Individualizing calcineurin inhibitor therapy in renal transplantation--current limitations and perspectives

Comparison of tacrolimus with or without prednisone therapy in primary membranous nephropathy: a retrospective clinical study

Previous studies showed tacrolimus monotherapy and dual therapy with tacrolimus and prednisone as effective treatment modalities in managing membranous nephropathy. However, few studies have compared these therapeutic regimens. The patients were divided into two groups based on the treatment regimen: (1) tacrolimus and prednisone dual therapy (T + P group, n = 67) treatment group; and (2) tacrolimus monotherapy (T group, n = 65) or the control group. Propensity matching method and subgroup analysis to eliminate the bias in the relationship between the treatment regimen and the outcomes. The mean remission times were 20.33 ± 2.75 weeks at T group and 9.50 ± 1.81 weeks at T + P group. The T group had a remission rates of 73.33, 76.66 and 66.66% at 12weeks, 24weeks and 48weeks, while the T + P group had a remission rate of 81.66, 86.66, 91.66%; At the follow-up of 48 weeks, the relapse rate for the T group was 21.66%, and that for the T + P group was 5%. The anti-PLA2R ab is positive and therapy may be the independent risk factors for predicting remission. Tacrolimus and low-dose prednisone dual therapy is efficacious in managing MN and lowers the recurrence rate in clinical practice.

Conversion from Twice-Daily Prograf® to Once-Daily Advagraf® in Multi-ethnic Asian Adult Renal Transplant Recipients With or Without Concomitant Use of Diltiazem: Impact of CYP3A5 and MDR1 Genetic Polymorphisms on Tacrolimus Exposure

BACKGROUND AND OBJECTIVES

Tacrolimus is the mainstay of immunosuppression in renal transplantation. Given that once-daily administration improves patient compliance, 1:1 dose conversion from twice-daily Prograf^® to once-daily Advagraf^® is recommended. Although cytochrome P450 (CYP) 3A5 and multi-drug resistance 1 (MDR1) polymorphisms influence tacrolimus concentrations, it is unknown if these impact on conversion. This study investigated the change in the pharmacokinetics of tacrolimus after conversion from Prograf^® to Advagraf^® and examined the impact of CYP3A5 and MDR1 C3435T polymorphisms on those pharmacokinetics.

METHODS

A prospective open-label pharmacokinetic study of 1:1 conversion from Prograf^® to Advagraf^® with or without diltiazem was conducted on 26 stable renal transplant recipients. Blood samples were collected over 24 h during each phase, tacrolimus concentrations were assayed, and noncompartmental pharmacokinetic analysis was performed. All participants were genotyped for CYP3A5*3 and MDR1 C3435T.

RESULTS

After conversion, without diltiazem, the area under the concentration-time curve at steady state from 0 to 24 h after dose administration (AUC_{ss, 0-24}) was significantly reduced [median 224 (range 172-366) vs. 184 (104-347) ng·h/mL, p = 0.006, n = 26]. A decrease in tacrolimus exposure (median 21%) was only evident among CYP3A5 expressors [227 (172-366) vs. 180 (104-347) ng·h/mL, p = 0.014, n = 18], not among non-expressors [215 (197-290) vs. 217 (129-281) ng·h/mL, p = 0.263, n = 8]. In contrast, among CYP3A5 expressors receiving diltiazem, AUC_{ss, 0-24} did not change significantly upon conversion [229 (170-296) vs. 221 (123-342) ng·h/mL, p = 0.575, n = 10]. An independent effect was not evident for MDR1 C3435T polymorphism.

CONCLUSION

The high prevalence of CYP3A5 polymorphism among Asians may lead to a significant reduction in tacrolimus exposure with 1:1 dose conversion of Prograf^® to Advagraf^®. These results advocate for CYP3A5 determination prior to conversion, and suggest that 1:1.25 conversion should be used for CYP3A5 expressors and 1:1 conversion for other patients.

