Impact of trough abiraterone level on adverse events in patients with prostate cancer treated with abiraterone acetate.

PURPOSE: We assessed the impact of plasma trough concentrations of abiraterone (ABI) and its metabolite Δ4-abiraterone (D4A) and related polymorphisms on adverse events (AEs) in patients with metastatic prostate cancer who received abiraterone acetate (AA). METHODS: This prospective study enrolled patients with advanced prostate cancer treated with AA between 2016 and 2021. Plasma trough concentrations of ABI and D4A were measured using high-performance liquid chromatography. The impact of HSD3B1 rs1047303, SRD5A2 rs523349, and cytochrome P450 family 3A member 4 rs2242480 polymorphisms on plasma concentrations of ABI and D4A and the incidence of AEs were also assessed. RESULTS: In 68 patients treated with AA, the median ABI and D4A concentrations were 18.1 and 0.94 ng/mL, respectively. The high plasma trough concentration of ABI (≥ 20.6 ng/mL) was significantly associated with the presence of any AE and its independent risk factor based on multivariable analysis (odds ratio, 7.20; 95% confidence interval (CI): 2.20-23.49). Additionally, a high plasma trough concentration of ABI was an independent risk factor of time to withdraw AA (hazard ratio, 4.89; 95% CI: 1.66-14.38). The risk alleles of three polymorphisms were not statistically associated with the ABI and D4A concentrations and the incidence of AEs. CONCLUSIONS: The plasma trough concentration of ABI is associated with the presence of AEs and treatment failure after AA administration. ABI concentration monitoring may be useful in patients with prostate cancer who received AA.

Effects of NR1I2 and ABCB1 Genetic Polymorphisms on Everolimus Pharmacokinetics in Japanese Renal Transplant Patients.

The purpose of this study was to evaluate the effects of NR1I2 (7635G>A and 8055C>T) and ABCB1 (1236C>T, 2677G>T/A, and 3435C>T) genetic polymorphisms on everolimus pharmacokinetics in 98 Japanese renal transplant patients. On day 15 after everolimus administration, blood samples were collected just prior to and 1, 2, 3, 4, 6, 9, and 12 h after administration. The dose-adjusted area under the blood concentration−time curve (AUC0-12) of everolimus was significantly lower in patients with the NR1I2 8055C/C genotype than in those with other genotypes (p = 0.022) and was significantly higher in male patients than female patients (p = 0.045). Significant correlations between the dose-adjusted AUC0-12 of everolimus and age (p = 0.001), aspartate transaminase (p = 0.001), and alanine transaminase (p = 0.005) were found. In multivariate analysis, aging (p = 0.008) and higher alanine transaminase levels (p = 0.032) were independently predictive of a higher dose-adjusted everolimus AUC0-12. Aging and hepatic dysfunction in patients may need to be considered when evaluating dose reductions in everolimus. In renal transplant patients, management using everolimus blood concentrations after administration may be more important than analysis of NR1I2 8055C>T polymorphism before administration.

Tacrolimus concentrations after renal transplantation in a mother-neonate dyad: Maternal, neonatal and breast milk measurements.

WHAT IS KNOWN AND OBJECTIVE: We aim to add to the few reports on tacrolimus concentrations in breast milk and in maternal, umbilical vein and neonatal blood after maternal renal transplantation. CASE SUMMARY: In a 30-year-old pregnant woman, the tacrolimus concentration at delivery was the same in maternal, umbilical vein and neonatal blood. The breast milk/maternal blood tacrolimus ratio ranged from 0.40 to 0.64. WHAT IS NEW AND CONCLUSION: The maternal and neonatal blood tacrolimus concentrations at birth are equivalent; thus, one must assume that maternal tacrolimus concentrations directly affect the foetus and/or neonate. Tacrolimus is not detectable in the neonate 3 weeks after birth, suggesting that there is minimal transfer through breast milk.

Changes in PCSK9 and LDL cholesterol concentrations by everolimus treatment and their effects on polymorphisms in PCSK9 and mTORC1.

