Assessment of the Impact of Renal Impairment on Systemic Exposure of New Molecular Entities: Evaluation of Recent New Drug Applications

Effects of Hepatic or Renal Impairment on Pharmacokinetics of Fruquintinib

Fruquintinib (FRUZAQLATM) is a highly selective tyrosine kinase inhibitor of all three vascular endothelial growth factor receptors (-1, -2, and -3). Two Phase 1, open-label, single-dose studies investigated the impact of hepatic or renal impairment on the pharmacokinetics and tolerability of fruquintinib. Participants with moderate renal impairment (creatinine clearance [CrCl] 30-59 mL/min; eight participants) and matched healthy controls (eight participants for each study) received fruquintinib 5 mg. Participants with moderate hepatic impairment (Child-Pugh B; eight participants) and severe renal impairment (CrCl 15-29 mL/min; eight participants) received fruquintinib 2 mg. Pharmacokinetic samples were collected over 240 h. Fruquintinib pharmacokinetics were similar between participants with moderate hepatic impairment and healthy controls; geometric mean ratios (GMRs) and 90% confidence intervals (CIs) for maximum plasma concentration (Cmax), area under the plasma concentration-time curve from 0 to time of last measurable concentration (AUC0-t), and AUC from 0 to infinity (AUC0-inf) were 1.04 (0.87-1.24), 0.89 (0.64-1.23), and 0.91 (0.66-1.26), respectively. Fruquintinib pharmacokinetics were similar between participants with severe or moderate renal impairment and healthy controls. Compared with healthy controls, the respective GMRs (90% CIs) for Cmax, AUC0-t, and AUC0-inf for participants with severe renal impairment were 0.89 (0.78-1.03), 0.97 (0.83-1.14), and 1.01 (0.85-1.19), and for participants with moderate renal impairment were 0.95 (0.78-1.15), 1.06 (0.89-1.26), and 1.07 (0.89-1.28). Fruquintinib was generally well tolerated. These results support fruquintinib use without dose adjustment (5 mg daily, 3 weeks on, and 1 week off) in patients with moderate hepatic impairment or moderate to severe renal impairment.

Pharmacokinetics and Side Effects of Δ9-Tetrahydrocannabinol and Cannabidiol in Patients with Different Stages of CKD

Introduction

Chronic kidney disease (CKD) affects approximately 10% of the global population and is associated with a large symptom burden. Medicinal cannabis is advised against in patients with severe CKD. However, pharmacokinetic and pharmacodynamic knowledge regarding their use in patients with CKD is lacking.

Methods

We aimed to investigate the pharmacokinetics and side effects of a single dose of Sativex, corresponding to 5.4 mg Δ9-tetrahydrocannabinol (THC) and 5 mg cannabidiol (CBD), in patients with CKD stages 4 and 5 compared with healthy volunteers (controls). The study was a nonrandomized and unblinded clinical study.

Results

Twenty controls and 29 patients with CKD completed the study. The area under the curve (AUC) for THC (median [interquartile range]) was 2.76 (1.77-3.48), 4.16 (3.35-5.28), and 4.31 (3.16-5.42) h × ng/ml for controls, and for patients with CKD stages 4 and 5, respectively, with significant differences between patients with CKD and controls. AUC for CBD and metabolites, and other pharmacokinetic parameters, such as maximum concentration (C max) and excretion of metabolites in urine were also significantly different between patients with CKD and controls. After 1.5 hours, numeric rating scale (NRS) scores for dizziness were significantly higher for each CKD group compared with controls (mean NRSscores: 0.7 and 1.5 vs. 0.1).

Conclusion

Total exposure to THC, CBD, and metabolites was higher in patients with CKD stages 4 and 5 compared with controls, and side effects may be more pronounced; however, the intersubject variability was high. If cannabis products are administered to patients with severe CKD, caution is needed.

Intestinal transport of organic food compounds and drugs: A scoping review on the alterations observed in chronic kidney disease

BACKGROUND AND AIMS

Around 850 million people worldwide are affected by chronic kidney disease (CKD). Patients with CKD often develop malnutrition and sarcopenia and changes in the pharmacokinetics of drugs. A reduced kidney function partially explains the prolonged half-life of certain drugs due to decreased renal clearance, which leads to an increased risk of adverse effects. While the intestine plays a fundamental role in this context, a systematic review of the effects of CKD on intestinal transport is lacking. We aimed to systematically summarize all the available evidence on intestinal transport of organic food components (carbohydrates/sugar, proteins/amino acids, fats, vitamins) and drugs (including drug transporters) in CKD.

METHODS

We conducted a systematic search of all the articles published until the 1st of April 2024, on five databases i.e. Embase, PubMed, Web of Science Core Collection, Cochrane Library, and Scopus. This systematic review was registered on the Open Science Framework (OSF) (osf.io/5e6wb) and was carried out according to the PRISMA 2020 guidelines.

RESULTS

From 9205 articles identified, 68 met the inclusion criteria. Absorption of organic food compounds seems to be altered, in general, and reduced for vitamins. The expression of intestinal efflux drug transporters may be altered in CKD.

CONCLUSIONS

Despite alterations in intestinal transport is suggested to be altered in CKD, the lack of recent studies, the paucity of human data and the heterogeneity of the methodologies used underscore the need for more research on the effect of CKD and uremia on intestinal transport.

Pharmacokinetic relevance of glomerular hyperfiltration for drug dosing

In chronic kidney disease (CKD) patients, hypofiltration may lead to the accumulation of drugs that are cleared mainly by the kidney and, vice versa, hyperfiltration may cause augmented renal excretion of the same drugs. In this review we mainly focus on the issue of whether hyperfiltration significantly impacts the renal clearance of drugs and whether the same alteration may demand an up-titration of the doses applied in clinical practice. About half of severely ill, septic patients and patients with burns show glomerular hyperfiltration and this may lead to enhanced removal of drugs such as hydrophilic antibiotics and a higher risk of antibiotic treatment failure. In general, hyperfiltering obese individuals show higher absolute drug clearances than non-obese control subjects, but this depends on the body size descriptor adopted to adjust for fat excess. Several mechanisms influence pharmacokinetics in type 2 diabetes, including renal hyperfiltration, reduced tubular reabsorption and augmented tubular excretion. However, no consistent pharmacokinetic alteration has been identified in hyperfiltering obese subjects and type 2 diabetics. Non-vitamin K antagonist oral anticoagulants (NOACs) have exhibited lower plasma concentrations in hyperfiltering patients in some studies in patients with atrial fibrillation, but a recent systematic review failed to document any excess risk for stroke and systemic embolism in these patients. Hyperfiltration is common among severely ill patients in intensive care units and drug levels should be measured whenever possible in these high-risk patients to prevent underdosing and treatment failure. Hyperfiltration is also common in patients with obesity or type 2 diabetes, but no consistent pharmacokinetic alteration has been described in these patients. No NOAC dose adjustment is indicated in patients with atrial fibrillation being treated with these drugs.

Emerging Roles of Uremic Toxins and Inflammatory Cytokines in the Alteration of Hepatic Drug Disposition in Patients with Kidney Dysfunction

Patients with kidney dysfunction exhibit distinct pharmacokinetic profiles compared to those with normal kidney function. Hence, it is desirable to monitor the drug efficacy and toxicity caused by fluctuations in plasma drug concentrations associated with kidney dysfunction. Recently, pharmacokinetic information of drugs excreted mainly through the urine of patients with kidney dysfunction has been reported via drug-labeling information. Pharmacokinetic changes in drugs mainly eliminated by the liver cannot be overlooked as drug metabolism and/or transport activity in the liver may also be altered in patients with kidney dysfunction; however, the underlying mechanisms remain unclear. To plan an appropriate dosage regimen, it is necessary to clarify the underlying processes of functional changes in pharmacokinetic proteins. In recent years, uremic toxins have been shown to reduce the activity and/or expression of renal and hepatic transporters. This inhibitory effect has been reported to be time-dependent. In addition, inflammatory cytokines, such as interleukin-6, released from immune cells activated by uremic toxins and/or kidney injury can reduce the expression levels of drug-metabolizing enzymes and transporters in human hepatocytes. In this mini-review, we have summarized the renal and hepatic pharmacokinetic changes as well as the potential underlying mechanisms in kidney dysfunction, such as the chronic kidney disease and acute kidney injury. SIGNIFICANCE STATEMENT: Patients with kidney dysfunction exhibit distinct pharmacokinetic profiles compared to those with normal kidney function. Increased plasma concentrations of uremic toxins and inflammatory cytokines during kidney disease may potentially affect the activities and/or expression levels of drug-metabolizing enzymes and transporters in the liver and kidneys.

