Cyclosporine A- and tacrolimus-mediated inhibition of CYP3A4 and CYP3A5 in vitro

Efficacy and safety of statin therapy in kidney transplant recipients: a systematic review and meta-analysis

BACKGROUND

Dyslipidemia represents an important risk factor for cardiovascular diseases, although its optimal management after kidney transplantation remains unclear. The present meta-analysis aimed to shed light on the efficacy and safety of statins among kidney transplant recipients, evaluating their potential effects on the risk of cardiovascular events, mortality and graft survival.

METHODS

Medline, Scopus, Web of Science, CENTRAL, Clinicaltrials.gov and Google Scholar were systematically searched from their inception through April 20, 2024. Both randomized controlled trials and observational studies evaluating the effects of statin administration after kidney transplantation were held eligible. Random-effects models were fitted using the maximum likelihood method, while the certainty of evidence was appraised following the GRADE (Grading of Recommendations, Assessment, Development, and Evaluations) approach.

RESULTS

Overall, 27 studies (10 randomized controlled trials and 17 observational studies) were included. Statin use compared to no use was associated with a lower risk of major adverse cardiovascular events [Relative risk (RR): 0.87, 95% confidence interval (CI): 0.67-0.96, moderate certainty] and overall mortality (RR: 0.84, 95% CI: 0.74-0.94, low certainty). The risk of graft loss did not differ between the compared groups (RR: 0.72, 95% CI: 0.48-1.08, very low certainty). Regarding safety endpoints, statin use was associated with a lower risk of hepatotoxicity (RR: 0.81, 95% CI: 0.70-0.93, moderate certainty), but with a greater risk of rhabdomyolysis (RR: 1.37, 95% CI: 1.10-1.70, low certainty) and cataract (RR: 1.22, 95% CI: 1.14-1.31, moderate certainty). No statistically significant differences between the compared groups with and without statin use were observed concerning the risk of creatine kinase elevation, post-transplant diabetes mellitus, hip fracture, venous thromboembolism, or cancer.

CONCLUSIONS

Among kidney transplant recipients, statin use is associated with a lower risk of cardiovascular events and better patient survival, presenting an acceptable safety profile. Further large-scale studies are needed to determine the optimal statin dosing strategy and lipid-lowering goals, depending on comorbidities and immunosuppression regimens.

REGISTRATION

https://doi.org/10.17504/protocols.io.5qpvok3yzl4o/v1 .

Immunosuppressive therapy and oral anticoagulation in kidney transplant recipients: Direct oral anticoagulants versus vitamin-k antagonists

BACKGROUND

direct oral anticoagulants (DOACs) are an alternative to conventional antagonist of vitamin-K (AVK). However, immune suppressive drugs (ISDs) may interfere with DOACs pharmacokinetic.

AIM OF THIS STUDY

evaluate safety and efficacy profile of DOACs compared to AVK in kidney transplant recipients (KTRs) treated with ISDs.

METHODS

a multi-center study from 4 Italian University hospitals enrolling consecutive KTRs on DOACs or AVK was carried out. Sixty-six patients on DOACs were compared with fifty patients on AVK with similar clinical features. Serial evaluation of renal function and serum levels of ISDs during 18 months follow-up (FU) was performed.

RESULTS

Mean age of DOACs patients was 67±9 and mean eGFR was 58,3± 30,4mL/min/1.73m2. ISDs included tacrolimus (n=47, 71%), cyclosporin (n=13, 20%), everolimus (n=10, 7%) and sirolimus (n=4, 6%). After 14 days of DOACs therapy initiation there was a slight increase of serum levels of tacrolimus (+0.19±0.67 p=0.80) and cyclosporine (+0.12±0.25 p=0.94) not statistically significant. Levels of Tacrolimus and cyclosporin were stable at serial evaluation during 18-months follow-up. There were no thromboembolic events among patients treated with DOACs or AVK and no differences in term of major bleeding (6% vs 4% p=0.69), at long-term follow-up. There was no difference in term of eGFR decline from start therapy to 18 months FU between DOACs vs AVK therapy (-3.9±1 vs -3.8±2 p=0.82).

CONCLUSION

DOACs have similar safety and efficacy than AVK among KTRs treated with ISDs. However, careful evaluation of potential drug interaction and ISDs serum levels is needed.

Plasma Venetoclax Concentrations in Patients with Acute Myeloid Leukemia Treated with CYP3A4 Inhibitors

Venetoclax (VEN) is used in patients with acute myeloid leukemia (AML) and is primarily metabolized by CYP3A4, a major drug-metabolizing enzyme. Patients with AML simultaneously administered VEN and CYP3A4 inhibitors require a more appropriate management of drug-drug interactions (DDIs). Here, we report two cases of patients with AML (54-year-old man and 22-year-old woman) administrated VEN and CYP3A4 inhibitors, such as posaconazole, cyclosporine, or danazol. In the first case, we evaluated the appropriateness of timing for adjusting VEN dosage subsequent to the cessation of posaconazole. Consequently, modifying the VEN dosage in conjunction with the cessation of Posaconazole simultaneously may result in elevated plasma VEN levels. In the second case, plasma VEN concentrations were markedly elevated when co-administered with several CYP3A4 inhibitors. Additionally, in vitro assays were conducted for reverse translational studies to analyze CYP3A4 inhibition. CYP3A4 inhibition by combinatorial administration of cyclosporine A and danazol was demonstrated in vitro, which potentially explains the increasing plasma VEN concentrations observed in clinical settings. Although the acquisition of therapeutic effects is a major priority for patients, frequent therapeutic drug monitoring and dosage adjustments considering DDIs would be important factors in chemotherapy.

Pharmacokinetics and pharmacodynamics of Rh2 and aPPD ginsenosides in prostate cancer: a drug interaction perspective

Ginsenoside Rh2 and its aglycon (aPPD) are one of the major metabolites from Panax ginseng. Preclinical studies suggest that Rh2 and aPPD have antitumor effects in prostate cancer (PCa). Our aims in this review are (1) to describe the pharmacokinetic (PK) properties of Rh2 and aPPD ginsenosides; 2) to provide an overview of the preclinical findings on the use of Rh2 and aPPD in the treatment of PCa; and (3) to highlight the mechanisms of its PK and pharmacodynamic (PD) drug interactions. Increasing evidence points to the potential efficacy of Rh2 or aPPD for PCa treatment. Based on the laboratory studies, Rh2 or aPPD combinations revealed an additive or synergistic interaction or enhanced sensitivity of anticancer drugs toward PCa. This review reveals that enhanced anticancer activities were demonstrated in preclinical studies through interactions of Rh2 and/or aPPD with the proteins related to PK (e.g., cytochrome P450 enzymes, transporters) or PD of the other anticancer drugs or PCa signaling pathways. In conclusion, combining Rh2 or aPPD with anti-prostate cancer drugs leads to PK or PD interactions which could facilitate either therapeutically beneficial or toxic effects.