Cyclosporin A Aggravates Calcification of Vascular Smooth Muscle Cells Under High-Glucose Conditions with a Calcifying Medium

BACKGROUND Vascular calcification (VC) progresses substantially even after kidney transplantation, and is a predictor of morbidity and mortality. However, the effect of cyclosporin A (CsA) on VC has not been reported in diabetic kidney transplant patients. In this study, we evaluated the effect of CsA on the VC of mouse vascular smooth muscle cells (VSMCs) under high glucose (HG). MATERIAL AND METHODS To demonstrate the effect of CsA (1.0 µmol/L) and HG (30 mM) in the induction of the VC of the VSMCs, we determined alkaline phosphatase (ALP) activity, microscopic morphology of calcification, the expressions of the calcification and inflammation-related genes, and the intracellular calcium concentrations in VSMCs. RESULTS Calcification was observed 14 days after exposure to a calcifying medium (sodium phosphate monobasic and dibasic mixture). On microscopic morphology, CsA alone did not induce calcification under HG conditions, but clearly increased calcification under HG with a calcifying medium. ALP activity increased under HG with CsA or a calcifying medium compared to HG conditions alone. CsA increased ALP activity under low glucose (LG, 5.5 mM) with a calcifying medium, but markedly increased under HG with a calcifying medium. CsA significantly increased the mRNA expressions of the calcification markers (core binding factor-alpha 1, bone morphologic proteins 2) as well as those of the inflammatory marker (interleukin 6), under HG with a calcifying medium. Intracellular calcium concentrations were unchanged in CsA alone but significantly increased with the presence of a calcifying medium under both LG and HG conditions. CONCLUSIONS Considering the effect of CsA on VC, the vascular adverse effects of CsA need to be verified in diabetic transplant patients in the future.

Early Conversion to Prednisolone/Everolimus as an Alternative Weaning Regimen Associates With Beneficial Renal Transplant Histology and Function: The Randomized-Controlled MECANO Trial

In renal transplantation, use of calcineurin inhibitors (CNIs) is associated with nephrotoxicity and immunosuppression with malignancies and infections. This trial aimed to minimize CNI exposure and total immunosuppression while maintaining efficacy. We performed a randomized controlled, open-label multicenter trial with early cyclosporine A (CsA) elimination. Patients started with basiliximab, prednisolone (P), mycophenolate sodium (MPS), and CsA. At 6 months, immunosuppression was tapered to P/CsA, P/MPS, or P/everolimus (EVL). Primary outcomes were renal fibrosis and inflammation. Secondary outcomes were estimated glomerular filtration rate (eGFR) and incidence of rejection at 24 months. The P/MPS arm was prematurely halted. The trial continued with P/CsA (N = 89) and P/EVL (N = 96). Interstitial fibrosis and inflammation were significantly decreased and the eGFR was significantly higher in the P/EVL arm. Cumulative rejection rates were 13% (P/EVL) and 19% (P/CsA), (p = 0.08). A post hoc analysis of HLA and donor-specific antibodies at 1 year after transplantation revealed no differences. An individualized immunosuppressive strategy of early CNI elimination to dual therapy with everolimus was associated with decreased allograft fibrosis, preserved allograft function, and good efficacy, but also with more serious adverse events and discontinuation. This can be a valuable alternative regimen in patients suffering from CNI toxicity.

NFATC1 genotypes affect acute rejection and long-term graft function in cyclosporine-treated renal transplant recipients

AIM

To investigate the effects of SNPs in the cyclophilin A/calcineurin/nuclear factor of activated T-cells (NFATs) pathway genes (PPIA, PPP3CB, PPP3R1, NFATC1 and NFATC2) on cyclosporine (CsA) efficacy in renal transplant recipients.

MATERIALS & METHODS

Seventy-six tag SNPs were detected in 155 CsA-treated renal recipients with at least a 5-year follow-up. The associations of SNPs with acute rejection, nephrotoxicity, pneumonia and estimated glomerular filtration rate post transplant were explored.

RESULTS

NFATC1 rs3894049 GC was a risk factor for acute rejection compared with CC carriers (p = 0.0005). NFATC1 rs2280055 TT carriers had a more stable estimated glomerular filtration rate level than CC (p = 0.0004).

CONCLUSION

Detecting NFATC1 polymorphisms could help predict CsA efficacy in renal transplant patients.

Exploring genetic and non-genetic risk factors for delayed graft function, acute and subclinical rejection in renal transplant recipients

AIMS

This study aimed at identifying pharmacological factors such as pharmacogenetics and drug exposure as new predictive biomarkers for delayed graft function (DGF), acute rejection (AR) and/or subclinical rejection (SCR).

METHODS

Adult renal transplant recipients (n = 361) on cyclosporine-based immunosuppression were followed for the first 6 months after transplantation. The incidence of DGF and AR were documented as well as the prevalence of SCR at 6 months in surveillance biopsies. Demographic, transplant-related factors, pharmacological and pharmacogenetic factors (ABCB1, CYP3A5, CYP3A4, CYP2C8, NR1I2, PPP3CA and PPP3CB) were analysed in a combined approach in relation to the occurrence of DGF, AR and prevalence of SCR at month 6 using a proportional odds model and time to event model.