Clinical Pharmacology of Brigatinib: A Next-Generation Anaplastic Lymphoma Kinase Inhibitor

Brigatinib, a next-generation anaplastic lymphoma kinase (ALK) inhibitor designed to overcome mechanisms of resistance associated with crizotinib, is approved for the treatment of ALK-positive advanced or metastatic non-small cell lung cancer. After oral administration of single doses of brigatinib 30-240 mg, the median time to reach maximum plasma concentration ranged from 1 to 4 h. In patients with advanced malignancies, brigatinib showed dose linearity over the dose range of 60-240 mg once daily. A high-fat meal had no clinically meaningful effect on systemic exposures of brigatinib (area under the plasma concentration-time curve); thus, brigatinib can be administered with or without food. In a population pharmacokinetic analysis, a three-compartment pharmacokinetic model with transit absorption compartments was found to adequately describe brigatinib pharmacokinetics. In addition, the population pharmacokinetic analyses showed that no dose adjustment is required based on body weight, age, race, sex, total bilirubin (< 1.5× upper limit of normal), and mild-to-moderate renal impairment. Data from dedicated phase I trials have indicated that no dose adjustment is required for patients with mild or moderate hepatic impairment, while a dose reduction of approximately 40% (e.g., from 180 to 120 mg) is recommended for patients with severe hepatic impairment, and a reduction of approximately 50% (e.g., from 180 to 90 mg) is recommended when administering brigatinib to patients with severe renal impairment. Brigatinib is primarily metabolized by cytochrome P450 (CYP) 3A, and results of clinical drug-drug interaction studies and physiologically based pharmacokinetic analyses have demonstrated that coadministration of strong or moderate CYP3A inhibitors or inducers with brigatinib should be avoided. If coadministration with a strong or moderate CYP3A inhibitor cannot be avoided, the dose of brigatinib should be reduced by approximately 50% (strong CYP3A inhibitor) or approximately 40% (moderate CYP3A inhibitor), respectively. Brigatinib is a weak inducer of CYP3A in vivo; data from a phase I drug-drug interaction study showed that coadministration of brigatinib 180 mg once daily reduced the oral midazolam area under the plasma concentration-time curve from time zero to infinity by approximately 26%. Brigatinib did not inhibit CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, or CYP2D6 at clinically relevant concentrations in vitro. Exposure-response analyses based on data from the ALTA (ALK in Lung Cancer Trial of AP26113) and ALTA-1L pivotal trials of brigatinib confirm the favorable benefit versus risk profile of the approved titration dosing regimen of 180 mg once daily (after a 7-day lead-in at 90 mg once daily).

Physiologically based pharmacokinetic modeling of daptomycin dose optimization in pediatric patients with renal impairment

Background and Objective: Daptomycin is used to treat Gram-positive infections in adults and children and its dosing varies among different age groups. We focused on the pharmacokinetics of daptomycin in children with renal impairment, which has not been evaluated.

Methods: A physiologically based pharmacokinetic (PBPK) model of daptomycin was established and validated to simulate its disposition in healthy populations and adults with renal impairment, along with a daptomycin exposure simulated in pediatric patients with renal impairment.

Results: The simulated PBPK modeling results for various regimens of intravenously administered daptomycin were consistent with observed data according to the fold error below the threshold of 2. The Cmax and AUC of daptomycin did not differ significantly between children with mild-to-moderate renal impairment and healthy children. The AUC increased by an average of 1.55-fold and 1.85-fold in severe renal impairment and end-stage renal disease, respectively. The changes were more significant in younger children and could reach a more than 2-fold change. This scenario necessitates further daptomycin dose adjustments.

Conclusion: Dose adjustments take into account the efficacy and safety of the drug; however, the steady-state Cmin of daptomycin may be above 24.3 mg/L in a few instances. We recommend monitoring creatine phosphokinase more than once a week when using daptomycin in children with renal impairment.

Determining the Effects of Chronic Kidney Disease on Organic Anion Transporter1/3 Activity Through Physiologically Based Pharmacokinetic Modeling

BACKGROUND AND OBJECTIVE

The renal excretion of drugs via organic anion transporters 1 and 3 (OAT1/3) is significantly decreased in patients with renal impairment. This study uses physiologically based pharmacokinetic models to quantify the reduction in OAT1/3-mediated secretion of drugs throughout varying stages of chronic kidney disease.

METHODS

Physiologically based pharmacokinetic models were constructed for four OAT1/3 substrates in healthy individuals: acyclovir, meropenem, furosemide, and ciprofloxacin. Observed data from drug-drug interaction studies with probenecid, a potent OAT1/3 inhibitor, were used to parameterize the contribution of OAT1/3 to the renal elimination of each drug. The models were then translated to patients with chronic kidney disease by accounting for changes in glomerular filtration rate, kidney volume, renal blood flow, plasma protein binding, and hematocrit. Additionally, a relationship was derived between the estimated glomerular filtration rate and the reduction in OAT1/3-mediated secretion of drugs based on the renal extraction ratios of ƿ-aminohippuric acid in patients with varying degrees of renal impairment. The relationship was evaluated in silico by evaluating the predictive performance of each final model in describing the pharmacokinetics (PK) of drugs across stages of chronic kidney disease.

RESULTS

OAT1/3-mediated renal excretion of drugs was found to be decreased by 27-49%, 50-68%, and 70-96% in stage 3, stage 4, and stage 5 of chronic kidney disease, respectively. In support of the parameterization, physiologically based pharmacokinetic models of four OAT1/3 substrates were able to adequately characterize the PK in patients with different degrees of renal impairment. Total exposure after intravenous administration was predicted within a 1.5-fold error and 85% of the observed data points fell within a 1.5-fold prediction error. The models modestly under-predicted plasma concentrations in patients with end-stage renal disease undergoing intermittent hemodialysis. However, results should be interpreted with caution because of the limited number of molecules analyzed and the sparse sampling in observed chronic kidney disease pharmacokinetic studies.

CONCLUSIONS

A quantitative understanding of the reduction in OAT1/3-mediated excretion of drugs in differing stages of renal impairment will contribute to better predictive accuracy for physiologically based pharmacokinetic models in drug development, assisting with clinical trial planning and potentially sparing this population from unnecessary toxic exposures.

Cancer Drug Dosing in Chronic Kidney Disease and Dialysis

Patients with malignancies have a high prevalence of kidney disease and are often treated with antineoplastic agents that undergo kidney metabolism or excretion or clearance via renal replacement therapies. Thus, the dosing of these agents, including classic chemotherapeutic drugs, targeted therapies, and immunotherapy, must take into account patients' kidney function. In this review, we will discuss the pitfalls of accurate measurement of kidney function and how kidney disease affects both pharmacodynamic and pharmacokinetic properties of drugs. Lastly, we will discuss specific agents and summarize current dosing strategies for use in patients with chronic kidney disease and end-stage kidney disease.

Interaction of Human Serum Albumin with Uremic Toxins: The Need of New Strategies Aiming at Uremic Toxins Removal

Chronic kidney disease (CKD) is acknowledged worldwide to be a grave threat to public health, with the number of US end-stage kidney disease (ESKD) patients increasing steeply from 10,000 in 1973 to 703,243 in 2015. Protein-bound uremic toxins (PBUTs) are excreted by renal tubular secretion in healthy humans, but hardly removed by traditional haemodialysis (HD) in ESKD patients. The accumulation of these toxins is a major contributor to these sufferers’ morbidity and mortality. As a result, some improvements to dialytic removal have been proposed, each with their own upsides and drawbacks. Longer dialysis sessions and hemodiafiltration, though, have not performed especially well, while larger dialyzers, coupled with a higher dialysate flow, proved to have some efficiency in indoxyl sulfate (IS) clearance, but with reduced impact on patients’ quality of life. More efficient in removing PBUTs was fractionated plasma separation and adsorption, but the risk of occlusive thrombosis was worryingly high. A promising technique for the removal of PBUTs is binding competition, which holds great hopes for future HD. This short review starts by presenting the PBUTs chemistry with emphasis on the chemical interactions with the transport protein, human serum albumin (HSA). Recent membrane-based strategies targeting PBUTs removal are also presented, and their efficiency is discussed.

Evaluation of hepatic CYP3A enzyme activity using endogenous markers in lung cancer patients treated with cisplatin, dexamethasone, and aprepitant

PURPOSE

Aprepitant is used with dexamethasone and 5-HT₃ receptor antagonists as an antiemetic treatment for chemotherapy, including cisplatin. Aprepitant is a substrate of cytochrome P450 (CYP) 3A4 and is known to cause its inhibition and induction. In addition, dexamethasone is a CYP3A4 substrate that induces CYP3A4 and CYP3A5 expression. In this study, we aimed to quantitatively evaluate the profile of CYP3A activity using its endogenous markers in non-small cell lung cancer patients receiving a standard cisplatin regimen with antiemetics, including aprepitant.

