Theoretical Formulation Strategies towards Neutralizing Inter-individual Variability Associated with Tacrolimus Immunosuppressant Therapy: A Case Study on Nextgeneration Personalized Medicine.

Individualizing drug therapy and attaining maximum benefits of a drug devoid of adverse reactions is the benefit of personalized medicine. One of the important factors contributing to inter-individual variability is genetic polymorphism. As of now, dose titration is the only followed golden standard for implementing personalized medicine. Converting the genotypic data into an optimized dose has become easier now due to technology development. However, for many drugs, finding an individualized dose may not be successful, which further leads to a trial and error approach. These dose titration strategies are generally followed at the clinical level, and so industrial involvement and further standardizations are not feasible. On the other side, technologically driven pharmaceutical industries have multiple smart drug delivery systems which are underutilized towards personalized medicine. Transdisciplinary research with drug delivery science can additionally support the personalization by converting the traditional concept of "dose titration towards personalization" with novel "dose-cum-dosage form modification towards next-generation personalized medicine"; the latter approach is useful to overcome gene-based inter-individual variability by either blocking, to downregulate, or bypassing the biological protein generated by the polymorphic gene. This article elaborates an advanced approach to implementing personalized medicine with the support of novel drug delivery systems. As a case study, we further reviewed the genetic polymorphisms associated with tacrolimus and customized novel drug delivery systems to overcome these challenges factored towards personalized medicine for better clinical outcomes, thereby paving a new strategy for implementing personalized medicine for all other drug candidates.

Population Pharmacokinetics of Tofacitinib in Patients With Moderate to Severe Ulcerative Colitis.

Tofacitinib is an oral, small molecule Janus kinase inhibitor for the treatment of ulcerative colitis (UC). We characterized tofacitinib pharmacokinetics in patients with moderate to severe UC, and the effects of covariates on variability in pharmacokinetic parameter estimates. Data were pooled from 1 8-week phase 2 and 2 8-week phase 3 induction studies, and a 52-week phase 3 maintenance study (N = 1096). Population pharmacokinetic analysis was conducted using nonlinear mixed-effects modeling. Potential predictors of apparent oral clearance (CL/F) and volume of distribution (V/F) were evaluated. The PK was described by a 1-compartment model parameterized in terms of CL/F (26.3 L/hour [h]) and V/F (115.8 L), with first-order absorption (Ka ; 9.85 h-1 ) and lag time (0.236 h). The derived elimination half-life was approximately 3.05 h. In the final model, baseline creatinine clearance, sex, and race (Asian vs non-Asian) were significant covariates for CL/F; significant covariates for V/F were age, sex, and body weight; baseline albumin and baseline Mayo score were not significant covariates. CL/F between-patient variability was estimated at 22%. Tofacitinib exposure did not change significantly over the duration of induction/maintenance treatment in patients with UC. Although statistically significant covariate effects on CL/F and V/F were observed, the magnitude of the effects are not clinically significant. Therefore, dose adjustment/restrictions for age, body weight, sex, race, or baseline disease severity are not required during tofacitinib treatment. ClinicalTrials.gov numbers: NCT00787202, NCT01465763, NCT01458951, NCT01458574.

ARDS Subphenotypes: Understanding a Heterogeneous Syndrome.

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency Medicine 2020. Other selected articles can be found online at https://www.biomedcentral.com/collections/annualupdate2020. Further information about the Annual Update in Intensive Care and Emergency Medicine is available from http://www.springer.com/series/8901.

Population Pharmacokinetics of Apalutamide and its Active Metabolite N-Desmethyl-Apalutamide in Healthy and Castration-Resistant Prostate Cancer Subjects.

