An up-date review on individualized dosage adjustment of calcineurin inhibitors in organ transplant patients

The interactions of age, genetics, and disease severity on tacrolimus dosing requirements after pediatric kidney and liver transplantation

Purpose

In children, data on the combined impact of age, genotype, and disease severity on tacrolimus (TAC) disposition are scarce. The aim of this study was to evaluate the effect of these covariates on tacrolimus dose requirements in the immediate post-transplant period in pediatric kidney and liver recipients.

Methods

Data were retrospectively collected describing tacrolimus disposition, age, CYP3A5 and ABCB1 genotype, and pediatric risk of mortality (PRISM) scores for up to 14 days post-transplant in children receiving liver and renal transplants. Initial TAC dosing was equal in all patients and adjusted using therapeutic drug monitoring. We determined the relationship between covariates and tacrolimus disposition.

Results

Forty-eight kidney and 42 liver transplant recipients (median ages 11.5 and 1.5 years, ranges 1.5–17.7 and 0.05–14.8 years, respectively) received TAC post-transplant. In both transplant groups, younger children (<5 years) needed higher TAC doses than older children [kidney: 0.15 (0.07–0.35) vs. 0.09 (0.02–0.20) mg/kg/12h, p = 0.046, liver: 0.12 (0.04–0.32) vs. 0.09 (0.01–0.18) mg/kg/12h, p = 0.038]. In kidney but not liver transplants, CYP3A5 expressors needed significantly higher TAC doses than nonexpressors [0.15 (0.07–0.20) vs. 0.09 (0.02–0.35) mg/kg/12h, P = 0.001]. In these patients, age and CYP3A5 genotype were independently associated with TAC dosing requirement. In liver, but not kidney transplant patients, homozygous ABCB1 T-T-T haplotype carriers needed higher TAC doses than noncarriers [0.26 (0.15–0.32) vs. 0.11 (0.01–0.25) mg/kg/12h, p = 0.013].

Conclusion

CYP3A5 genotype may explain variation in tacrolimus disposition early after transplant in pediatric kidney recipients, independent of age-related variation. In contrast, in pediatric liver recipients, variation in tacrolimus disposition appears related to age and ABCB1 genotype. These findings illustrate the importance of the interplay among age, genotype, and transplant organ on tacrolimus disposition.

A prospective, open-label, observational clinical cohort study of the association between delayed renal allograft function, tacrolimus exposure, and CYP3A5 genotype in adult recipients

BACKGROUND

Tacrolimus, a calcineurin inhibitor with a macrolide lactone structure, is currently used as a cornerstone immunosuppressive drug in solid organ transplantation. It is metabolized by hepatic and intestinal cytochrome P450 (CYP) 3A4/3A5 enzymes and is a substrate for P-glycoprotein (ABCB1). The disposition of tacrolimus might be influenced by severe renal allograft dysfunction (eg, in cases of delayed graft function [DGF]). New-onset diabetes after transplantation (NODAT) is a known adverse effect of tacrolimus therapy and has been associated with DGF.

OBJECTIVES

The impact of DGF on tacrolimus C(min) and dose requirements was evaluated in renal transplant recipients in the first postoperative week. The effects of the CYP3A5*3 A6986G polymorphism on initial mean tacrolimus C(min) and dose requirements in the presence and absence of DGF were assessed. This study also tested the hypothesis that if DGF influences early tacrolimus exposure, this would lead to a higher risk for NODAT (defined as the need for glucose-lowering medication for an uninterrupted period of ≥ 26 weeks).

METHODS

This prospective, open-label, observational clinical cohort study enrolled renal allograft recipients aged ≥ 18 years. Tacrolimus was administered as an oral loading dose of 0.2 mg/kg/d and adjusted to achieve a target mean daily tacrolimus C(min) between 12 and 15 ng/mL. C(min) values and oral dose requirements in the first postoperative week were compared between patients with and without DGF. Patients were genotyped for the CYP3A4*1B -290A>G, CYP3A5*3 A6986G, ABCB1 Exon26 C3435T, ABCB1 Exon21 G2677T, and ABCB1 Exon21 G2677A single nucleotide polymorphisms. NODAT that occurred within the first 12 weeks after transplantation was confirmed using an oral glucose tolerance test.

RESULTS

A total of 304 patients were enrolled (184 men, 120 women; mean [SD] age, 52.9 [14.1] years). Through day 3 after transplantation, mean (SD) 12-hour tacrolimus C(min) values were significantly higher in recipients experiencing DGF despite identical loading doses of 0.2 mg/kg. Mean tacrolimus dose requirements were significantly lower in patients with DGF during the first week. After recovery of DGF, mean tacrolimus dose requirements were not significantly different between recipients with and without DGF. In homozygous CYP3A5*3 carriers (n = 252), mean (SD) tacrolimus dose requirements remained significantly lower during DGF, while in CYP3A5*1 carriers with DGF (n = 52), lower mean dose requirements were observed only after postoperative day 4. The proportion of patients in whom NODAT developed was significantly greater in patients with DGF and tacrolimus C(min) >15 ng/mL on the first day after transplantation (27.2%) compared with recipients who remained free of DGF and had C(min) ≤15 ng/mL on day 1 (6.5%) (P = 0.016). On logistic regression analysis, greater recipient age (odds ratio [OR] = 1.044; 95% CI, 1.009-1.080), higher tacrolimus C(min) on day 1 (OR = 1.048; 95% CI, 1.017-1.080), and DGF (OR = 2.968; 95% CI, 1.107-7.959) were associated with an increased risk for NODAT.

CONCLUSION

In this open-label, observational study, DGF was associated with higher initial mean tacrolimus C(min) values and lower daily dose requirements predominantly in CYP3A5 nonexpressers.

Novel polymorphisms associated with tacrolimus trough concentrations: results from a multicenter kidney transplant consortium

BACKGROUND

The CYP4503A5*1 genotype is associated with lower tacrolimus concentrations. Although its effect is important, it incompletely explains the variability in tacrolimus concentrations and has a relatively low minor allele frequency in whites relative to African Americans (AA).

METHODS

We studied clinical and recipient genetic correlates of dose-normalized tacrolimus troughs (n=12,277) in the first 6 months posttransplant using a customized single-nucleotide polymorphism chip with 2722 variants in a large, ethnically diverse (144 AA and 551 non-AA) adult kidney transplant population through a seven-center consortium.

