Effects of renal failure on drug transport and metabolism

Impact of hepatic impairment and renal failure on the pharmacokinetics of linezolid and its metabolites: contribution of hepatic metabolism and renal excretion

Linezolid, an oxazolidinone antibiotic, is used in patients with liver or kidney disease. However, the effects and mechanisms of hepatic impairment or renal failure on the pharmacokinetics of linezolid and its metabolites (PNU-142586 and PNU-142300) remain unclear. We used carbon tetrachloride-induced impaired hepatic function and 5/6 nephrectomy-induced renal failure rat models to investigate linezolid and metabolite pharmacokinetics. Isolated primary rat hepatocytes were used to evaluate the impact of hepatic impairment or renal failure on linezolid metabolism. Uptake and efflux transport studies were also conducted. The influence of hepatic impairment or renal failure on the pharmacokinetics of linezolid and two metabolites did not differ between intragastric gavage and intravenous administration in rats. Linezolid did not accumulate in the brain, heart, lung, liver, kidney, and small intestinal tissues of the hepatic impairment or renal failure rats. And PNU-142300 did not accumulate in the liver or kidney tissue. Compared to the isolated normal rat hepatocytes, the in vitro hepatic clearance of linezolid in hepatic impairment and renal failure rat hepatocytes decreased by 61.3% and 44.1%, respectively. Organic anion transporting polypeptide (OATP)1B1, OATP1B3, OATP2B1, Na+-taurocholate co-transporting polypeptide (NTCP), organic anion transporter (OAT)1, OAT3, multidrug resistance-associated protein 2 (MRP2), or multidrug resistance protein 1 (MDR) did not mediate linezolid transport. Hepatic impairment primarily increases linezolid exposure through reduced hepatic metabolism, whereas renal failure increases both linezolid and two metabolites exposure through reduced hepatic metabolism and renal glomerular filtration. These findings guide adjusting the dose of linezolid in patients with hepatic and renal insufficiency.

Organic cation transporters 2: Structure, regulation, functions, and clinical implications

The SLC22A2 gene encodes organic cation transporter 2 (OCT2), which is predominantly expressed in renal proximal tubule cells. OCT2 is critical for the active renal excretion of various cationic drugs and endogenous metabolites. OCT2 expression varies across species, with higher levels in mice and monkeys compared with humans and rats. The human OCT2 protein consists of 555 amino acids and contains 12 transmembrane domains. OCT2 functions as a uniporter, facilitating the bidirectional transport of organic cations into renal tubular cells, driven by the inside-negative membrane potential. Its expression is regulated by sex hormones, contributing to potential sex differences in Oct2 activity in rodents. OCT2 has been linked to tissue toxicity, such as cisplatin-induced nephrotoxicity. Factors such as genetic variants, age, disease states, and the coadministration of drugs, including tyrosine kinase inhibitors, contribute to interindividual variability in OCT2 activity. This, in turn, impacts the systemic exposure and elimination of drugs and endogenous substances. Regulatory agencies recommend evaluating the potential of a drug to inhibit OCT2 through in vitro and clinical drug-drug interaction (DDI) studies, often using metformin as a probe substrate. Emerging tools like transporter biomarkers and physiologically based pharmacokinetic modeling hold promise in predicting OCT2-mediated DDIs. While several OCT2 biomarkers, such as N1-methylnicotinamide, have been proposed, their reliability in predicting renal DDIs remains uncertain and requires further study. Ultimately, a better understanding of the factors influencing OCT2 activity is essential for achieving precision medicine and minimizing renal and systemic toxicity. SIGNIFICANCE STATEMENT: Organic cation transporter 2 (OCT2) is essential for the active tubular secretion of xenobiotics and endogenous cationic substances in the kidneys. This article offers a comprehensive overview of the tissue distribution, interspecies differences, and factors affecting its activity-critical for evaluating tissue toxicity and systemic exposure to cationic substances. Using OCT2 biomarkers and integrating OCT2 activity and expression data into physiologically based pharmacokinetic models are valuable tools for predicting OCT2 function and its clinical implications.

A population pharmacokinetic analysis to evaluate the impact of renal impairment on the pharmacokinetics of iberdomide

Iberdomide, a novel potent cereblon E3 ligase modulator, is under investigation for multiple myeloma. This study assessed how renal impairment (RI) affects iberdomide pharmacokinetics (PK). Twenty-six subjects with varying renal function, including those with severe renal impairment and those requiring intermittent hemodialysis (IHD), received a single oral 1 mg dose of iberdomide. Plasma, urine, and dialysate samples were analyzed to evaluate the PK of iberdomide and its major active metabolite, M12. Data were subsequently pooled with PK data from four other clinical trials involving 354 patients to develop a parent - metabolite population PK model using nonlinear mixed-effects modeling to assess the impact of various degrees of RI on drug exposure. The population PK model effectively described the PK of iberdomide and M12, showing that normal, mild, and moderate RI had no significant impact on iberdomide PK exposure, whereas severe RI reduced total clearance and increased PK exposure of iberdomide and M12. Subjects with kidney failure on IHD had comparable total clearance and PK exposure to those with normal renal function. These findings systematically examined the effects of various degrees of RI on iberdomide PK and provide a basis for informing iberdomide dosing in patients with varying degrees of renal impairment.

Physiologically Based Pharmacokinetic Model of Cefotaxime in Patients with Impaired Renal Function

BACKGROUND

Cefotaxime is a widely prescribed cephalosporin antibiotic used to treat various infections. It is mainly eliminated unchanged by the kidney through tubular secretion and glomerular filtration. Therefore, a reduction of kidney function may increase exposure to the drug and induce toxic side effects.

OBJECTIVES

The objectives of this study were to develop a physiologically based pharmacokinetic (PBPK) model of cefotaxime in healthy European adults, to mechanistically describe the impact of chronic kidney disease (CKD) on cefotaxime pharmacokinetics, and to assess the applicability of the model to patients requiring intensive care.

METHODS

Using PK-Sim® software, we developed a PBPK model for cefotaxime, including basolateral and apical renal transporters and renal esterases, in healthy subjects and then extrapolated to patients with CKD by incorporating pathophysiological changes and reductions in activity of drug-metabolizing enzymes and transporters into the model. We then evaluated the predictive performance of the model in patients requiring intensive care using clinical routine data.

RESULTS

Model predictions were considered adequate in healthy subjects and patients with CKD, with predicted-to-observed area under the curve ratios within the two-fold acceptance criterion. Mean prediction error and mean absolute prediction error did not exceed ± 30 and 30%, respectively, except in patients with stage 4 CKD, where they were 70.5 and 75.6%, respectively. The model showed good predictive performance when applied to patients requiring intensive care, but its clinical applicability in this population needs to be further evaluated.

CONCLUSION

We successfully developed whole-body PBPK models to predict cefotaxime pharmacokinetics in different populations. These models represent an additional step toward improving personalized cefotaxime dosing regimens in vulnerable populations.

Risk Prediction of Liver Injury in Pediatric Tuberculosis Treatment: Development of an Automated Machine Learning Model

Purpose

Drug-induced liver injury (DILI) is one of the most common and serious adverse drug reactions related to first-line anti-tuberculosis drugs in pediatric tuberculosis patients. This study aims to develop an automatic machine learning (AutoML) model for predicting the risk of anti-tuberculosis drug-induced liver injury (ATB-DILI) in children.

Methods

A retrospective study was performed on the clinical data and therapeutic drug monitoring (TDM) results of children initially treated for tuberculosis at the affiliated Changsha Central Hospital of University of South China. After the features were screened by univariate risk factor analysis, AutoML technology was used to establish predictive models. The area under the receiver operating characteristic curve (AUC) was used to evaluate model's performance, and then the TreeShap algorithm was employed to interpret the variable contributions.

Results

A total of 184 children were enrolled in this study, of whom 19 (10.33%) developed ATB-DILI. Univariate analysis showed that seven variables were risk factors for ATB-DILI, including the plasma peak concentration (Cmax) of rifampicin, body mass index (BMI), alanine aminotransferase, total bilirubin, total bile acids, aspartate aminotransferase and creatinine. Among the numerous predictive models constructed by the "H2O" AutoML platform, the gradient boost machine (GBM) model exhibited the superior performance with AUCs of 0.838 and 0.784 on the training and testing sets, respectively. The TreeShap algorithm showed that Cmax of rifampicin and BMI were important features that affect the AutoML model's performance.

Conclusion

The GBM model established by AutoML technology shows high predictive accuracy and interpretability for ATB-DILI in children. The prediction model can assist clinicians to implement timely interventions and mitigation strategies, and formulate personalized medication regimens, thereby minimizing potential harm to high-risk children of ATB-DILI.