BACKGROUND: Apalutamide is a next-generation androgen receptor inhibitor approved for treatment of subjects with high-risk, non-metastatic, castration-resistant prostate cancer (NM-CRPC). OBJECTIVE: The objective of this study was to characterize the population pharmacokinetics of apalutamide and its metabolite N-desmethyl-apalutamide in healthy male and castration-resistant prostate cancer subjects. METHODS: Plasma concentration data for apalutamide and N-desmethyl-apalutamide from 1092 subjects (seven clinical studies) receiving oral apalutamide (30-480 mg) once daily were pooled for a population pharmacokinetic analysis using a non-linear mixed-effect modelling approach. The impact of clinically relevant covariates was also assessed. RESULTS: Apalutamide absorption was rapid, and the apparent steady-state volume of distribution was large (276 L), reflecting a wide body distribution. Apalutamide was eliminated slowly, with its apparent clearance increasing from 1.31 L/h after the first dose to 2.04 L/h at steady state. No evidence of time-dependent disposition was observed for N-desmethyl-apalutamide, which was also widely distributed and slowly cleared (1.5 L/h). After 4 weeks of treatment, more than 95% of steady-state exposure of apalutamide and N-desmethyl-apalutamide was reached. At a dose of apalutamide 240 mg/day, apalutamide and N-desmethyl-apalutamide exposure exhibited 5.3- and 85.2-fold accumulation in plasma, respectively. Inter-individual variability in apalutamide apparent clearance is low (< 20%). Among the covariates evaluated, apalutamide and N-desmethyl-apalutamide exposure were statistically associated only with health status, body weight, and albumin concentration, and the effect was low (< 25%). CONCLUSIONS: A population pharmacokinetic modelling approach was successfully applied to describe the pharmacokinetics of apalutamide and N-desmethyl-apalutamide. No clinically relevant covariates were identified as predictors of apalutamide and N-desmethyl-apalutamide pharmacokinetics.

Itraconazole Increases Ibrutinib Exposure 10-Fold and Reduces Interindividual Variation-A Potentially Beneficial Drug-Drug Interaction.

The oral bioavailability of ibrutinib is low and variable, mainly due to extensive first-pass metabolism by cytochrome P450 (CYP) 3A4. The unpredictable exposure can compromise its safe and effective dosing. We examined the impact of itraconazole on ibrutinib pharmacokinetics. In a randomized crossover study, 11 healthy subjects were administered itraconazole 200 mg or placebo twice on day 1, and once on days 2-4. On day 3, 1 hour after itraconazole (placebo) and breakfast, ibrutinib (140 mg during placebo; 15 mg during itraconazole) was administered. Itraconazole increased the dose-adjusted geometric mean area under the concentration-time curve from zero to infinity (AUC0-∞ ) of ibrutinib 10.0-fold (90% confidence interval (CI) 7.2-13.9; P < 0.001) and peak plasma concentration (Cmax ) 8.8-fold (90% CI 6.3-12.1; P < 0.001). During itraconazole, the intersubject variation for the AUC0-∞ (55%) and Cmax (53%) was around half of that during placebo (104%; 99%). In conclusion, itraconazole markedly increases ibrutinib bioavailability and decreases its interindividual variability, offering a possibility to improved dosing accuracy and cost savings.

Clinical Pharmacokinetics and Pharmacodynamics of Rifampicin in Human Tuberculosis.

The introduction of rifampicin (rifampin) into tuberculosis (TB) treatment five decades ago was critical for shortening the treatment duration for patients with pulmonary TB to 6 months when combined with pyrazinamide in the first 2 months. Resistance or hypersensitivity to rifampicin effectively condemns a patient to prolonged, less effective, more toxic, and expensive regimens. Because of cost and fears of toxicity, rifampicin was introduced at an oral daily dose of 600 mg (8-12 mg/kg body weight). At this dose, clinical trials in 1970s found cure rates of ≥ 95% and relapse rates of < 5%. However, recent papers report lower cure rates that might be the consequence of increased emergence of resistance. Several lines of evidence suggest that higher rifampicin doses, if tolerated and safe, could shorten treatment duration even further. We conducted a narrative review of rifampicin pharmacokinetics and pharmacodynamics in adults across a range of doses and highlight variables that influence its pharmacokinetics/pharmacodynamics. Rifampicin exposure has considerable inter- and intra-individual variability that could be reduced by administration during fasting. Several factors including malnutrition, HIV infection, diabetes mellitus, dose size, pharmacogenetic polymorphisms, hepatic cirrhosis, and substandard medicinal products alter rifampicin exposure and/or efficacy. Renal impairment has no influence on rifampicin pharmacokinetics when dosed at 600 mg. Rifampicin maximum (peak) concentration (Cmax) > 8.2 µg/mL is an independent predictor of sterilizing activity and therapeutic drug monitoring at 2, 4, and 6 h post-dose may aid in optimizing dosing to achieve the recommended rifampicin concentration of ≥ 8 µg/mL. A higher rifampicin Cmax is required for severe forms TB such as TB meningitis, with Cmax ≥ 22 µg/mL and area under the concentration-time curve (AUC) from time zero to 6 h (AUC6) ≥ 70 µg·h/mL associated with reduced mortality. More studies are needed to confirm whether doses achieving exposures higher than the current standard dosage could translate into faster sputum conversion, higher cure rates, lower relapse rates, and less mortality. It is encouraging that daily rifampicin doses up to 35 mg/kg were found to be safe and well-tolerated over a period of 12 weeks. High-dose rifampicin should thus be considered in future studies when constructing potentially shorter regimens. The studies should be adequately powered to determine treatment outcomes and should include surrogate markers of efficacy such as Cmax/MIC (minimum inhibitory concentration) and AUC/MIC.