LaGAT: link-aware graph attention network for drug-drug interaction prediction

MOTIVATION

Drug-drug interaction (DDI) prediction is a challenging problem in pharmacology and clinical applications. With the increasing availability of large biomedical databases, large-scale biological knowledge graphs containing drug information have been widely used for DDI prediction. However, large knowledge graphs inevitably suffer from data noise problems, which limit the performance and interpretability of models based on the knowledge graph. Recent studies attempt to improve models by introducing inductive bias through an attention mechanism. However, they all only depend on the topology of entity nodes independently to generate fixed attention pathways, without considering the semantic diversity of entity nodes in different drug pair links. This makes it difficult for models to select more meaningful nodes to overcome data quality limitations and make more interpretable predictions.

RESULTS

To address this issue, we propose a Link-aware Graph Attention method for DDI prediction, called LaGAT, which is able to generate different attention pathways for drug entities based on different drug pair links. For a drug pair link, the LaGAT uses the embedding representation of one of the drugs as a query vector to calculate the attention weights, thereby selecting the appropriate topological neighbor nodes to obtain the semantic information of the other drug. We separately conduct experiments on binary and multi-class classification and visualize the attention pathways generated by the model. The results prove that LaGAT can better capture semantic relationships and achieves remarkably superior performance over both the classical and state-of-the-art models on DDI prediction.

AVAILABILITYAND IMPLEMENTATION

The source code and data are available at https://github.com/Azra3lzz/LaGAT.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Tacrolimus induces a pro-fibrotic response in donor-derived human proximal tubule cells dependent on common variants of the CYP3A5 and ABCB1 genes

BACKGROUND

Common genetic variants of the enzymes and efflux pump involved in tacrolimus disposition have been associated with calcineurin inhibitor nephrotoxicity, but their importance is unclear because of the multifactorial background of renal fibrosis. This study explores the pro-fibrotic response of tacrolimus exposure in relation to the differential capacity for tacrolimus metabolism in proximal tubule cells (PTCs) with a variable (pharmaco)genetic background.

METHODS

PTCs were obtained from protocol allograft biopsies with different combinations of CYP3A5 and ABCB1 variants and were incubated with tacrolimus within the concentration range found in vivo. Gene and protein expression, CYP3A5 and P-glycoprotein function, and tacrolimus metabolites were measured in PTC. Connective tissue growth factor (CTGF) expression was assessed in protocol biopsies of kidney allograft recipients.

RESULTS

PTCs produce CTGF in response to escalating tacrolimus exposure, which is approximately 2-fold higher in cells with the CYP3A5*1 and ABCB1 TT combination in vitro. Increasing tacrolimus exposure results in relative higher generation of the main tacrolimus metabolite {13-O-desmethyl tacrolimus [M1]} in cells with this same genetic background. Protocol biopsies show a larger increase in in vivo CTGF tissue expression over time in TT vs. CC/CT but was not affected by the CYP3A5 genotype.

CONCLUSIONS

Tacrolimus exposure induces a pro-fibrotic response in a PTC model in function of the donor pharmacogenetic background associated with tacrolimus metabolism. This finding provides a mechanistic insight into the nephrotoxicity associated with tacrolimus treatment and offers opportunities for a tailored immunosuppressive treatment.

Pharmacokinetics of Apixaban and Tacrolimus or Cyclosporine in Kidney and Lung Transplant Recipients

Apixaban is frequently used off‐label in transplant recipients. However, a potential drug interaction exists with the calcineurin inhibitors. We conducted an open‐label drug–drug interaction study to determine the pharmacokinetics of apixaban in lung and kidney transplant recipients who were taking a calcineurin inhibitor. A single dose of apixaban 10 mg was administered orally to kidney and lung transplant recipients maintained on either tacrolimus or cyclosporine, and pharmacokinetic parameters were compared to a reference cohort of 12 healthy subjects who used the same apixaban dose and pharmacokinetic blood sampling. Fourteen participants were enrolled (n = 6 kidney, n = 8 lung), with 10 maintained on tacrolimus and four on cyclosporine. Data from 13 participants was usable. Participants were taking triple therapy immunosuppression and had a mean (SD) of 12 (3) medications. Participants receiving tacrolimus and cyclosporine had area under the plasma concentration–time curve from time zero to infinity (AUC_0‐inf) geometric least square means (90% confidence interval [CI]) of 4312 (95% CI 3682, 5049) and 5388 (95% CI 3277, 8858), respectively. Compared to healthy subjects, the associated geometric mean ratios (GMRs) for apixaban maximum plasma concentration (C_max), AUC from time zero to the last quantifiable concentration (AUC_0‐tlast) and AUC_0‐inf were 197% (95% CI 153, 295), 244% (95% CI 184, 323), and 224% (95% CI 170, 295) for transplant recipients on tacrolimus. The GMR (90% CI) C_max, AUC_0‐tlast, and AUC_0‐inf of apixaban for patients on cyclosporine were 256% (95% CI 184, 358), 287% (95% CI 198, 415), and 280% (95% CI 195, 401). Kidney and lung transplant recipients receiving tacrolimus had higher apixaban exposure. A similar trend was noted for patients receiving cyclosporine, but additional patients are needed to confirm this interaction. Future studies are needed before apixaban can be safely recommended in this population, and the impact of dose staggering should be investigated. This study highlights the importance of pharmacokinetic studies in actual patient populations.

Effect of Wuzhi capsules on cyclosporine A concentration in children with aplastic anemia immunotherapy: a single-center observational study

OBJECTIVE

This research aimed to assess the effect of Wuzhi capsules (WZC) on the blood concentration of cyclosporine A (CsA) in renal aplastic anemia recipients.

METHODS

: This observational study was carried out at the Hematology Oncology Center, Beijing Children's Hospital between November 2019 and February 2020. A total of 102 Chinese AA recipients receiving CsA (6mg/kg/d) with or without WZC were included in this study. Baseline data, such as age, therapeutic drug monitoring data, and follow-up information were collected. The promotion concentration of CsA was calculated, and the pharmaceutical economics evaluation with combination of two drugs was also carried out.

RESULTS

: Dose- and body weight-adjusted trough concentrations (C₀/D/W) of CsA in the WZC group were found to be significantly higher than that in the non-WZC group (P<0.01). The average C₀ of CsA increased by (63.27±45.81) ng/mL. The incidence of adverse events was also not statistically significant between the two groups (P>0.05).

CONCLUSION

:WZC can increase CsA concentration without increasing adverse drug reactions. Efficient and convenient immunosuppressive effects on AA recipients can be achieved via immunosuppressant therapy in combination with WZC.

