamide (CYC). This study was aimed to compare enteric-coated mycophenolate sodium (EC-MPS) versus intravenous CYC as an induction therapy. Methods The study was a 12-month period of multicentre, open-labelled randomised controlled trial. Fifty-nine patients who had relapsed (36%) or who were resistant to previous CYC treatment (64%) and all who were biopsy-proven class III/IV, were randomised into CYC (n=32) and EC-MPS groups (n=27). The CYC group received intravenous CYC 0.5–1 g/m2 monthly and the EC-MPS group was treated with EC-MPS 1440 mg/day for first 6 months. After induction therapy, both groups received EC-MPS 720 mg/day until the end of study at 12 months. Results The study was prematurely terminated due to high rate of serious adverse events in CYC arm. Death and serious infections were observed more in the CYC group (15.6% in CYC and 3.5% in EC-MPS; p=0.04). The early discontinuation rates, mainly from serious infections, were significantly higher in CYC group (percentage differences of 16.9; 95% CI 1.3 to 32.4). At the 12th month, both arms were comparable in terms of complete and partial remission rates (68% CYC and 71% EC-MPS) and times to remission (96 days CYC and 97 days EC-MPS). Composites of unfavourable outcomes (death, doubling of serum creatinine, non-remission and intolerance to treatment) were 46.9% and 37% in CYC and EC-MPS (risk difference=9.84; p=0.44). Conclusions EC-MPS may have comparable efficacy, but was better tolerated than CYC. EC-MPS should be an alternative choice of treatment for difficult-to-treat LN, particularly in CYC-experienced LN patients. Due to an early termination of the study, further clinical implementation could be cautiously used. Trial registration number Clinicaltrials.gov ID#NCT01015456.

Chimerism and Tolerance Induction in Kidney Transplantation

Chimerism is a state in which bone marrow hematopoietic stem cells from two genetically different animals coexist. To date, the approach has been used successfully to induce the state of immunologic tolerance in the animal models and is now being evaluated in clinical trials of both HLA-identical and HLA-mismatched living-donor kidney transplant recipients in some transplant centers with varying degrees of success. Although the results are promising, the current conditioning regimens are not optimal and longer-term follow up and multicenter studies are needed to ensure the efficacy and safety of the procedures.

Indications for Renal Transplantation: Evaluation of Transplant Candidates

Abstract Kidney transplantation is currently the treatment of choice in patients with end-stage kidney disease and should be considered in most patients if there are no contraindications. Unfortunately, the demand for kidney transplants surpasses the supply of available organs, causing an increase in the number of patients on the waiting list, increase in the waiting time for a cadaveric kidney transplant and increase in the proportion of elderly patients undergoing kidney transplant. All transplant candidates should undergo pretransplant evaluation based on their underlying diseases and comorbidities to ensure the successful transplant outcome. Special attention should be given to patients with high cardiovascular risk factors, high risk or past history of malignancy, patients with active or occult infections and patients with specific underlying renal or systemic diseases.