BACKGROUND: The purpose of this study was to evaluate the effects of concentrations of proprotein convertase subtilisin/kexin type 9 (PCSK9) and low-density lipoprotein (LDL) cholesterol by the mammalian target of rapamycin (mTOR) inhibitor everolimus and their effects on genetic polymorphisms in the PCSK9 and mTORC1 genes in 53 renal transplant recipients. METHODS: Prior to and on day 15 after everolimus administration, the concentrations of everolimus in blood and PCSK9 and LDL cholesterol in plasma were evaluated. Additionally, mTORC1 (rs2536T>C and rs2295080T>G) and PCSK9 (rs505151G>A, rs562556G>A, and rs11593680C>T) polymorphisms were analyzed. RESULTS: Mean PCSK9 plasma concentrations on day 15 after everolimus treatment were significantly higher than those before treatment (295 versus 214 ng/mL, respectively; p = 0.004). Significant correlations between the area under the blood concentration-time curves (AUC)0-12 on day 15 of everolimus treatment and the change rate in PCSK9 concentrations were found (r = 0.316, p = 0.021). However, there were no significant correlations between the change rate in PCSK9 and LDL cholesterol concentrations. The change rate in PCSK9 concentrations by everolimus treatment was significantly greater in patients with the mTORC1 rs2295080G allele than the T/T genotype (p = 0.006); however, there were no significant differences between PCSK9 rs505151G>A and rs11583680C>T genotypes. In multivariate analyses, patients with mTORC1 rs2295080G (p = 0.010), higher everolimus AUC0-12 (p = 0.006), and female sex (p = 0.029) showed higher change rates of PCSK9 following everolimus therapy. CONCLUSIONS: Administration of everolimus significantly elevated plasma PCSK9 concentrations, potentially causing everolimus-induced hyperlipidemia.

Association of immunosuppressive agents and cytomegalovirus infection with de novo donor-specific antibody development within 1 year after renal transplantation.

The association between immunosuppressive therapy or cytomegalovirus (CMV) infection and detection of de novo donor-specific antibody (dnDSA) at 1 year after transplantation was evaluated. The impact of dnDSA positivity at 1 year after transplantation on long-term death-censored renal graft survival was also evaluated. One hundred and sixty adults receiving living renal allografts were studied. Inclusion criteria were renal graft survival for at least 1 year and a standard regimen of immunosuppressive therapy with tacrolimus, mycophenolate mofetil (MMF), steroids, and basiliximab. DSA were measured retrospectively by the Luminex assay. The coefficient of variation (CV) was calculated and receiver operating characteristic (ROC) analysis was employed to clarify the association of tacrolimus with development of dnDSA. Seven of the 160 patients (4.4%) were positive for dnDSA. The intra-patient minimum trough level of tacrolimus (cutoff value: 3.2 ng/mL) was associated with development of dnDSA. Discontinuation of MMF and treatment of CMV infection were more frequent in patients with dnDSA than in those without dnDSA. In multivariate analysis, a low trough level of tacrolimus, discontinuation of MMF, and treatment of CMV infection within 1 year after transplantation were independently associated with detection of dnDSA at 1 year. In patients with or without dnDSA at 1 year, the 10-year allograft survival rate was 51.4 versus 87.9%, respectively (P = 0.002). A lower tacrolimus trough level, discontinuation of MMF, and treatment of CMV infection were associated with dnDSA positivity. Further investigation is needed to determine whether a new immunosuppressive regimen that avoids these factors can reduce dnDSA positivity.

Influence of CYP3A5 genetic differences in tacrolimus on quantitative interstitial fibrosis and long-term graft function in kidney transplant recipients.