METHODS

Urinary 11β-hydroxytestosterone (11β-OHT)/testosterone concentration ratio and plasma 4β-hydroxycholesterol (4β-OHC) concentrations were measured before and after cisplatin treatment (days 1, 4, and 8). CYP3A5 was genotyped, and plasma aprepitant concentrations were measured on day 4 to examine its influence on CYP3A endogenous markers.

RESULTS

The urinary 11β-OHT/testosterone concentration ratio in the 35 patients included in this study increased by 2.65-fold and 1.21-fold on days 4 and 8 compared with day 1, respectively. Their plasma 4β-OHC concentration increased by 1.46-fold and 1.66-fold, respectively. The mean plasma aprepitant concentration on day 4 was 1,451 ng/mL, which is far lower than its inhibitory constant. The allele frequencies of CYP3A5*1 and CYP3A5*3 were 0.229 and 0.771, respectively. In patients with the CYP3A5*1 allele, the plasma 4β-OHC concentration was significantly lower at baseline but more potently increased with chemotherapy.

CONCLUSION

CYP3A activity was significantly induced from day 4 to day 8 in patients receiving cisplatin and three antiemetic drugs.

Drug-drug interactions in polypharmacy patients: The impact of renal impairment

Chronic kidney disease (CKD) is a long-term condition characterized by a gradual loss of kidney functions, usually accompanied by other comorbidities including cardiovascular diseases (hypertension, heart failure and stroke) and diabetes mellitus. Therefore, multiple pharmacological prescriptions are very common in these patients. Epidemiological and clinical observations have shown that polypharmacy may increase the probability of adverse drug reactions (ADRs), possibly through a higher risk of drug-drug interactions (DDIs). Renal impairment may further worsen this scenario by affecting the physiological and biochemical pathways underlying pharmacokinetics and ultimately modifying the pharmacodynamic responses. It has been estimated that the prevalence of DDIs in CKD patients ranged between 56.9% and 89.1%, accounting for a significant increase in healthcare costs, length and frequency of hospitalization, with a detrimental impact on health and quality of life of these patients. Despite these recognized high-risk conditions, scientific literature released on this topic is still limited. Basing on the most commonly prescribed therapies in patients with CKD, the present short review summarizes the current state of knowledge of the putative DDIs occurring in CKD patients undergoing polytherapy. The most relevant underlying mechanisms and their clinical significance are also debated.

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.

High-Trough Plasma Concentration of Afatinib Is Associated with Dose Reduction

Afatinib is used to treat non-small-cell lung cancer (NSCLC) harboring epidermal growth factor receptor (EGFR) mutation as a second-generation EGFR-tyrosine kinase inhibitor (TKI). Early prediction of adverse effects based on the pharmacokinetics of afatinib enables support for quality of life (QOL) in patients with no change in efficacy. We examined the pharmacokinetic relationship between trough plasma concentration and adverse effects and evaluated the utility of measuring the trough plasma concentration of afatinib as the first EGFR-TKI treatment for NSCLC in a prospective multicenter study. Twenty-four patients treated with afatinib were enrolled in this study. All blood samples were collected at the trough point, and plasma concentrations were measured using high-performance liquid chromatography-tandem mass spectrometry. Logistic regression analysis for the dose reduction of afatinib was performed, and the receiver operating characteristic (ROC) curve was plotted. Although all patients started afatinib at 40 mg/day, plasma concentrations were variable, and mean and median trough plasma concentrations were 32.9 ng/mL and 32.5 ng/mL in this study, respectively. Minimum and maximum trough plasma concentrations were 10.4 ng/mL and 72.7 ng/mL, respectively. This variability was speculated to involve personal parameters such as laboratory data. However, no patient characteristics or laboratory data examined correlated with the trough plasma concentration of afatinib, except albumin. Albumin showed a weak correlation with plasma concentration (r = 0.60, p = 0.009). The trough plasma concentration of afatinib was significantly associated with the dose reduction of afatinib (p = 0.047). The area under the ROC curve (AUC) for the trough plasma concentration of afatinib was 0.81. The cut-off value was 21.4 ng/mL. The sensitivity and specificity of the cut-off as a risk factor were 0.80 and 0.75. In summary, the trough plasma concentration of afatinib was associated with continued or reduced dosage because of the onset of several adverse effects, and a threshold was seen. Adverse effects not only lower QOL but also hinder continued treatment. Measuring plasma concentrations of afatinib appears valuable to predict adverse effects and continue effective therapy.

Association of CYP3A5 polymorphisms and parathyroid hormone with blood level of tacrolimus in patients with end-stage renal disease

Because tacrolimus is predominantly metabolized by CYP3A, the blood concentration/dose (C/D) ratio is affected by CYP3A5 polymorphism. Parathyroid hormone (PTH) expression increases in secondary hyperparathyroidism, which is frequently associated with end‐stage renal disease. Recently, PTH has been shown to downregulate CYP3A expression at mRNA level. In this study, we examined the influence of CYP3A5 polymorphism on and association of serum intact‐PTH (iPTH) level with blood tacrolimus concentration in patients with end‐stage renal disease just before kidney transplantation. Forty‐eight patients who satisfied the selection criteria were analyzed. Subjects were classified into two phenotype subgroups: CYP3A5 expressor (CYP3A5*1/*1 and *1/*3; n = 15) and CYP3A5 nonexpressor (CYP3A5*3/*3; n = 33). The blood tacrolimus C/D (per body weight) ratio was significantly lower in CYP3A5 expressors than that in CYP3A5 nonexpressors. A significant positive correlation was found between tacrolimus C/D and iPTH concentrations (r = 0.305, p = 0.035), and the correlation coefficient was higher after excluding 20 patients co‐administered CYP3A inhibitor or inducer (r = 0.428, p = 0.023). A multiple logistic regression analysis by stepwise selection identified CYP3A5 polymorphism and serum iPTH level as significant factors associated with tacrolimus C/D. These results may suggest the importance of dose design considering not only the CYP3A5 phenotype but also serum iPTH level when using tacrolimus in patients who undergo renal transplantation.

Design and conduct considerations for studies in patients with impaired renal function

An impaired renal function, including acute and chronic kidney disease and end‐stage renal disease, can be the result of aging, certain disease conditions, the use of some medications, or as a result of smoking. In patients with renal impairment (RI), the pharmacokinetics (PKs) of drugs or drug metabolites may change and result in increased safety risks or decreased efficacy. In order to make specific dose recommendations in the label of drugs for patients with RI, a clinical trial may have to be conducted or, when not feasible, modeling and simulations approaches, such as population PK modeling or physiologically‐based PK modelling may be applied. This tutorial aims to provide an overview of the global regulatory landscape and a practical guidance for successfully designing and conducting clinical RI trials or, alternatively, on applying modeling and simulation tools to come to a dose recommendation for patients with RI in the most efficient manner.

Physiologically-based pharmacokinetic model for alectinib, ruxolitinib, and panobinostat in the presence of cancer, renal impairment, and hepatic impairment

Renal (RIP) and hepatic (HIP) impairments are prevalent conditions in cancer patients. They can cause changes in gastric emptying time, albumin levels, hematocrit, glomerular filtration rate, hepatic functional volume, blood flow rates, and metabolic activity that can modify drug pharmacokinetics. Performing clinical studies in such populations has ethical and practical issues. Using predictive physiologically-based pharmacokinetic (PBPK) models in the evaluation of the PK of alectinib, ruxolitinib, and panobinostat exposures in the presence of cancer, RIP, and HIP can help in using optimal doses with lower toxicity in these populations. Verified PBPK models were customized under scrutiny to account for the pathophysiological changes induced in these diseases. The PBPK model-predicted plasma exposures in patients with different health conditions within average 2-fold error. The PBPK model predicted an area under the curve ratio (AUCR) of 1, and 1.8, for ruxolitinib and panobinostat, respectively, in the presence of severe RIP. On the other hand, the severe HIP was associated with AUCR of 1.4, 2.9, and 1.8 for alectinib, ruxolitinib, and panobinostat, respectively, in agreement with the observed AUCR. Moreover, the PBPK model predicted that alectinib therapeutic cerebrospinal fluid levels are achieved in patients with non-small cell lung cancer, moderate HIP, and severe HIP at 1-, 1.5-, and 1.8-fold that of healthy subjects. The customized PBPK models showed promising ethical alternatives for simulating clinical studies in patients with cancer, RIP, and HIP. More work is needed to quantify other pathophysiological changes induced by simultaneous affliction by cancer and RIP or HIP.