RESULTS

Fourteen per cent of the patients experienced at least one clinical rejection episode and only DGF showed a significant effect on the time to AR. The incidence of DGF correlated with a deceased donor kidney transplant (27% vs. 0.6% of living donors). Pharmacogenetic factors were not associated with risk for DGF, AR or SCR. A deceased donor kidney and acute rejection history were the most important determinants for SCR, resulting in a 52% risk of SCR at 6 months (vs. 11% average). In a sub-analysis of the patients with AR, those treated with rejection treatment including ATG, significantly less frequent SCR was found in the 6-month biopsy (13% vs. 50%).

CONCLUSIONS

Transplant-related factors remain the most important determinants of DGF, AR and SCR. Furthermore, rejection treatment with depleting antibodies effectively prevented SCR in 6-month surveillance biopsies.

Investigation of CYP 3A5 and ABCB1 gene polymorphisms in the long-term following renal transplantation: Effects on tacrolimus exposure and kidney function

The clinical use of tacrolimus (Tac) is complicated by the large inter-individual variability in its pharmacokinetics as well as by chronic adverse effects on renal function. The main goal of this study was to evaluate the potential influence of cytochrome P450 3A5 (CYP 3A5) and ATP-binding cassette transporter B1 (ABCB1) gene polymorphisms on Tac dose requirements and dose-adjusted concentrations in different long-term periods following renal transplantation. Another aim was to investigate whether these polymorphisms affect renal function in late post-transplant period. A total of 91 renal transplant recipients were enrolled for genotyping analysis, and 53 of these entered into a pharmacokinetic-pharmacogenetic study. Allele-specific polymerase chain reaction was used for CYP 3A5 and ABCB1 polymorphism determination. Pharmacokinetic data (dose, trough concentration and dose-adjusted concentration of Tac) and renal function parameters [creatinine (Cre) clearance and serum Cre level] were analyzed in relation to patient genotype at 6, 12 and 24 months after transplantation. Also, linear regression analysis was performed to evaluate the effect of CYP 3A5 and ABCB1 genotypes on Tac exposure and renal function up to 24 months post-transplant. Individuals carrying the CYP 3A5*1/*3 genotype had higher Tac dose requirements than CYP 3A5*3/*3 carriers at 6, 12 and 24 months after renal transplantation. The results revealed that ABCB1 polymorphism did not influence Tac dose requirements independently. Regression analysis showed that CYP 3A5 influenced the Tac dose-adjusted concentration as well as renal function up to 24 months post-transplant. These findings confirmed that CYP 3A5 polymorphism represents the most important determinant of Tac dose and exposure in the late period following renal transplantation. Furthermore, the obtained results indicate that the decline in renal function may be more pronounced in patients with CYP 3A5*1 in the long-term period after renal transplantation.

Relationship between pharmacokinetics and pharmacodynamics of calcineurin inhibitors in renal transplant patients

The calcineurin inhibitors (CNIs) cyclosporine A (CsA) and tacrolimus (Tac) are immunosuppressive drugs, which are typically employed in the field of organ transplantation. Both drugs have narrow therapeutic indices, highly variable pharmacokinetics, and are associated with severe adverse effects. In current clinical routine, the dose finding of CNIs is based on the measurement of their blood concentrations. However, this method is limited in its ability to determine the biological impact of the drug. Alternative monitoring strategies, focusing on the pharmacodynamics of CNIs, could help to personalize drug dosing and optimize the treatment with CNIs. Therefore, we analyzed the relationship between pharmacokinetic and pharmacodynamic of the CNIs CsA (n = 9) and Tac (n = 8) in stable renal transplant patients during a 12-h dosing period. We observed a significant decrease in the drug-blood concentration during the course of the day and in parallel a significant recovery of T cell function. In addition, our data document that analysis of intracellular interleukin (IL)-2 production and determination of the IL-2 release are accurate parameters for monitoring the pharmacodynamics of CNIs.