The impact of CYP3A5 polymorphisms on clinical outcomes is controversial. The present study investigated the impact of CYP3A5 genetic differences on the development of interstitial fibrosis (IF) from 0 h to 1 year post-transplantation in biopsy sections from 96 living kidney recipients under the same target trough regimen of tacrolimus. The relationships between CYP3A5 polymorphisms and long-term graft function and death-censored graft survival were also examined. A quantitative analysis of IF was performed using computer-assisted imaging on virtual slides. Percent IF (%IF) in the cortical region at 0 h was defined as the baseline, and increases in the ratio of %IF 1 year post-transplantation were calculated. The relationships between CYP3A5 genetic differences and the development of IF, the incidence of clinical events, and the long-term function and death-censored survival of grafts were assessed. The mean increase in the ratio of %IF from 0 h to 1 year was 1.38 ±â€¯0.74-fold. Despite therapeutic drug monitoring (TDM), trough levels of tacrolimus were lower in carriers with the CYP3A5*1 allele (expressers) than in those with the CTP3A5*3/*3 genotype (non-expressers) throughout the 1-year post-transplantation period. However, CYP3A5 genetic differences were not associated with the development of IF, any clinical events, or the long-term function and survival of grafts. The clinical impact of CYP3A5 genetic differences may be small under the current immunosuppressive regimen consisting of mycophenolate mofetil, steroids, basiliximab, and lower target trough levels of tacrolimus with suitable TDM in a low immunological risk population.

Prediction of Tacrolimus Exposure by CYP3A5 Genotype and Exposure of Co-Administered Everolimus in Japanese Renal Transplant Recipients.

While tacrolimus and everolimus have common metabolic pathways through CYP3A4/5, tacrolimus is metabolized solely by CYP3A4 in recipients with the CYP3A5*3/*3. The purpose of this study was to evaluate how the area under the blood concentration-time curves (AUC) of tacrolimus could be predicted based on CYP3A5 genotype and the AUC of everolimus in renal transplant patients taking both drugs. The dose-adjusted AUC (AUC/D) of tacrolimus and everolimus were calculated at one month and one year after transplantation. Significant correlations between the AUC/D of tacrolimus and everolimus were found for patients with the CYP3A5*1 allele or CYP3A5*3/*3 at both one month and one year. At both stages, the determination coefficients were higher and the slopes of regression equations were larger for patients with CYP3A5*3/*3 compared to the CYP3A5*1 allele. A good correlation between single doses of tacrolimus and everolimus was found for CYP3A5*3/*3 patients at 1 year after transplantation (r = 0.794, p < 0.001). The variability of the AUC0-24/D of tacrolimus for each CYP3A5 genotype could be predicted based on the AUC0-12/D of everolimus. Clinicians may be able to comprehensively carry out the dose adjustments of tacrolimus and everolimus based on relationship with AUCs of both drugs in each CYP3A5 genotype.

Contribution of UGT1A1 genetic polymorphisms related to axitinib pharmacokinetics to safety and efficacy in patients with renal cell carcinoma.

Axitinib is a potent second-line molecular-targeted agent for metastatic renal cell carcinoma (mRCC). Axitinib pharmacokinetics and its relation with genetic polymorphisms were evaluated to predict the adverse events (AEs) and efficacy of axitinib. We analyzed 46 patients with mRCC who were treated with axitinib. The plasma axitinib level was measured at 0, 2, 4, 8, and 12 h after administration (C0, C2, C4, C8, and C12; ng/mL) on day 7 of the treatment. Genetic polymorphisms related to axitinib pharmacokinetics, including SLCO1B1, SLCO1B3, SLCO2B1, ABCB1, ABCG2, CYP2C19, CYP3A5, and UGT1A1, were analyzed. Axitinib C0 and AUC0-12 in patients with UGT1A1 poor metabolisers (*6/*6, *6/*28, and *28/*28; n = 10) were significantly higher than those in patients with UGT1A1 extensive metabolisers (*1/*1, *1/*6,*1/*28, and *27/*28; n = 36) (23.6 vs. 7.8 ng/mL, p = 0.030, and 441.3 vs. 217.1 ng h/mL, p = 0.007). The cutoff levels of C0 to predict ≥ G2 hypothyroidism and ≥ G2 anorexia were 6.6 and 7.1 ng/mL, respectively (p = 0.005 and p = 0.035). The overall survival (OS) in patients with C0 > 5 ng/mL was significantly better than that in patients with C0 < 5 ng/mL (p = 0.022). Genetic polymorphisms in UGT1A1 were significantly associated with the plasma axitinib level. The plasma axitinib level was significantly associated with the frequency of AEs and OS in patients with mRCC. No direct relationship was observed between UGT1A1 genotypes and the frequency of AEs or OS.