Towards next-generation personalization of tacrolimus treatment: a review on advanced diagnostic and therapeutic approaches

The benefit of personalized medicine is that it allows the customization of drug therapy - maximizing efficacy while avoiding side effects. Genetic polymorphisms are one of the major contributors to interindividual variability. Currently, the only gold standard for applying personalized medicine is dose titration. Because of technological advancements, converting genotypic data into an optimum dose has become easier than in earlier years. However, for many medications, determining a personalized dose may be difficult, leading to a trial-and-error method. On the other hand, the technologically oriented pharmaceutical industry has a plethora of smart drug delivery methods that are underutilized in customized medicine. This article elaborates the genetic polymorphisms of tacrolimus as case study, and extensively covers the diagnostic and therapeutic technologies which aid in the delivery of personalized tacrolimus treatment for better clinical outcomes, thereby providing a new strategy for implementing personalized medicine.

Drug interaction profile of TKI alectinib allows effective and safe treatment of ALK+ lung cancer in the kidney transplant recipient

ALK targeting with tyrosine kinase inhibitors (TKIs) is a highly potent treatment option for the therapy of ALK positive non-small cell lung cancer (NSCLC). However, pharmacokinetics of TKIs leads to clinically significant drug interactions, and the interfering co-medication may hamper the anti-cancer therapeutic management. Here, we present for the first time a drug interaction profile of ALK-TKIs, crizotinib and alectinib, and immunosuppressive agent cyclosporine A in kidney transplant recipients diagnosed with ALK+ lung cancer. Based on therapeutic drug monitoring of cyclosporin A plasma level, the dose of cyclosporine A has been adjusted to achieve a safe and effective therapeutic level in terms of both cancer treatment and kidney transplant condition. Particularly, 15 years upon the kidney transplantation, the stage IV lung cancer patient was treated with the 1st-line chemotherapy, the 2nd-line ALK-TKI crizotinib followed by ALK-TKI alectinib. The successful therapy with ALK-TKIs has been continuing for more than 36 months, including the period when the patient was treated for COVID-19 bilateral pneumonia. Hence, the therapy of ALK+ NSCLC with ALK-TKIs in organ transplant recipients treated with cyclosporine A may be feasible and effective.

In Vitro Metabolism Study of Seongsanamide A in Human Liver Microsomes Using Non-Targeted Metabolomics and Feature-Based Molecular Networking

Seongsanamide A is a bicyclic peptide with an isodityrosine residue discovered in Bacillus safensis KCTC 12796BP which exhibits anti-allergic activity in vitro and in vivo without significant cytotoxicity. The purpose of this study was to elucidate the in vitro metabolic pathway and potential for drug interactions of seongsanamide A in human liver microsomes using non-targeted metabolomics and feature-based molecular networking (FBMN) techniques. We identified four metabolites, and their structures were elucidated by interpretation of high-resolution tandem mass spectra. The primary metabolic pathway associated with seongsanamide A metabolism was hydroxylation and oxidative hydrolysis. A reaction phenotyping study was also performed using recombinant cytochrome P450 isoforms. CYP3A4 and CYP3A5 were identified as the major metabolic enzymes responsible for metabolite formation. Seongsanamide A did not inhibit the cytochrome P450 isoforms commonly involved in drug metabolism (IC₅₀ > 10 µM). These results will contribute to further understanding the metabolism and drug interaction potential of various bicyclic peptides.

QTc interval prolongation in patients with systemic lupus erythematosus treated with hydroxychloroquine

OBJECTIVES

The primary objective is to reveal the effect of hydroxychloroquine (HCQ) treatment on corrected QT (QTc) interval in patients with systemic lupus erythematosus (SLE). The secondary objective is to investigate factors that affect QTc prolongation.

METHODS

SLE patients who had electrocardiograms between 2015 and 2020 were recruited and assigned to two groups based on whether they were treated with HCQ (HCQ group) or not (control group). Change of QTc before and after HCQ administration in the HCQ group was measured and compared with the control group. Patients treated with HCQ were further divided into two groups based on presence or absence of QTc prolongation and the characteristics were compared.

RESULTS

In total, 126 patients were recruited, of whom 42 were treated with HCQ. In the HCQ group, the mean QTc significantly increased (p < .001), while there was no significant difference of mean QTc in the control group. Moreover, those in the HCQ group with QTc prolongation showed a significantly higher proportion of hypertension and longer SLE duration compared to those without QTc prolongation. However, the multiple logistic regression analysis showed that there were no significant differences among them.

CONCLUSION

HCQ could induce QTc prolongation in SLE patients. It might be better that the possibility of QTc prolongation was taken into consideration when HCQ was administered in the patients with longer disease duration of SLE and coincidence of hypertension.

Intestinal Efflux Transporters P-gp and BCRP Are Not Clinically Relevant in Apixaban Disposition

PURPOSE

The involvement of the intestinally expressed xenobiotic transporters P-glycoprotein (P-gp) and Breast Cancer Resistance Protein (BCRP) have been implicated in apixaban disposition based on in vitro studies. Recommendations against co-administration of apixaban with inhibitors of these efflux transporters can be found throughout the literature as well as in the apixaban FDA label. However, the clinical relevance of such findings is questionable due to the high permeability and high solubility characteristics of apixaban.

METHODS

Using recently published methodologies to discern metabolic- from transporter- mediated drug-drug interactions, a critical evaluation of all published apixaban drug-drug interaction studies was conducted to investigate the purported clinical significance of efflux transporters in apixaban disposition.

RESULTS

Rational examination of these clinical studies using basic pharmacokinetic theory does not support the clinical significance of intestinal efflux transporters in apixaban disposition. Further, there is little evidence that efflux transporters are clinically significant determinants of systemic clearance.

CONCLUSIONS

Inhibition or induction of intestinal CYP3A4 can account for exposure changes of apixaban in all clinically significant drug-drug interactions, and lack of intestinal CYP3A4 inhibition can explain all studies with no exposure changes, regardless of the potential for these perpetrators to inhibit intestinal or systemic efflux transporters.

Model-based assessment of pharmacokinetic changes of sunitinib, tacrolimus, and everolimus in a patient with metastatic renal cell carcinoma after renal transplantation

The safety of the coadministration of sunitinib with tacrolimus and everolimus with regard to therapeutic drug monitoring has not been demonstrated. Here, we report a patient who showed high sunitinib concentrations, in addition to pharmacokinetic changes in tacrolimus and everolimus after sunitinib therapy. A living-donor renal transplant patient treated with tacrolimus and everolimus was diagnosed with pulmonary and pleural metastases of renal cell carcinoma. The patient received sunitinib therapy (37.5 mg/day, 2 weeks on and 1 week off). This patient exhibited a high total sunitinib concentration (sunitinib, 105.8 ng/mL; N-desethyl sunitinib, 27.9 ng/mL) on day 10 postinitiation and experienced grade 3 diarrhea. The observed sunitinib concentrations were a little higher than those reported in the 421C>A polymorphism of the ATP-binding cassette subfamily G member 2 gene carrier. The observed concentrations of both tacrolimus and everolimus gradually decreased compared with the Bayesian-predicted values after the onset of sunitinib therapy, and the doses of tacrolimus and everolimus were increased. Careful therapeutic drug monitoring of sunitinib, tacrolimus, and everolimus concentrations is necessary during combination therapy, especially after episodes of diarrhea.