RESULTS

During the 6-month study, AAs had consistently lower median (interquartile range) troughs than non-AAs, 6.2 (4.4-8.4) ng/mL vs. 8.3 (6.4-10.4) ng/mL (P<0.0001), despite 60% higher daily doses, 8 (5-10) mg vs. 5 (4-7) mg (P<0.0001). The median tacrolimus trough concentration in week 1 posttransplant was particularly low in AAs (2.1 [1.2-3.5] ng/mL) compared with non-AAs (5.0 [3.1-8.2] ng/mL) (P<0.0001), despite similar initial doses. In single-variant analysis, CYP3A5*3 (rs776746) was the top variant (P=2.4×10) associated with troughs. After adjustment for CYP3A5*3, clinical factors and race, 35 additional variants were identified (P<0.01, not significant at false discovery rate 20%). In the final multivariant, regression models beginning with these variants and clinical factors, seven variants were identified in the non-AA and seven variants in the AA group towards the first trough concentrations. Rs776746 (CYP3A5), rs2239393 (COMT) and diabetes were the only factors common in both populations.

CONCLUSION

We identified variants beyond CYP3A5*3, which may further explain pharmacokinetic variability of tacrolimus and demonstrated that important variants differ by race.

Tacrolimus dosing in Chinese renal transplant recipients: a population-based pharmacogenetics study

OBJECTIVES

The aims of this study were to examine the effects of genetic and clinical factors on the maintenance dose of tacrolimus in patients following renal transplantation and to develop a tacrolimus-dosing model that could be combined with associated factors.

PATIENTS AND METHODS

This study included 142 renal transplant recipients who received tacrolimus as immunosuppressive agent. CYP3A5, MDR1 and NR1I2 gene polymorphisms were identified based on the SNaPshot assay. The relationship between the genetic and clinical factors and tacrolimus maintenance dose as well as between dose-corrected tacrolimus concentration was examined.

RESULTS

CYP3A5 genotype, body weight, haematocrit, haemoglobin and total bilirubin significantly influenced the maintenance tacrolimus dose. The tacrolimus-dosing model derived from linear regression model accounted for 40.5% of total variations in the tacrolimus maintenance dose.

CONCLUSIONS

A pharmacogenetics-based dosing model has been developed for the prediction of the tacrolimus maintenance dose in renal transplant recipients. This model may be useful in helping clinicians prescribe the initial tacrolimus dose with greater safety and effectiveness.

Efficacy and safety of tacrolimus for induction therapy in patients with active lupus nephritis

After the completion of a double-blind placebo-controlled trial, tacrolimus (TAC) was approved for the treatment of lupus nephritis (LN) in Japan. However, the approved maximal dose, 3 mg/day, is almost half the dose used for induction therapy outside Japan. In this study, we retrospectively evaluated the efficacy and safety of low-dose TAC (≤3 mg/day) for induction therapy in 13 adult patients (2 men and 11 women) with active LN. Eight patients were treated for LN flares. Twelve patients underwent renal biopsies: 8 with class IV, 2 with class III + V, 1 with class IV + V, and 1 with class V renal histology, according to the International Society of Nephrology/Renal Pathology Society (ISN/RPS) classification. The mean initial doses of prednisone and TAC were 34.6 ± 14.5 and 2.7 ± 0.6 mg/day, respectively. All the patients achieved a complete remission (CR) at 7.7 ± 6.7 months (mean ± SD) after the last administration of TAC, except for 2 patients who discontinued TAC treatment; 1 because of worsening systemic lupus erythematosus and 1 because of hypertension. Two patients experienced a flare-up after achieving CR. The mean blood TAC concentration 12 h after the last administration (C12) was significantly lower among the patients with flare-ups than among those with a sustained CR (1.5 ± 1.5 vs. 5.1 ± 1.9 ng/mL, P = 0.034). These data showed that low-dose TAC was effective for induction therapy in patients with active LN, although a lower TAC concentration may be associated with a poor outcome.

Effect of Thai plant extracts on P-glycoprotein function and viability in paclitaxel-resistant HepG2 cells

The effects of ethanol extracts from Thai plants on P-glycoprotein (P-gp) function and cell viability were examined using paclitaxel-resistant HepG2 (PR-HepG2) cells. KP018 from Ellipeiopsis cherrevensis and AT80 from Ancistrocladus tectorius increased both rhodamine 123, a typical P-gp substrate, and [(3)H]paclitaxel uptake in PR-HepG2 cells. However, some extracts such as MT80 from Microcos tomentosa increased rhodamine 123, but not [(3)H]paclitaxel, uptake, while MM80 from Micromelum minutum increased only [(3)H]paclitaxel uptake. Thus, the effects of extracts of Thai plants on rhodamine 123 uptake were not necessarily the same as those on [(3)H]paclitaxel uptake. Purified compounds such as bergapten did not affect the uptake of either substrate. KP018, AT80, and MM80 increased [(3)H]paclitaxel uptake and decreased the cell viability in a concentration-dependent manner. Among these extracts, KP018 showed the most potent cytotoxicity. The cytotoxic potency of KP018 on PR-HepG2 cells was similar to that on wild-type HepG2 cells, and was not potentiated by verapamil. At concentrations resulting in no cytotoxicity, AT80 and MM80 potentiated paclitaxel-induced cytotoxicity in PR-HepG2 cells. These results indicate that K018 may be a useful source to search for a new anticancer drug, while AT80 and MM80 may be useful as modulators of P-gp-mediated multidrug resistance in cancer cells.

Impact of ATP-binding cassette, subfamily B, member 1 pharmacogenetics on tacrolimus-associated nephrotoxicity and dosage requirements in paediatric patients with liver transplant

IMPORTANCE OF THE FIELD

Tacrolimus is the most commonly used immunosuppressive agent following solid-organ transplantation in children. Its clinical use, however, is complicated by side effects (mainly nephrotoxicity), narrow therapeutic index and pharmacokinetic variability which can result in an increased risk of treatment failure or toxicity. Studies examining interindividual differences in the expression of the ABCB1 (ATP-binding cassette, subfamily B, member 1) gene (which encodes the drug transporter, P-gp) and its genetic polymorphisms have attempted to elucidate variations in tacrolimus response and disposition in children.

AREAS COVERED IN THIS REVIEW

This review explores pharmacogenetic knowledge developed over the last decade regarding the impact of ABCB1 polymorphisms on tacrolimus toxicity and dosage requirements in children.