A comparison of the effects of CYP3A5 polymorphism on tacrolimus blood concentrations measured by 4 immunoassay methods in renal transplant patients.

WHAT IS KNOWN AND OBJECTIVE: The anti-tacrolimus antibodies used in commercial immunoassay methods have cross-reactivity with tacrolimus metabolites. The aim of this study was to investigate differences in the effects of CYP3A5 polymorphism on tacrolimus concentrations obtained by four immunoassay methods in renal transplant patients. METHODS: Samples (n = 508) were evaluated using four immunoassays (chemiluminescence enzyme immunoassay [CLIA], affinity column-mediated immunoassay [ACMIA], electrochemiluminescence immunoassay [ECLIA] and latex agglutination turbidimetric immunoassay [LTIA]). RESULTS: Bland-Altman plots showed average biases of -0.12 (±1.96 SD: -1.30-1.05) ng/mL for CLIA, -0.30 (-1.59-1.00) ng/mL for ECLIA, 0.42 (-1.21-2.05) ng/mL for ACMIA and 1.88 (-0.51-4.28) ng/mL for LTIA, when considering the mean of the three immunoassays (CLIA, ECLIA and ACMIA). In multiple regression analysis, the difference (CLIA-mean) was affected by haematocrit levels. Differences in ECLIA were correlated with red blood cell counts. For LTIA, CYP3A5 genotype and haematocrit levels were identified as independent predictors for this bias. WHAT IS NEW AND CONCLUSION: The results obtained by CLIA, ECLIA and ACMIA were not affected by CYP3A5 polymorphism. However, in LTIA, CYP3A5*1/*3-derived data exhibited an inverse relationship in Bland-Altman analysis (slope: -0.0824). Higher cross-reactivity with 12-hydroxy tacrolimus at lower concentrations may occur in patients with the CYP3A5*1/*3 genotype. Because patients with the CYP3A5*1 allele identified using LTIA may show higher blood concentrations of tacrolimus at lower target concentrations, for example 3.0 ng/mL, compared with other immunoassay methods, there is a need for sufficient consideration of the interpretation of values measured by LTIA.

Impact of the CYP3A5 genotype on the distributions of dose-adjusted trough concentrations and incidence of rejection in Japanese renal transplant recipients receiving different tacrolimus formulations.

BACKGROUND: We investigated the impact of the CYP3A5 genotype on the distributions of dose-adjusted trough concentrations (C 0h/D) and the incidence of rejection in Japanese recipients taking twice-daily (Tac-BID, n = 140) or modified-release once-daily (Tac-QD, n = 80) tacrolimus formulations for 1 year after renal transplantation. METHODS: Logistic regression analysis was carried out to estimate the distinction rate of CYP3A5 genotypes based on the C 0h/D of Tac-BID or Tac-QD. The coefficients of variation (%CVs) were compared in each recipient to estimate the stability of tacrolimus C 0h/D between formulations or CYP3A5 genotypes. RESULTS: Recipients with at least one CYP3A5*1 wild-type allele (EMs) and recipients with homozygous expression of the variant allele CYP3A5*3 (PMs) were significantly identified using the tacrolimus C 0h/D cut-off values of 2.77 and 0.85 ng/mL/mg, respectively, and discrimination rates of 75.3 and 85.4%, respectively, for Tac-BID and Tac-QD groups. The %CV of the tacrolimus C 0h/D in CYP3A5 EMs taking Tac-QD was significantly lower than that in those taking Tac-BID (20.4 versus 23.3%, P = 0.003). The %CV of the tacrolimus C 0h/D was an independent risk factor for rejection (odds ratio = 1.028, P = 0.033). CONCLUSIONS: The tacrolimus C 0h/D values with definite cut-offs for CYP3A5 genotypes were specifically identified in Japanese renal transplant recipients taking Tac-QD. In addition, a larger %CV for the tacrolimus C 0h/D correlated with the incidence of rejection. Consequently, the stability of the C 0h/D achieved using Tac-QD, which was clearly influenced by the CYP3A5 polymorphism, may prevent the development of rejection.