Screening of tau protein kinase inhibitors in a tauopathy-relevant cell-based model of tau hyperphosphorylation and oligomerization

Tauopathies are a class of neurodegenerative disorders characterized by abnormal deposition of post-translationally modified tau protein in the human brain. Tauopathies are associated with Alzheimer's disease (AD), chronic traumatic encephalopathy (CTE), and other diseases. Hyperphosphorylation increases tau tendency to aggregate and form neurofibrillary tangles (NFT), a pathological hallmark of AD. In this study, okadaic acid (OA, 100 nM), a protein phosphatase 1/2A inhibitor, was treated for 24h in mouse neuroblastoma (N2a) and differentiated rat primary neuronal cortical cell cultures (CTX) to induce tau-hyperphosphorylation and oligomerization as a cell-based tauopathy model. Following the treatments, the effectiveness of different kinase inhibitors was assessed using the tauopathy-relevant tau antibodies through tau-immunoblotting, including the sites: pSer202/pThr205 (AT8), pThr181 (AT270), pSer202 (CP13), pSer396/pSer404 (PHF-1), and pThr231 (RZ3). OA-treated samples induced tau phosphorylation and oligomerization at all tested epitopes, forming a monomeric band (46-67 kDa) and oligomeric bands (170 kDa and 240 kDa). We found that TBB (a casein kinase II inhibitor), AR and LiCl (GSK-3 inhibitors), cyclosporin A (calcineurin inhibitor), and Saracatinib (Fyn kinase inhibitor) caused robust inhibition of OA-induced monomeric and oligomeric p-tau in both N2a and CTX culture. Additionally, a cyclin-dependent kinase 5 inhibitor (Roscovitine) and a calcium chelator (EGTA) showed contrasting results between the two neuronal cultures. This study provides a comprehensive view of potential drug candidates (TBB, CsA, AR, and Saracatinib), and their efficacy against tau hyperphosphorylation and oligomerization processes. These findings warrant further experimentation, possibly including animal models of tauopathies, which may provide a putative Neurotherapy for AD, CTE, and other forms of tauopathy-induced neurodegenerative diseases.

Albumin is a secret factor involved in multidirectional interactions among the serotoninergic, immune and endocrine systems that supervises the mechanism of CYP1A and CYP3A regulation in the liver

This review focuses on albumin, which is involved in multidirectional interactions among the immune, endocrine and serotoninergic systems and supervises the regulation of cytochrome P450 (CYP) isoforms under conditions of both normal liver function and liver insufficiency. Special attention is paid to albumin, thyroid hormones, testosterone and tryptophan hydroxylase in these interactions as well as their potential roles in liver regeneration. The association of these factors with inflammation and the modification of the mechanism of hepatic drug-metabolizing CYP isoform regulation are also presented because changes in the expression of CYP isoforms in the liver may result in subsequent changes to a marker substance used for testing CYP activity, thus providing a simple way to control the liver regeneration process or the dangerous stimulation of hepatocarcinogenesis.

Bioinformatics analyses on the immune status of renal transplant patients, a systemic research of renal transplantation

BACKGROUND

Kidney transplantation is the most effective treatment for end-stage renal disease. Allograft rejections severely affect survivals of allograft kidneys and recipients.

METHODS

Using bioinformatics approaches, the present study was designed to investigate immune status in renal transplant recipients. Fifteen datasets from Gene Expression Omnibus (GEO) were collected and analysed. Analysis of gene enrichment and protein-protein interactions were also used.

RESULTS

There were 40 differentially expressed genes (DEGs) identified in chronic rejection group when compared with stable recipients, which were enriched in allograft rejection module. There were 135 DEGs identified in acute rejection patients, compared with stable recipients, in which most genes were enriched in allograft rejection and immune deficiency. There were 288 DEGs identified in stable recipients when compared to healthy subjects. Most genes were related to chemokine signalling pathway. In integrated comparisons, expressions of MHC molecules and immunoglobulins were increased in both acute and chronic rejection; expressions of LILRB and MAP 4 K1 were increased in acute rejection patients, but not in stable recipients. There were no overlapping DEGs in blood samples of transplant recipients.

CONCLUSION

By performing bioinformatics analysis on the immune status of kidney transplant patients, the present study reports several DEGs in the renal biopsy of transplant recipients, which are requested to be validated in clinical practice.

Statin-Related Myotoxicity: A Comprehensive Review of Pharmacokinetic, Pharmacogenomic and Muscle Components

Statins are a cornerstone in the pharmacological prevention of cardiovascular disease. Although generally well tolerated, a small subset of patients experience statin-related myotoxicity (SRM). SRM is heterogeneous in presentation; phenotypes include the relatively more common myalgias, infrequent myopathies, and rare rhabdomyolysis. Very rarely, statins induce an anti-HMGCR positive immune-mediated necrotizing myopathy. Diagnosing SRM in clinical practice can be challenging, particularly for mild SRM that is frequently due to alternative aetiologies and the nocebo effect. Nevertheless, SRM can directly harm patients and lead to statin discontinuation/non-adherence, which increases the risk of cardiovascular events. Several factors increase systemic statin exposure and predispose to SRM, including advanced age, concomitant medications, and the nonsynonymous variant, rs4149056, in SLCO1B1, which encodes the hepatic sinusoidal transporter, OATP1B1. Increased exposure of skeletal muscle to statins increases the risk of mitochondrial dysfunction, calcium signalling disruption, reduced prenylation, atrogin-1 mediated atrophy and pro-apoptotic signalling. Rare variants in several metabolic myopathy genes including CACNA1S, CPT2, LPIN1, PYGM and RYR1 increase myopathy/rhabdomyolysis risk following statin exposure. The immune system is implicated in both conventional statin intolerance/myotoxicity via LILRB5 rs12975366, and a strong association exists between HLA-DRB1*11:01 and anti-HMGCR positive myopathy. Epigenetic factors (miR-499-5p, miR-145) have also been implicated in statin myotoxicity. SRM remains a challenge to the safe and effective use of statins, although consensus strategies to manage SRM have been proposed. Further research is required, including stringent phenotyping of mild SRM through N-of-1 trials coupled to systems pharmacology omics- approaches to identify novel risk factors and provide mechanistic insight.