WHAT THE READER WILL GAIN

A better understanding of the role of ABCB1 genetic polymorphisms (and corresponding haplotypes) and ABCB1 expression levels in various tissues and organs on tacrolimus outcomes in children with liver transplant.

TAKE HOME MESSAGE

Pharmacogenetics offers significant potential for optimising tacrolimus use. ABCB1 donor genotypes and ABCB1 expression level in the intestine and leukocytes may be useful in dosage selection. Large prospective studies are, however, required to further explore the potential of genetic testing in identifying children who are at risk of toxicity and to better individualise tacrolimus therapy.

Effect of CYP3A and ABCB1 single nucleotide polymorphisms on the pharmacokinetics and pharmacodynamics of calcineurin inhibitors: Part I

The calcineurin inhibitors ciclosporin (cyclosporine) and tacrolimus are immunosuppressant drugs used for the prevention of organ rejection following transplantation. Both agents are metabolic substrates for cytochrome P450 (CYP) 3A enzymes--in particular, CYP3A4 and CYP3A5--and are transported out of cells via P-glycoprotein (ABCB1). Several single nucleotide polymorphisms (SNPs) have been identified in the genes encoding for CYP3A4, CYP3A5 and P-glycoprotein, including CYP3A4 -392A>G (rs2740574), CYP3A5 6986A>G (rs776746), ABCB1 3435C>T (rs1045642), ABCB1 1236C>T (rs1128503) and ABCB1 2677G>T/A (rs2032582). The aim of this review is to provide the clinician with an extensive overview of the recent literature on the known effects of these SNPs on the pharmacokinetics of ciclosporin and tacrolimus in solid-organ transplant recipients. Literature searches were performed, and all relevant primary research articles were critiqued and summarized. Influence of the CYP3A4 -392A>G SNP on the pharmacokinetics of either ciclosporin or tacrolimus appears limited. Variability in CYP3A4 expression due to environmental factors is likely to be more important than patient genotype. Influence of the CYP3A5 6986A>G SNP on the pharmacokinetics of ciclosporin is also uncertain and likely to be small. CYP3A4 may play a more dominant role than CYP3A5 in the metabolism of ciclosporin. The CYP3A5 6986A>G SNP has a well established influence on the pharmacokinetics of tacrolimus. Several studies in kidney, heart and liver transplant recipients have reported an approximate halving of tacrolimus dose-adjusted trough concentrations and doubling of tacrolimus dose requirements in heterozygous or homozygous carriers of a CYP3A5*1 wild-type allele compared with homozygous carriers of a CYP3A5*3 variant allele. Carriers of a CYP3A5*1 allele take a longer time to reach target blood tacrolimus concentrations. Influence of ABCB1 3435C>T, 1236C>T and 2677G>T/A SNPs on the pharmacokinetics of ciclosporin and tacrolimus remains uncertain, with inconsistent results. Genetic linkage between the three variant genotypes suggests that the pharmacokinetic effects are complex and not related to any one ABCB1 SNP. It is likely that these polymorphisms exert a small but combined effect, which is additive to the effects of the CYP3A5 6986A>G SNP. In liver transplant patients, recipient and donor liver genotypes may act together in determining overall drug disposition, hence the importance of assessing both. Studies with low patient numbers may account for many inconsistent results to date. Meta-analyses of the current data should help resolve some discrepancies. The majority of studies have only evaluated the effects of individual SNPs; however, multiple polymorphisms may interact to produce a combined effect. Further haplotype analyses are likely to be useful. It is not yet clear whether pharmacogenetic profiling of calcineurin inhibitors will be a useful clinical tool for personalizing immunosuppressant therapy.

Influence of ABCB1 polymorphisms and haplotypes on tacrolimus nephrotoxicity and dosage requirements in children with liver transplant

AIMS

The aim of this study was to investigate the influence of genetic polymorphisms in ABCB1 on the incidence of nephrotoxicity and tacrolimus dosage-requirements in paediatric patients following liver transplantation.

METHODS

Fifty-one paediatric liver transplant recipients receiving tacrolimus were genotyped for ABCB1 C1236>T, G2677>T and C3435>T polymorphisms. Dose-adjusted tacrolimus trough concentrations and estimated glomerular filtration rates (EGFR) indicative of renal toxicity were determined and correlated with the corresponding genotypes.

RESULTS

The present study revealed a higher incidence of the ABCB1 variant-alleles examined among patients with renal dysfunction (> or =30% reduction in EGFR) at 6 months post-transplantation (1236T allele: 63.3% vs 37.5% in controls, P= 0.019; 2677T allele: 63.3% vs. 35.9%, p = 0.012; 3435T allele: 60% vs. 39.1%, P= 0.057). Carriers of the G2677->T variant allele also had a significant reduction (%) in EGFR at 12 months post-transplant (mean difference = 22.6%; P= 0.031). Haplotype analysis showed a significant association between T-T-T haplotypes and an increased incidence of nephrotoxicity at 6 months post-transplantation (haplotype-frequency = 52.9% in nephrotoxic patients vs 29.4% in controls; P= 0.029). Furthermore, G2677->T and C3435->T polymorphisms and T-T-T haplotypes were significantly correlated with higher tacrolimus dose-adjusted pre-dose concentrations at various time points examined long after drug initiation.

CONCLUSIONS

These findings suggest that ABCB1 polymorphisms in the native intestine significantly influence tacrolimus dosage-requirement in the stable phase after transplantation. In addition, ABCB1 polymorphisms in paediatric liver transplant recipients may predispose them to nephrotoxicity over the first year post-transplantation. Genotyping future transplant recipients for ABCB1 polymorphisms, therefore, could have the potential to individualize better tacrolimus immunosuppressive therapy and enhance drug safety.

Pharmacokinetics of orally administered tacrolimus in lupus nephritis patients

The pharmacokinetics of orally administered tacrolimus were examined in six female lupus nephritis patients (mean age 43 years, range 24-55 years). Tacrolimus (3 mg) was administered after supper, and blood tacrolimus concentrations were measured just prior to dosing and 1, 2, 4, 6, 8, 12 and 24 h after administration. The maximum blood concentration (C(max)) was observed 4-8 h (mean: 6.7 h) after administration. The mean C(max) and area under the tacrolimus concentrationti-me curve (AUC(0-24 h)) were 12.7 ng/ml and 163.1 ng x h/ml, respectively. Although there was a weak correlation between AUC(0-24 h) values and tacrolimus concentrations 2, 4, and 6 h after administration, concentrations at 12 h and 24 h were highly correlated with AUC(0-24 h) values, suggesting that the trough concentration (C(24 h)) and C(12 h) are valid markers for therapeutic tacrolimus monitoring. Enzyme-linked immunoabsorbent assay (ELISA) and microparticle enzyme immunoassay (MEIA) measurements of blood tacrolimus concentrations were similar. We recommend that monitoring should be carried out by C(12 h) in lupus nephritis outpatients.