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.

Drug dosing in cancer patients with decreased kidney function: A practical approach

Correct drug dosing of anticancer agents is essential to obtain optimal outcomes. Overdosing will result in increased toxicity, treatment interruption and possible cessation of anticancer treatment. Underdosing may result in suboptimal anti-cancer effects and may increase the risk of cancer-related mortality. As it is practical nor feasible to perform therapeutic drug monitoring for all anti-cancer drugs, kidney function is used to guide drug dosing for those drugs whose primary mode of excretion is through the kidney. However, it is not well-established what method should be utilized to measure or estimate kidney function and the choice of method does influence treatment decisions regarding eligibility for anti-cancer drugs and their dose. In this review, we will provide an overview regarding the importance of drug dosing, the preferred method to determine kidney function and a practical approach to drug dosing of anticancer drugs.

End-stage renal disease reduces the expression of drug-metabolizing cytochrome P450s

BACKGROUND

End-stage renal disease is an irreversible status of kidney dysfunction that reduces both renal and non-renal drug clearance. Accumulation of uremic toxins seems to modify the activities of drug-metabolizing cytochrome P450 (CYP) enzymes. The aim of the present work was to refine gene expression analysis for efficient and accurate quantification of CYP mRNAs in patients' leukocytes.

METHODS

We compared six liquid-liquid extraction reagents for RNA isolation and five reverse transcriptase kits for RNA-to-cDNA conversion, and developed quantitative polymerase chain reaction methods for duplex measurements of CYP target genes and the reference gene. The expression of CYP1A2, CYP2C9, CYP2C19 and CYP3A4 in patients with end-stage kidney disease (N = 105) and in organ donors with healthy kidney function (N = 110) was compared.

RESULTS

Regarding the RNA yield and purity, TRIzol, Trizolate and TRI reagents were equal; however, TRI reagent was the most advantageous in terms of financial cost. Reverse transcription using Maxima First Strand cDNA Synthesis kit appeared to be the most efficient with the widest range for quantification of the target transcript. The refined method with the detection of various CYPs and the reference gene in duplex PCR efficiently quantified even the low-level CYP expression. In leukocytes of patients with end-stage renal disease, all four CYPs were expressed at significantly lower level than in organ donors with normal kidney function (p < 0.0001).

CONCLUSIONS

Reduced CYP expression was a direct evidence of transcriptional down-regulation of CYP genes in patients with impaired kidney function.

Dose Optimization in Kidney Disease: Opportunities for PBPK Modeling and Simulation

Kidney disease affects pharmacokinetic (PK) profiles of not only renally cleared drugs but also nonrenally cleared drugs. The impact of kidney disease on drug disposition has not been fully elucidated, but describing the extent of such impact is essential for conducting dose optimization in kidney disease. Accurate evaluation of kidney function has been a clinical interest for dose optimization, and more scientists pay attention and conduct research for clarifying the role of drug transporters, metabolic enzymes, and their interplay in drug disposition as kidney disease progresses. Physiologically based pharmacokinetic (PBPK) modeling and simulation can provide valuable insights for dose optimization in kidney disease. It is a powerful tool to integrate discrete knowledge from preclinical and clinical research and mechanistically investigate system- and drug-dependent factors that may contribute to the changes in PK profiles. PBPK-based prediction of drug exposures may be used a priori to adjust dosing regimens and thereby minimize the likelihood of drug-related toxicity. With real-time clinical studies, parameter estimation may be performed with PBPK approaches that can facilitate identification of sources of interindividual variability. PBPK modeling may also facilitate biomarker research that aids dose optimization in kidney disease. U.S. Food and Drug Administration guidances related to conduction of PK studies in kidney impairment and PBPK documentation provide the foundation for facilitating model-based dose-finding research in kidney disease.

Lack of Effect of 12-Week Treatment with Risankizumab on the Pharmacokinetics of Cytochrome P450 Probe Substrates in Patients with Moderate to Severe Chronic Plaque Psoriasis

OBJECTIVE

The objective of this study was to characterize the effects of risankizumab on the in vivo activity of cytochrome P450 (CYP) 1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A in psoriasis patients using a cocktail approach.

METHODS

Patients with moderate to severe chronic plaque psoriasis (n = 21) received single oral doses of sensitive probe substrates for CYP1A2 (caffeine 100 mg), CYP2C9 (warfarin 10 mg), CYP2C19 (omeprazole 20 mg), CYP2D6 (metoprolol 50 mg), and CYP3A (midazolam 2 mg) on day 1, followed by 12 weeks of subcutaneous risankizumab treatment of 150 mg once every 4 weeks from day 8 to day 92, and again the same cocktail of substrates on day 98. Serial blood samples were collected for determination of the CYP probe drugs and metabolites with and without risankizumab. Trough samples were collected for risankizumab.

RESULTS

The 90% confidence intervals (CIs) for the area under the plasma concentration-time curve (AUC) from time zero to infinity (AUC_∞) ratios for the CYP probe substrates administered with risankizumab versus without risankizumab were within the default 0.8-1.25 equivalence bounds. Similar results were observed for maximum plasma concentration (C_max), except for omeprazole, for which the lower bound of the 90% CI for C_max (0.73) extended slightly below the default equivalence limit. No differences were observed in metabolite-to-parent drug C_max or AUC ratios with risankizumab versus without risankizumab. Risankizumab trough plasma concentrations significantly exceeded those of the phase III regimen of risankizumab in psoriasis (150 mg subcutaneously at weeks 0 and 4 and every 12 weeks thereafter).

CONCLUSIONS

Risankizumab did not affect the in vivo activity of CYP1A2, CYP2C9, CYP2C19, CYP2D6, or CYP3A enzymes in patients with moderate or severe plaque psoriasis and therefore has no potential for drug interactions through these enzymes.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02772601.

Clinical Pharmacology Considerations for Developing Small-Molecule Treatments for COVID-19

Numerous drugs are being investigated for the treatment of COVID‐19, including antivirals and therapies targeting complications related to COVID‐19. The clinical presentation of COVID‐19 varies from mild fever, cough, and dyspnea in the early stages of disease to severe complications such as acute respiratory distress syndrome, systemic hyperinflammation, and sepsis. A thorough understanding of the disease pathogenesis and the disease complications is essential to developing effective therapies to treat this potentially life‐threatening disease. This review offers key clinical pharmacology considerations involved in the development of small molecules for the treatment of COVID‐19. They are based on the major observed disease complications that impact drug absorption, distribution, metabolism, and elimination. We also address considerations regarding potential drug interactions, alternative routes and methods of administration, and dosing in patients on hemodialysis.

The Magnitude of the Warfarin-Amiodarone Drug-Drug Interaction Varies With Renal Function: A Propensity-Matched Cohort Study

Amiodarone inhibits warfarin metabolism and is associated with major bleeding during warfarin therapy. Managing this drug-drug interaction (DDI) is challenging because of substantial interpatient variability in DDI magnitude. Because renal dysfunction induces changes in drug metabolism and protein binding that could alter cytochrome P450 inhibition mechanisms, we hypothesized that renal dysfunction alters the impact of the warfarin-amiodarone DDI. We tested this question in a propensity-matched cohort study of hospitalized patients with atrial fibrillation. Patients were queried from an electronic health record database. Renal function was estimated with creatinine clearance (CrCl). Warfarin response was measured with the warfarin sensitivity index (WSI), a dose-normalized international normalized ratio (INR) measure, and was modeled with multilevel mixed-effects linear regression. Time to supratherapeutic INR (> 4) was modeled using Cox regression. Propensity score matching resulted in 4,518 patients administered amiodarone and 4,518 controls. Amiodarone's effect on warfarin response varied threefold across the renal function range, increasing WSI by 36% in patients with normal renal function (CrCl 115 mL/minute), but by only 11.8% in patients with severe renal dysfunction (CrCl 15 mL/minute). Similarly, amiodarone had a strong effect in patients with normal renal function (hazard ratio (HR) 1.80; 1.23, 2.64), but a negligible effect on supratherapeutic INR hazard in patients with severe renal dysfunction (HR 1.01; 0.75, 1.37). These results suggest that renal function is a novel factor that explains substantial variability in the warfarin-amiodarone DDI. This information could inform warfarin dosage adjustment and monitoring and may have implications for the selection of oral anticoagulation agents in patients treated with amiodarone.