Pharmacokinetic study of polymyxin B in healthy subjects and subjects with renal insufficiency

Polymyxin B is a viable option for treating antibiotic-resistant infections; however, current data on its pharmacokinetics, particularly in patients with renal insufficiency, remain inconclusive and necessitates further investigation. To address this gap, we conducted an open-label, single-center, single-dose, parallel-group pharmacokinetic study. Participants received an intravenous dose of 0.75 mg/kg of polymyxin B and were categorized based on their renal function: those with normal function (creatinine clearance [CLcr] ≥ 90 mL/min), mild renal insufficiency (CLcr 60-89 mL/min), and end-stage kidney disease patients on intermittent hemodialysis (IHD) (CLcr < 10 mL/min). The pharmacokinetic parameters assessed included the area under the curve (AUC), maximum concentration (Cmax), clearance rate (CL), volume of distribution (Vz), and half-life (t1/2). Results indicated that subjects with mild renal insufficiency exhibited pharmacokinetic profiles similar to healthy individuals. Nevertheless, in patients undergoing long-term IHD, we observed significant differences: the AUC was 58% higher, Cmax was 29% lower, CL was 42% lower, Vz was 60% larger, and t1/2 was extended by 10 h compared to healthy controls. Secondary outcomes revealed good tolerability of polymyxin B across all groups, with no serious adverse effects related to renal function. In summary, while kidney function may have a slight impact on the pharmacokinetic of polymyxin B, it does not compromise the drug's therapeutic effectiveness.

Simultaneous determination of the combined and free concentrations of atorvastatin and its major metabolite in vitro and in vivo based on ultrafiltration coupled with UPLC-MS/MS method: an application in a protein binding rate and metabolism ability study in uremic hemodialysis patients

Introduction

A rapid, accurate, and specific ultrafiltration with ultra-performance liquid chromatographic-tandem mass spectrometry method was validated for the simultaneous determination of the protein binding rate of atorvastatin in uremic patients. Methods: The plasma samples were centrifuged at 6,000 r/min for 15 min at 37°C and the ultrafiltrate was collected. An ACQUITY UPLC® BEH C18 Column with gradient elution of water (0.1% formic acid) and acetonitrile was used for separation at a flow rate of 0.4 ml/min.

Results

The calibration curves of two analytes in the serum showed excellent linearity over the concentration ranges of 0.05-20.00 ng/ml for atorvastatin, and 0.05-20.00 ng/ml for orthohydroxy atorvastatin, respectively. This method was validated according to standard US food and drug administration and European medicines agency guidelines in terms of selectivity, linearity, detection limits, matrix effects, accuracy, precision, recovery, and stability. This assay can be easily implemented in clinical practice to determine the free and combined concentrations of atorvastatin in the plasma of uremic patients. The final result showed that the average plasma protein binding rate in uremic patients was 86.58 ± 2.04%, relative standard deviation (RSD) (%) = 1.98, while the plasma protein binding rate in patients with normal renal function was 97.62 ± 1.96%, RSD (%) = 2.04. There was a significant difference in the protein binding rate in different types of plasma (P < 0.05), and the protein binding rate decreased with increasing creatinine until it stabilized at nearly 80%. The mean metabolite/prototype ratio of atorvastatin in patients with normal renal function and in patients with uremia was 1.085 and 0.974, respectively.

Discussion

The metabolic process of atorvastatin may be inhibited in uremic hemodialysis patients, but the total concentration of atorvastatin did not change significantly; due to the decrease of protein binding rate increase the drug distribution of atorvastatin in the liver or muscle tissue, which may increase the risk of certain adverse reactions. We recommend that clinicians use free drug concentration monitoring to adjust the dose of atorvastatin to ensure patient safety for uremic hemodialysis patients.

Evaluation of 14 PFAS for permeability and organic anion transporter interactions: Implications for renal clearance in humans

Per- and polyfluoroalkyl substances (PFAS) encompass a diverse group of synthetic fluorinated chemicals known to elicit adverse health effects in animals and humans. However, only a few studies investigated the mechanisms underlying clearance of PFAS. Herein, the relevance of human renal transporters and permeability to clearance and bioaccumulation for 14 PFAS containing three to eleven perfluorinated carbon atoms (ηpfc = 3-11) and several functional head-groups was investigated. Apparent permeabilities and interactions with human transporters were measured using in vitro cell-based assays, including the MDCK-LE cell line, and HEK293 stable transfected cell lines expressing organic anion transporter (OAT) 1-4 and organic cation transporter (OCT) 2. The results generated align with the Extended Clearance Classification System (ECCS), affirming that permeability, molecular weight, and ionization serve as robust predictors of clearance and renal transporter engagement. Notably, PFAS with low permeability (ECCS 3A and 3B) exhibited substantial substrate activity for OAT1 and OAT3, indicative of active renal secretion. Furthermore, we highlight the potential contribution of OAT4-mediated reabsorption to the renal clearance of PFAS with short ηpfc, such as perfluorohexane sulfonate (PFHxS). Our data advance our mechanistic understanding of renal clearance of PFAS in humans, provide useful input parameters for toxicokinetic models, and have broad implications for toxicological evaluation and regulatory considerations.

Re-discover the value of protein binding assessments in hepatic and renal impairment studies and its contributions in drug labels and dose decisions

One of the key pharmacokinetic properties of most small molecule drugs is their ability to bind to serum proteins. Unbound or free drug is responsible for pharmacological activity while the balance between free and bound drug can impact drug distribution, elimination, and other safety parameters. In the hepatic impairment (HI) and renal impairment (RI) clinical studies, unbound drug concentration is often assessed; however, the relevance and impact of the protein binding (PB) results is largely limited. We analyzed published clinical safety and pharmacokinetic studies in subjects with HI or RI with PB assessment up to October 2022 and summarized the contribution of PB results on their label dose recommendations. Among drugs with HI publication, 32% (17/53) associated product labels include PB results in HI section. Of these, the majority (9/17, 53%) recommend dose adjustments consistent with observed PB change. Among drugs with RI publication, 27% (12/44) of associated product labels include PB results in RI section with the majority (7/12, 58%) recommending no dose adjustment, consistent with the reported absence of PB change. PB results were found to be consistent with a tailored dose recommendation in 53% and 58% of the approved labels for HI and RI section, respectively. We further discussed the interpretation challenges of PB results, explored treatment decision factors including total drug concentration, exposure-response relationships, and safety considerations in these case examples. Collectively, comprehending the alterations in free drug levels in HI and RI informs treatment decision through a risk-based approach.

Pharmacokinetics of long-acting lenacapavir in participants with hepatic or renal impairment

Lenacapavir is a novel, first-in-class, multistage inhibitor of HIV-1 capsid function approved for the treatment of multidrug-resistant HIV-1 infection in combination with other antiretrovirals for heavily treatment-experienced people with HIV. Two Phase 1, open-label, parallel-group, single-dose studies assessed the pharmacokinetics (PK) of lenacapavir in participants with moderate hepatic impairment [Child-Pugh-Turcotte (CPT) Class B: score 7-9] or severe renal impairment [15 ≤ creatinine clearance (CLcr) ≤29 mL/min] to inform lenacapavir dosing in HIV-1-infected individuals with organ impairment. In both studies, a single oral dose of 300 mg lenacapavir was administered to participants with normal (n = 10) or impaired (n = 10) hepatic/renal function who were matched for age (±10 years), sex, and body mass index (±20%). Lenacapavir exposures [area under the plasma concentration-time curve from time 0 to infinity (AUCinf) and maximum concentration (Cmax)] were approximately 1.47- and 2.61-fold higher, respectively, in participants with moderate hepatic impairment compared to those with normal hepatic function, whereas lenacapavir AUCinf and Cmax were approximately 1.84- and 2.62-fold higher, respectively, in participants with severe renal impairment compared to those with normal renal function. Increased lenacapavir exposures with moderate hepatic or severe renal impairment were not considered clinically meaningful. Lenacapavir was considered generally safe and well tolerated in both studies. These results support the use of approved lenacapavir dosing regimen in patients with mild (CPT Class A: score 5-6) or moderate hepatic impairment as well as in patients with mild (60 ≤ CLcr ≤ 89 mL/min), moderate (30 ≤ CLcr ≤ 59 mL/min), and severe renal impairment.

A multi-center cross-sectional study of Chinese Herbal Medicine-Drug adverse reactions using active surveillance in Singapore's Traditional Chinese Medicine clinics

BACKGROUND

This study aimed to investigate the rates and causality of patient-reported adverse events (AEs) associated with concomitant Chinese Herbal Medicine (CHM) and Western Medicine prescription drug (WMPD) consumption through active surveillance in Singapore's Traditional Chinese Medicine (TCM) clinics.

METHODS

A cross-sectional study was conducted at five TCM clinics across Singapore from 8th May till 8th July 2023. Patients were screened to determine rates of CHM and WMPD consumption, and then interviewed if an AE was reported. An expert committee assessed the AE reports to determine causality. Along with descriptive statistics, odds ratios were calculated to determine AE occurrence likelihoods for patients who consumed both CHM and WMPD compared to CHM consumption alone.

RESULTS

1028 patients were screened and 62.65% of them reported concurrent CHM-WMPD consumption. Patients who consumed CHM and WMPD were 3.65 times more likely to experience an AE as compared to CHM consumption alone. 18 AE reports were adjudicated, with most AEs deemed unlikely due to CHM consumption.