Evaluation of molecular profiles in calcineurin inhibitor toxicity post-kidney transplant: input to chronic allograft dysfunction

The molecular basis of calcineurin inhibitor toxicity (CNIT) in kidney transplantation (KT) and its contribution to chronic allograft dysfunction (CAD) with interstitial fibrosis (IF) and tubular atrophy (TA) were evaluated by: (1) identifying specific CNIT molecular pathways that associate with allograft injury (cross-sectional study) and (2) assessing the contribution of the identified CNIT signature in the progression to CAD with IF/TA (longitudinal study). Kidney biopsies from well-selected transplant recipients with histological diagnosis of CNIT (n = 14), acute rejection (n = 13) and CAD with IF/TA (n = 10) were evaluated. Normal allografts (n = 18) were used as controls. To test CNIT contribution to CAD progression, an independent set of biopsies (n = 122) from 61 KT patients collected at 3 and ~12 months post-KT (range = 9-18) were evaluated. Patients were classified based on 2-year post-KT graft function and histological findings as progressors (n = 30) or nonprogressors to CAD (n = 31). Molecular signatures characterizing CNIT samples were identified. Patients classified as progressors showed an overlap of 7% and 22% with the CNIT signature at 3 and at ~12 months post-KT, respectively, while the overlap was <1% and 1% in nonprogressor patients, showing CNIT at the molecular level as a nonimmunological factor involved in the progression to CAD.

Progress in pharmacogenomics: bridging the gap from research to practice

Genetic information is increasingly used to optimize clinical treatment of patients, but obstacles remain to practical implementation as well as challenges to our understanding of genetic variation in drug response. These areas that particularly require research attention include gene-environment interactions, the consequences of genetic variation, and the impact of epigenetics on gene expression and function. In this issue of Clinical Pharmacology & Therapeutics focused on pharmacogenetics, we discuss some of the recent advances in understanding from a variety of viewpoints.

Teplizumab (anti-CD3 mAb) treatment preserves C-peptide responses in patients with new-onset type 1 diabetes in a randomized controlled trial: metabolic and immunologic features at baseline identify a subgroup of responders

Trials of immune therapies in new-onset type 1 diabetes (T1D) have shown success, but not all subjects respond, and the duration of response is limited. Our aim was to determine whether two courses of teplizumab, an Fc receptor-nonbinding anti-CD3 monoclonal antibody, reduces the decline in C-peptide levels in patients with T1D 2 years after disease onset. We also set out to identify characteristics of responders. We treated 52 subjects with new-onset T1D with teplizumab for 2 weeks at diagnosis and after 1 year in an open-label, randomized, controlled trial. In the intent to treat analysis of the primary end point, patients treated with teplizumab had a reduced decline in C-peptide at 2 years (mean -0.28 nmol/L [95% CI -0.36 to -0.20]) versus control (mean -0.46 nmol/L [95% CI -0.57 to -0.35]; P = 0.002), a 75% improvement. The most common adverse events were rash, transient upper respiratory infections, headache, and nausea. In a post hoc analysis we characterized clinical responders and found that metabolic (HbA1c and insulin use) and immunologic features distinguished this group from those who did not respond to teplizumab. We conclude that teplizumab treatment preserves insulin production and reduces the use of exogenous insulin in some patients with new-onset T1D. Metabolic and immunologic features at baseline can identify a subgroup with robust responses to immune therapy.

Inhibitory effect of tacrolimus on p38 mitogen-activated protein kinase signaling in kidney transplant recipients measured by whole-blood phosphospecific flow cytometry

BACKGROUND

Tacrolimus (TAC), the cornerstone of immunosuppressive therapy after solid organ transplantation, inhibits calcineurin activation. Despite pharmacokinetic monitoring, patients frequently experience toxicity or lack of efficacy, which could be prevented by pharmacodynamic monitoring. In Jurkat T-cell lines, it has been shown that TAC, in addition to calcineurin, inhibits the p38 mitogen-activated protein kinase (MAPK) pathway, which is important in T-cell activation and is therefore a potential drug-specific biomarker. We studied whether TAC inhibits p38 MAPK signaling in primary human T cells and ex vivo in healthy volunteers and kidney transplant recipients.

METHODS

Phorbol-12-myristate-13-acetate/ionomycin-induced MAPK signaling was measured by whole-blood phosphospecific flow cytometry.