Transporter-Mediated Drug-Drug Interactions and Their Significance

Drug transporters are considered to be determinants of drug disposition and effects/toxicities by affecting the absorption, distribution, and excretion of drugs. Drug transporters are generally divided into solute carrier (SLC) family and ATP binding cassette (ABC) family. Widely studied ABC family transporters include P-glycoprotein (P-GP), breast cancer resistance protein (BCRP), and multidrug resistance proteins (MRPs). SLC family transporters related to drug transport mainly include organic anion-transporting polypeptides (OATPs), organic anion transporters (OATs), organic cation transporters (OCTs), organic cation/carnitine transporters (OCTNs), peptide transporters (PEPTs), and multidrug/toxin extrusions (MATEs). These transporters are often expressed in tissues related to drug disposition, such as the small intestine, liver, and kidney, implicating intestinal absorption of drugs, uptake of drugs into hepatocytes, and renal/bile excretion of drugs. Most of therapeutic drugs are their substrates or inhibitors. When they are comedicated, serious drug-drug interactions (DDIs) may occur due to alterations in intestinal absorption, hepatic uptake, or renal/bile secretion of drugs, leading to enhancement of their activities or toxicities or therapeutic failure. This chapter will illustrate transporter-mediated DDIs (including food drug interaction) in human and their clinical significances.

A mechanistic modelling approach for the determination of the mechanisms of inhibition by cyclosporine on the uptake and metabolism of atorvastatin in rat hepatocytes using a high throughput uptake method

Determine the inhibition mechanism through which cyclosporine inhibits the uptake and metabolism of atorvastatin in fresh rat hepatocytes using mechanistic models applied to data generated using a high throughput oil spin method.Atorvastatin was incubated in fresh rat hepatocytes (0.05-150 nmol/ml) with or without 20 min pre-incubation with 10 nmol/ml cyclosporine and sampled over 0.25-60 min using a high throughput oil spin method. Micro-rate constant and macro-rate constant mechanistic models were ranked based on goodness of fit values.The best fitting model to the data was a micro-rate constant mechanistic model including non-competitive inhibition of uptake and competitive inhibition of metabolism by cyclosporine (Model 2). The association rate constant for atorvastatin was 150-fold greater than the dissociation rate constant and 10-fold greater than the translocation into the cell. The association and dissociation rate constants for cyclosporine were 7-fold smaller and 10-fold greater, respectively, than atorvastatin. The simulated atorvastatin-transporter-cyclosporine complex derived using the micro-rate constant parameter estimates increased in line with the incubation concentration of atorvastatin.The increased amount of data generated with the high throughput oil spin method, combined with a micro-rate constant mechanistic model helps to explain the inhibition of uptake by cyclosporine following pre-incubation.

Therapeutic concentration achievement and allograft survival comparing usage of conventional tacrolimus doses and CYP3A5 genotype-guided doses in renal transplantation patients

AIMS

Although cytochromeP450(CYP)3A5 gene polymorphism affects personalized tacrolimus doses, there is no consensus as to whether CYP3A5 genotypes should be determined to adjust the doses. The aims were to compare the therapeutic ranges and clinical outcomes between the conventional and genotype-guided tacrolimus doses.

METHODS

This randomized controlled study compared 63 cases of the conventional tacrolimus dose group (0.1 mg/kg/day) with 62 cases of the genotype-guided doses group of 0.125, 0.1 and 0.08 mg/kg for CYP3A5*1/*1, *1/*3, and *3/*3 genotypes for the initial 3 days of kidney transplantation. After day 3, dose adjustment occurred in both groups to achieve therapeutic concentrations.

RESULTS

The genotype-guided group had an increased proportion of patients with tacrolimus concentrations in the therapeutic range at the steady state on day 3 (40.3 vs 23.8%, P = .048). A lower proportion of over-therapeutic concentration patients was noted in the genotype-guided group in the CYP3A5*3/*3 genotype (9.7 vs 27%, P = .013). Unexpectedly, more delayed graft functions (DGFs) were in the genotype-guided group (41.9 vs 22.2%, P = .018) especially in the CYP3A5*1/*1 participants who might have had an aggravated DGF by a longer ischaemic time and higher serum donor creatinine levels than in the control group. There were no significant differences of glomerular filtration rates or graft or patient survivals over a median 37-month follow-up period.

CONCLUSIONS

Determination of the CYP3A5 genotype improved therapeutic range achievement. CYP3A5*1/*1 patients who have high risks of DGF should be closely monitored because of an increased risk of DGF and reduced glomerular filtration rate with high tacrolimus doses.

Drug-Drug Interaction Study of Apixaban with Cyclosporine and Tacrolimus in Healthy Volunteers

Apixaban is metabolized by cytochrome P450 (CYP) 3A4 in the liver and intestine, undergoes direct intestinal excretion, and is a substrate to permeability glycoprotein (P-gp) and breast cancer resistance protein (BCRP) transporters. We examined the drug interactions between cyclosporine and tacrolimus (combined inhibitors of CYP3A4, P-gp, and BCRP) with apixaban in 12 healthy adult male volunteers. Apixaban 10 mg was administered orally alone, in combination with 100 mg cyclosporine or 5 mg tacrolimus. Co-administration with cyclosporine resulted in increase in apixaban maximum plasma concentration (Cmax ) and area under the plasma concentration-time curve from time zero to the last quantifiable concentration (AUC(0-tlast) ) with associated geometric mean ratios (GMRs) and 90% confidence intervals (CIs) of 143% (112, 183) and 120% (97, 148), respectively. Co-administration with tacrolimus resulted in reduction in apixaban Cmax and AUC(0-tlast) with associated GMRs (90% CI) of 87% (69, 112) and 78% (63, 97), respectively. The observed changes in apixaban exposure margins with cyclosporine or tacrolimus are within the range of the historical clinical development program, therefore, apixaban dose adjustments are not warranted.

Comparison of base-line and chemical-induced transcriptomic responses in HepaRG and RPTEC/TERT1 cells using TempO-Seq

The utilisation of genome-wide transcriptomics has played a pivotal role in advancing the field of toxicology, allowing the mapping of transcriptional signatures to chemical exposures. These activities have uncovered several transcriptionally regulated pathways that can be utilised for assessing the perturbation impact of a chemical and also the identification of toxic mode of action. However, current transcriptomic platforms are not very amenable to high-throughput workflows due to, high cost, complexities in sample preparation and relatively complex bioinformatic analysis. Thus, transcriptomic investigations are usually limited in dose and time dimensions and are, therefore, not optimal for implementation in risk assessment workflows. In this study, we investigated a new cost-effective, transcriptomic assay, TempO-Seq, which alleviates the aforementioned limitations. This technique was evaluated in a 6-compound screen, utilising differentiated kidney (RPTEC/TERT1) and liver (HepaRG) cells and compared to non-transcriptomic label-free sensitive endpoints of chemical-induced disturbances, namely phase contrast morphology, xCELLigence and glycolysis. Non-proliferating cell monolayers were exposed to six sub-lethal concentrations of each compound for 24 h. The results show that utilising a 2839 gene panel, it is possible to discriminate basal tissue-specific signatures, generate dose-response relationships and to discriminate compound-specific and cell type-specific responses. This study also reiterates previous findings that chemical-induced transcriptomic alterations occur prior to cytotoxicity and that transcriptomics provides in depth mechanistic information of the effects of chemicals on cellular transcriptional responses. TempO-Seq is a robust transcriptomic platform that is well suited for in vitro toxicity experiments.