CONCLUSIONS

A large proportion of patients consumed CHM and WMPD concurrently, thus increasing their risk of experiencing AEs compared to those consuming CHM only. Active surveillance is applicable for detecting AEs, collecting data for causality assessment, and analysis.

Relationship of plasma 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid concentration with OATP1B activity in patients with chronic kidney disease

Organic anion-transporting polypeptides (OATP)1B are drug transporters mainly expressed in the sinusoidal membrane. Many studies have suggested that OATP1B activity is affected by genetic factor, the uremic toxin 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF), and inflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). Coproporphyrin-I (CP-I) is spotlighted as a highly accurate endogenous substrate of OATP1B. We previously reported a positive correlation between plasma CMPF and CP-I concentrations in patients with chronic kidney disease (CKD). The present study evaluated the impact of genetic polymorphisms, CMPF, IL-6, TNF-α, and estimated glomerular filtration rate (eGFR) on individual differences in OATP1B activity in patients with CKD. Seventy-three patients with CKD who received kidney transplant at least 3 months earlier were analyzed. Plasma CP-I concentration was higher in OATP1B1*15 carriers than in non-carriers. In all patients, CP-I did not correlate significantly with CMPF, IL-6, TNF-α, or eGFR. However, when the dataset was cut off at CMPF concentration of 8 and 7 μg/mL, 4 μg/mL, 3 μg/mL or 2 μg/mL, CMPF correlated positively with CP-I, and correlation coefficient tended to be higher as plasma CMPF concentration was lower. In conclusion, OATP1B1*15 impacted OATP1B activity in patients with CKD, but IL-6 and TNF-α did not. However, the impact of CMPF on OATP1B activity was limited to low CMPF concentrations, and the effect could be saturated at high concentrations. When prescribing an OATP1B substrate drug for patients with CKD, the OATP1B1*15 carrier status and plasma CMPF concentration may need to be considered to decide the dose regimen.

Thioacetamide-Induced Acute Liver Injury Increases Metformin Plasma Exposure by Downregulating Renal OCT2 and MATE1 Expression and Function

Metformin plasma exposure is increased in rats with thioacetamide (TAA)-induced liver failure. The absorption, distribution, and excretion process of metformin is mainly mediated by organic cation transporters (OCTs) and multidrug and toxin extrusion transporters (MATEs). To investigate the mechanisms of the increase in TAA-induced metformin plasma exposure, we employed intestinal perfusion and urinary excretion assays to evaluate the changes in the absorption and excretion of metformin and used Western blotting to investigate the metformin-related transport proteins' expression changes and mechanisms. The results showed that neither intestinal OCT2 expression nor metformin intestinal absorption were significantly altered by TAA-induced liver failure, while significantly decreased expression and function of renal OCT2 and MATE1 as well as impaired metformin excretion were observed in TAA rats. HK-2 cells were used as an in vitro model to explore the mechanism of liver-failure-mediated downregulation in renal OCT2 and MATE1. The results demonstrated that among numerous abnormal substances that changed in acute liver failure, elevated estrogen levels and tumor necrosis factor-α were the main factors mediating the downregulation of OCT2 and MATE1. In conclusion, this study highlights the downregulation of renal OCT2 and MATE1 in liver injury and its regulatory mechanism and reveals its roles in the increase in TAA-mediated metformin plasma exposure.

Acute kidney injury interacts with VKORC1 genotype on initiative warfarin dose among heart surgery recipients: a real-world research

Patients who receive heart valve surgery need anticoagulation prophylaxis to reduce the risk of thrombosis. Warfarin often is a choice but its dosage varies due to gene and clinical factors. We aim to study, among them, if there is an interaction between acute kidney injury and two gene polymorphisms from this study. We extracted data of heart valve surgery recipients from the electronic health record (EHR) system of a medical center. The primary outcome is about the average daily dose of warfarin, measured as an additive interaction effect (INTadd) between acute kidney injury (AKI) and warfarin-related gene polymorphisms. The confounders, including age, sex, body surface area (BSA), comorbidities (i.e., atrial fibrillation [AF], hypertension [HTN], congestive heart failure [CHF]), serum albumin level, warfarin-relevant gene polymorphism (i.e., CYP2C9, VKORC1), prosthetic valve type (i.e., metal, bio), and warfarin history were controlled via a multivariate-linear regression model. The study included 200 patients, among whom 108 (54.00%) are female. Further, the mean age is 54.45 years, 31 (15.50%) have CHF, and 40 (20.00%) patients were prescribed concomitant amiodarone, which potentially overlays with the warfarin prophylaxis period. During the follow-up, AKI occurred in 30 (15.00%) patients. VKORC1 mutation (1639G>A) occurred in 25 (12.50%) patients and CYPC29 *2 or *3 mutations presented in 20 patients (10.00%). We found a significant additive interaction effect between AKI and VKORC1 (- 1.17, 95% CI - 1.82 to - 0.53, p = 0.0004). This result suggests it is probable that there is an interaction between acute kidney injury and the VKORC1 polymorphism for the warfarin dose during the initial period of anticoagulation prophylaxis.

Comparative pharmacokinetics of six bioactive components of Shen-Wu-Yi-Shen tablets in normal and chronic renal failure rats based on UPLC-TSQ-MS/MS

ETHNOPHARMACOLOGICAL RELEVANCE

Shen-Wu-Yi-Shen tablets (SWYST), a Chinese patent medicine consisting of 12 herbal medicines, was formulated by a famous TCM nephrologist, Zou Yunxiang. It is clinically used to improve the symptoms of nausea, vomiting, poor appetite, dry mouth and throat, and dry stool in patients with chronic renal failure (CRF) accompanied by qi and yin deficiency, dampness, and turbidity. SWYST can reduce urea nitrogen, blood creatinine, and urinary protein loss, and increase the endogenous creatinine clearance rate. However, little is known about its pharmacokinetics.

AIM OF STUDY

To compare the pharmacokinetics of six bioactive components after oral administration of SWYST in normal and adenine-induced CRF rats.

MATERIALS AND METHODS

A method based on ultra-performance liquid chromatography coupled with a triple-stage quadrupole mass spectrometer (UPLC-TSQ-MS/MS) was developed and validated to determine the six bioactive compounds (albiflorin, paeoniflorin, plantagoguanidinic acid, rhein, aloe-emodin, and emodin) in rat plasma. Rat plasma samples were prepared using protein precipitation. Chromatography was performed on an Agilent Eclipse Plus C18 column (3.0 × 50 mm, 1.8 μm) using gradient elution with a mobile phase composed of acetonitrile and water containing 0.1% (v/v) formic acid, while detection was achieved by electrospray ionization MS under the multiple selective reaction monitoring modes. After SWYST administration, rat plasma was collected at different time points, and the pharmacokinetic parameters of six analytes were calculated and analyzed based on the measured plasma concentrations.

RESULTS

The UPLC-TSQ-MS/MS method was fully validated for its satisfactory linearity (r ≥ 0.9913), good precisions (RSD <11.5%), and accuracy (RE: -13.4∼13.1%), as well as acceptable limits in the extraction recoveries, matrix effects, and stability (RSD <15%). In normal rats, the six analytes were rapidly absorbed (Tmax ≤ 2 h), and approximately 80% of their total exposure was eliminated within 10 h. Moreover, in normal rats, the AUC0-t and Cmax of albiflorin, plantagoguanidinic acid, and rhein exhibited linear pharmacokinetics within the dose ranges, while that of paeoniflorin is non-linear. However, in CRF rats, the six analytes exhibited reduced elimination and significantly different AUC or Cmax values. These changes may reflect a decreased renal clearance rate or inhibition of drug-metabolizing enzymes and transporters in the liver and gastrointestinal tract caused by CRF.

CONCLUSIONS

A sensitive UPLC-TSQ-MS/MS method was validated and used to investigate the pharmacokinetics of SWYST in normal and CRF rats. This is the first study to investigate the pharmacokinetics of SWYST, and our findings elucidate the causes of their different pharmacokinetic behaviors in CRF rats. Furthermore, the results provide useful information to guide further research on the pharmacokinetic-pharmacodynamic correlation and clinical application of SWYST.