Clinical effects of single nucleotide polymorphisms on drug-related genes in Japanese metastatic renal cell carcinoma patients treated with sunitinib.

Although sunitinib is a well-established chemotherapeutic for metastatic renal cell carcinoma (mRCC), there are no robust markers that predict efficacy and toxicity. We analyzed the effect of single nucleotide polymorphisms (SNPs) in genes involved in sunitinib pharmacokinetics on clinical outcomes in Japanese patients with mRCC. We analyzed the effect of SNPs in genes involved in sunitinib pharmacokinetics on the clinical outcome in mRCC patients in a Japanese population. We evaluated seven SNPs in four candidate genes, the transport proteins ATP-binding cassette (ABC) B1 (rs1045642, rs1128503, rs2032582, and rs7779562) and ABCG2 (rs2231142), and the metabolic proteins cytochrome P450 (CYP) 3A4 (rs35599367) and CYP3A5 (rs776746) in 70 patients. No significant association was observed between the genotypes of each SNP and time to dose reduction, progression-free survival, overall survival, and best objective response. Meanwhile, the incidence of grade 2 or greater hypertension and hand-foot syndrome, and multiple adverse events (>3), was significantly higher in patients carrying the ABCB1 rs2032582 GG genotype [odds ratio (OR): 5.37, 95% confidence interval (CI) 1.02-14.63, P=0.035; OR: 3.17, 95% CI 1.06-9.52, P=0.036, OR: 3.35; 95% CI 1.14-9.84; P=0.025, respectively]. In conclusion, our data showed that the ABCB1 rs2032582 GG genotype was associated with individual adverse events' susceptibility among Japanese patients treated with sunitinib in routine clinical settings.

Effect of hepatic drug transporter polymorphisms on the pharmacokinetics of mycophenolic acid in patients with severe renal dysfunction before renal transplantation.

1. The objective of this study was to examine the association of UGT1A9, SLCO, and ABCC polymorphisms with mycophenolic acid (MPA) pharmacokinetics in ABO blood type (ABO) incompatible patients with severe renal dysfunction pre-transplantation. 2. In all patients, on day 14 after beginning mycophenolate mofetil (MMF) treatment (1 week before transplantation) and on day 28 after renal transplantation, samples were collected just prior to and 1, 2, 3, 4, 6, 9, and 12 h after oral MMF administration. 3. The median dose-adjusted AUC0-12 of MPA after renal transplantation was significantly lower than before transplantation (57.9 versus 76.5 µg h/mL, respectively, p = 0.002). 4. Although the enterohepatic circulation of MPA pre-transplantation was extremely high (57.6%), this level was significantly reduced after renal transplantation (34.6%). 5. In the multivariate analysis, pre-transplantation, patients with the SLCO1B3 334T allele (p = 0.003), higher alanine aminotransferase (p = 0.002), and lower body weight were independently predictive for a higher dose-adjusted AUC0-12 of MPA. 6. In patients with severe renal dysfunction pre-transplantation, MPA is excreted mainly to bile from the liver, and as a consequence, the SLCO1B3 334T > G polymorphism was found to be significantly associated with MPA exposure.

Influence of everolimus on the pharmacokinetics of tacrolimus in Japanese renal transplant patients.