Population pharmacokinetics and pharmacogenetics of tacrolimus in de novo pediatric kidney transplant recipients

The aim of this study was to develop a population pharmacokinetic model of tacrolimus in pediatric kidney transplant patients, identify factors that explain variability, and determine dosage regimens. Pharmacokinetic samples were collected from 50 de novo pediatric kidney transplant patients (age 2-18 years) who were on tacrolimus treatment. Population pharmacokinetic analysis of tacrolimus was performed using NONMEM, and the impact of variables (demographic and clinical factors, and CYP3A4-A5, ABCB1, and ABCC2 polymorphisms) was tested. The pharmacokinetic data were described by a two-compartment model that incorporated first-order absorption and lag time. The apparent oral clearance (CL/F) was significantly related to body weight (allometric scaling); in addition, it was higher in patients with low hematocrit levels and lower in patients with CYP3A5*3/*3. The population pharmacokinetic-pharmacogenetic model developed in de novo pediatric kidney transplant patients demonstrated that, in children, tacrolimus dosage should be based on weight, hematocrit levels, and CYP3A5 polymorphism. Individualization of therapy will enable the optimization of tacrolimus exposure, with resultant beneficial effects on kidney function in the initial post-transplantation period.

Immunotherapy in elderly transplant recipients: a guide to clinically significant drug interactions

Currently, >50% of candidates for solid organ transplantation in Europe and the US are aged >50 years while approximately 15% of potential recipients are aged >or=65 years. Elderly transplant candidates are characterized by specific co-morbidity profiles that compromise graft and patient outcome after transplantation. The presence of coronary artery or peripheral vascular disease, cerebrovascular disease, history of malignancy, chronic obstructive lung disease or diabetes mellitus further increases the early post-transplant mortality risk in elderly recipients, with infections and cardiovascular complications as the leading causes of death. Not only are elderly patients more prone to developing drug-related adverse effects, but they are also more susceptible to pharmacokinetic and pharmacodynamic drug interactions because of polypharmacy. The majority of currently used immunosuppressant drugs in organ transplantation are metabolized by cytochrome P450 (CYP) or uridine diphosphate-glucuronosyltransferases and are substrates of the multidrug resistance (MDR)-1 transporter P-glycoprotein, the MDR-associated protein 2 or the canalicular multispecific organic anion transporter, which predisposes these immunosuppressant compounds to specific interactions with commonly prescribed drugs. In addition, important drug interactions between immunosuppressant drugs have been identified and require attention when choosing an appropriate immunosuppressant drug regimen for the frail elderly organ recipient. An age-related 34% decrease in total body clearance of the calcineurin inhibitor ciclosporin was observed in elderly renal recipients (aged >65 years) compared with younger patients, while older recipients also had 44% higher intracellular lymphocyte ciclosporin concentrations. Similarly, using a Bayesian approach, an inverse relationship was noted between sirolimus clearance and age in stable kidney recipients. Ciclosporin and tacrolimus have distinct pharmacokinetics, but both are metabolized by intestinal and hepatic CYP3A4/3A5 and transported across the cell membrane by P-glycoprotein. The most common drug interactions with ciclosporin are therefore also observed with tacrolimus, but the two drugs do not interact identically when administered with CYP3A inhibitors or inducers. The strongest effects on calcineurin-inhibitor disposition are observed with azole antifungals, macrolide antibacterials, rifampicin, calcium channel antagonists, grapefruit juice, St John's wort and protease inhibitors. Drug interactions with mycophenolic acids occur mainly through inhibition of their enterohepatic recirculation, either by interference with the intestinal flora (antibacterials) or by limiting drug absorption (resins and binders). Rifampicin causes a reduction in mycophenolic acid exposure probably through induction of uridine diphosphate-glucuronosyltransferases. Proliferation signal inhibitors (PSIs) such as sirolimus and everolimus are substrates of CYP3A4 and P-glycoprotein and have a macrolide structure very similar to tacrolimus, which explains why common drug interactions with PSIs are comparable to those with calcineurin inhibitors. Ciclosporin, in contrast to tacrolimus, inhibits the enterohepatic recirculation of mycophenolic acids, resulting in significantly lower concentrations and hence risk of underexposure. Therefore, when switching from tacrolimus to ciclosporin and vice versa or when reducing or withdrawing ciclosporin, this interaction needs to be taken into account. The combination of ciclosporin with PSIs requires dose reductions of both drugs because of a synergistic interaction that causes nephrotoxicity when left uncorrected. Conversely, when switching between calcineurin inhibitors, intensified monitoring of PSI concentrations is mandatory. Increasing age is associated with structural and functional changes in body compartments and tissues that alter absorptive capacity, volume of distribution, hepatic metabolic function and renal function and ultimately drug disposition. While these age-related changes are well-known, few specific effects of the latter on immunosuppressant drug metabolism have been reported. Therefore, more clinical data from elderly organ recipients are urgently required.

Genetic polymorphisms in CYP3A5 and MDR1 genes and their correlations with plasma levels of tacrolimus and cyclosporine in renal transplant recipients

Immunosuppressive drugs, such as tacrolimus (FK506) and cyclosporine (CsA), play an essential role in graft survival, preventing rejection. Large interindividual differences in drug-metabolizing enzymes as well as in drug transporters make the task of reaching the optimal concentrations difficult. The bioavailability of CsA and FK506 seems to be associated with the cytocrhome P450 IIIA (CYP3A) gene. It has also been described that the Multi Drug Resistance 1 (MDR1) gene that encodes for polyglycoprotein-P (P-gp) may influence the metabolizing action of FK506 and CsA. Therefore, we sought, to correlate single nucleotide polymorphisms (SNPs) in the CYP3A and MDR1 genes with the concentrations of FK506 and CsA. For this purpose we analyzed 2 groups of renal transplant recipients by sequencing: one receiving a CsA immunosuppressive regime, and other, an FK506-immunosuppression. This study showed that subjects in the FK506 group who had encoded the 1236C>T substitution in the MDR1 gene displayed 44.4% higher drug concentrations compared with ("wild-type") individuals. Individuals carrying the 2677G>T,A mutation showed FK506 concentrations that were 44.7% higher than the wild-type individuals. Concerning the CsA group, individuals carrying the 22915A>C substitution displayed CsA concentrations 52.1% higher than wild-type individuals.