Innovations, Opportunities, and Challenges for Predicting Alteration in Drug-Metabolizing Enzyme and Transporter Activity in Specific Populations

Drug-metabolizing enzymes and transporters (DMETs) are key regulators of the pharmacokinetics, efficacy, and toxicity of therapeutics. Over the past two decades, significant advancements in in vitro methodologies, targeted proteomics, in vitro to in vivo extrapolation methods, and integrated computational approaches such as physiologically based pharmacokinetic modeling have unequivocally contributed to improving our ability to quantitatively predict the role of DMETs in absorption, distribution, metabolism, and excretion and drug-drug interactions. However, the paucity of data regarding alterations in DMET activity in specific populations such as pregnant individuals, lactation, pediatrics, geriatrics, organ impairment, and disease states such as, cancer, kidney, and liver diseases and inflammation has restricted our ability to realize the full potential of these recent advancements. We envision that a series of carefully curated articles in a special supplementary issue of Drug Metabolism and Disposition will summarize the latest progress in in silico, in vitro, and in vivo approaches to characterize alteration in DMET activity and quantitatively predict drug disposition in specific populations. In addition, the supplementary issue will underscore the current scientific knowledge gaps that present formidable barriers to fully understand the clinical implications of altered DMET activity in specific populations and highlight opportunities for multistakeholder collaboration to advance our collective understanding of this rapidly emerging area. SIGNIFICANCE STATEMENT: This commentary highlights current knowledge and identifies gaps and key challenges in understanding the role of drug-metabolizing enzymes and transporters (DMETs) in drug disposition in specific populations. With this commentary for the special issue in Drug Metabolism and Disposition, the authors intend to increase interest and invite potential contributors whose research is focused or has aided in expanding the understanding around the role and impact of DMETs in drug disposition in specific populations.

Research Methods and New Advances in Drug-Drug Interactions Mediated by Renal Transporters

The kidney is critical in the human body's excretion of drugs and their metabolites. Renal transporters participate in actively secreting substances from the proximal tubular cells and reabsorbing them in the distal renal tubules. They can affect the clearance rates (CLr) of drugs and their metabolites, eventually influence the clinical efficiency and side effects of drugs, and may produce drug-drug interactions (DDIs) of clinical significance. Renal transporters and renal transporter-mediated DDIs have also been studied by many researchers. In this article, the main types of in vitro research models used for the study of renal transporter-mediated DDIs are membrane-based assays, cell-based assays, and the renal slice uptake model. In vivo research models include animal experiments, gene knockout animal models, positron emission tomography (PET) technology, and studies on human beings. In addition, in vitro-in vivo extrapolation (IVIVE), ex vivo kidney perfusion (EVKP) models, and, more recently, biomarker methods and in silico models are included. This article reviews the traditional research methods of renal transporter-mediated DDIs, updates the recent progress in the development of the methods, and then classifies and summarizes the advantages and disadvantages of each method. Through the sorting work conducted in this paper, it will be convenient for researchers at different learning stages to choose the best method for their own research based on their own subject's situation when they are going to study DDIs mediated by renal transporters.

A State-of-the-Science Review of Interactions of Per- and Polyfluoroalkyl Substances (PFAS) with Renal Transporters in Health and Disease: Implications for Population Variability in PFAS Toxicokinetics

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are ubiquitous in the environment and have been shown to cause various adverse health impacts. In animals, sex- and species-specific differences in PFAS elimination half-lives have been linked to the activity of kidney transporters. However, PFAS molecular interactions with kidney transporters are still not fully understood. Moreover, the impact of kidney disease on PFAS elimination remains unclear.

OBJECTIVES

This state-of-the-science review integrated current knowledge to assess how changes in kidney function and transporter expression from health to disease could affect PFAS toxicokinetics and identified priority research gaps that should be addressed to advance knowledge.

METHODS

We searched for studies that measured PFAS uptake by kidney transporters, quantified transporter-level changes associated with kidney disease status, and developed PFAS pharmacokinetic models. We then used two databases to identify untested kidney transporters that have the potential for PFAS transport based on their endogenous substrates. Finally, we used an existing pharmacokinetic model for perfluorooctanoic acid (PFOA) in male rats to explore the influence of transporter expression levels, glomerular filtration rate (GFR), and serum albumin on serum half-lives.

RESULTS

The literature search identified nine human and eight rat kidney transporters that were previously investigated for their ability to transport PFAS, as well as seven human and three rat transporters that were confirmed to transport specific PFAS. We proposed a candidate list of seven untested kidney transporters with the potential for PFAS transport. Model results indicated PFOA toxicokinetics were more influenced by changes in GFR than in transporter expression.

DISCUSSION

Studies on additional transporters, particularly efflux transporters, and on more PFAS, especially current-use PFAS, are needed to better cover the role of transporters across the PFAS class. Remaining research gaps in transporter expression changes in specific kidney disease states could limit the effectiveness of risk assessment and prevent identification of vulnerable populations. https://doi.org/10.1289/EHP11885.

Development of a PBPK model to quantitatively understand absorption and disposition mechanism and support future clinical trials for PB-201

PB-201 is the second glucokinase activator in the world to enter the phase III clinical trials for the treatment of type 2 diabetes mellitus (T2DM). Combined with the efficacy advantages and the friendly absorption, distribution, metabolism, and excretion characteristics, the indication population of PB-201 will be broad. Because the liver is the primary organ for PB-201 elimination, and the elderly account for 20% of patients with T2DM, it is essential to estimate PB-201 exposure in specific populations to understand the pharmacokinetic characteristics and avoid hypoglycemia. Despite the limited contribution of CYP3A4 to PB-201 metabolism in vivo, the dual effects of nonspecific inhibitors/inducers on PB-201 (substrate for CYP3A4 and CYP2C9 isoenzymes) exposure under fasted and fed states also need to be evaluated to understand potential risks of combination therapy. To grasp the unknown information, the physiologically-based pharmacokinetic (PBPK) model was first developed and the influence of internal and external factors on PB-201 exposure was evaluated. Results are shown that the predictive performance of the mechanistic PBPK model meets the predefined criteria, and can accurately capture the absorption and disposition characteristics. Impaired liver function and age-induced changes in physiological factors may significantly increase the exposure under fasted state by 36%-158% and 48%-82%, respectively. The nonspecific inhibitor (fluconazole) and inducer (rifampicin) may separately increase/decrease PB-201 systemic exposure by 44% and 58% under fasted state, and by 78% and 47% under fed state. Therefore, the influence of internal and external factors on PB-201 exposure deserves attention, and the precision dose can be informed in future clinical studies based on the predicted results.

Predicting the Effect of Renal Function on Systemic Clearance: Is a simple scaling method sufficient?

PURPOSE

To employ a simple scaling method to predict systemic or oral clearance for drugs that are primarily renally cleared knowing the fraction eliminated in urine (f_e) and a patient's renal function relative to healthy controls (S_GFR).

METHODS

Observations evaluating drug clearance as a function of creatinine clearance for renally cleared drugs (f_e >0.3) were obtained from literature sources. The analysis comprised of 82 unique drugs from 124 studies including 31 drugs with replicate studies. A simple scaler for renal function was employed and compared to the linear regression of available data. For drugs in which replicate studies were available, the ability of the linear regression (Cl vs Cl_CR) from one pharmacokinetic study was used to predict observations from an assigned replicate and compared to the scaling approach.

RESULTS

For patients categorized as severe kidney disease (Cl_CR fixed at 20 ml/min), the scalar tended to over predict some observations, but 92% of the predictions were within 50 - 200% of the observed data. For drugs with available replicates, the scalar was as good or better in predicting the influence of Cl_CR on systemic clearance from a separate study when comparing against the linear regression approach.

CONCLUSION

A scaling approach to account for alterations in drug clearance appears to have its advantages and represents a simple and generalizable method for guiding dose adjustments in patients with decreased renal function for drugs that are renally cleared (f_e >0.3). In addition to its use in clinical practice, validation of this approach may have implications in facilitating more efficient drug development processes for designing dose-adjusted pharmacokinetic studies in patients with renal disease.

Population total and unbound pharmacokinetics and pharmacodynamics of ciprofol and M4 in subjects with various renal functions

AIMS

The aim of this study was to develop a population pharmacokinetic (PK) model to simultaneously describe both total and unbound concentrations of ciprofol and its major glucuronide metabolite, M4, and to link it to the population pharmacodynamics (PD) model in subjects with various renal functions.

METHODS

A total of 401 and 459 pairs of total and unbound plasma concentrations of ciprofol and M4, respectively, as well as 2190 bispectral index (BIS) data from 24 Chinese subjects with various renal functions were available. Covariates that may potentially contribute to the PK and PD variability of ciprofol were screened using a stepwise procedure. The optimal ciprofol induction dosing regimen was determined by model-based simulations.

RESULTS

The PK of unbound ciprofol could best be described by a three-compartment model, while a two-compartment model could adequately describe unbound M4 PK. The concentrations of total and unbound ciprofol and M4 were linked using a linear protein binding model. The relationship between plasma concentrations of ciprofol and BIS data was best described by an inhibitory sigmoidal E_max model with a two-compartment biophase distribution compartment. Hemoglobin was the identified covariate determining the central compartment clearance of ciprofol; uric acid was a covariate affecting the central compartment clearance of M4 and protein binding rate, k_B . The included covariates had no effect on the PD of ciprofol. Simulation results indicated that the label-recommended dose regimen was adequate for anaesthesia induction.

CONCLUSIONS

The developed model fully characterized the population PK and PD profiles of ciprofol. No dose adjustment is required in patients with mild and moderate renal impairment.

