Abstract-The objective of this study was to test whether a glycosaminoglycan component of the surface glycocalyx layer is a fluid shear stress sensor on endothelial cells (ECs). Because enhanced nitric oxide (NO) production in response to fluid shear stress is a characteristic and physiologically important response of ECs, we evaluated NO x (NO 2 Ϫ and NO 3 Ϫ ) production in response to fluid shear stress after enzymatic removal of heparan sulfate, the dominant glycosaminoglycan of the EC glycocalyx, from cultured ECs. The significant NO x production induced by steady shear stress (20 dyne/cm 2 ) was inhibited completely by pretreatment with 15 mU/mL heparinase III (E.C.4.2.2.8) for 2 hours. Oscillatory shear stress (10Ϯ15 dyne/cm 2 ) induced an even greater NO x production than steady shear stress that was completely inhibited by pretreatment with heparinase III. Addition of bradykinin (BK) induced significant NO x production that was not inhibited by heparinase pretreatment, demonstrating that the cells were still able to produce abundant NO after heparinase treatment. Fluorescent imaging with a heparan sulfate antibody revealed that heparinase III treatments removed a substantial fraction of the heparan sulfate bound to the surfaces of ECs. In summary, these experiments demonstrate that a heparan sulfate component of the EC glycocalyx participates in mechanosensing that mediates NO production in response to shear stress. The full text of this article is available online at http://www.circresaha.org. Key Words: shear stress Ⅲ endothelial cells Ⅲ heparan sulfate Ⅲ nitric oxide Ⅲ glycocalyx T he inner surfaces of blood vessels are lined with a monolayer of endothelial cells (ECs) that is continually exposed to the mechanical shearing forces (stresses) of blood flow. Variations in shear stress magnitude as well as temporal and spatial distribution have been shown to induce alterations in endothelial permeability and hydraulic conductivity, 1-3 cytoskeletal structure, 4 -7 surface adhesion molecule expression, 8 and gene expression. 9,10 In addition, the exposure of endothelial cells to shear (both steady and oscillatory) has been shown to alter the production of vasoregulating agents of which nitric oxide (NO) is perhaps the most notable. [11][12][13] NO is a vasodilator produced by the conversion of L-arginine to L-citrulline that is catalyzed by endothelial nitric oxide synthase (eNOS). NO modulates vascular tone by eliciting relaxation of smooth muscle cells while inhibiting smooth muscle cell growth. 14 NO production responds to changes in shear stress in a biphasic manner in human umbilical vein endothelial cells (HUVECs) and bovine aortic endothelial cells (BAECs). 11,12 There is an initial rapid NO production phase that is G protein and Ca 2ϩ -dependent and is influenced by rate of change of shear and not the shear level per se. The subsequent phase is characterized by a lower rate of NO production rate that is G protein and Ca 2ϩ -independent but is shear level dependent. 12,15 Both phases of the NO respo...

To increase our understanding of important subject characteristics and design variables affecting the performance of oral moxifloxacin in thorough QT studies, population pharmacokinetic and concentration-QTc models were developed by pooling data from 20 studies. A 1-compartment model with first-order elimination described the pharmacokinetics. Absorption delay was modeled using 8 transit compartments. Mean (95% confidence interval) values for oral clearance, apparent volume of distribution, the first-order absorption rate constant, and mean transit time were 11.7 (11.5-11.9) L/h, 147 (144-150) L, 1.9 (1.7-2.1) 1/h, and 0.3 (0.28-0.34) hours, respectively. Overencapsulating the moxifloxacin tablet increased mean transit time by 138% and delayed time to maximum concentration by 0.5 hours but had a minimal effect on overall exposure. Administration with food decreased absorption rate constant by 27%. Women had higher moxifloxacin exposure compared with men, which was explained by lower body weights. A linear model described the concentration-QTc relationship with a mean slope of 3.1 (2.8-3.3) milliseconds per µg/mL moxifloxacin. Mean slopes for individual studies ranged from 1.6 to 4.8 milliseconds per µg/mL. Hysteresis between moxifloxacin plasma concentrations and QTc was modest, and incorporating this delay did not result in a different slope (3.3 milliseconds per µg/mL). There were no differences in slope estimates between men and women or among race categories.