Quantification of the tyrosine kinase inhibitor erlotinib in human scalp hair by liquid chromatography-tandem mass spectrometry: Pitfalls for clinical application.

An LC-MS/MS method was developed and validated to quantify the tyrosine kinase inhibitor erlotinib in human scalp hair, as alternative matrix to monitor long-term erlotinib exposure. Hair samples from 10 lung cancer patients were measured and correlated with plasma concentrations. Hair segments of 1 ± 0.1 cm each were pulverized and for at least 18 h incubated in methanol at ambient temperature. A liquid-liquid extraction purified the extracts and they were analyzed with LC-MS/MS, using erlotinib-d6 as internal standard. The procedure method was validated for selectivity, sensitivity, precision, lower limit of detection, linearity and accuracy. The within and between run precisions including the lower limit of quantification did not exceed 12.5%, while the accuracy ranged from 103 to 106%. A weak correlation between hair and plasma concentration was found (R2 = 0.48). Furthermore, a large inter-individual variability was noted in the disposition of both plasma and hair samples. The highest hair concentrations were observed in black hair compared with other (grey and brown) hair colors. Generally, a linear reduction in hair concentration was found from proximal to distal hair segments. Additional in vitro experiments suggest an accelerated degradation of erlotinib in hair by artificial UV light and also wash-out by shampoo mixtures pretreatment compared with control samples. In conclusion, a reliable and robust LC-MS/MS method was developed to quantify erlotinib in hair. However, clinical and in vitro evaluations showed that the method is not suitable for monitoring long-term erlotinib exposure. The pitfalls of this application outweigh the current benefits.

Use of Physiologically Based Pharmacokinetic Modeling to Identify Physiological and Molecular Characteristics Driving Variability in Axitinib Exposure: A Fresh Approach to Precision Dosing in Oncology.

Axitinib is a second-generation small-molecule vascular endothelial growth factor receptor inhibitor. An axitinib steady-state area under the plasma concentration-time curve (AUCSS ) >300 ng/mL/hr is associated with superior progression-free and overall survival. This study sought to characterize the physiological and molecular characteristics driving variability in axitinib AUCSS using physiologically based pharmacokinetic modeling to identify exposure biomarkers for this drug. The capacity to predict subjects likely to fail to achieve an axitinib AUCSS >300 ng/mL/hr was evaluated as a secondary outcome. A full physiologically based pharmacokinetic model incorporating mechanistic absorption was developed and verified for axitinib in accordance with the US Food and Drug Administration Guidance using Simcyp (Version 17.1). This model was used to simulate axitinib exposure over 7 days with twice-daily dosing (5 mg) in a cohort of 1000 virtual cancer patients. Multiple linear regression modeling was used to identify patient characteristics associated with differences in axitinib exposure. A multivariable linear regression model incorporating hepatic cytochrome P450 (CYP) 3A4 abundance, albumin concentration, hepatic CYP1A2 abundance, hepatic CYP2C19 abundance, and intestinal CYP2C19 abundance provided robust prediction of axitinib AUCSS (R2 = 0.890; P < .001). By accounting for these variables, it was possible to identify subjects who would fail to achieve an effective axitinib AUCSS with a specificity of 88.7% and a sensitivity of 92.6%. Variability in axitinib AUCSS is primarily driven by differences in hepatic CYP3A4 abundance and albumin concentration. Consideration of these 2 characteristic is likely to be sufficient to individualize axitinib dosing.