OBJECTIVES: To examine whether a trough concentration of everolimus in the therapeutic range of 3-5 ng/mL affects the pharmacokinetics of tacrolimus in renal transplant patients. METHODS: A total of 52 Japanese renal transplant patients receiving tacrolimus were enrolled in this study. In 28 of them, everolimus was co-administered on day 14 after surgery. Changes in the dose-adjusted blood trough concentration of tacrolimus from day 14 to 28 after surgery were investigated. RESULTS: The dose-adjusted blood trough concentration of tacrolimus on day 28 was affected by CYP3A5*3/*3 and hemoglobin level (P < 0.001 and P = 0.007), but not by everolimus (P = 0.171). In addition, there was no change in the dose-adjusted blood trough concentration of tacrolimus in patients before or after everolimus coadministration (P = 0.165). On day 28, there was no correlation between the rate of change in the dose-adjusted blood trough concentration of tacrolimus and the blood trough concentration or area under the plasma concentration-time curve from 0 to 12 h for everolimus after initiation of combination therapy (r = 0.341, P = 0.076 and r = 0.234, P = 0.231). CONCLUSIONS: A pharmacokinetic interaction between tacrolimus and everolimus was not observed clinically in renal transplant patients. Safe and reliable immunosuppressive therapy in renal transplant patients might be achieved using a combination of tacrolimus and everolimus.

Characterization of clinical and genetic risk factors associated with dyslipidemia after kidney transplantation.

We determined the prevalence of dyslipidemia in a Japanese cohort of renal allograft recipients and investigated clinical and genetic characteristics associated with having the disease. In total, 126 patients that received renal allograft transplants between February 2002 and August 2011 were studied, of which 44 recipients (34.9%) were diagnosed with dyslipidemia at 1 year after transplantation. Three clinical factors were associated with a risk of having dyslipidemia: a higher prevalence of disease observed among female than male patients (P = 0.021) and treatment with high mycophenolate mofetil (P = 0.012) and prednisolone (P = 0.023) doses per body weight at 28 days after transplantation. The genetic association between dyslipidemia and 60 previously described genetic polymorphisms in 38 putative disease-associated genes was analyzed. The frequency of dyslipidemia was significantly higher in patients with the glucocorticoid receptor (NR3C1) Bcl1 G allele than in those with the CC genotype (P = 0.001). A multivariate analysis revealed that the NR3C1 Bcl1 G allele was a significant risk factor for the prevalence of dyslipidemia (odds ratio = 4.6; 95% confidence interval = 1.8-12.2). These findings may aid in predicting a patient's risk of developing dyslipidemia.

Capability of utilizing CYP3A5 polymorphisms to predict therapeutic dosage of tacrolimus at early stage post-renal transplantation.

While CYP3A5 polymorphisms are used to predict the initial dosage of tacrolimus therapy, the predictive capability of genetic information for dosing at early stage post-renal transplantation is unknown. We investigated the influence of polymorphisms over time. An initial oral dose of modified-release once-daily tacrolimus formulation (0.20 mg/kg) was administered to 50 Japanese renal transplant patients every 24 h. Stepwise multiple linear regression analysis for tacrolimus dosing was performed each week to determine the effect of patient clinical characteristics. The dose-adjusted trough concentration was approximately 70% higher for patients with the CYP3A5*3/*3 than patients with the CYP3A5*1 allele before the second pre-transplantation tacrolimus dose (0.97 (0.78-1.17) vs. 0.59 (0.45-0.87) ng/mL/mg; p < 0.001). The contribution of genetic factors (CYP3A5*1 or *3) for tacrolimus dosing showed increased variation from Day 14 to Day 28 after transplantation: 7.2%, 18.4% and 19.5% on Days 14, 21 and 28, respectively. The influence of CYP3A5 polymorphisms on the tacrolimus maintenance dosage became evident after Day 14 post-transplantation, although the tacrolimus dosage was determined based only on patient body weight for the first three days after surgery. Tacrolimus dosage starting with the initial administration should be individualized using the CYP3A5 genotype information.

Pharmacokinetic and CYP3A5 pharmacogenetic differences between once- and twice-daily tacrolimus from the first dosing day to 1 year after renal transplantation.