Effects of medicines used to treat gastrointestinal diseases on the pharmacokinetics of coadministered drugs: a PEARRL Review

Objectives

Drugs used to treat gastrointestinal diseases (GI drugs) are widely used either as prescription or over-the-counter (OTC) medications and belong to both the 10 most prescribed and 10 most sold OTC medications worldwide. The objective of this review article is to discuss the most frequent interactions between GI and other drugs, including identification of the mechanisms behind these interactions, where possible.

Key findings

Current clinical practice shows that in many cases, these drugs are administered concomitantly with other drug products. Due to their metabolic properties and mechanisms of action, the drugs used to treat gastrointestinal diseases can change the pharmacokinetics of some coadministered drugs. In certain cases, these interactions can lead to failure of treatment or to the occurrence of serious adverse events. The mechanism of interaction depends highly on drug properties and differs among therapeutic categories. Understanding these interactions is essential to providing recommendations for optimal drug therapy.

Summary

Interactions with GI drugs are numerous and can be highly significant clinically in some cases. While alterations in bioavailability due to changes in solubility, dissolution rate, GI transit and metabolic interactions can be (for the most part) easily identified, interactions that are mediated through other mechanisms, such as permeability or microbiota, are less well-understood. Future work should focus on characterising these aspects.

Amenamevir: Studies of Potential CYP3A-Mediated Pharmacokinetic Interactions With Midazolam, Cyclosporine, and Ritonavir in Healthy Volunteers

Amenamevir (formerly ASP2151) is a helicase‐primase inhibitor being developed for the treatment of herpesvirus infection. Amenamevir is both a substrate and inducer of cytochrome P450 (CYP) 3A4. Three studies were done in healthy volunteers to investigate potential CYP3A pharmacokinetic interactions with the following drugs: (1) Midazolam (probe substrate for CYP3A): After 10 days’ pretreatment with amenamevir 400 mg daily, geometric mean maximum concentration of drug in blood plasma (C_max) and area under the plasma drug concentration‐time curve from time zero to infinity (AUC_0‐∞) of midazolam 7.5 mg were about 68% and 51%, respectively, of those after midazolam alone. (2) Cyclosporine (substrate and inhibitor of CYP3A): After 5 days’ pretreatment with cyclosporine 100 mg twice daily, geometric mean C_max of amenamevir after 400‐mg and 1200‐mg single doses was, respectively, about 66% and 69%, and AUC_0‐∞ about 82% and 79%, of those after amenamevir alone. (3) Ritonavir (inhibitor of CYP3A): When given with single doses of ritonavir 600 mg, geometric mean C_max of amenamevir after 400‐mg and 1200‐mg single doses was, respectively, about 1.4 and 1.6 times higher, and geometric mean AUC_0‐∞ about 2.6 and 3.3 times higher, than after amenamevir alone. Amenamevir has the potential to be involved in CYP3A‐mediated pharmacokinetic interactions in clinical practice.

Clinical Pharmacokinetics and Drug-Drug Interaction Potential for Coadministered SCY-078, an Oral Fungicidal Glucan Synthase Inhibitor, and Tacrolimus

SCY-078 is an orally bioavailable triterpenoid glucan synthase inhibitor in clinical development as an intravenous and oral treatment of fungal infections caused by Candida and Aspergillus species. This was a sequential, single-center, open-label phase 1 study to assess the drug-drug interaction potential between SCY-078 and tacrolimus during concomitant administration in healthy subjects. In cohort 1, period 1, subjects received a single oral dose of tacrolimus 2 mg in the fasted state. In period 2 after a ≥15 day washout, subjects received a single loading dose of SCY-078 1250 mg on day 1 followed by maintenance doses of SCY-780 750 mg on days 2 through 8. On day 3 of period 2, subjects also received a single dose of tacrolimus 2 mg concurrent with SCY-078. In cohort 2, subjects received a loading dose of SCY-078 1250 mg on day 1 followed by maintenance doses of SCY-780 750 mg on days 2 and 3. Pharmacokinetic (PK) parameters were compared to assess both the impact of steady-state SCY-078 on tacrolimus and the impact of tacrolimus on the PK of steady-state SCY-078. The concurrent coadministration of tacrolimus and SCY-078 had no effect on the maximum blood levels of tacrolimus, as evidenced by no change in maximum concentration of drug in blood plasma and a 1.4-fold increase in total area under the plasma drug concentration-time curve. The concurrent coadministration of tacrolimus and SCY-078 resulted in a weaker interaction than typically observed with the azole class of antifungals. The current data indicate that an initial dose adjustment for tacrolimus may not be warranted when combined with SCY-078, as the modest increase in exposure is less than the therapeutic window, although tacrolimus monitoring, as with addition of any new medication, is recommended. These results support the coadministration of SCY-078 and tacrolimus.

Transplant Drug Interactions and a Word of Caution for the HIV Provider. A Case Report

Electronic medical record platforms fail to support provider alerts when a drug is discontinued. Protease inhibitors, often boosted by ritonavir or cobicistat, increase the serum concentration of calcineurin inhibitors. This case demonstrates acute liver transplant rejection in an HIV-positive recipient due to a failure to recognize the loss of protease inhibitor interaction with his immunosuppressive regimen.

Drug interactions of meglitinide antidiabetics involving CYP enzymes and OATP1B1 transporter

Meglitinides such as repaglinide and nateglinide are useful to treat type 2 diabetes patients who follow a flexible lifestyle. They are short-acting insulin secretagogues and are associated with less risk of hypoglycemia, weight gain and chronic hyperinsulinemia compared with sulfonylureas. Meglitinides are the substrates of cytochrome P450 (CYP) enzymes and organic anion transporting polypeptide 1B1 (OATP1B1 transporter) and the coadministration of the drugs affecting them will result in pharmacokinetic drug interactions. This article focuses on the drug interactions of meglitinides involving CYP enzymes and OATP1B1 transporter. To prevent the risk of hypoglycemic episodes, prescribers and pharmacists must be aware of the adverse drug interactions of meglitinides.