14-Base pair polymorphism of human leukocyte antigen-G as genetic determinant in heart transplantation and cyclosporine therapy monitoring

The 14-base pair (bp) polymorphism within the HLA-G gene has been investigated in heart transplant patients for the first time. The 14-bp polymorphism is associated with HLA-G mRNA stability and the patterns of alternative isoforms splicing, and therefore may influence the functionality of the HLA-G molecule. In heart transplantation, the highest production of soluble HLA-G was related to the -14/-14-bp genotype in the pre- and post-transplantation periods. Our study findings showed that the 14-bp polymorphism of the HLA-G gene influenced the expression of soluble HLA-G in heart transplantation and accordingly resulted in low rejection rates, being a possible marker of genetic variability associated with heart transplantation. In addition, the 14-bp polymorphism of the HLA-G gene is related to the absorber status of cyclosporine of each individual patient, and is useful for determining the oral dose of cyclosporine to manage patients (to adjust immunosuppressive protocols) so as to minimize the risk of a low or high immunosuppression and the side effects in the early stages of heart transplantation.

Tacrolimus concentrations in relation to CYP3A and ABCB1 polymorphisms among solid organ transplant recipients in Korea

BACKGROUND

Cytochrome P450 3A (CYP3A) and the drug transporter P-glycoprotein (P-gp) affect the bioavailability of tacrolimus, the most commonly used immunosuppressive agent in organ transplant recipients. We have determined the genotypic frequencies of the CYP3A and ATP-binding cassette sub-family B member 1 (ABCB1) genes, which encode the CYP3A and P-gp proteins, respectively, in Korean organ transplant recipients and donors, and have assessed the influence of CYP3A and ABCB1 polymorphisms on tacrolimus concentrations.

METHODS

Using chip-based MALDI-TOF mass spectrometry, 506 solid organ transplant recipients and 62 corresponding of liver transplant donors were genotyped for CYP3A4*6, CYP3A4*18, CYP3A5*3, CYP3A5P1*3, ABCB1 c.2677G>A/T, and ABCB1 c.3435C>T alleles, and their steady-state blood concentrations of tacrolimus were measured.

RESULTS

Frequencies of variant alleles among the transplant recipients were CYP3A5*3 76.8%, CYP3A5P1*3 75.9%, ABCB1 c.2677A/T 52.8%, ABCB1 c.3435T 36.9%, CYP3A4*18 1.9%, and CYP3A4*6 0.3%. The CYP3A5P1*3 allele was strongly linked to the CYP3A5*3 allele (r=0.816). Patients with the CYP3A5*3 and CYP3A5P1*3 alleles showed higher blood tacrolimus concentrations per adjusted dose ratio than did patients with wild-type alleles, among both liver transplant donors and renal transplant recipients.

CONCLUSION

The CYP3A5 genotype of the liver is considered to show the most important association with tacrolimus concentrations. Ultimately, genotyping for CYP3A5 may help optimal individualization of immunosuppressive drug therapy for patients undergoing solid organ transplantation.

CYP3A7, CYP3A5, CYP3A4, and ABCB1 genetic polymorphisms, cyclosporine concentration, and dose requirement in transplant recipients

Cyclosporine is a substrate of cytochrome P450 (CYP) 3A and of the transporter ABCB1, for which polymorphisms have been described. In particular, CYP3A5 *3/*3 genotype results in the absence of CYP3A5 activity, whereas CYP3A7 *1/*1C genotype results in high CYP3A7 expression in adults. Log-transformed dose-adjusted cyclosporine trough concentration and daily dose per weight were compared 1, 3, 6, and 12 months after transplantation between CYP3A and ABCB1 genotypes in 73 renal (n = 64) or lung (n = 9) transplant recipients. CYP3A5 expressors (*1/*3 genotype; n = 8-10) presented significantly lower dose-adjusted cyclosporine trough concentrations (P < 0.05) and required significantly higher daily doses per weight (P < 0.01) than the nonexpressors (*3/*3 genotype; n = 55-59) 1, 3, 6, and 12 months after transplantation. In addition, 7 days after transplantation, more CYP3A5 expressors had uncorrected trough cyclosporine concentration below the target concentration of 200 ng/mL than the nonexpressors (odds ratio = 7.2; 95% confidence interval = 1.4-37.3; P = 0.009). CYP3A4 rs4646437C>T influenced cyclosporine kinetics, the T carriers requiring higher cyclosporine dose. CYP3A7*1C carriers required a 1.4-fold to 1.6-fold higher cyclosporine daily dose during the first year after transplantation (P < 0.05). In conclusion, CYP3A4, CYP3A5, and CYP3A7 polymorphisms affect cyclosporine metabolism, and therefore, their genotyping could be useful, in association with therapeutic drug monitoring, to prospectively optimize cyclosporine prescription in transplant recipients. The administration of a CYP3A genotype-dependent cyclosporine starting dose should therefore be tested prospectively in a randomized controlled clinical trial to assess whether it leads to an improvement of the patients outcome after transplantation, with adequate immunosuppression and decreased toxicity.

Treatment of Severe Alopecia Areata: Combination Therapy Using Systemic Cyclosporine A with Low Dose Corticosteroids

BACKGROUND

Combination therapy using cyclosporine A (CsA) together with low-dose corticosteroids has adequate efficacy with little toxicity for the treatment of severe alopecia areata (AA).

OBJECTIVE

We wanted to evaluate the clinical efficacy of combination therapy using CsA with low-dose corticosteroid for the treatment of severe AA and we also wanted to determine the safe therapeutic concentration of CsA in the peripheral blood.

METHODS

We treated 34 cases of severe AA with combination therapy for 24 weeks and we evaluated the efficacy at 12 and 24 weeks. We monitored the peripheral blood concentration of CsA to determine the therapeutic range of CsA that has the fewest side effects.