Advanced Drug Delivery Systems for Renal Disorders

Kidney disease management and treatment are currently causing a substantial global burden. The kidneys are the most important organs in the human urinary system, selectively filtering blood and metabolic waste into urine via the renal glomerulus. Based on charge and/or molecule size, the glomerular filtration apparatus acts as a barrier to therapeutic substances. Therefore, drug distribution to the kidneys is challenging, resulting in therapy failure in a variety of renal illnesses. Hence, different approaches to improve drug delivery across the glomerulus filtration barrier are being investigated. Nanotechnology in medicine has the potential to have a significant impact on human health, from illness prevention to diagnosis and treatment. Nanomaterials with various physicochemical properties, including size, charge, surface and shape, with unique biological attributes, such as low cytotoxicity, high cellular internalization and controllable biodistribution and pharmacokinetics, have demonstrated promising potential in renal therapy. Different types of nanosystems have been employed to deliver drugs to the kidneys. This review highlights the features of the nanomaterials, including the nanoparticles and corresponding hydrogels, in overcoming various barriers of drug delivery to the kidneys. The most common delivery sites and strategies of kidney-targeted drug delivery systems are also discussed.

Single-dose Pharmacokinetics of Eluxadoline in Healthy Participants With Normal Renal Function and Participants With Renal Impairment

Eluxadoline is approved for the treatment of diarrhea-predominant irritable bowel syndrome in the United States. The impact of renal impairment on the pharmacokinetic (PK) parameters of eluxadoline is currently unknown. This phase 1, open-label, parallel-group study evaluated the PK and safety profile of eluxadoline in 8 participants with renal impairment and 8 matched healthy controls. Of the participants with renal impairment, 2 had severe renal impairment (estimated glomerular filtration rate [eGFR] <30 mL/min/1.73 m² ) and 6 had end-stage renal disease while not yet on dialysis (eGFR <15 mL/min/1.73 m² ). The primary objective was to assess plasma and urine PKs, and plasma protein binding of eluxadoline. In participants with renal impairment, mean plasma concentrations of eluxadoline were consistently higher compared with matched healthy controls: 1.4-fold higher for mean maximum plasma concentration (C_max ) and 2.2-fold higher for mean area under the plasma concentration-time curve from time 0 to time t. The median time to C_max was 2.5 hours in both groups. Although eluxadoline is a locally acting drug with low oral bioavailability, because of the increased systemic exposure in participants with renal impairment as a cautionary measure the lower approved dose of 75 mg twice daily is recommended for individuals with severe renal impairment and end-stage renal disease while not yet on dialysis. Eluxadoline 100 mg single dose was well tolerated in participants with renal impairment and matched healthy controls.

Assessment of alteration in antiviral plasma concentration across dialysis days: computational and analytical study

Aim: Protein-bound uremic toxins (PBUTs) may displace drugs from the plasma proteins and render them more liable to clearance. This study aims to investigate the possible interplay between PBUTs and directly acting antivirals (DAAs). Methods: PBUT plasma protein binding was compared to those of paritaprevir (PRT), ombitasivir (OMB) and ritonavir (RTV) in silico to assess the possible competitive displacement. The three drugs were LC-MS/MS determined in seven patients across dialysis and non-dialysis days and results were compared. Results & conclusion: Results showed that the PBUT exhibited a lower binding than DAA reducing the liability of their competitive displacement. This was echoed by an unaltered plasma concentration across dialysis days. Results may indicate that PBUT accumulation may have limited effect on disposition of DAA.

Protective effect of Rhein against vancomycin-induced nephrotoxicity through regulating renal transporters and Nrf2 pathway

Vancomycin (VCM)'s nephrotoxicity limits its application and therapeutic efficiency. The aim of this study was to determine the protective effect of rhein against VCM-induced nephrotoxicity (VIN). VIN models were established in rats and NRK-52E cells. Rhein up-regulated the expressions of renal organic anion transporter (Oat) 1, Oat3, organic cation transporter 2 (Oct2), multidrug resistance-associated protein 2 (Mrp2), mammal multidrug and toxin extrusion proteins 1 (Mate 1) and P-glycoprotein (P-gp) to facilitate the efflux of plasma creatinine, blood urea nitrogen (BUN), and plasma indoxyl sulfate. Rhein increased the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) to regulate the expression of Mrp2, P-gp, and Mate 1. The increased level of superoxide dismutase (SOD), decreased level of malondialdehyde (MDA) and reduced number of apoptosis cells were observed after treatment of rhein. Rhein decreased the number of apoptosis cells as well as increased the expression of B-cell lymphoma-2 (Bcl-2) and decreased expressions of Bcl-2-like protein 4 (Bax). ML385, as a typical inhibitor of Nrf2, reversed the protective effects of rhein in cells. Rhein oriented itself in the site of Keap1, inhibiting the Keap1-Nrf2 interaction. Rhein ameliorated VIN mainly through regulating the expressions of renal transporters and acting on Nrf2 pathway.

Differences in Multicomponent Pharmacokinetics, Tissue Distribution, and Excretion of Tripterygium Glycosides Tablets in Normal and Adriamycin-Induced Nephrotic Syndrome Rat Models and Correlations With Efficacy and Hepatotoxicity

Tripterygium glycosides tablets (TGT) are widely used for treating nephrotic syndrome (NS), but hepatotoxicity is frequently reported. The presence of underlying disease(s) can alter the disposition of drugs and affect their efficacy and toxicity. However, no studies have reported the impact of NS on the ADME profiles of TGT or its subsequent impact on the efficacy and toxicity. Thus, the efficacy and hepatotoxicity of TGT were evaluated in normal and NS rats after oral administration of TGT (10 mg/kg/day) for 4 weeks. The corresponding ADME profiles of the six key TGT components (triptolide (TPL), wilforlide A (WA), wilforgine (WFG), wilfortrine (WFT), wilfordine (WFD), and wilforine (WFR)) were also measured and compared in normal and NS rats after a single oral gavage of 10 mg/kg TGT. Canonical correlation analysis (CCA) of the severity of NS and the in vivo exposure of the six key TGT components was performed to screen the anti–NS and hepatotoxic material bases of TGT. Finally, the efficacy and hepatotoxicity of the target compounds were evaluated in vitro. The results showed that TGT decreased the NS symptoms in rats, but caused worse hepatotoxicity under the NS state. Significant differences in the ADME profiles of the six key TGT components between the normal and NS rats were as follows: higher plasma and tissue exposure, lower urinary and biliary excretion, and higher fecal excretion for NS rats. Based on CCA and in vitro verification, TPL, WA, WFG, WFT, WFD, and WFR were identified as the anti–NS material bases of TGT, whereas TPL, WFG, WFT, and WFD were recognized as the hepatotoxic material bases. In conclusion, NS significantly altered the ADME profiles of the six key TGT components detected in rats, which were related to the anti–NS and hepatotoxic effects of TGT. These results are useful for the rational clinical applications of TGT.

Effects of black tea and black brick tea with fungal growth on lowering uric acid levels in hyperuricemic mice

Black tea, a traditional drink, can induce urination and quench thirst. Black brick tea with fungal growth, prepared by steaming, pressing, inducing fungal growth, and drying the black tea, is a new type of black tea with different sensory qualities and is suitable for storage. However, the effects of black brick tea with fungal growth on lowering uric acid are still unexplored. Therefore, the potassium oxonate was administered for 7 consecutive days to establish the hyperuricemic mice. Then allopurinol, black tea, and black brick tea with fungal growth were orally administered with hyperuricemic mice for 14 days. Serum uric acid levels, liver xanthine oxidase (XOD) and adenosine deaminase (ADA) activities, and expression of renal urate transporters and inflammatory response were detected. Compared to the model group, both types of black tea lowered serum uric acid by decreasing the uric acid production with inhibiting the activities of XOD and ADA, and increasing uric acid excretion because of downregulating urate transporter 1 (URAT1) and glucose transporter 9 (GLUT9) expressions, and upregulating organic anion transporter 1 (OAT1), organic anion transporter 3 (OAT3), and organic cation transporter 1 (OCT1) expressions. They could also improve renal injury by suppressing the activation of the NOD-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome, and nuclear factor-κB (NF-κB) signaling, thereby reducing renal proinflammatory cytokine levels. Compared with black tea, black brick tea with fungal growth with a higher content of theabrownins had a better effect on lowering serum uric acid. PRACTICAL APPLICATIONS: Black tea accounts for approximately 78% of the total consumed tea in the world. Black brick tea with fungal growth is a new kind of black tea product with different sensory qualities and is suitable for storage. The study found that black brick tea with fungal growth is superior to black tea in reducing serum uric acid levels, which make a significant contribution to promote people's health and stimulate the production and consumption of black brick tea with fungal growth. In addition, it provides a clue for future research to identify the effective components of black brick tea with fungal growth lowering uric acid.