Pharmacokinetics and safety of revefenacin in subjects with impaired renal or hepatic function

Purpose

Revefenacin, a long-acting muscarinic antagonist for nebulization, has been shown to improve lung function in patients with chronic obstructive pulmonary disease. Here we report pharmacokinetic (PK) and safety results from two multicenter, open-label, single-dose trials evaluating revefenacin in subjects with severe renal impairment (NCT02578082) and moderate hepatic impairment (NCT02581592).

Subjects and methods

The renal impairment trial enrolled subjects with normal renal function and severe renal impairment (estimated glomerular filtration rate <30 mL/min/1.73 m²). The hepatic impairment trial enrolled subjects with normal hepatic function and moderate hepatic impairment (Child-Pugh class B). Subjects received a single 175-µg dose of revefenacin through nebulization. PK plasma samples and urine collections were obtained at multiple time points for 5 days following treatment; all subjects were monitored for adverse events.

Results

In the renal impairment study, the maximum observed plasma revefenacin concentration (C_max) was up to 2.3-fold higher and area under the concentration–time curve from time 0 to infinity (AUC_inf) was up to 2.4-fold higher in subjects with severe renal impairment compared with those with normal renal function. For THRX-195518, the major metabolite of revefenacin, the corresponding changes in C_max and AUC_inf were 1.8- and 2.7-fold higher, respectively. In the hepatic impairment study, revefenacin C_max and AUC_inf were 1.03- and 1.18-fold higher, respectively, in subjects with moderate hepatic impairment compared with those with normal hepatic function. The corresponding changes in THRX-195518 C_max and AUC_inf were 1.5- and 2.8-fold higher, respectively.

Conclusion

Systemic exposure to revefenacin increased modestly in subjects with severe renal impairment but was similar between subjects with moderate hepatic impairment and normal hepatic function. The increase in plasma exposure to THRX-195518 in subjects with severe renal or moderate hepatic impairment is unlikely to be of clinical consequence given its low antimuscarinic potency, low systemic levels after inhaled revefenacin administration, and favorable safety profile.

Population pharmacokinetics of pevonedistat alone or in combination with standard of care in patients with solid tumours or haematological malignancies

AIMS

A population pharmacokinetic (PK) analysis was conducted to quantify the impact of patient-specific and concurrent medication factors on pevonedistat PK.

METHODS

Data were pooled from 6 clinical studies consisting of 335 patients with solid tumours or haematological malignancies administered pevonedistat alone or in combination with azacitidine, docetaxel, carboplatin + paclitaxel, or gemcitabine. Model development and covariate analysis followed standard methods. Parameters and bootstrap 95% confidence intervals were estimated using nonlinear mixed-effects modelling. The final model was evaluated using visual predictive checks and other goodness-of-fit criteria.

RESULTS

A linear 2-compartment model best described pevonedistat PK. The final model included the effect of body surface area (BSA) on clearance (CL and Q) and volume of distribution of pevonedistat, effect of concomitantly administered carboplatin + paclitaxel on CL, and effect of albumin on Q. Race, sex, age, tumour type (haematological vs solid), mild or moderate renal impairment (creatinine clearance ≥30 mL/min), or mild hepatic impairment, had no impact on pevonedistat PK.

CONCLUSIONS

The clinical PK profile of pevonedistat is comparable in patients with solid tumours or haematological malignancies. All PK parameters exhibited ≥20% change over the observed BSA range (1.38-3 m² ) with CL ranging from 75.5 to 208% of the reference value, with simulations supporting BSA-based dosing to minimize interindividual variability in drug exposures. Concurrent administration of carboplatin + paclitaxel decreased pevonedistat CL by approximately 44%, while coadministration with azacitidine, gemcitabine or docetaxel did not alter pevonedistat CL. No other factors were identified as influencing pevonedistat PK.

Pharmacokinetics of Lapatinib, a Nonrenally Cleared Drug, in Patients With End-Stage Renal Disease on Maintenance Hemodialysis

Lapatinib, a tyrosine kinase inhibitor, is approved for the treatment of breast cancer. The literature shows that it is metabolized by CYP3A4 and eliminated predominantly (>90%) by the fecal route, with minimal (<2%) renal elimination in healthy subjects (dose of 250 mg); in cancer patients, renal elimination is minimal at therapeutic doses. For nonrenally cleared drugs, while there is ample evidence of pharmacokinetic alterations secondary to renal impairment-induced effects on drug metabolizing enzymes and/or transporters, the effect of end-stage renal disease (ESRD) on lapatinib pharmacokinetics has not been determined. Rather, as stated in the drug's label, the expectation is lack of effect of renal impairment on lapatinib pharmacokinetics based on its minimal renal elimination. The current report addresses this gap with pharmacokinetic data (obtained in a 1-way drug interaction study) in ESRD patients (n = 11) on maintenance hemodialysis and compared with published data in 37 healthy subjects in 3 separate studies. Following a 250-mg oral dose in ESRD patients, the median t_max was 3.0 hours, and geometric mean (95%CI) values for C_max , AUC_inf , and t_1/2 were 349 ng/mL (245-499 ng/mL), 4410 ng·h/mL (2960-6580 ng·h/mL), and 14.8 hours (9.7-22.5 hours), respectively. These parameters approximated published values in healthy subjects and demonstrated that renal impairment and hemodialysis did not affect lapatinib pharmacokinetics. The results of the present study in this renally impaired population, the only such information available to date, support the drug's label and are valuable in view of the recognized difficulties in enrolling organ-impaired patients in oncology trials.

Emerging Roles of Aryl Hydrocarbon Receptors in the Altered Clearance of Drugs during Chronic Kidney Disease

Chronic kidney disease (CKD) is a major public health problem, since 300,000,000 people in the world display a glomerular filtration rate (GFR) below 60 mL/min/1.73m². Patients with CKD have high rates of complications and comorbidities. Thus, they require the prescription of numerous medications, making the management of patients very complex. The prescription of numerous drugs associated with an altered renal- and non-renal clearance makes dose adjustment challenging in these patients, with frequent drug-related adverse events. However, the mechanisms involved in this abnormal drug clearance during CKD are not still well identified. We propose here that the transcription factor, aryl hydrocarbon receptor, which is the cellular receptor for indolic uremic toxins, could worsen the metabolism and the excretion of drugs in CKD patients.

Clinical Pharmacology of Ixazomib: The First Oral Proteasome Inhibitor

Ixazomib, the first oral proteasome inhibitor, is approved in combination with lenalidomide and dexamethasone for the treatment of patients with multiple myeloma (MM) who have received at least one prior therapy. Ixazomib is a selective, potent, and reversible inhibitor of the 20S proteasome, and preferentially binds to and inhibits the β5 chymotrypsin-like proteolytic site. Ixazomib absorption is rapid, with a median time to reach maximum plasma concentration of approximately 1 h post-dose. Ixazomib pharmacokinetics (PK) are adequately described by a three-compartment model (terminal half-life of 9.5 days) with first-order linear absorption (oral bioavailability of 58%). Plasma exposures of ixazomib increase in a dose-proportional manner. A high-fat meal decreases both the rate and extent of ixazomib absorption, supporting administration on an empty stomach. Population PK analyses demonstrated that no dose adjustment is required based on age, body size/weight, race, sex, mild-to-moderate renal impairment, or mild hepatic impairment. Results from dedicated studies indicate that a reduced starting dose (from 4 to 3 mg) is appropriate for patients with severe renal impairment, end-stage renal disease requiring dialysis, or moderate-to-severe hepatic impairment. Non-cytochrome P450 (CYP)-mediated metabolism appears to be the major clearance mechanism for ixazomib. Drug-drug interaction studies have shown no meaningful effects of strong inhibitors of CYP3A on ixazomib PK; however, the strong inducer rifampin caused a clinically relevant reduction in ixazomib exposure, supporting the recommendation to avoid concomitant administration of ixazomib with strong CYP3A inducers. Exposure-response analyses of data from the phase III TOURMALINE-MM1 registrational study demonstrate a favorable benefit-risk profile for the approved dose and regimen of weekly ixazomib 4 mg on days 1, 8, and 15 of each 28-day cycle.