IMPORTANCEThe US Food and Drug Administration (FDA) has provided guidance that sunscreen active ingredients with systemic absorption greater than 0.5 ng/mL or with safety concerns should undergo nonclinical toxicology assessment including systemic carcinogenicity and additional developmental and reproductive studies. OBJECTIVE To determine whether the active ingredients (avobenzone, oxybenzone, octocrylene, and ecamsule) of 4 commercially available sunscreens are absorbed into systemic circulation. DESIGN, SETTING, AND PARTICIPANTS Randomized clinical trial conducted at a phase 1 clinical pharmacology unit in the United States and enrolling 24 healthy volunteers. Enrollment started in July 2018 and ended in August 2018.INTERVENTIONS Participants were randomized to 1 of 4 sunscreens: spray 1 (n = 6 participants), spray 2 (n = 6), a lotion (n = 6), and a cream (n = 6). Two milligrams of sunscreen per 1 cm 2 was applied to 75% of body surface area 4 times per day for 4 days, and 30 blood samples were collected over 7 days from each participant. MAIN OUTCOMES AND MEASURESThe primary outcome was the maximum plasma concentration of avobenzone. Secondary outcomes were the maximum plasma concentrations of oxybenzone, octocrylene, and ecamsule. RESULTS Among 24 participants randomized (mean age, 35.5 [SD, 10.5] years; 12 [50%] women; 14 [58%] black or African American), 23 (96%) completed the trial. Systemic concentrations greater than 0.5 ng/mL were reached for all 4 products after 4 applications on day 1. The most common adverse event was rash (1 participant with each sunscreen).

Drug-induced long QT syndrome has resulted in many drugs being withdrawn from the market. At the same time, the current regulatory paradigm for screening new drugs causing long QT syndrome is preventing drugs from reaching the market, sometimes inappropriately. In this study, we report the results of a first-of-a-kind clinical trial studying late sodium (mexiletine and lidocaine) and calcium (diltiazem) current blocking drugs to counteract the effects of hERG potassium channel blocking drugs (dofetilide and moxifloxacin). We demonstrate that both mexiletine and lidocaine substantially reduce heart-rate corrected QT (QTc) prolongation from dofetilide by 20 ms. Furthermore, all QTc shortening occurs in the heart-rate corrected J-T peak (J-T peak c) interval, the biomarker we identified as a sign of late sodium current block. This clinical trial demonstrates that late sodium blocking drugs can substantially reduce QTc prolongation from Correspondence: DG Strauss David.Strauss@fda.hhs.gov. Additional Supporting Information may be found in the online version of this article.Author Contributions: All authors have contributed as follows: protocol development (L.J., J.V., J.W.M., C.S., K.W.L., J.F., N.S., D.G.S.), data collection (C.E., C.S., K.W.L., M.H., J.L., P.G., A.M., J.W., W.J.C.), data analysis (L.J., J.V., J.F., D.G.S.), and preparing the manuscript (L.J., D.G.S.). All authors discussed the results and implications and commented on the manuscript. Conflict of HHS Public Access Author Manuscript Author ManuscriptAuthor ManuscriptAuthor Manuscript hERG potassium channel block and assessment of J-T peak c may add value beyond only assessing QTc.Drug-induced QT prolongation increases the risk for torsade de pointes, a potentially fatal ventricular arrhythmia. 1 QT prolongation and increased risk for torsade de pointes have resulted in 14 drugs being removed from the market worldwide. 2 Furthermore, many drugs remain on the market with a known torsade de pointes risk, including numerous antibiotics, antimalarial, antiviral, psychiatric, oncology, and cardiac drugs. 3 At the same time, the current regulatory paradigm for assessing drug effects on cardiac repolarization is preventing potentially effective medicines from reaching the market, sometimes inappropriately. 2 To address this, the US Food and Drug Administration (FDA) and multiple public-private partnerships are studying novel approaches to assess the cardiac safety of new drugs with a Comprehensive in vitro Proarrhythmia Assay and in Phase 1 clinical trials. 4,5 Essential to the novel approaches is a focus on understanding mechanisms by studying the effects of drugs on multiple cardiac ion channels, which can be either proarrhythmic or antiarrhythmic depending on the combination. 6Almost all drugs on the market that can cause torsade de pointes block the hERG potassium channel 7 and prolong the QT interval of the electrocardiogram (ECG). 8 However, some drugs block the hERG potassium channel and prolong QT with a minimal torsade de pointes risk (e....