Pharmacokinetic Study of Coadministration with Cefuroxime Sodium for Injection Influencing ReDuNing Injection-Derived Seven Phytochemicals and Nine Metabolites in Rats

According to the sixth edition of China's "New Coronavirus Diagnosis and Treatment Plan (NCDTP)," ReDuNing injection (RDN) was firstly introduced to treat severe and critical COVID-19, whereas its combination with broad-spectrum antibiotics was suggested to take with extreme caution and full reasons. Therefore, we aim to describe the pharmacokinetics of seven active phytochemicals and semiquantification of nine relevant metabolites in ReDuNing injection (RDN) after combining with cefuroxime sodium (CNa) for injection in rat plasma. Male Sprague-Dawley rats were randomly assigned to six groups, and they were intravenously administered, respectively, with different prescriptions of RDN (2 mL/kg) and CNa (225 mg/kg). At different time points (0.03, 0.08, 0.17, 0.24, 0.33, 0.50, 0.67, 1, and 6 h) after administration, the drug concentrations of iridoids glycosides, organic acids, and metabolites in rat plasma were determined using ultrahigh-pressure liquid chromatography coupled with linear ion rap-orbitrap tandem mass spectrometry (UHPLC-LTQ-Orbitrap-MS), and main pharmacokinetic parameters were estimated by noncompartment model. The results showed that there were differences in pharmacokinetic parameters, AUC_(0-t), T_1/2, C _max, CL of iridoids glycosides, and organic acids, after the intravenous administration of the different combinations of RDN and CNa. Moreover, different combinations of the injections also resulted in different curves of relative changes of each metabolite. The obtained results suggested that RDN and CNa existed pharmacokinetic drug-herb interactions in rats. The findings not only lay the foundation for evaluating the safety of RDN injection combined with CNa but also make contributions to clinically applying RDN injection combined with CNa, which works potentially against severe forms of COVID-19.

Quantification of CYP3A and Drug Transporters Activity in Healthy Young, Healthy Elderly and Chronic Kidney Disease Elderly Patients by a Microdose Cocktail Approach

Background: Ageing and chronic kidney disease (CKD) affect pharmacokinetic (PK) parameters. Since mechanisms are related and remain unclear, cytochrome P450 (CYP) 3A and drug transporter activities were investigated in the elderly with or without CKD and compared to healthy adults using a microdose cocktail. Methods: Healthy young participants (n = 20), healthy elderly participants (n = 16) and elderly patients with CKD (n = 17) received, in study period 1, a single dose of microdose cocktail probe containing 30 µg midazolam, 750 µg dabigatran etexilate, 100 µg atorvastatin, 10 µg pitavastatin, and 50 µg rosuvastatin. After a 14-day wash-out period, healthy young participants continued to study period 2 with the microdose cocktail plus rifampicin. PK parameters including area under the plasma concentration-time curve (AUC), maximum plasma drug concentration (C_max), and half-life were estimated before making pairwise comparisons of geometric mean ratios (GMR) between groups. Results: AUC and C_max GMR (95% confidence interval; CI) of midazolam, a CYP3A probe substrate, were increased 2.30 (1.70-3.09) and 2.90 (2.16-3.88) fold in healthy elderly and elderly patients with CKD, respectively, together with a prolonged half-life. AUC and C_max GMR (95%CI) of atorvastatin, another CYP3A substrate, was increased 2.14 (1.52-3.02) fold in healthy elderly and 4.15 (2.98-5.79) fold in elderly patients with CKD, indicating decreased CYP3A activity related to ageing. Associated AUC changes in the probe drug whose activity could be modified by intestinal P-glycoprotein (P-gp) activity, dabigatran etexilate, were observed in patients with CKD. However, whether the activity of pitavastatin and rosuvastatin is modified by organic anion transporting polypeptide 1B (OATP1B) and of breast cancer resistance protein (BCRP), respectively, in elderly participants with or without CKD was inconclusive. Conclusions: CYP3A activity is reduced in ageing. Intestinal P-gp function might be affected by CKD, but further confirmation appears warranted. Clinical Trial Registration:http://www.thaiclinicaltrials.org/ (TCTR 20180312002 registered on March 07, 2018).

A Physiological Approach to Pharmacokinetics in Chronic Kidney Disease

The conventional approach to approximating the pharmacokinetics of drugs in patients with chronic kidney disease (CKD) only accounts for changes in the estimated glomerular filtration rate. However, CKD is a systemic and multifaceted disease that alters many body systems. Therefore, the objective of this exercise was to develop and evaluate a whole-body mechanistic approach to predicting pharmacokinetics in patients with CKD. Physiologically based pharmacokinetic models were developed in PK-Sim v8.0 (www.open-systems-pharmacology.org) to mechanistically represent the disposition of 7 compounds in healthy human adults. The 7 compounds selected were eliminated by glomerular filtration and active tubular secretion by the organic cation transport system to varying degrees. After a literature search, the healthy adult models were adapted to patients with CKD by numerically accounting for changes in glomerular filtration rate, kidney volume, renal perfusion, hematocrit, plasma protein concentrations, and gastrointestinal transit. Literature-informed interindividual variability was applied to the physiological parameters to facilitate a population approach. Model performance in CKD was evaluated against pharmacokinetic data from 8 clinical trials in the literature. Overall, integration of the CKD parameterization enabled exposure predictions that were within 1.5-fold error across all compounds and patients with varying stages of renal impairment. Notable improvement was observed over the conventional approach to scaling exposure, which failed in all but 1 scenario in patients with advanced CKD. Further research is required to qualify its use for first-in-CKD dose selection and clinical trial planning for a wider selection of renally eliminated compounds, including those subject to anion transport.

Changes of renal transporters in the kinetic process of VCM-induced nephrotoxicity in mice

Renal transporters involved in tubular excretion pathway are considered to be the key concern in drug evaluations in nephrotoxicity. However, the relationship between the alternation of renal transporters and the kinetic process of vancomycin (VCM)-induced nephrotoxicity has not been fully elucidated. The present study investigated the alteration of renal transporters expression in the kinetic process of VCM-induced nephrotoxicity in mice. C57BL/6 mice were administrated with normal saline or VCM for 7 days. Biochemical and pathological analyses were conducted to investigate the nephrotoxicity induced by VCM administration. Renal oxidative status, plasma, and kidney content of VCM were monitored. Quantitative real-time polymerase chain reaction and immunohistochemistry analyses were performed to analyze the expression of renal transporters. Finally, our data showed that the exposure of VCM (400 mg/kg) caused a slight nephrotoxicity in mice, whereas exposure of VCM (600 mg/kg) resulted in the severe nephrotoxicity in mice as evidenced by biochemical parameters and renal morphological changes. In addition, the accumulation of VCM in kidney is higher than plasma. Interestingly, VCM (600 mg/kg, body weight) resulted in the induction of Oct2-Mate1 and Oat1/3-Mrp2/Mrp4/Bcrp pathways. However, VCM (400 mg/kg, body weight) caused the induction of Oct2-Mate1/Mate2 and Oat1/3-Mrp4/Bcrp pathways. The changes of renal transporters in association with the kinetic process of VCM-induced nephrotoxicity may exert important practical implications for its optimal use in clinic.

Impact of kidney dysfunction on hepatic and intestinal drug transporters

Emerging information suggests that pathology of the kidney may not only affect expression and function of membrane transporters in the organ, but also in the gastrointestinal tract and the liver. Transporter dysfunction may cause effects on handling of drug as well as endogenous compounds with subsequent clinical consequences. A literature search was conducted on Ovid and PubMed databases to select relevant in vitro, animal and human studies that have reported expression, protein abundance and function of the gastrointestinal and liver localized ABC transporters and SLC carriers in kidney dysfunction or uremia states. The altered function of drug transporters in the liver and intestines in kidney failure subjects may provide compensatory activity in handling endogenous compounds (e.g. uremic toxins), which is expected to affect drug pharmacokinetics and local drug actions.

Concordance of Exposure Changes Because of Renal Impairment Between Results of Dedicated Renal Impairment Studies and Population Pharmacokinetic Predictions

This analysis compared the results from noncompartmental analysis and population pharmacokinetic (PopPK) predictions of exposure changes in patients with renal impairment (RI) for 27 new molecular entities (NMEs) approved between 2000 and 2015. Renal function was identified as a covariate in the final PopPK model for 17 NMEs. The final PopPK model was used to simulate (n  =  1000 replicates/individual) the results of a dedicated PK study in subjects with renal impairment. For the majority of NMEs, concordance between observed, and predicted area under the curve (AUC) geometric mean ratio (GMR) was observed (ie, in 17, 11, and 11 NMEs for mild, moderate, and severe renal impairment groups, respectively, the observed and predicted AUC GMR were within the same fold of change). Inclusion of colinear covariates in the PopPK model appeared to be the major driver for the NMEs for which there was discordance. PopPK, when done properly, is a valuable tool for supporting labeling recommendations for subjects with renal impairment.

A comprehensive strategy to clarify the pharmacodynamic constituents and mechanism of Wu-tou decoction based on the constituents migrating to blood and their in vivo process under pathological state

ETHNOPHARMACOLOGICAL RELEVANCE

As a traditional Chinese medicine (TCM) formula, Wu-tou decoction has been used for treating rheumatoid arthritis (RA) for more than a thousand years. Identifying pharmacodynamic constituents (PCs) of WTD and exploring their in vivo process are very meaningful for promoting the modernization of TCM. However, the pathological state might change this process.