CYP3A4 is a crosslink between vitamin D and calcineurin inhibitors in solid organ transplant recipients: implications for bone health

The use of calcineurin inhibitors (CNIs) and vitamin D deficiency may contribute to the pathogenesis of post-transplant bone disease. CNIs and 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) are substrates of the drug-metabolizing enzyme CYP3A4. This review summarizes the indications for the use of activated vitamin D analogs in post-transplant care and the current knowledge on the impact of CNIs on bone. We searched for clinical evidence of the interaction between CNIs and 1,25(OH)₂D₃. We also provide an overview of the literature on the interplay between vitamin D metabolism and CYP3A4 in experimental and clinical settings and discuss its possible implications for solid organ transplant recipients. In conclusion, there is a body of evidence on the interplay between vitamin D and the drug-metabolizing enzyme CYP3A4, which may have therapeutic implications.

Construction and verification of CYP3A5 gene polymorphisms using a Saccharomyces cerevisiae expression system to predict drug metabolism

The present study evaluated the ability of a Saccharomyces cerevisiae expression system to predict the pharmacokinetic (PK) activity of a calcium channel blocker in patients with distinct cytochrome P450 3A5 (CYP3A5) polymorphisms. The blood pressure lowering activity of amlodipine in 57 hypertensive patients with CYP3A5*1/*1, CYP3A5*1/*3, CYP3A5*4 and CYP3A5*6 polymorphisms was evaluated by the current study. Subsequently, a Saccharomyces cerevisiae expression system for CYP3A5 gene polymorphisms was constructed to examine the PK activity of CYP3A5*1/*1, CYP3A5*4 and CYP3A5*6 polymorphisms. This system was used to predict the PK of amlodipine and was compared with the in vivo data from different gene polymorphism groups. The blood pressure lowering activity of amlodipine in hypertensive patients varied among CYP3A5 polymorphisms. The in vivo results demonstrated that CYP3A5*6 exhibited the highest metabolic rate, followed by CYP3A5*1/*1, CYP3A5*4 and CYP3A5*1/*3. The difference between CYP3A5*6 and CYP3A5*1/*1 was not statistically significant (P=0.5). In accordance with in vivo data, CYP3A5*1/*1 exhibited the highest in vitro metabolic rate, followed by CYP3A5*6 and CYP3A5*4. With the exception of the comparison between CYP3A5*6 and CYP3A5*1/*1, polymorphisms exhibited statistically significant differences compared with CYP3A5*1/*1 (P<0.05). The Saccharomyces cerevisiae expression system may be a cost effective and potentially useful tool for assessing the PK activity of drugs that are metabolized by CYP3A5.

Post-transplant dyslipidemia: Mechanisms, diagnosis and management

Post-transplant dyslipidemia is highly prevalent and presents unique management challenges to the clinician. The two major outcomes to consider with post-transplant therapies for dyslipidemia are preserving or improving allograft function, and reducing cardiovascular risk. Although there are other cardiovascular risk factors such as graft dysfunction, hypertension, and diabetes, attention to dyslipidemia is warranted because interventions for dyslipidemia have an impact on reducing cardiac events in clinical trials specific to the transplant population. Dyslipidemia is not synonymous with hyperlipidemia. Numerous mechanisms exist for the occurrence of post-transplant dyslipidemia, including those mediated by immunosuppressive drug therapy. Statin therapy has received the most attention in all solid organ transplant recipient populations, although the effect of proper dietary advice and adjuvant pharmacological and non-pharmacological agents should not be dismissed. At all stages of treatment appropriate monitoring strategies for side effects should be implemented so that the benefits from these therapies can be achieved. Clinicians have a choice when there is a conflict between various transplant society and lipid society guidelines for therapy and targets.

The impact of CYP3A5*3 polymorphism on sirolimus pharmacokinetics: insights from predictions with a physiologically-based pharmacokinetic model

AIMS

Sirolimus is an mTOR inhibitor metabolized by CYP3A4 and CYP3A5. Reported effects of CYP3A5 polymorphisms on sirolimus pharmacokinetics (PK) have shown unexplained discrepancies across studies. We quantitatively assessed the effect of CYP3A5*3 status on sirolimus PK by in vitro assessment and simulation using a physiologically-based PK (PBPK) model. In addition, we explored designs for an adequately powered pharmacogenetic association study.

METHOD

In vitro metabolism studies were conducted to confirm individual CYP contribution to sirolimus metabolism. PK profiles were simulated in CYP3A5 expressers and non-expressers with a PBPK model. The pre-dose concentration predictions were used as the outcome parameter to estimate the required sample size for a pharmacogenetic association study.

RESULTS

Sirolimus metabolism was inhibited by over 90% by ketoconazole, a CYP3A specific inhibitor. The PBPK model developed based on CL(int) of recombinant CYP3A4, CYP3A5 and CYP2C8 predicted a small CYP3A5*3 effect on simulated sirolimus PK profiles. A subsequent power analysis based on these findings indicated that at least 80 subjects in an enrichment design, 40 CYP3A5 expressers and 40 non-expressers, would be required to detect a significant difference in the predicted trough concentrations at 1 month of therapy (P < 0.05, 80% power).

CONCLUSIONS

This study suggests that CYP3A5 contribution to sirolimus metabolism is much smaller than that of CYP3A4. Observed discrepancies across studies could be explained as the result of inadequate sample size. PBPK model simulations allowed mechanism-based evaluation of the effects of CYP3A5 genotype on sirolimus PK and provided preliminary data for the design of a future prospective study.

Pharmacokinetic and nephroprotective benefits of using Schisandra chinensis extracts in a cyclosporine A-based immune-suppressive regime

Cyclosporine A (CsA) is a powerful immunosuppressive drug. However, nephrotoxicity resulting from its long-term usage has hampered its prolonged therapeutic usage. Schisandra chinensis extracts (SCE) have previously been used in traditional Chinese medicine and more recently coadministered with Western medicine for the treatment of CsA-induced side effects in the People’s Republic of China. This study aimed to investigate the possible effects of SCE on the pharmacokinetics of CsA in rats and elucidate the potential mechanisms by which it hinders the development of CsA-induced nephrotoxicity. A liquid chromatography/tandem mass spectrometry method was developed and validated for determining the effect of SCE on the pharmacokinetics of CsA. Male Sprague Dawley rats, which were administered with CsA (25 mg/kg/d) alone or in combination with SCE (54 mg/kg/d and 108 mg/kg/d) for 28 days, were used to evaluate the nephroprotective effects of SCE. Our study showed that SCE increased the mean blood concentration of CsA. Furthermore, we found that the concomitant administration of SCE alongside CsA prevented the disruption of catalase activity and reduction in creatinine, urea, renal malondialdehyde, and glutathione peroxidase levels that would have otherwise occurred in the absence of SCE administration. SCE treatment markedly suppressed the expression of 4-hydroxynonenal, Bcl-2-associated X protein, cleaved caspase 3, and autophagy-related protein LC3 A/B. On the other hand, the expression of heme oxygenase-1, nuclear factor erythroid 2-related factor 2 (Nrf2), and P-glycoprotein was enhanced by the very same addition of SCE. SCE was also able to increase the systemic exposure of CsA in rats. The renoprotective effects of SCE were thought to be mediated by its antiapoptotic and antioxidant abilities, which caused the attenuation of CsA-induced autophagic cell death. All in all, these findings suggest the prospective use of SCE as an effective adjunct in a CsA-based immunosuppressive regimen.