UNLABELLED: Aim & patients & methods: This study investigated 24-h pharmacokinetic and CYP3A5 pharmacogenetic differences between once-daily tacrolimus (Tac-q.d.) versus twice-daily tacrolimus (Tac-b.i.d.) pretransplantation and at 1 month and 1 year post-transplantaion. RESULTS: The dose-adjusted trough level (Cmin) and area under the blood concentration-time curve from 0 to 24 h (AUC0₋24) increased twofold within 1 year post-transplantation with both formulations and the two genotypes. Good correlations were observed between the AUC0₋24 and Cmin for both formulations. However, the dose-adjusted Cmin, but not dose-adjusted AUC0₋24, was approximately 30% lower for Tac-q.d. than for Tac-b.i.d. Although the dose-adjusted Cmin was lower for Tac-q.d. than for Tac-b.i.d. in both genotypes, the dose-adjusted AUC0₋24 was approximately 25% lower for Tac-q.d. than for Tac-b.i.d. in CYP3A5 expressers, but not in nonexpressers during the study period. CONCLUSION: These results suggested that the approximately 30% lower Cmin for Tac-q.d. than for Tac-b.i.d. may have achieved the same AUC0₋24 with both formulations and may be associated with CYP3A5 pharmacogenomic differences, especially in CYP3A5 expressers, between Tac-b.i.d. and Tac-q.d.

Pharmaceutical and genetic determinants for interindividual differences of tacrolimus bioavailability in renal transplant recipients.

PURPOSE: The pharmacokinetics of orally administered immediate-release, twice-daily (BID) and modified-release, once-daily (QD) formulations of tacrolimus have high interindividual variability. We investigated factors affecting interindividual variability of tacrolimus bioavailability in renal transplant patients. METHODS: Ninety-seven Japanese renal transplant patients (47 patients on tacrolimus BID and 50 patients on tacrolimus QD) were enrolled in this study. The tacrolimus absolute bioavailability was calculated using the area under the concentration-time curve from 0 to 24 h (AUC0-24) after continuous intravenous infusion and oral formulations of tacrolimus in the same recipient. RESULTS: The median (quartile 1-quartile 3) tacrolimus relative bioavailability for recipients with the CYP3A5*1 or CYP3A5*3/*3 alleles was significantly lower for the tacrolimus QD group [9.1 % (6.3-10.7 %) and 15.4 % (11.5-18.7 %), respectively] than for the tacrolimus BID group [12.6 % (9.9-14.2 %) and 19.3 % (16.5-24.8 %), respectively] (P = 0.004 and 0.028, respectively). Consequently, tacrolimus absolute bioavailability was lowest for recipients with the CYP3A5*1 allele taking tacrolimus QD. The CYP3A5 polymorphism had no impact on the dose-adjusted AUC0-24 of tacrolimus in patients on continuous intravenous infusion (P = 0.906). CONCLUSION: The larger interindividual variability of tacrolimus bioavailability for oral formulations appears to be due to the effects of the CYP3A5 polymorphism and the tacrolimus oral formulation. These factors should therefore be taken into account when determining individualized tacrolimus dosing.

A limited sampling strategy to estimate the area under the concentration-time curve of tacrolimus modified-release once-daily preparation in renal transplant recipients.

OBJECTIVES: The aim of this study was to develop a limited sampling strategy to estimate the area under the concentration-time curve (AUC) of a modified-release, once-daily formulation of tacrolimus (Advagraf, Japanese trade name Graceptor) with Japanese renal transplant patients. METHODS: Among the 43 enrolled patients, 23 patients continued to take Graceptor for 1 year. A total of 66 profiles on day 28 and day 365 from the 43 patients were randomly divided into a training group (N = 33) and a validation group (N = 33) without any overlap. RESULTS: The prediction formula for the AUC 0-24 using the single C 12h time point gave the highest correlation with the observed AUC 0-24 (r2 = 0.9057). When 2 sampling times were used, C 0h-C 12h were the best time points for the estimation of the AUC 0-24 (AUC 0-24 = 26.8 + 8.0C 0h + 17.8C 12h, r2 = 0.9221, P < 0.0001). There was no significant difference in the prediction error for the prediction formulas with the C 0h-C 12h combination between CYP3A5 genotypes. The % mean prediction error, % mean absolute error, and % root mean squared prediction error of the prediction formula using C 0h-C 12h were 0.1%, 7.6%, and 8.8%, respectively. CONCLUSIONS: In a hospital setting, a limited sampling strategy using C 0h-C 12h would be applicable to estimating the AUC 0-24 of tacrolimus once daily.