RESULTS

In vitro, 10-ng/mL TAC inhibited p38 MAPK phosphorylation by a mean of 27% in CD3, 26% in CD4, and 34% in CD8 T cells (P<0.01 compared with baseline). In healthy adults (n=4), 2 hr after a single oral dose of 10-mg TAC, the p38 MAPK activation was inhibited by 35% in CD3, CD4, and CD8 T cells (P<0.05 compared with baseline). In kidney transplant recipients (n=24), TAC predose concentrations (range, 3.2-10.5 ng/mL) were inversely correlated with p38 MAPK activation in CD3, CD4, and CD8 T cells (r=0.51, 0.34, and 0.37, respectively; P<0.01).

CONCLUSIONS

TAC inhibits activation of the MAPK pathway in a dose-dependent manner in kidney transplant patients and may be a potential marker for immune monitoring.

Tacrolimus as a part of immunosuppressive treatment in kidney transplantation patients: sex differences

BACKGROUND

Metabolism interaction between corticosteroids and tacrolimus (Tac) exists and can be an important factor in providing rational pharmacotherapy in kidney transplantation patients. Both Tac and corticosteroids can induce adverse metabolic effects, such as hyperglycemia, post-transplantation diabetes mellitus, and dyslipidemia.

OBJECTIVE

The main goal of this study was to detect corticosteroid dose influence on Tac level within the first 6 months of immunosuppressive therapy. The secondary goal of this research was to investigate sex differences on Tac-corticosteroid interaction. We also monitored biochemical-parameter changes, which are related to immunosuppressive treatment.

METHODS

This retrospective pharmacokinetic study included 30 Serbian patients after kidney transplantation. Patients received a quaternary immunosuppressive regimen including Tac, mycophenolate, mofetil, basiliximab, and corticosteroids. To compare dose-normalized level and dose of Tac in different days after transplantation, we performed the Friedman test and Wilcoxon matched-pairs signed rank sum test. Mann-Whitney test was performed to compare differences in dose of Tac, level of Tac, and dose-normalized level of Tac between male and female patient groups. We used the Friedman test to compare biological and clinical data.

RESULTS

Obtained results show statistical significance between dose of Tac on day 180 post transplantation and dose on days 7, 14, 21, and 60 post transplantation. There was a statistical difference in dose-normalized level of Tac between days 7 and 21 post transplantation (P < 0.01), days 7 and 60 (P < 0.01), and between days 7 and 180 (P < 0.05). There is a statistical significance between male and female levels of Tac on day 21 after transplantation (P < 0.01). Significance also exists on day 60 after transplantation between male and female dose-normalized levels (P < 0.05). There is also a statistical difference in glucose, cholesterol, triglyceride, serum creatinine, and urea level and activity of alanine aminotransferase and alkaline phosphatase before and after operation.

CONCLUSION

Our study shows that dose of corticosteroid affects Tac level in kidney transplantation patients. Tac dose and level changes showed that corticosteroid-Tac interaction has more influence on male than female patients. According to biochemical monitoring, the immunosuppressive therapy used at present is quite well tolerated.

The potential of steroids and xenobiotic receptor polymorphisms in forecasting cyclosporine pharmacokinetic variability in young kidney transplant recipients

The steroids and xenobiotics receptor (SXR) up-regulates the expression and the synthesis of key enzymes in CyA metabolism. In this study, we examined the possible interactions between CyA exposure and SXR polymorphisms during the first year after renal transplantation. The study involved 66 pediatric renal transplant recipients (25 women and 41 men, mean age 13.9 ± 7.4 yr). All patients were genotyped for two sequence variations in the NR1I2 gene: g.-205_-200delGAGAAG and 7635 A>G. CyA trough levels and CyA weight-adjusted daily dose were recorded at 30, 90, 180, and 360 days after transplantation and compared between the different genotypes. A third newly discovered SXR polymorphism was characterized and also included in the study. CyA trough levels and CyA weight-adjusted daily dose were comparable on four time points throughout the first year post-transplant in all three groups. GEE showed a significant reduction in weight-adjusted CyA daily dose in patients carrying the deletion of 6 bp in SXR with a significant group-by-time effect that persisted also when analysis was corrected for age, prednisone dose, and acute rejection episodes. In our group of patients, only the g.-205_-200delGAGAAG SXR polymorphism was able to influence the metabolism of CyA continuously, during the first year after transplantation.

Applications of stable isotopes in clinical pharmacology

This review aims to present an overview of the application of stable isotope technology in clinical pharmacology. Three main categories of stable isotope technology can be distinguished in clinical pharmacology. Firstly, it is applied in the assessment of drug pharmacology to determine the pharmacokinetic profile or mode of action of a drug substance. Secondly, stable isotopes may be used for the assessment of drug products or drug delivery systems by determination of parameters such as the bioavailability or the release profile. Thirdly, patients may be assessed in relation to patient-specific drug treatment; this concept is often called personalized medicine. In this article, the application of stable isotope technology in the aforementioned three areas is reviewed, with emphasis on developments over the past 25 years. The applications are illustrated with examples from clinical studies in humans.