Population Pharmacokinetic Modeling of Acetaminophen and Metabolites in Children After Cardiac Surgery With Cardiopulmonary Bypass.

Children undergoing cardiac surgery often receive acetaminophen (paracetamol) as part of their postoperative pain treatment. To date, there is no information on the pharmacokinetics (PK) of acetaminophen in this special population, even though differences, as a result of altered hemodynamics and/or use of cardiopulmonary bypass, may be anticipated. Therefore, the aim of this study was to investigate the PK of intravenous acetaminophen in children after cardiac surgery with cardiopulmonary bypass. In the study, both children with and without Down syndrome were included. A population PK analysis, using NONMEM 7.2, was performed based on 161 concentrations of acetaminophen, acetaminophen sulfate, acetaminophen glucuronide, and oxidative metabolites from 17 children with Down syndrome and 13 children without Down syndrome of a previously published study (median age, 177 days [range, 92-944], body weight, 6.1 kg [4.0-12.9]). All children received 3 intravenous acetaminophen doses of 7.5 mg/kg (<10 kg) or 15 mg/kg (≥10 kg) at 8-hour intervals after cardiac surgery. For acetaminophen and its metabolites, 1-compartment models were identified. Clearance of acetaminophen and metabolites increased linearly with body weight. Acetaminophen clearance in a typical child of 6.1 kg is 0.96 L/h and volume of distribution 7.96 L. Down syndrome did not statistically significantly impact any of the PK parameters for acetaminophen, nor did any other remaining covariate. When comparing the PK parameters of acetaminophen in children after cardiac surgery with cardiopulmonary bypass with those from children of the same age following noncardiac surgery reported in the literature, clearance of acetaminophen was lower and volume of distribution higher.

Population Pharmacokinetics of the Interleukin-23 Inhibitor Risankizumab in Subjects with Psoriasis and Crohn's Disease: Analyses of Phase I and II Trials.

BACKGROUND AND OBJECTIVES: Risankizumab is a humanized anti-interleukin-23 monoclonal antibody in development for the treatment of several inflammatory diseases. This work characterized the pharmacokinetics of risankizumab and evaluated covariates that may affect its exposures using phase I and II trial data in subjects with psoriasis and Crohn's disease. METHODS: Plasma concentration measurements from a phase I study and a phase II study in subjects with psoriasis (n = 157; single doses of 0.01-5 mg/kg intravenously, 0.25-1 mg/kg subcutaneously, and 18 mg subcutaneously, and multiple doses of 90 and 180 mg subcutaneously), and a phase II study in subjects with Crohn's disease (n = 115; doses of 200 or 600 mg intravenously every 4 weeks followed by 180 mg subcutaneously every 8 weeks) were analyzed using non-linear mixed-effects modeling. The model was qualified using bootstrap and simulation-based diagnostics. RESULTS: A two-compartment model with first-order absorption and elimination described the pharmacokinetics of risankizumab. Considering the body weight and baseline albumin central tendency differences between disease populations, risankizumab clearance, steady-state volume of distribution, and terminal-phase elimination half-life were estimated to be approximately 0.35 L/day, 11.7 L, and 27 days, respectively, for a typical 90-kg subject with psoriasis with an albumin level of 42 g/L, and 0.31 L/day, 8.45 L, and 22 days, respectively, for a typical 65-kg subject with Crohn's disease with an albumin level of 37 g/L. Risankizumab absolute subcutaneous bioavailability and absorption rate constant were 72% and 0.18 day-1, respectively. Inter-individual variability for clearance was 37%. CONCLUSIONS: Risankizumab displayed pharmacokinetic characteristics typical for an IgG1 monoclonal antibody with no apparent target-mediated disposition. Accounting for the effects of body weight and baseline albumin explained the small differences in the pharmacokinetics of risankizumab between psoriasis and Crohn's disease, with no further differences between the patient populations.