Simulating the Impact of Elevated Levels of Interleukin-6 on the Pharmacokinetics of Various CYP450 Substrates in Patients with Neuromyelitis Optica or Neuromyelitis Optica Spectrum Disorders in Different Ethnic Populations

A physiologically based pharmacokinetic (PBPK) model was used to simulate the impact of elevated levels of interleukin (IL)-6 on the exposure of several orally administered cytochrome P450 (CYP) probe substrates (caffeine, S-warfarin, omeprazole, dextromethorphan, midazolam, and simvastatin). The changes in exposure of these substrates in subjects with rheumatoid arthritis (and hence elevated IL-6 levels) compared with healthy subjects were predicted with a reasonable degree of accuracy. The PBPK model was then used to simulate the change in oral exposure of the probe substrates in North European Caucasian, Chinese, and Japanese population of patients with neuromyelitis optica (NMO) or NMO spectrum disorder with elevated plasma IL-6 levels (up to 100 pg/mL). Moderate interactions [mean AUC fold change, ≤ 2.08 (midazolam) or 2.36 (simvastatin)] was predicted for CYP3A4 probe substrates and weak interactions (mean AUC fold change, ≤ 1.29-1.97) were predicted for CYP2C19, CYP2C9, and CYP2D6 substrates. No notable interaction was predicted with CYP1A2. Although ethnic differences led to differences in simulated exposure for some of the probe substrates, there were no marked differences in the predicted magnitude of the change in exposure following IL-6-mediated suppression of CYPs. Decreased levels of serum albumin (as reported in NMO patients) had little impact on the magnitude of the simulated IL-6-mediated drug interactions. This PBPK modeling approach allowed us to leverage knowledge from different disease and ethnic populations to make predictions of cytokine-related DDIs in a rare disease population where actual clinical studies would otherwise be difficult to conduct.

Effect of renal function and dialysis modality on daprodustat and predominant metabolite exposure

Background

Current therapies for anemia of chronic kidney disease (CKD) include administration of supplemental iron (intravenous and/or oral), blood transfusions and replacement of erythropoietin through the administration of recombinant human erythropoietin (rhEPO) and rhEPO analogs, each with limitations. Daprodustat is an orally active, small molecule hypoxia-inducible factor-prolyl hydroxylase inhibitor that is currently in Phase 3 clinical studies. As it is well appreciated that the kidney represents a major route of elimination of many drugs, and daprodustat will be administered to patients with advanced CKD as well as patients with end-stage kidney disease, it is important to characterize the pharmacokinetic profile in these patient populations to safely dose this potential new medicine.

Methods

The primary objective of these studies, conducted under two separate protocols and with identical assessments and procedures, was to characterize the steady-state pharmacokinetics of daprodustat and the six predominant metabolites (i.e. metabolites present in the highest concentration in circulation) in subjects with normal renal function, anemic non-dialysis (ND)-dependent CKD subjects (CKD Stage 3/4) and anemic subjects on either hemodialysis (HD) or peritoneal dialysis (PD). All enrolled subjects were administered daprodustat 5 mg once daily for 14 days (all except HD subjects) or 15 days (for HD subjects). Blood, urine and peritoneal dialysate were collected at various times for measurement of daprodustat, predominant metabolite, erythropoietin and hepcidin levels.

Results

The pharmacokinetic properties of steady-state daprodustat peak plasma concentration (Cmax), area under the plasma daprodustat concentration-time curve (AUC) and the time of Cmax (tmax) were comparable between all cohorts in this study. In addition, there was no clinically relevant difference in these properties in the HD subjects between a dialysis and ND day. For CKD Stage 3/4, HD (dialysis day) and PD subjects, the AUC of all daprodustat metabolites assessed was higher, while the C_max was slightly higher than that in subjects with normal renal function. Over the course of the 14 or 15 days of daprodustat administration, hemoglobin levels were seen to be relatively stable in the subjects with normal renal function, CKD Stage 3/4 and PD subjects, while HD subjects had a decrease of 1.9 gm/dL. All renally impaired subjects appeared to have similar erythropoietin responses to daprodustat, with approximately a 3-fold increase in these levels. In subjects with minimal to no change in hemoglobin levels, hepcidin levels remained relatively stable. Daprodustat, administered 5 mg once daily for 14–15 days, was generally well tolerated with a safety profile consistent with this patient population.

Conclusion

These studies demonstrated no clinically meaningful change in the pharmacokinetic properties of daprodustat when administered to subjects with various degrees of renal impairment, while for CKD Stage 3/4, HD (dialysis day) and PD subjects, the C_max and AUC of all daprodustat metabolites assessed were higher than in subjects with normal renal function. Administration of daprodustat in this study appeared to be generally safe and well tolerated.

Pharmacokinetics of elbasvir and grazoprevir in subjects with end-stage renal disease or severe renal impairment

PURPOSE

To describe the phase 1 and population pharmacokinetic investigations that support dosing recommendations for elbasvir/grazoprevir (EBR/GZR) in hepatitis C virus-infected people with advanced chronic kidney disease.

METHODS

This was an open-label, two-part, multiple-dose trial (MK-5172 PN050; NCT01937975) in 24 non-HCV-infected participants with end-stage renal disease (ESRD) or severe renal impairment who received once-daily EBR 50 mg and GZR 100 mg for 10 days. Population pharmacokinetic analyses from the phase 3 C-SURFER study (PN052, NCT02092350) were also conducted.

RESULTS

When comparing haemodialysis (HD) and non-HD days in participants with ESRD, geometric mean ratios (GMRs) (90% confidence intervals [CIs]) for EBR and GZR AUC_0-24 were 1.14 (1.08-1.21) and 0.97 (0.87-1.09). When comparing ESRD and healthy participants, GMRs (90% CIs) for EBR and GZR AUC_0-24 were 0.99 (0.75-1.30) and 0.83 (0.56-1.22) on HD days, and 0.86 (0.65-1.14) and 0.85 (0.58-1.25) on non-HD days. GMRs (90% CIs) for AUC_0-24 in participants with severe renal impairment relative to healthy controls were 1.65 (1.09-2.49) for GZR and 1.86 (1.38-2.51) for EBR. In population modelling of data from C-SURFER, absolute geometric means of steady-state EBR AUC_0-24 were 2.78 and 3.07 μM*h (HD and non-HD recipients) and GZR AUC_0-24 were 1.80 and 2.34 μM*h (HD and non-HD recipients).

CONCLUSIONS

EBR/GZR represents an important treatment option for HCV infection in people with severe renal impairment and those with ESRD. No dosage adjustment of EBR/GZR is required in people with any degree of renal impairment, including those receiving dialysis.

Population Pharmacokinetic Analyses and Model Validation of Tolvaptan in Subjects With Autosomal Dominant Polycystic Kidney Disease

Tolvaptan is the first approved drug treatment to slow kidney function decline in adults at risk of rapidly progressing autosomal dominant polycystic kidney disease (ADPKD). The objective is to develop (1091 subjects, 7335 observations) and validate (678 subjects, 3012 observations) a population pharmacokinetic model to describe tolvaptan pharmacokinetics in ADPKD subjects. The final model was evaluated with a bootstrapping method. The final model was internally and externally evaluated using visual predictive checks (VPC). Pharmacokinetics was best described by a 1‐compartmental model with 0‐order absorption, nonlinear relative bioavailability (F1), and first‐order elimination. Accounting for changes in F1 significantly improved the model: as the dose increased from 15 mg to 120 mg, F1 decreased by 36%. Population estimates for clearance/F (CL/F), volume of distribution/F (Vd/F), duration of absorption (D1), the highest dose at which F1 is lowest, and the amount of dose at which F1 is 50% were 12.6 L·h^‐1, 110 L, 0.58 hour, 182 mg, and 166 mg, respectively. The interindividual variability was 64% in CL/F, 70% in Vd/F, and 238% in D1. Residual variability was described by a combined‐error model. The VPC (500 data sets simulated) showed that 76% to 92% of the observed data fell within the 90% prediction intervals. The model stability assessed by a 1000‐run bootstrap analysis showed that the mean parameter estimates of data were within 10% of those obtained with the final model. The developed model is robust and stable. Internal and external validation confirmed the model ability to describe the data optimally.

Quantitative Assessment of the Effect of Chronic Kidney Disease on the Nonrenal Clearance of 10 Drugs After Intravenous Administration

The investigation identified 10 publications that reported the individual values of total clearance (CL), renal clearance (CLr), nonrenal clearance (CLnr), and the glomerular filtration rate (GFR), in subjects with varying renal functions. We used these data to estimate extent and prevalence of changes in CLnr in chronic kidney disease (CKD) by examining the relationship between clearances and renal function. The investigation was restricted to drugs given intravenously and eliminated by mixed renal and nonrenal pathways. Six drugs showed a significant reduction of CLnr of 61% to 63% in subjects with severe renal impairment, suggesting that the decline of CLnr in advanced CKD can be clinically relevant and may not be uncommon. The decline of CLnr in CKD for these 6 drugs is linearly correlated with the decline of CLr. With 4 of the drugs studied, a significant reduction of CLnr in CKD was not seen. Renal clearance is a more reliable measure of renal function than GFR assessed by creatinine clearance. Chronic kidney disease affects the elimination more than the distribution of the 10 drugs.