The interactions of age, sex, body mass index, genetics, and steroid weight-based doses on tacrolimus dosing requirement after adult kidney transplantation

PURPOSE

The aim of this study was to evaluate the effect of different clinical covariates on tacrolimus dose requirements in adult kidney transplant patients with a specific focus on drug interactions.

PATIENTS

Tacrolimus dosing requirement, normalized by drug levels and expressed as the concentration/dose (C/D) ratio as a surrogate index of tacrolimus bioavailability, was employed to identify four categories of tacrolimus dosing requirement, namely, very high, high, small, and very-small, in very fast, fast, slow, and very slow metabolizers, respectively. Steroid weight-based doses were analyzed instead of fixed doses, and genetic analysis of cytochrome P450 (CYP) 3A5*1/*3 and multi-drug resistance 1 (MDR1) C3435T and C1236T polymorphisms were performed

RESULTS

Multivariate analysis on 450 adult transplant patients identified six risk factors for being slow metabolizers and therefore requiring small tacrolimus doses: male sex (OR 1.615, p = 0.020); age >60 years (OR 2.456, p = 0.0005); body mass index ≥ 25 (OR 1.546, p = 0.046), hepatitis C virus positivity (OR 2.800, p = 0.0004); low steroid dose <0.06 mg/kg (OR 3.101, p < 0.0001). Patients with a small tacrolimus requirement were at increased risk for multiple infections (OR 1.533, p = 0.0008) and higher systolic blood pressure (OR 1.385, p = 0.022) and showed a significant association with the CYP3A5*3/*3 genotype adjusted by MDR1 polymorphisms C3435T and C1236T (OR 8.104, p = 0.0001).

CONCLUSIONS

Our results demonstrate the importance of the interaction among genetic and clinical factors in conditioning tacrolimus disposition, with corticosteroid weight-based dose being the only modifiable risk factor for tacrolimus requirement. As the tacrolimus dosing requirement increases with increasing tacrolimus clearance through concomitant steroid use, undesirable changes in tacrolimus levels may occur when steroid doses are tapered, predominantly in slow metabolizers. This often neglected drug interaction has to be monitored to optimize tacrolimus exposure in kidney transplant patients.

How genetic variation affects patient response and outcome to therapy for psoriasis

Psoriasis is a prevalent chronic inflammatory condition that affects the skin. There are many treatments available for psoriasis but they are not universally effective and some have associated toxicities. Pharmacogenetics and pharmacogenomics explore the relationship between individual genetic variation and drug effect to allow targeted 'personalized' therapy for patients. There has been very limited pharmacogenetic research regarding psoriasis, with most limited to small retrospective case-control studies looking at single-nucleotide polymorphisms in candidate genes involved in drug pharmacokinetics. We review the pharmacogenetic investigation of treatments for psoriasis to date, including emerging pharmacogenomic studies. In addition, we discuss how such genetic data could be incorporated into routine clinical practice and future areas for development in this field.

Deciphering calcineurin inhibitor nephrotoxicity: a pharmacological approach

The calcineurin inhibitors ciclosporin and tacrolimus are used to prevent acute rejection of solid organs after transplantation. Their use can lead to chronic renal damage characterized by progressive and irreversible deterioration of renal function associated with interstitial fibrosis, tubular atrophy, arteriolar hyalinosis and glomerulosclerosis. Many approaches to better understand the mechanisms of this toxicity are in use. The aim of these approaches is to find biomarkers of early kidney injury and potential therapeutic targets. Despite these efforts, the biological processes leading to calcineurin inhibitor nephrotoxicity remain poorly understood. Furthermore, the diagnosis of chronic renal damage remains inaccurate without definitive diagnostic tools, no effective prevention exists and a therapy to treat the damage has yet to be developed. In this article, theories of pharmacodynamics, pharmacokinetics, therapeutic drug monitoring and pharmacogenetics are synthesized in ways that may improve the understanding of mechanisms leading to calcineurin inhibitor toxicity. The importance of global approaches such as toxicogenomics is emphasized to characterize early cellular responses implicated in calcineurin inhibitor nephrotoxicity.