RESULTS

Of the patients, 77.4% (n=24) and 22.6% (n=10) were classified in the responder and poor-responder groups, respectively. The mean trough concentration of CsA was 95.1 and 101.2 ng/ml in the responder and poor-responder groups, respectively. For the patients with side effects associated with CsA, the mean CsA concentration was 195.8 ng/ml.

CONCLUSION

We found that combination therapy with systemic CsA and low-dose corticosteroids effectively treats severe AA and this therapy results in a safe, therapeutic concentration of CsA in the peripheral blood.

Calcineurin inhibitor sparing in paediatric solid organ transplantation : managing the efficacy/toxicity conundrum

Despite their efficacy, the calcineurin inhibitors (CNIs) ciclosporin and tacrolimus carry a risk of debilitating adverse effects, especially nephrotoxicity, that affect the long-term outcome and survival of children who are given organ transplants. Simple reduction in dosage of CNI has little or no long-term benefit on their adverse effects, and complete withdrawal without threatening graft outcome may only be possible after liver transplantation. Until the last decade, the only option was to increase corticosteroid and/or azathioprine doses, which imposed additional long-term hazards. Considered here are the emerging generation of new agents offering an opportunity for improving long-term graft survival, minimizing CNI-related adverse events and ensuring patient well-being.A holistic, multifaceted strategy may need to be considered - initial selection and optimized use and monitoring of immunosuppressant regimens, early recognition of indicators of patient and graft dysfunction, and, where applicable, early introduction of CNI-sparing regimens facilitating CNI withdrawal. The evidence reviewed here supports these approaches but remains far from definitive in paediatric solid organ transplantation. Because de novo immunosuppression uses CNI in more than 93% of patients, reduction of CNI-related adverse effects has focused on CNI sparing or withdrawal.A recurring theme where sirolimus and mycophenolate mofetil have been used for this purpose is the importance of their early introduction to limit CNI damage and provide long-term benefit: for example, long-term renal function critically reflects that at 1 year post-transplant. While mycophenolic acid shows advantages over sirolimus in preserving renal function because the latter is associated with proteinuria, sirolimus appears the more potent immunosuppressant but also impairs early wound healing. The use of CNI-free immunosuppressant regimens with depleting or non-depleting antibodies plus sirolimus and mycophenolic acid needs much wider investigation to achieve acceptable rejection rates and conserve renal function. The adverse effects of the alternative immunosuppressants, particularly the dyslipidaemia associated with sirolimus, needs to be minimized to avoid replacing one set of adverse effects (from CNIs) with another. While we can only conjecture that judicious combinations with the second generation of novel immunosuppressants currently in development will provide these solutions, a rationale of low-dose therapy with multiple immunosuppressants acting by complementary mechanisms seems to hold the promise for efficacy with minimal toxicity until the vision of tolerance achieves reality.

Impact of MDR1 and CYP3A5 on the oral clearance of tacrolimus and tacrolimus-related renal dysfunction in adult living-donor liver transplant patients

OBJECTIVE

The potential influence of the multidrug resistance 1 (MDR1) gene and the cytochrome P450 (CYP) genes, CYP3A4 and CYP3A5, on the oral clearance (CL/F) of tacrolimus in adult living-donor liver transplant patients was examined. Furthermore, the development of renal dysfunction was analyzed in relation to the CYP3A5 genotype.

METHODS

Sixty de novo adult liver transplant patients receiving tacrolimus were enrolled in this study. The effects of various covariates (including intestinal and hepatic mRNA levels of MDR1 and CYP3A4, measured in each tissue taken at the time of transplantation, and the CYP3A5*3 polymorphism) on CL/F during the first 50 days after surgery were investigated with the nonlinear mixed-effects modeling program.

RESULTS

CL/F increased linearly until postoperative day 14, and thereafter reached a steady state. The initial CL/F immediately after liver transplantation was significantly affected by the intestinal MDR1 mRNA level (P<0.005). Furthermore, patients carrying the CYP3A5*1 allele in the native intestine, but not in the graft liver, showed a 1.47 times higher (95% confidence interval, 1.17-1.77 times, P<0.005) recovery of CL/F with time than patients having the intestinal CYP3A5*3/*3 genotype. The cumulative incidence of renal dysfunction within 1 year after transplantation, evaluated by the Kaplan-Meier method, was significantly associated with the recipient's but not donor's CYP3A5 genotype (*1/*1 and *1/*3 vs. *3/*3: recipient, 17 vs. 46%, P<0.05; donor, 35 vs. 38%, P=0.81).

CONCLUSION

These findings suggest that the CYP3A5*1 genotype as well as the MDR1 mRNA level in enterocytes contributes to interindividual variation in the CL/F of tacrolimus in adult recipients early after living-donor liver transplantation. Furthermore, CYP3A5 in the kidney may play a protective role in the development of tacrolimus-related nephrotoxicity.

On the action of cyclosporine A, rapamycin and tacrolimus on M. avium including subspecies paratuberculosis

Background

Mycobacterium avium subspecies paratuberculosis (MAP) may be zoonotic. Recently the “immuno-modulators” methotrexate, azathioprine and 6-MP and the “anti-inflammatory” 5-ASA have been shown to inhibit MAP growth in vitro. We concluded that their most plausible mechanism of action is as antiMAP antibiotics. The “immunosuppressants” Cyclosporine A, Rapamycin and Tacrolimus (FK 506) treat a variety of “autoimmune” and “inflammatory” diseases. Rapamycin and Tacrolimus are macrolides. We hypothesized that their mode of action may simply be to inhibit MAP growth.

Methodology

The effect on radiometric MAP ¹⁴CO₂ growth kinetics of Cyclosporine A, Rapamycin and Tacrolimus on MAP cultured from humans (Dominic & UCF 4) or ruminants (ATCC 19698 & 303) and M. avium subspecies avium (ATCC 25291 & 101) are presented as “percent decrease in cumulative GI” (%-ΔcGI.)

Principal Findings

The positive control clofazimine has 99%-ΔcGI at 0.5 µg/ml (Dominic). Phthalimide, a negative control has no dose dependent inhibition on any strain. Against MAP there is dose dependent inhibition by the immunosuppressants. Cyclosporine has 97%-ΔcGI by 32 µg/ml (Dominic), Rapamycin has 74%-ΔcGI by 64 µg/ml (UCF 4) and Tacrolimus 43%-ΔcGI by 64 µg/ml (UCF 4)

Conclusions

We show heretofore-undescribed inhibition of MAP growth in vitro by “immunosuppressants;” the cyclic undecapeptide Cyclosporine A, and the macrolides Rapamycin and Tacrolimus. These data are compatible with our thesis that, unknowingly, the medical profession has been treating MAP infections since 1942 when 5-ASA and subsequently azathioprine, 6-MP and methotrexate were introduced in the therapy of some “autoimmune” and “inflammatory” diseases.