Physiologically-Based Pharmacokinetic model for Ciprofloxacin in children with complicated Urinary Tract Infection

In a recent multicenter population pharmacokinetic study of ciprofloxacin administered to children suffering from complicated urinary tract infection (cUTI), the apparent volume of distribution (V) and total plasma clearance (CL) were decreased by 83.6% and 41.5% respectively, compared to healthy children. To understand these differences, a physiologically-based pharmacokinetic model (PBPK) for ciprofloxacin was developed for cUTI children. First, a PBPK model in adults was developed, modified incorporating age-dependent functions and evaluated with paediatric data generated from a published model in healthy children. Then, the model was then adapted to a cUTI paediatric population according to the degree of renal impairment (KF) affecting renal clearance (CL_Renal,) and CYP1A2 clearance (CL_CYP1A2). Serum and urine samples obtained from 22 cUTI children were used for model evaluation. Lastly, a parameter sensitivity analysis identified the most influential parameters on V and CL. The PBPK model predicted the ciprofloxacin exposure in adults and children, capturing age-related pharmacokinetic changes. Plasma concentrations and fraction excreted unchanged in urine (f_e) predictions improved in paediatric cUTI patients once CL_renal and CL_CYP1A2 were corrected by KF. The presented PBPK model for ciprofloxacin demonstrates its adequacy to simulate different dosing scenarios to obtain PK predictions in a healthy population from 3 months old onwards. Model adaptation of CL_Renal and CL_CYP1A2 according to KF explained partially the differences seen in the plasma drug concentrations and f_e vs time profiles between healthy and cUTI children. Nevertheless, it is necessary to further investigate the disease-related changes in cUTI to improve model predictions.

Clinical Pharmacokinetics in Kidney Disease: Application to Rational Design of Dosing Regimens

A change in pharmacokinetics can alter drug exposure and predispose the patient to either over- or underdosing, potentially resulting in adverse drug reactions or therapeutic failure. Kidney disease is characterized by multiple physiologic effects, which induce clinically significant changes in pharmacokinetics. These vary between individuals and may be quantitated in certain instances. An understanding of pharmacokinetic concepts is, therefore, important for a rational approach to the design of drug dosing regimens for the delivery of personalized medical care. Whether kidney disease is acute or chronic, drug clearance decreases and the volume of distribution may remain unchanged or increase. AKI is defined by dynamic changes in kidney function, which complicates attempts to accurately quantify drug clearance. In contrast, changes in drug clearance progress more slowly with CKD. In general, kidney replacement therapies increase drug clearance, but the extent to which this occurs depends on the modality used and its duration, the drug's properties, and the timing of drug administration. However, the changes in drug handling associated with kidney disease are not isolated to reduced kidney clearance and an appreciation of the scale of potential derangements is important. In most instances, the first dose administered in patients with kidney disease is the same as in patients with normal kidney function. However, in some cases, a higher (loading) initial dose is given to rapidly achieve therapeutic concentrations, followed by a lower maintenance dose, as is well described when prescribing anti-infectives to patients with sepsis and AKI. This review provides an overview of how pharmacokinetic principles can be applied to patients with kidney disease to personalize dosage regimens. Patients with kidney disease are a vulnerable population and the increasing prevalence of kidney disease means that these considerations are important for all prescribers.

Severe Renal Impairment Has Minimal Impact on Doravirine Pharmacokinetics

Doravirine is a novel nonnucleoside reverse transcriptase inhibitor in development for use with other antiretroviral therapies to treat human immunodeficiency virus type 1 (HIV-1) infection. Doravirine metabolism predominantly occurs via cytochrome P450 3A with <10% of elimination occurring via the renal pathway. As severe renal impairment can alter the pharmacokinetics (PK) of metabolically eliminated drugs, the effect of severe renal impairment on doravirine PK was assessed. A single dose of doravirine 100 mg was administered to subjects aged 18 to 75 years with an estimated glomerular filtration rate (eGFR) of <30 ml/min/1.73 m² (severe renal impairment group) and healthy controls with an eGFR of ≥80 ml/min/1.73 m², matched to the mean of the renal impairment group by age (±10 years) and weight (±10 kg). Doravirine plasma concentrations were determined at regular intervals, and safety was monitored throughout. The geometric mean ratios (90% confidence interval) for severe renal impairment/healthy subjects were 1.43 (1.00, 2.04), 1.38 (0.99, 1.92), and 0.83 (0.61, 1.15) for the plasma doravirine area under the curve from zero to infinity (AUC_0-∞), plasma concentration at 24 h postdose (C₂₄), and maximum plasma concentration (C_max), respectively. Doravirine was generally well tolerated in both groups. Based on the overall efficacy, safety, and PK profile of doravirine, the minor effect of severe renal impairment on doravirine PK observed in this study is not considered clinically meaningful. (This study has been registered at ClinicalTrials.gov under identifier NCT02641067.).

Clinical Pharmacokinetics in Kidney Disease: Fundamental Principles

Kidney disease is an increasingly common comorbidity that alters the pharmacokinetics of many drugs. Prescribing to patients with kidney disease requires knowledge about the drug, the extent of the patient's altered physiology, and pharmacokinetic principles that influence the design of dosing regimens. There are multiple physiologic effects of impaired kidney function, and the extent to which they occur in an individual at any given time can be difficult to define. Although some guidelines are available for dosing in kidney disease, they may be on the basis of limited data or not widely applicable, and therefore, an understanding of pharmacokinetic principles and how to apply them is important to the practicing clinician. Whether kidney disease is acute or chronic, drug clearance decreases, and the volume of distribution may remain the same or increase. Although in CKD, these changes progress relatively slowly, they are dynamic in AKI, and recovery is possible depending on the etiology and treatments. This, and the use of kidney replacement therapies further complicate attempts to quantify drug clearance at the time of prescribing and dosing in AKI. The required change in the dosing regimen can be estimated or even quantitated in certain instances through the application of pharmacokinetic principles to guide rational drug dosing. This offers an opportunity to provide personalized medical care and minimizes adverse drug events from either under- or overdosing. We discuss the principles of pharmacokinetics that are fundamental for the design of an appropriate dosing regimen in this review.

Acceleration of carboxylesterase-mediated activation of irinotecan to SN-38 by serum from patients with end-stage kidney disease

PURPOSE

Pharmacokinetics and pharmacodynamics of irinotecan have been reported to be altered in cancer patients with end-stage kidney disease (ESKD). Carboxylesterase (CES) has an important role in metabolism of irinotecan to its active metabolite, SN-38, in human liver. The purpose of the present study was to investigate whether CES activity was altered in ESKD patients.

METHODS

The present study investigated the effects of uremic serum, uremic toxins, and fatty acids on the hydrolysis of irinotecan and a typical CES substrate, p-nitrophenyl acetate (PNPA), in human liver microsomes. Normal and uremic serum samples were deproteinized by treatment with methanol were used in the present study.

RESULTS

The present study showed that both normal and uremic serum significantly inhibited CES-mediated metabolism of both irinotecan and PNPA. The inhibition by uremic serum was weaker than that by normal serum, suggesting that CES activity may be higher in ESKD patients. Although four uremic toxins did not affect PNPA metabolism, arachidonic acid inhibited it. There was no difference in inhibitory effect of PNPA metabolism between both mixtures of seven fatty acids used at concentrations equivalent to those present in 10% normal or uremic serum. Interestingly, those mixtures had a more pronounced effect than either 10% normal or uremic serum.

CONCLUSIONS

The present study showed that the inhibition of CES activity by uremic serum was weaker than that by normal serum, suggesting that an increase in maximum plasma concentration of SN-38 in cancer patients with ESKD can be attributed to an accelerated CES-mediated irinotecan hydrolysis.

β-Blocker Dialyzability in Maintenance Hemodialysis Patients: A Randomized Clinical Trial

BACKGROUND AND OBJECTIVES

There is a paucity of data available to describe drug dialyzability. Of the available information, most was obtained before implementation of modern hemodialysis membranes. Our study characterized dialyzability of the most commonly prescribed β-blockers in patients undergoing high-flux hemodialysis.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Patients on hemodialysis (n=8) were recruited to an open label, pharmacokinetic, four-way crossover trial. Single doses of atenolol, metoprolol, bisoprolol, and carvedilol were administered on separate days in random order to each patient. Plasma and dialysate drug concentrations were measured, and dialyzability was determined by the recovery clearance and arterial venous difference methods.