Colony and Single Cell Level Analysis of the Heterogeneous Response of Cryptococcus neoformans to Fluconazole.

Cryptococcus neoformans is a human fungal pathogen that can cause fatal meningitis in immunocompromised individuals. Fluconazole (FLC) is a fungistatic drug administered to treat cryptococcosis. When exposed to the inhibitory concentration of FLC, C. neoformans exhibits heteroresistance where a small subpopulation of cells develops into FLC-resistant colonies. FLC-resistant cells are aneuploids with regard to specific beneficial chromosomal regions. Factors underlying the potential for only certain C. neoformans cells in a genetically isogenic population to become FLC-resistant are unknown. In this study, we systematically examine the heterogeneous response of C. neoformans to FLC at a colony and individual cell level. We find that the heterogeneity in response to FLC is reflected by variable diminishment of the ergosterol at the plasma membrane. A population of C. neoformans spread on a semi-solid medium displays two types of outcomes following FLC exposure. The first outcome is colonies consisting of non-resistant cells (survivors). The size of colonies consisting of survivors ranges from a few cells to visible colonies, which reflects intrinsic phenotypic heterogeneity of the C. neoformans population. The second outcome is FLC-resistant cells forming colonies of sizes significantly larger as compared to colonies made of survivors. We propose a model that describes how a distribution of these types of cellular responses within a population changes depending on FLC concentration and factors that influence the rate of cellular growth including temperature, media type, growth phase, and the age of cells. Our findings highlight a complex nature of the response to a fungistatic drug and provide insights that may help to optimize FLC therapy.

Unraveling Individual Differences In The HIV-1 Transgenic Rat: Therapeutic Efficacy Of Methylphenidate.

Despite the heterogeneity of HIV-1 associated neurocognitive disorders (HAND), assignment of categorical diagnoses based on the level of impairment (e.g., Frascati criteria) obfuscates the well-acknowledged variability observed within the population of HIV-1+ individuals. The present study sought to elucidate the natural heterogeneity in adult HIV-1 transgenic (Tg) rats using three interrelated aims. First, heterogeneity of the HIV-1 transgene was examined using a pretest-posttest design to assess therapeutic efficacy of oral self-administration (OSA) of methylphenidate (MPH; 2.4 ± 0.2 mg/kg), targeting neurotransmitter alterations in HIV-1, on temporal processing. Approximately 42% of HIV-1 Tg animals displayed an improvement in temporal processing following OSA of MPH. Second, repeated OSA of MPH (22-27 days) altered dendritic spine morphology in layer II-III pyramidal neurons in the medial prefrontal cortex. HIV-1 Tg animals exhibited a population shift towards longer spines with decreased head diameter on lower order branches; a shift associated with temporal processing impairment. Third, in HIV-1 Tg animals, dendritic spine backbone length (µm) was associated with temporal processing impairment; a brain/behavior relationship not observed in control animals. Assessing the therapeutic efficacy of MPH revealed heterogeneity in the neural mechanisms underlying neurocognitive impairments, providing a key target for individualized therapeutic and diagnostic approaches for HAND.

Intra- and inter-subject variability for increases in serum ketone bodies in patients with type 2 diabetes treated with the sodium glucose co-transporter 2 inhibitor canagliflozin.

Sodium glucose co-transporter 2 (SGLT2) inhibitors have been associated with increased serum ketone body levels in patients with type 2 diabetes mellitus (T2DM). In the present analysis we evaluated serum ketone body levels and variability in 1278 Japanese patients with T2DM treated with canagliflozin 100 or 200 mg. Similar mean increases in ketone body concentrations of ~2-fold were seen with both canagliflozin doses. The median (interquartile range) percent change from baseline was 62% (0;180) for acetoacetate and 78% (2;236) for ß-hydroxybutyrate. Approximately two-thirds of the variability in each ketone measure was attributed to intra-subject variability. Intra-subject variability was higher for serum ketones than other metabolites. Patients in the lowest response tertile exhibited no increase in ketones. Those in the highest response tertile tended to be male and have higher fasting plasma glucose levels, lower insulin levels, and longer T2DM duration at baseline. Moreover, changes in serum ketones were not fully explained by changes in plasma fatty acids, suggesting downstream effects of SGLT2 inhibition on hepatic metabolism that favour ketogenesis. In summary, increases in serum ketone bodies with canagliflozin were greater and more variable than changes in other metabolic measures in Japanese patients with T2DM.