AIM OF THE STUDY

Hence, it is necessary and significant to compare the process in vivo of drugs both in normal and disease state and clarify their action mechanism.

MATERIALS AND METHODS

Taking Wu-tou decoction (WTD) as the research object, a comprehensive strategy based on liquid chromatography coupled with mass spectrometry (LC-MS) was developed to identify PCs, clarify and compare their absorption and distribution in normal and model rats, and then explore the potential mechanism of TCM. Firstly, the PCs in WTD were identified. Then, the pharmacokinetics (PK) and tissue distribution of these ingredients were studied. Finally, the constituents with the difference between normal and model rats were selected for target network pharmacological analysis to clarify the mechanism.

RESULTS

A total of 27 PCs of WTD were identified. The absorption and distribution of 20 PCs were successfully analyzed. In the disease state, the absorption and distribution of all these components were improved to have better treatment effects. The results of target network pharmacological analysis indicated that PTGS1, PTGS2, ABCB1, SLC6A4, CHRM2, ESR1, ESR2, CDK2, TNF and IL-6 are 10 key targets for WTD against RA. The regulatory effects of WTD on the expression of PTGS2 and TNF were further verified. Pathway enrichment analysis showed that the key mechanism of WTD against RA is to reduce inflammation and regulate the immune response.

CONCLUSION

These results indicated that this strategy could better understand the in vivo process and mechanism of WTD under the pathological state. Furthermore, this strategy is also appropriate for other TCM.

Effect of Chronic Kidney Disease on Hepatic Clearance of Drugs in Rats

The pharmacokinetics of some hepatically cleared drugs have been reported to fluctuate in patients with renal impairment, but the definitive factors have not been clarified. We compared the pharmacokinetics of some drugs with different hepatic elimination processes in a chronic kidney disease (CKD) rat model, to optimize their administration during kidney injury. We chose indocyanine green (ICG), midazolam (MDZ), and acetaminophen (APAP) as reference drugs to determine changes in hepatic clearance pathways in presence of CKD. Drugs were intravenously administered via the jugular vein to the CKD model rats, previously established by adenine administration, and then, blood, bile, and urine samples were collected. The plasma concentration of ICG, which is eliminated into the bile without biotransformation, increased; and its total body clearance (CL_tot) significantly decreased in the CKD group compared to the control group. Moreover, the plasma concentrations of MDZ and APAP, metabolized in the liver by CYP3A and Ugt1a6 enzymes, respectively, were higher in the CKD group than in the control group. The biliary clearances of APAP and its derivative APAP-glucuronide increased in the CKD group, whereas their renal clearances were markedly decreased with respect to those in the control group. Altogether, plasma concentrations of some hepatically eliminated drugs increased in the CKD rat model, but depending on their pharmacokinetic characteristics. This study provides useful information for optimizing the administration of some hepatically cleared drugs in CKD patients.

Renal and non-renal response of ABC and SLC transporters in chronic kidney disease

INTRODUCTION

The solute carrier (SLC) and the ATP-binding cassette (ABC) transporter superfamilies play essential roles in the disposition of small molecules (endogenous metabolites, uremic toxins, drugs) in the blood, kidney, liver, intestine, and other organs. In chronic kidney disease (CKD), the loss of renal function is associated with altered function of remote organs. As renal function declines, many molecules accumulate in the plasma. Many studies now support the view that ABC and SLC transporters as well as drug metabolizing enzymes (DMEs) in renal and non-renal tissues are directly or indirectly affected by the presence of various types of uremic toxins, including those derived from the gut microbiome; this can lead to aberrant inter-organ communication.

AREAS COVERED

Here, the expression, localization and/or function of various SLC and ABC transporters as well as DMEs in the kidney and other organs are discussed in the context of CKD and systemic pathophysiology.

EXPERT OPINION

According to the Remote Sensing and Signaling Theory (RSST), a transporter and DME-centric network that optimizes local and systemic metabolism maintains homeostasis in the steady state and resets homeostasis following perturbations due to renal dysfunction. The implications of this view for pharmacotherapy of CKD are also discussed.

Renohepatic crosstalk: a review of the effects of acute kidney injury on the liver

Several theories regarding acute kidney injury (AKI)-related mortality have been entertained, although mounting evidence supports the paradigm that impaired kidney function directly and adversely affects the function of several remote organs. The kidneys and liver are fundamental to human metabolism and detoxification, and it is therefore hardly surprising that critical illness complicated by hepatorenal dysfunction portends a poor prognosis. Several diseases can simultaneously impact the proper functioning of the liver and kidneys, although this review will address the impact of AKI on liver function. While evidence for this relationship in humans remains sparse, we present supportive studies and then discuss the most likely mechanisms by which AKI can cause liver dysfunction. These include 'traditional' complications of AKI (uremia, volume overload and acute metabolic acidosis, among others) as well as systemic inflammation, hepatic leukocyte infiltration, cytokine-mediated liver injury and hepatic oxidative stress. We conclude by addressing the therapeutic implications of these findings to clinical medicine.

Sources of Interindividual Variability

The efficacy, safety, and tolerability of drugs are dependent on numerous factors that influence their disposition. A dose that is efficacious and safe for one individual may result in sub-therapeutic or toxic blood concentrations in others. A significant source of this variability in drug response is drug metabolism, where differences in presystemic and systemic biotransformation efficiency result in variable degrees of systemic exposure (e.g., AUC, C_max, and/or C_min) following administration of a fixed dose.Interindividual differences in drug biotransformation have been studied extensively. It is recognized that both intrinsic factors (e.g., genetics, age, sex, and disease states) and extrinsic factors (e.g., diet , chemical exposures from the environment, and the microbiome) play a significant role. For drug-metabolizing enzymes, genetic variation can result in the complete absence or enhanced expression of a functional enzyme. In addition, upregulation and downregulation of gene expression, in response to an altered cellular environment, can achieve the same range of metabolic function (phenotype), but often in a less predictable and time-dependent manner. Understanding the mechanistic basis for variability in drug disposition and response is essential if we are to move beyond the era of empirical, trial-and-error dose selection and into an age of personalized medicine that will improve outcomes in maintaining health and treating disease.

A GFR-Based Method to Predict the Effect of Renal Impairment on the Exposure or Clearance of Renally Excreted Drugs: A Comparative Study Between a Simple GFR Method and a Physiologically Based Pharmacokinetic Model

Objective

The objective of this study was to compare the predictive performances of a glomerular filtration rate (GFR) model with a physiologically based pharmacokinetic (PBPK) model to predict total or renal clearance or area under the curve of renally excreted drugs in subjects with varying degrees of renal impairment.

Methods

From the literature, 11 studies were randomly selected in which total or renal clearance or area under the curve of drugs in subjects with different degrees of renal impairment were predicted by PBPK models. In these published studies, drugs were given to subjects intravenously or orally. The PBPK model was generally a whole-body model whereas the GFR model was as follows: Predicted total clearance (CL_T) = CL_T in healthy subjects × (GFR in RI/GFR in H), Predicted AUC = AUC in healthy subjects × (GFR in H/GFR in RI), where H is the healthy subjects and RI is renal impairment. The predicted clearance or area under the curve values using PBPK and GFR models were compared with the observed (experimental pharmacokinetic) values. The acceptable prediction error was within the 0.5- to 2-fold or 0.5- to 1.5-fold prediction error.

Results

There were 33 drugs with a total number of 101 observations (area under the curve, total and renal clearance in subjects with mild, moderate, and severe renal impairment). From PBPK and GFR models, out of 101 observations, 94 (93.1%) and 96 (95.0%) observations were within the 0.5- to 2-fold prediction error, respectively.

Conclusions

This study indicates that the predictive power of a simple GFR model is similar to a PBPK model for the prediction of clearance or area under the curve in subjects with renal impairment. The GFR method is simple, robust, and reliable and can replace complex empirical PBPK models.

Impaired Tubular Secretion of Organic Solutes in Acute Kidney Injury

BACKGROUND

Impairment of kidney function is routinely assessed by measuring the accumulation of creatinine, an organic solute cleared largely by glomerular filtration. We tested whether the clearance of solutes that undergo tubular secretion is reduced in proportion to the clearance of creatinine in humans with AKI.

METHODS

Four endogenously produced organic solutes (phenylacetylglutamine [PAG], hippurate [HIPP], indoxyl sulfate [IS], and p-cresol sulfate [PCS]) were measured in spot urine and plasma samples from ten patients with AKI and 17 controls. Fractional clearance relative to creatinine was calculated to assess tubular secretion. Fractional clearance values were calculated in terms of the free, unbound levels of HIPP, IS, and PCS that bind to plasma proteins.