RESULTS

Using the recovery clearance method, the dialytic clearance values for atenolol, metoprolol, bisoprolol, and carvedilol were 72, 87, 44, and 0.2 ml/min, respectively (P<0.001). Applying the arterial venous difference method, the dialytic clearance values of atenolol, metoprolol, bisoprolol, and carvedilol were 167, 114, 96, and 24 ml/min, respectively (P<0.001).

CONCLUSIONS

Atenolol and metoprolol are extensively cleared by hemodialysis compared with the negligible dialytic clearance of carvedilol. Contrary to estimates of dialyzability on the basis of previous literature, our data indicate that bisoprolol is also dialyzable. This finding highlights the importance of conducting dialyzability studies to definitively characterize drug dialytic clearance.

Mycophenolic Acid and Its Metabolites in Kidney Transplant Recipients: A Semimechanistic Enterohepatic Circulation Model to Improve Estimating Exposure

Mycophenolic acid (MPA) is an approved immunosuppressive agent widely prescribed to prevent rejection after kidney transplantation. Wide between-subject variability (BSV) in MPA exposure exists which in part may be due to variability in enterohepatic recirculation (EHC). Several modeling strategies were developed to evaluate EHC as part of MPA pharmacokinetics, however mechanistic representation of EHC is limited. These models have not provided a satisfactory representation of the physiology of EHC in their modeling assumptions. The aim of this study was i) to develop an integrated model of MPA (total and unbound) and its metabolites (MPAG and acyl-MPAG) in kidney recipients, where this model provides a more physiological representation of EHC process, and ii) to evaluate the effect of donor and recipient clinical covariates and genotypes on MPA disposition. A five-compartment model with first-order input into an unbound MPA compartment connected to the MPAG, acyl-MPAG, and gallbladder compartment best fit the data. To represent the EHC process, the model was built based on the physiological concepts related to the hepatobiliary system and the gallbladder filling and emptying processes. The effect of cyclosporine versus tacrolimus on clearance of unbound MPA was included in the base model. Covariate analysis showed creatinine clearance to be significant on oral clearance of unbound MPA. The hepatic nuclear factor 1 alpha (HNF1A) genetic single nucleotide polymorphism (SNP) (rs2393791) in the recipient significantly affected the fraction of enterohepatically-circulated drug. Oral clearance of MPAG was affected by recipient IMPDH1 SNP (rs2288553), diabetes at the time of transplant, and donor sex.

Clinical Pharmacokinetics and Pharmacodynamics of Afatinib

Afatinib is an oral, irreversible ErbB family blocker that covalently binds to the kinase domains of epidermal growth factor receptor (EGFR), human EGFRs (HER) 2, and HER4, resulting in irreversible inhibition of tyrosine kinase autophosphorylation. Studies in healthy volunteers and patients with advanced solid tumours have shown that once-daily afatinib has time-independent pharmacokinetic characteristics. Maximum plasma concentrations of afatinib are reached approximately 2–5 h after oral administration and thereafter decline, at least bi-exponentially. Food reduces total exposure to afatinib. Over the clinical dose range of 20–50 mg, afatinib exposure increases slightly more than dose proportional. Afatinib metabolism is minimal, with unchanged drug predominantly excreted in the faeces and approximately 5 % in urine. Apart from the parent drug afatinib, the major circulation species in human plasma are the covalently bound adducts to plasma protein. The effective elimination half-life is approximately 37 h, consistent with an accumulation of drug exposure by 2.5- to 3.4-fold based on area under the plasma concentration–time curve (AUC) after multiple dosing. The pharmacokinetic profile of afatinib is consistent across a range of patient populations. Age, ethnicity, smoking status and hepatic function had no influence on afatinib pharmacokinetics, while females and patients with low body weight had increased exposure to afatinib. Renal function is correlated with afatinib exposure, but, as for sex and body weight, the effect size for patients with severe renal impairment (approximately 50 % increase in AUC) is only mildly relative to the extent of unexplained interpatient variability in afatinib exposure. Afatinib has a low potential as a victim or perpetrator of drug–drug interactions, especially with cytochrome P450-modulating agents. However, concomitant treatment with potent inhibitors or inducers of the P-glycoprotein transporter can affect the pharmacokinetics of afatinib. At a dose of 50 mg, afatinib does not have proarrhythmic potential.

A phase I study to assess the mass balance, excretion, and pharmacokinetics of [14C]-ixazomib, an oral proteasome inhibitor, in patients with advanced solid tumors

This two-part, phase I study evaluated the mass balance, excretion, pharmacokinetics (PK), and safety of ixazomib in patients with advanced solid tumors. In Part A of the study, patients received a single 4.1 mg oral solution dose of [¹⁴C]-ixazomib containing ~500 nCi total radioactivity (TRA), followed by non-radiolabeled ixazomib (4 mg capsule) on days 14 and 21 of the 35-day PK cycle. Patients were confined to the clinic for the first 168 h post dose and returned for 24 h overnight clinic visits on days 14, 21, 28, and 35. Blood, urine, and fecal samples were collected during Part A to assess the mass balance (by accelerator mass spectrometry), excretion, and PK of ixazomib. During Part B of the study, patients received non-radiolabeled ixazomib (4 mg capsules) on days 1, 8, and 15 of 28-day cycles. After oral administration, ixazomib was rapidly absorbed with a median plasma T_max of 0.5 h and represented 70% of total drug-related material in plasma. The mean total recovery of administered TRA was 83.9%; 62.1% in urine and 21.8% in feces. Only 3.23% of the administered dose was recovered in urine as unchanged drug up to 168 h post dose, suggesting that most of the TRA in urine was attributable to metabolites. All patients experienced a treatment-emergent adverse event, which most commonly involved the gastrointestinal system. These findings suggest that ixazomib is extensively metabolized, with urine representing the predominant route of excretion of drug-related material.Trial ID: ClinicalTrials.gov # NCT01953783.

Parathyroid hormone contributes to the down-regulation of cytochrome P450 3A through the cAMP/PI3K/PKC/PKA/NF-κB signaling pathway in secondary hyperparathyroidism

Chronic kidney disease (CKD), which affects, not only renal clearance, but also non-renal clearance, is accompanied by a decline in renal function. Although it has been suggested that humoral factors, such as uremic toxins that accumulate in the body under CKD conditions, could be involved in the changes associated with non-renal drug clearance, the overall process is not completely understood. In this study, we report on the role of parathyroid hormone (PTH), a middle molecule uremic toxin, on the expression of drug metabolizing or transporting proteins using rats with secondary hyperparathyroidism (SHPT) as models. In SHPT rats, hepatic and intestinal CYP3A expression was suppressed, but the changes were recovered by the administration of the calcimimetic cinacalcet, a PTH suppressor. Under the same experimental conditions, a pharmacokinetic study using orally administered midazolam, a substrate for CYP3A, showed that the AUC was increased by 5 times in SHPT rats, but that was partially recovered by a cinacalcet treatment. This was directly tested in rat primary hepatocytes and intestinal Caco-2 cells where the expression of the CYP3A protein was down-regulated by PTH (1-34). In Caco-2 cells, PTH (1-34) down-regulated the expression of CYP3A mRNA, but an inactive PTH derivative (13-34) had no effect. 8-Bromo-cyclic adenosine monophosphate, a membrane-permeable cAMP analog, reduced mRNA expression of CYP3A whereas the inhibitors of PI3K, NF-κB, PKC and PKA reversed the PTH-induced CYP3A down-regulation. These results suggest that PTH down-regulates CYP3A through multiple signaling pathways, including the PI3K/PKC/PKA/NF-κB pathway after the elevation of intracellular cAMP, and the effect of PTH can be prevented by cinacalcet treatment.

The Role of the Kidney in Drug Elimination: Transport, Metabolism, and the Impact of Kidney Disease on Drug Clearance

Recent advances in the identification and characterization of renal drug transporters and drug-metabolizing enzymes has led to greater understanding of their roles in drug and chemical elimination and in modulation of the intrarenal exposure and response to drugs, nephrotoxic compounds, and physiological mediators. Furthermore, there is increasing awareness of the potential importance of drug-drug interactions (DDIs) arising from inhibition of renal transporters, and regulatory agencies now provide recommendations for the evaluation of transporter-mediated DDIs. Apart from the well-recognized effects of kidney disease on renal drug clearance, there is a growing body of evidence demonstrating that the nonrenal clearances of drugs eliminated by certain transporters and drug-metabolizing enzymes are decreased in patients with chronic kidney disease (CKD). Based on these observations, renal impairment guidance documents of regulatory agencies recommend pharmacokinetic characterization of both renally cleared and nonrenally cleared drugs in CKD patients to inform possible dosage adjustment.