Personalized medicine, pharmacogenomic and companion biomarker.

The aim of this review is to provide a brief overview of personalized medicine, pharmacogenetics and companion tests. Personalized or stratified medicine is a new paradigm in the management of patients, aimed at better taking into account inter-individual variability. The response to drugs' intake varies considerably, depending on the transport and metabolism of the drugs, the target and the pathophysiological characteristics of the organism. Each stage is very variable and can be modified by endogenous factors (pathophysiology, age, sex, genetics…) or exogenous (environmental: taking other medicines, food, tobacco, alcohol…). Pharmacogenetics studies the genetic factors involved in the pharmacological or toxicological response to drugs. Companion tests that are often based on a pharmacogenetic principle aim to identify in a patient's population those who will respond to a given treatment.

Effect of gastric acid-suppressive therapy and biological variation of serum gastrin concentrations in dogs with chronic enteropathies.

BACKGROUND: Serum gastrin concentration can help diagnose gastrinomas in dogs if >3-10× the upper reference limit (URL), but antisecretory therapy and other conditions can also cause hypergastrinemia. Effects of antisecretory therapy (famotidine or ranitidine, omeprazole) on serum gastrin concentration in dogs with chronic enteropathy (CE) and its biological variation (BV) are unknown. Aim of the study was to evaluate serum gastrin in acid-suppressant-treated or -naïve CE dogs; test the association between serum gastrin and histopathologic findings in acid-suppressant-naïve CE dogs; and evaluate the BV of serum gastrin in dogs not receiving any gastric acid suppressive therapy. Samples from 231 dogs were used and serum gastrin was measured by chemiluminescence assay. Gastric and duodenal histologic lesions were evaluated and graded. BV of serum gastrin was evaluated in serial samples. RESULTS: Serum gastrin concentrations were significantly higher in acid-suppressant-treated than acid-suppressant-naïve dogs (P = 0.0245), with significantly higher concentrations in proton pump inhibitor (PPI)- than H2-antihistamine-treated patients (P = 0.0053). More PPI- than H2-antihistamine-treated dogs had gastrin concentrations above URL (P = 0.0205), but not >3× nor >10× the URL. Serum gastrin concentrations correlated with the severity of gastric antral epithelial injury (P = 0.0069) but not with any other lesions or the presence/numbers of spiral bacteria in gastric biopsies. Intra- and inter-individual BV were 43.4 and 21.6%, respectively, in acid-suppressant-naïve dogs, with a reciprocal individuality index of 0.49 and a critical difference of ≥29.5 ng/L. CONCLUSIONS: Antisecretory (particularly PPI) treatment leads to hypergastrinemia in CE dogs, but the concentrations seen in this study are unlikely to compromise a diagnosis of gastrinoma. Use of a population-based URL for canine serum gastrin and a URL of ≤27.8 ng/L are appropriate.

Current assessment of heart rate variability and QTc interval length in HIV/AIDS.

PURPOSE OF REVIEW: The increasing prevalence of cardiovascular disease comorbidity in persons infected with the HIV has become a global concern. The electrocardiogram (ECG) is increasingly being utilized to provide clinically relevant information regarding cardiac arrhythmias and cardio-autonomic dysfunction. The purpose of this review is to summarize the latest research comparing QT and R-to-R interval length as a function of HIV+ status or antiretroviral therapy (ART) regimen. RECENT FINDINGS: Prolongation of the corrected QTc interval may be acquired in HIV+ ART-naive individuals, exacerbated by various classes of ART drugs, and is generally predictive of lethal cardiac arrhythmias, with effects observed from childhood to adulthood. Recent literature also suggests the trend of lower heart rate variability in HIV is indicative of cardiorespiratory and inflammatory-immune dysfunction. SUMMARY: These emergent studies support the clinical relevance of the ECG across the age and HIV disease spectrum. Furthermore, the reported findings have implications for the management of cardiovascular and chronic inflammatory disease comorbidity in persons living with HIV.