[Therapeutic monitoring of immunosuppressive drugs: interest of calcineurin activity assessment in liver transplantation]

Therapeutic monitoring of calcineurin inhibitors (ciclosporin and tacrolimus) consists in pharmacokinetic monitoring. Pharmacodynamics based on calcineurin activity may be particularly interesting in liver transplantation due to the large intra- and interindividual variability of pharmacokinetics of ciclosporin and tacrolimus. A recent investigation on the pharmacokinetic-pharmacodynamic relationship of tacrolimus showed that monitoring of calcineurin activity in PBMC may be particularly relevant within the first three post-transplantation months. Thereafter, the monitoring of trough blood concentrations of tacrolimus remains adequate. Moreover, two clinical investigations carried out within the early and late post-transplantation periods reported a promising result which is a positive correlation between calcineurin activity and incidence of graft rejection, whatever graft type and calcineurin inhibitors. In each study, transplanted recipients with a graft rejection exhibited a greater trough calcineurin activity compared to patients without graft rejection. However, prospective investigations are required because of the small cohorts of patients enrolled in both studies. The aim of these investigations will be to confirm the interest of calcineurin activity monitoring as a marker of cellular immunity and its positive link with pharmacokinetic monitoring.

Pharmacogenetics of immunosuppressive drugs: prospect of individual therapy for transplant patients

The immunosuppressive drugs used in solid-organ transplantation are potent and toxic agents with narrow therapeutic ranges. Underdosing is associated with immunological rejection of the transplanted organ, whereas overdosing results in infections, malignancy and direct toxicity to a number of organs. Pharmacokinetic heterogeneity makes initial dose determination difficult, as there is a poor correlation between dose and blood concentration. Therapeutic drug monitoring is available but the pharmacokinetic–pharmacodynamic association is imperfect and it does not help in achieving target blood concentrations during the critical early 2–3 days after transplantation. Genetic polymorphisms in drug targets, drug-metabolizing enzymes and drug efflux pumps have been identified as potential targets for developing a pharmacogenetic strategy to individualize initial drug choice and dose. To date, use of the CYP3A5 genotype to predict the appropriate initial dose of tacrolimus is the most promising option for individualization of drug therapy in organ transplantation.

Influence of ABCB1 genetic polymorphisms on cyclosporine intracellular concentration in transplant recipients

OBJECTIVE

The expression on lymphocytes of P-glycoprotein, an efflux transporter encoded by the ABCB1 gene, might influence cyclosporine intracellular concentration.

METHODS

ABCB1 genotypes, cyclosporine intracellular and blood concentrations were determined in 64 stable renal, liver or lung transplant recipients.

RESULTS

Cyclosporine intracellular concentration correlated moderately with blood concentration (r=0.30, P<0.00005). The ABCB1 1199A carriers presented a 1.8-fold decreased cyclosporine intracellular concentration (P=0.04), whereas the 3435T carriers presented a 1.7-fold increase (P=0.02) as well as a 1.2-fold increased blood concentration (P=0.04). In contrast, ABCB1 61A>G, 1236C>T and 2677G>T polymorphisms did not influence cyclosporine intracellular and blood concentrations.

CONCLUSION

This is the first report demonstrating that ABCB1 polymorphisms influence cyclosporine intracellular concentration. Interestingly, its influence on intracellular concentration is significantly higher than on blood concentration (P<0.002). This may therefore modulate cyclosporine immunosuppressive activity.

Pharmacokinetics/genotype associations for major cytochrome P450 enzymes in native and first- and third-generation Japanese populations: comparison with Korean, Chinese, and Caucasian populations

Application of foreign clinical data across geographic regions can accelerate drug development. Drug disposition can be variable, and identification of factors influencing responsible pharmacokinetic/pharmacogenomic approaches could facilitate the universal application of foreign data and reduce the total amount of phase III clinical trials evaluating risks in different populations. Our objective was to establish and compare genotype (major cytochrome P450 (CYP) enzymes)/phenotype associations for Japanese (native and first- and third-generation Japanese living abroad), Caucasian, Chinese, and Korean populations using a standard drug panel. The mean metabolic ratios (MRs) for the four ethnic groups were similar except for a lower activity of CYP2D6 in Caucasians and CYP2C19 in Asians. Genotype, not ethnicity, impacted the MR for CYP2C9, CYP2C19, and CYP2D6; neither affected CYP1A2, CYP2E1, and CYP3A4/5 activities. We conclude that equivalent plasma drug concentrations and metabolic profiles can be expected for native Japanese, first- and third-generation Japanese, Koreans, and Chinese for compounds handled through these six CYP enzymes.

Relation between mRNA expression level of multidrug resistance 1/ABCB1 in blood cells and required level of tacrolimus in pediatric living-donor liver transplantation

It has been difficult to set an individualized therapeutic window of tacrolimus after organ transplantation, because of wide interindividual variation of responsiveness to immunosuppressive therapy. In this study, we examined the significance of multidrug resistance 1 (MDR1) in the peripheral blood cells by comparing the trough concentration of tacrolimus with the occurrence of acute cellular rejection (ACR) in retrospectively collected pediatric living-donor liver transplant patients, who were enrolled after obtaining written informed consent. No significant difference in the intraindividual variation in MDR1 mRNA expression in the peripheral blood cells was observed between postoperative days 3 and 7. The average trough concentration of tacrolimus during the 15-day postoperative period was significantly higher in the event-free patients than in those who experienced ACR (21 of 44 cases), and they had higher levels of blood MDR1 mRNA. In addition, the average trough concentration of tacrolimus significantly correlated with the logarithmically transformed MDR1 mRNA data from the blood cells in patients of both the event-free (r = 0.5406; P = 0.0077) and ACR (r = 0.4772; P = 0.0284). The cellular accumulation of [(14)C]tacrolimus in the peripheral blood mononuclear cells was 2-fold higher in mdr1a/1b-knockout mice than in wild-type mice (P = 0.0182). These results suggest that MDR1 in blood cells decreases the leukocytic concentration of tacrolimus, and it could be a useful marker to establish an individualized target concentration of tacrolimus to prevent ACR in pediatric patients after liver transplantation.