Effect of itraconazole on the concentrations of tacrolimus and cyclosporine in the blood of patients receiving allogeneic hematopoietic stem cell transplants.

PURPOSE: The purpose of this study was to investigate the interactions of itraconazole (ITCZ) with orally administered calcineurin inhibitors (CNIs) in Japanese allogeneic hematopoietic stem cell transplant (HSCT) recipients. METHODS: Sixteen HSCT patients (8 patients each receiving tacrolimus or cyclosporine) were enrolled. An ITCZ oral solution was administered from day 30 after the initiation of ITCZ administration as a loading dose. Before the co-administration of ITCZ and CNI and 1 week daily thereafter, whole blood ITCZ and CNI (tacrolimus or cyclosporine) concentrations were measured in samples taken just before (C0h) and 2 h (C2h) after CNI administration. RESULTS: The median dose-adjusted C0h values of tacrolimus and cyclosporine on day 7 after the start of ITCZ co-administration were 5.6- and 2.7-fold higher, respectively, than the corresponding values obtained before the initiation of ITCZ treatment. On day 7 after ITCZ treatment, the mean single dosages of tacrolimus and cyclosporine were reduced to 33.7 and 66.5 % of the dosages before ITCZ co-administration, respectively, to adjust the CNI target concentration. Although ITCZ co-administration did not alter the dose-adjusted C0h values of tacrolimus in a patient with a CYP3A5 1/ 1 allele, it did change this value of tacrolimus in patients with CYP3A5 3 alleles. However, in patients receiving cyclosporine, no such tendency was observed. CONCLUSION: The magnitude of the interaction between orally administered tacrolimus and ITCZ was significantly greater than that between cyclosporine and ITCZ. Prospective analysis of the CYP3A5 polymorphism may be important to ensure safe and reliable immunosuppressive therapy with tacrolimus in patients treated with ITCZ.

Comparison of pharmacokinetics and pharmacogenetics of once- and twice-daily tacrolimus in the early stage after renal transplantation.

BACKGROUND: This study investigated pharmacokinetic and pharmacogenetic differences between a modified-release once-daily formulation of tacrolimus (Tac-QD) and the original formulation requiring twice-daily intake (Tac-BID) in de novo renal transplant recipients. METHODS: Forty-seven and 25 patients who received Tac-BID and Tac-QD, respectively, were enrolled. The pharmacokinetics and CYP3A5 6986A>G and ABCB1 3435C>T pharmacogenetics of each formulation were analyzed on day 28 posttransplantation. RESULTS: The dose-adjusted trough level (C0) and area under the concentration-time curve (AUC0-24) of tacrolimus were approximately 25% lower for Tac-QD than Tac-BID. However, there was a good correlation between the AUC0-24 and C0 in the Tac-BID and Tac-QD groups (r=0.575, P<0.001; and r=0.638, P<0.001, respectively) and a similar coefficient in each regression equation. The dose-adjusted AUC0-24 was approximately 25% lower in carriers of the CYP3A*1 allele (CYP3A5 expressers), but not individuals with the CYP3A*3/*3 genotype (nonexpressers), for TAC-QD than Tac-BID. In the Tac-QD group, the interpatient variability for dose-adjusted parameters was small, and the interquatile ranges of dose-adjusted parameters differed between CYP3A5 expressers and nonexpressers and did not overlap. The ABCB1 polymorphism was not associated with any pharmacokinetic parameters of Tac-QD. CONCLUSIONS: C0-guided monitoring may lead to similar AUC0-24 values for both formulations. However, to maintain the same AUC0-24 value, a higher dose of Tac-QD than Tac-BID may be needed, especially for CYP3A5 expressers, in the early stage posttransplantation. The narrow interindividual variability of Tac-QD pharmacokinetics and its difference between CYP3A5 expressers and nonexpressers might contribute to a dosing strategy based on CYP3A5 genotype.