RESULTS

Fractional clearance values for PAG, HIPP, IS, and PCS were >1.0 in patients with AKI as well as controls, indicating that these solutes were still secreted by the tubules of the injured kidneys. Fractional clearance values were, however, significantly lower in patients with AKI than controls, indicating that kidney injury reduced tubular secretion more than glomerular filtration (AKI versus control: PAG, 2.1±0.7 versus 4.6±1.4, P<0.001; HIPP, 10±5 versus 15±7, P=0.02; IS, 10±6 versus 28±7, P<0.001; PCS, 3.3±1.8 versus 10±3, P<0.001). Free plasma levels rose out of proportion to total plasma levels for each of the bound solutes in AKI, so that calculating their fractional clearance in terms of their total plasma levels failed to reveal their impaired secretion.

CONCLUSIONS

Tubular secretion of organic solutes can be reduced out of proportion to glomerular filtration in AKI. Impaired secretion of protein-bound solutes may be more reliably detected when clearances are expressed in terms of their free, unbound levels in the plasma.

Pharmacokinetics in children with chronic kidney disease

In children, the main causes of chronic kidney disease (CKD) are congenital diseases and glomerular disorders. CKD is associated with multiple physiological changes and may therefore influence various pharmacokinetic (PK) parameters. A well-known consequence of CKD on pharmacokinetics is a reduction in renal clearance due to a decrease in the glomerular filtration rate. The impact of renal impairment on pharmacokinetics is, however, not limited to a decreased elimination of drugs excreted by the kidney. In fact, renal dysfunction may lead to modifications in absorption, distribution, transport, and metabolism as well. Currently, insufficient evidence is available to guide dosing decisions on many commonly used drugs. Moreover, the impact of maturation on drug disposition and action should be taken into account when selecting and dosing drugs in the pediatric population. Clinicians should take PK changes into consideration when selecting and dosing drugs in pediatric CKD patients in order to avoid toxicity and increase efficiency of drugs in this population. The aim of this review is to summarize known PK changes in relation to CKD and to extrapolate available knowledge to the pediatric CKD population to provide guidance for clinical practice.

Assessing Potential Drug-Drug Interactions Between Dabigatran Etexilate and a P-Glycoprotein Inhibitor in Renal Impairment Populations Using Physiologically Based Pharmacokinetic Modeling

Plasma concentrations of dabigatran, an active principle of prodrug dabigatran etexilate (DABE), are increased by renal impairment (RI) or coadministration of a P‐glycoprotein inhibitor. Because the combined effects of drug–drug interactions and RI have not been evaluated by means of clinical studies, the decision of DABE dosing for RI patients receiving P‐glycoprotein inhibitors is empirical at its best. We conducted virtual drug–drug interactions studies between DABE and the P‐glycoprotein inhibitor verapamil in RI populations using physiologically based pharmacokinetic modeling. The developed physiologically based pharmacokinetic model for DABE and dabigatran was used to predict trough dabigatran concentrations in the presence and absence of verapamil in virtual RI populations. The population‐based physiologically based pharmacokinetic model provided the most appropriate dosing regimen of DABE for likely clinical scenarios, such as drug–drug interactions in this RI population based on available knowledge of the systems changes and in the absence of actual clinical studies.

Drugs Commonly Applied to Kidney Patients May Compromise Renal Tubular Uremic Toxins Excretion

In chronic kidney disease (CKD), the secretion of uremic toxins is compromised leading to their accumulation in blood, which contributes to uremic complications, in particular cardiovascular disease. Organic anion transporters (OATs) are involved in the tubular secretion of protein-bound uremic toxins (PBUTs). However, OATs also handle a wide range of drugs, including those used for treatment of cardiovascular complications and their interaction with PBUTs is unknown. The aim of this study was to investigate the interaction between commonly prescribed drugs in CKD and endogenous PBUTs with respect to OAT1-mediated uptake. We exposed a unique conditionally immortalized proximal tubule cell line (ciPTEC) equipped with OAT1 to a panel of selected drugs, including angiotensin-converting enzyme inhibitors (ACEIs: captopril, enalaprilate, lisinopril), angiotensin receptor blockers (ARBs: losartan and valsartan), furosemide and statins (pravastatin and simvastatin), and evaluated the drug-interactions using an OAT1-mediated fluorescein assay. We show that selected ARBs and furosemide significantly reduced fluorescein uptake, with the highest potency for ARBs. This was exaggerated in presence of some PBUTs. Selected ACEIs and statins had either no or a slight effect at supratherapeutic concentrations on OAT1-mediated fluorescein uptake. In conclusion, we demonstrate that PBUTs may compete with co-administrated drugs commonly used in CKD management for renal OAT1 mediated secretion, thus potentially compromising the residual renal function.

Advanced oxidation protein products upregulate efflux transporter expression and activity through activation of the Nrf-2-mediated signaling pathway in vitro and in vivo

Clinical and benchtop studies suggest that chronic kidney disease (CKD) alters both renal and nonrenal clearance of drugs. Although studies have documented that the accumulating uremic toxins in the body under CKD conditions are humoral factors that alter the expression and/or activity of drug transporters, the specific process is poorly understood. In this study, we found that advanced oxidation protein products (AOPPs), which are a modified protein uremic toxin, could upregulate efflux transporters, including P-glycoprotein (ABCB1), multi-drug resistance-associated protein 2 (ABCC2) and breast cancer resistance protein (ABCG2) expression in CKD rat models and in HepG2 cells. Our research shows that renal function decline was associated with the accumulation of AOPPs in serum and the upregulation of efflux transporters in the liver in two rat models of CKD. In HepG2 cells, AOPPs significantly increased the expression of efflux transporters in a dose- and time-dependent manner and upregulated the mRNA expression, protein expression and activity of efflux transporters, but bovine serum albumin (BSA), a synthetic precursor of AOPPs, had no effect. This effect correlated with AOPPs activation of the nuclear factor E2-related factor 2 (Nrf-2)-mediated signaling pathway. Further investigation of the regulation of Nrf-2 by AOPPs revealed that ML385 and siNrf-2 abolished the upregulatory effects of AOPPs. These findings suggest that AOPPs upregulate ABCB1, ABCG2 and ABCC2 through Nrf-2 signaling pathways. Protein uremic toxins, such as AOPPs, may modify the nonrenal clearance of drugs in patients with CKD through effects on drug transporters.

The Effect of Liver and Kidney Disease on the Pharmacokinetics of Clozapine and Sildenafil: A Physiologically Based Pharmacokinetic Modeling

Background and Objectives

Physiologically based pharmacokinetic (PBPK) modeling permits clinical scientists to reduce practical constraints for clinical trials on patients with special diseases. In this study, simulations were carried out to validate the pharmacokinetic parameters of clozapine and sildenafil using Simcyp^® simulator in young male adults and compare the effect of renal or hepatic impairment on the pharmacokinetic parameters of clozapine and sildenafil. Also, the effect of age on pharmacokinetic parameters of both drugs was investigated in healthy population and in patients with renal and hepatic impairment.

Methods

A full PBPK model was built in the simulator for clozapine and sildenafil based on physicochemical properties and observed clinical results. The model used was Advanced, Dissolution, Absorption and Metabolism (ADAM) for both drugs.

Results

The PBPK model adequately predicted the pharmacokinetic parameters of clozapine and sildenafil for the healthy adult population. In the simulation results, the bioavailability of both drugs was remarkably raised in both renal and hepatic impairment in young and elderly populations.

Conclusion

PBPK modeling could be helpful in the investigation and comparison of the pharmacokinetics in populations with specific disease conditions.

The Effect of Renal Impairment on the Pharmacokinetics and Safety of Itacitinib

Itacitinib is a novel, selective, Janus kinase 1 inhibitor in development for treatment of graft‐versus‐host disease. The objective of this study was to assess pharmacokinetics and safety of 300‐mg itacitinib dosed in participants with normal renal function (n = 10), severe renal impairment (n = 8), and end‐stage renal disease (ESRD) on hemodialysis (n = 8). Serial plasma and urine samples (urine from normal and severe groups only) were collected before dosing until 72 hours after dosing. In the ESRD group, itacitinib was evaluated in 2 periods, when dosed before (period 1) and after (period 2) a hemodialysis session. Geometric mean ratios (90% confidence interval) in participants with severe renal impairment, ESRD period 1 and ESRD period 2 relative to participants with normal renal function were 1.65 (1.13‐2.39), 0.71 (0.49‐1.03), and 0.83 (0.57‐1.20) for maximum plasma drug concentration and 2.23 (1.56‐3.18), 0.81 (0.57‐1.16), and 0.95 (0.66‐1.35) for area under the plasma concentration–time curve from time zero to infinity. Itacitinib was well tolerated, and 3 grade 1 treatment‐emergent adverse events were reported over the course of the study. Given the magnitude of exposure changes in participants with severe renal impairment or ESRD and the historic risk‐benefit profile, no dose adjustment is recommended for itacitinib in patients with impaired renal function, although the final dosage recommendation will be based on cumulative pharmacokinetics and safety from this study and from the pivotal graft‐versus‐host disease trial. Additionally, itacitinib may be administered to patients undergoing dialysis regardless of the time of dialysis.