IMPORTANCE A prior pilot study demonstrated the systemic absorption of 4 sunscreen active ingredients; additional studies are needed to determine the systemic absorption of additional active ingredients and how quickly systemic exposure exceeds 0.5 ng/mL as recommended by the US Food and Drug Administration (FDA). OBJECTIVE To assess the systemic absorption and pharmacokinetics of the 6 active ingredients (avobenzone, oxybenzone, octocrylene, homosalate, octisalate, and octinoxate) in 4 sunscreen products under single-and maximal-use conditions. DESIGN, SETTING, AND PARTICIPANTS Randomized clinical trial at a clinical pharmacology unit (West Bend, Wisconsin) was conducted in 48 healthy participants. The study was conducted between January and February 2019. INTERVENTIONS Participants were randomized to 1 of 4 sunscreen products, formulated as lotion (n = 12), aerosol spray (n = 12), nonaerosol spray (n = 12), and pump spray (n = 12). Sunscreen product was applied at 2 mg/cm 2 to 75% of body surface area at 0 hours on day 1 and 4 times on day 2 through day 4 at 2-hour intervals, and 34 blood samples were collected over 21 days from each participant. MAIN OUTCOMES AND MEASURES The primary outcome was the maximum plasma concentration of avobenzone over days 1 through 21. Secondary outcomes were the maximum plasma concentrations of oxybenzone, octocrylene, homosalate, octisalate, and octinoxate over days 1 through 21. RESULTS Among 48 randomized participants (mean [SD] age, 38.7 [13.2] years; 24 women [50%]; 23 white [48%], 23 African American [48%], 1 Asian [2%], and 1 of unknown race/ethnicity [2%]), 44 (92%) completed the trial. Geometric mean maximum plasma concentrations of all 6 active ingredients were greater than 0.5 ng/mL, and this threshold was surpassed on day 1 after a single application for all active ingredients. The overall maximum plasma concentrations for each active ingredient for each product formulation are shown in the table. The most common adverse event was rash, which developed in 14 participants.

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The use of computational models in drug development has grown during the past decade. These model‐informed drug development (MIDD) approaches can inform a variety of drug development and regulatory decisions. When used for regulatory decision making, it is important to establish that the model is credible for its intended use. Currently, there is no consensus on how to establish and assess model credibility, including the selection of appropriate verification and validation activities. In this article, we apply a risk‐informed credibility assessment framework to physiologically‐based pharmacokinetic modeling and simulation and hypothesize this evidentiary framework may also be useful for evaluating other MIDD approaches. We seek to stimulate a scientific discussion around this framework as a potential starting point for uniform assessment of model credibility across MIDD. Ultimately, an overarching framework may help to standardize regulatory evaluation across therapeutic products (i.e., drugs and medical devices).

Balanced multi‐ion channel‐blocking drugs have low torsade risk because they block inward currents. The Comprehensive In Vitro Proarrhythmia Assay (Ci PA ) initiative proposes to use an in silico cardiomyocyte model to determine the presence of balanced block, and absence of heart rate corrected J‐T peak (J‐T peak c) prolongation would be expected for balanced blockers. This study included three balanced blockers in a 10‐subject‐per‐drug parallel design; lopinavir/ritonavir and verapamil met the primary end point of ΔΔJ‐T peak c upper bound < 10 ms, whereas ranolazine did not (upper bounds of 8.8, 6.1, and 12.0 ms, respectively). Chloroquine, a predominant blocker of the potassium channel encoded by the ether‐à‐go‐go related gene (hERG), prolonged ΔΔ QT c and ΔΔJ‐T peak c by ≥ 10 ms. In a separate crossover design, diltiazem (calcium block) did not shorten dofetilide‐induced Δ QT c prolongation, but shortened ΔJ‐T peak c and prolonged ΔT peak ‐T end . Absence of J‐T peak c prolongation seems consistent with balanced block; however, small sample size (10 subjects) may be insufficient to characterize concentration‐response in some cases.