1199G>A and 2677G>T/A polymorphisms of ABCB1 independently affect tacrolimus concentration in hepatic tissue after liver transplantation

OBJECTIVE

Tacrolimus is an immunosuppressive drug widely used in hepatic transplantation to avoid graft rejection. Its pharmacokinetics is characterized by a large interindividual variability requiring the use of therapeutic drug monitoring in daily clinical practice. Some genetic polymorphisms in biotransformation enzymes or transporter proteins, such as CYP3A5 and P-glycoprotein (ABCB1), in donors and/or recipients, appear as important determinants of the Tac blood pharmacokinetics. A recent study has shown that Tac hepatic tissue concentrations vary greatly among patients and are well correlated with graft outcome. The aim of our study was to investigate the effect of genetic polymorphisms in biotransformation enzymes (CYP3A5 and CYP3A7) or in their regulatory protein pregnane X receptor as well as in transporter proteins (ABCB1 and OATP-C) on Tac pharmacokinetics in liver transplant patients and more specifically on Tac hepatic concentrations.

METHODS

One hundred and fifty liver donors were genotyped for 13 different polymorphisms. Tac blood and hepatic concentrations were compared according to hepatic genotypes.

RESULTS AND CONCLUSION

We confirmed that Tac dose requirement (on the basis of blood therapeutic drug monitoring) was higher among patients expressing hepatic CYP3A5 (at least one CYP3A5*1 allele) compared with patients who did not (CYP3A5*3/*3). Hepatic expression of CYP3A5, however, did not seem to influence Tac hepatic concentrations. In contrast, ABCB1 genetic polymorphisms significantly influenced Tac hepatic concentrations, whereas their impact on blood concentrations seemed negligible. Among these ABCB1 polymorphisms, the 1199G>A and 2677G>T/A single nucleotide polymorphisms seemed to reduce the activity of P-gp on Tac. As Tac hepatic concentrations have been significantly related to the graft outcome, it might be interesting, in the future, to genotype donors for ABCB1 polymorphisms to better individualize the Tac immunosuppressive therapy in hepatic transplantation.

[Individualized dosage regimen of immunosuppressive drugs based on pharmacokinetic and pharmacodynamic analysis]

The calcineurin inhibitors cyclosporine and tacrolimus are widely used to prevent allograft rejection after transplantation. Since these drugs have narrow therapeutic windows and show considerable pharmacokinetic variability, therapeutic drug monitoring (TDM) is essential to avoid adverse effects such as nephrotoxicity while maximizing immunosuppressive efficacy. On the other hand, some patients experience acute rejection episodes or postoperative complications despite achieving therapeutic blood drug levels. Therefore, pharmacokinetic and pharmacodynamic factors by which to establish individualized dosage adjustment for these drugs should be identified. Recently, it was recognized that pharmacogenomics has the potential to facilitate personalized medicine by translating knowledge of human genome variability into rational therapeutics. In this paper, we review the population pharmacokinetic and pharmacogenomic analysis of tacrolimus, focusing on an efflux transporter P-glycoprotein (multidrug resistance 1 [MDR1/ABCB1]) and drug-metabolizing enzymes cytochrome P450 (CYP) 3A4 and 3A5, and describe Bayesian forecasting to individualize the tacrolimus dose in de novo living-donor liver transplant recipients. Furthermore, the pharmacodynamic properties of tacrolimus and cyclosporine, which were evaluated by measuring calcineurin phosphatase activity in peripheral blood mononuclear cells, are reviewed in relation to an optimal monitoring strategy as well as a rational dosage regimen for these drugs.

CYP3A5 and CYP3A4 but not MDR1 single-nucleotide polymorphisms determine long-term tacrolimus disposition and drug-related nephrotoxicity in renal recipients

The impact of CYP3A and MDR1 gene single-nucleotide polymorphisms on long-term tacrolimus disposition and drug-related toxicity has not been assessed. A study was performed in 95 genotyped recipients by measuring (12 and 4 h) concentration-time curves on day 7; 3, 6 months; 1, 2, 3, 4, and 5 years after transplantation. In contrast to recipients carrying the CYP3A4*1/CYP3A5*1 or CYP3A4*1B/CYP3A5*1 genotypes, dose-corrected tacrolimus exposure almost doubled over 5 years in patients with the CYP3A4*1/ CYP3A5*3 genotype (AUC(0-12 h): from 41.7+/-18.7 to 80+/-39.2 ng h/ml/mg; P<0.05), whereas apparent oral steady-state clearance and dose requirements significantly decreased accordingly. The CYP3A4*1/CYP3A5*1 and CYP3A4*1B/CYP3A5*1 genotypes were significantly more frequently associated with the development of biopsy-proven tacrolimus-related nephrotoxicity than the CYP3A4*1/ CYP3A5*3 genotype (37.5 vs 11.2%; P=0.03 and 42.8 vs 11.2%; P=0.02). The lack of a time-related increase in dose-corrected tacrolimus exposure observed with the CYP3A4*1/CYP3A5*1 and CYP3A4*1B/CYP3A5*1 genotypes is associated with tacrolimus-related nephrotoxicity, possibly as a result of higher concentrations of toxic metabolites.

Cyclosporine and tacrolimus for the treatment of rheumatoid arthritis

PURPOSE OF REVIEW

The calcineurin inhibitors cyclosporine and tacrolimus are important treatments for patients with active rheumatoid arthritis, especially in cases of resistance or intolerance to methotrexate or other disease-modifying antirheumatic drugs. Here, we discuss the mechanism, efficacy and safety of cyclosporine and tacrolimus in the treatment of rheumatoid arthritis.

RECENT FINDINGS

Recent clinical trials of cyclosporine have shown the advantages of its combination with methotrexate, glucocorticoids and leflunomide in the treatment of active rheumatoid arthritis. In Japan, tacrolimus monotherapy was found to be quite effective and combination therapy with methotrexate had positive results in an American study. The inhibitory effects of both drugs not only on T lymphocytes, but also on human osteoclast formation, have been demonstrated in basic studies.

SUMMARY

Cyclosporine and tacrolimus are clinically available disease-modifying antirheumatic drugs. Numerous clinical studies have shown the usefulness of these calcineurin inhibitors in monotherapy and also when combined with methotrexate. Although these drugs have similar effects, there are some differences in adverse reactions.