Progressive decline in tacrolimus clearance after renal transplantation is partially explained by decreasing CYP3A4 activity and increasing haematocrit

AIMS

The long-term disposition of tacrolimus following kidney transplantation is characterized by a gradual decrease in dose requirements and increase in dose-corrected exposure. This phenomenon has been attributed to a progressive decline in cytochrome P450 3A4 (CYP3A4) activity, although this has never been demonstrated in vivo.

METHODS

Sixty-five tacrolimus- and 10 cyclosporine-treated renal transplant recipients underwent pharmacokinetic testing at day 7 and months 1, 3, 6 and 12 after transplantation, including 8-h area under the concentration-time curve (AUC) for tacrolimus or cyclosporine and assessment of CYP3A4 activity using oral and intravenous midazolam (MDZ) drug probes.

RESULTS

Tacrolimus clearance decreased gradually throughout the entire first year but only in CYP3A5*3/*3 homozygous recipients (25.6 ± 11.1 l h(-1) at day 7; 17 ± 9.1 l h(-1) at month 12; P < 0.001). In mixed model analysis, decreasing CYP3A4 activity, measured by apparent oral MDZ clearance (924 ± 443 ml min(-1) at day 7 vs. 730 ± 344 ml min(-1) at month 1; P < 0.001), explained 55.4% of the decline in tacrolimus clearance in the first month. CYP3A4 activity decreased by 18.9 ml min(-1) for every milligram of methylprednisolone dose tapering within the first month; beyond this point it remained stable. A gradual rise in haematocrit throughout the entire first year explained 31.7% of the decrease in tacrolimus clearance in the first month and 23.6% of the decrease between months 1 and 12. Cyclosporine clearance did not change over time.

CONCLUSIONS

The maturation of tacrolimus disposition in the first year after renal transplantation observed in CYP3A5*3/*3 homozygous patients can partly be explained by a (steroid tapering-related) decline in CYP3A4 activity and a progressive increase in haematocrit.

Metabolic activation of hepatotoxic drug (benzbromarone) induced mitochondrial membrane permeability transition

The risk of drug-induced liver injury (DILI) is of great concern to the pharmaceutical industry. It is well-known that metabolic activation of drugs to form toxic metabolites (TMs) is strongly associated with DILI onset. Drug-induced mitochondrial dysfunction is also strongly associated with increased risk of DILI. However, it is difficult to determine the target of TMs associated with exacerbation of DILI because of difficulties in identifying and purifying TMs. In this study, we propose a sequential in vitro assay system to assess TM formation and their ability to induce mitochondrial permeability transition (MPT) in a one-pot process. In this assay system, freshly-isolated rat liver mitochondria were incubated with reaction solutions of 44 test drugs preincubated with liver microsomes in the presence or absence of NADPH; then, NADPH-dependent MPT pore opening was assessed as mitochondrial swelling. In this assay system, several hepatotoxic drugs, including benzbromarone (BBR), significantly induced MPT in a NADPH-dependent manner. We investigated the rationality of using BBR as a model drug, since it showed the most prominent MPT in our assay system. Both the production of a candidate toxic metabolite of BBR (1',6-(OH)2 BBR) and NADPH-dependent MPT were inhibited by several cytochrome P450 (CYP) inhibitors (clotrimazole and SKF-525A, 100μM). In summary, this assay system can be used to evaluate comprehensive metabolite-dependent MPT without identification or purification of metabolites.

Drug biokinetic and toxicity assessments in rat and human primary hepatocytes and HepaRG cells within the EU-funded Predict-IV project

The overall aim of Predict-IV (EU-funded collaborative project #202222) was to develop improved testing strategies for drug safety in the late discovery phase. One major focus was the prediction of hepatotoxicity as liver remains one of the major organ leading to failure in drug development, drug withdrawal and has a poor predictivity from animal experiments. In this overview we describe the use and applicability of the three cell models employed, i.e., primary rat hepatocytes, primary human hepatocytes and the human HepaRG cell line, using four model compounds, chlorpromazine, ibuprofen, cyclosporine A and amiodarone. This overview described the data generated on mode of action of liver toxicity after long-term repeat-dosing. Moreover we have quantified parent compound and its distribution in various in vitro compartments, which allowed us to develop biokinetic models where we could derive real exposure concentrations in vitro. In conclusion, the complex data set enables quantitative measurements that proved the concept that we can define human relevant free and toxic exposure levels in vitro. Further compounds have to be analyzed in a broader concentration range to fully exploit these promising results for improved prediction of hepatotoxicity and hazard assessment for humans.

Pharmacokinetics and dose recommendations for cyclosporine and tacrolimus when coadministered with ABT-450, ombitasvir, and dasabuvir

ABT-450, ombitasvir, and dasabuvir are direct-acting antiviral agents (DAAs) that have been developed for combination treatment of chronic hepatitis C virus (HCV) infection. Because these DAAs have metabolic and transporter profiles that overlap with cyclosporine and tacrolimus disposition, there is potential for drug interactions. Two Phase 1 studies assessed effects of ABT-450 (150 mg coadministered with ritonavir 100 mg once daily), ombitasvir (25 mg once daily), and dasabuvir (400 mg twice daily) on the pharmacokinetics, safety, and tolerability of a single dose of cyclosporine (30 mg) or tacrolimus (2 mg) in healthy volunteers (N = 12 per study). In the presence of steady-state concentrations of all 3 DAAs, dose-normalized cyclosporine concentration at 24 hours (C₂₄), and area under the concentration-time curve from time 0 to infinity (AUC(∞)) were 15.8-fold and 5.8-fold, respectively, and dose-normalized tacrolimus C₂₄ and AUC(∞) were 17-fold and 57-fold, respectively, of either agent alone. Cyclosporine and tacrolimus half-lives increased from 7 to 25 h and 32 to 232 h, respectively. There were no major safety or tolerability issues in these studies. The results suggest that cyclosporine and tacrolimus doses and dosing frequency should be reduced in HCV-infected posttransplant patients being treated with this 3-DAA regimen.