Pharmacologic characterization of atogepant: A potent and selective calcitonin gene-related peptide receptor antagonist.

BACKGROUND: The trigeminal sensory neuropeptide calcitonin gene-related peptide (CGRP) is identified as an essential element in migraine pathogenesis. METHODS: In vitro and in vivo studies evaluated pharmacologic properties of the CGRP receptor antagonist atogepant. Radioligand binding using 125I-CGRP and cyclic adenosine monophosphate (cAMP) accumulation assays were conducted in human embryonic kidney 293 cells to assess affinity, functional potency and selectivity. Atogepant in vivo potency was assessed in the rat nitroglycerine model of facial allodynia and primate capsaicin-induced dermal vasodilation (CIDV) pharmacodynamic model. Cerebrospinal fluid/brain penetration and behavioral effects of chronic dosing and upon withdrawal were evaluated in rats. RESULTS: Atogepant exhibited high human CGRP receptor-binding affinity and potently inhibited human α-CGRP-stimulated cAMP responses. Atogepant exhibited significant affinity for the amylin1 receptor but lacked appreciable affinities for adrenomedullin, calcitonin and other known neurotransmitter receptor targets. Atogepant dose-dependently inhibited facial allodynia in the rat nitroglycerine model and produced significant CIDV inhibition in primates. Brain penetration and behavioral/physical signs during chronic dosing and abrupt withdrawal were minimal in rats. CONCLUSIONS: Atogepant is a competitive antagonist with high affinity, potency and selectivity for the human CGRP receptor. Atogepant demonstrated a potent, concentration-dependent exposure/efficacy relationship between atogepant plasma concentrations and inhibition of CGRP-dependent effects.

Clinician perspectives regarding CYP2C19 genotype testing in patients with critical limb ischemia: A Delphi approach.

OBJECTIVES: Antiplatelet therapy is an essential element in the management of patients with arterial vascular disease. In peripheral arterial disease (PAD), dual antiplatelet therapy (DAPT), primarily clopidogrel and aspirin, is routinely prescribed following intervention. There is sparse data regarding the need for DAPT, the appropriate duration, or the heterogeneity of treatment effects for antiplatelet regimens across patients, leading to potential uncertainty and heterogeneity around treatment practices. An example of heterogeneity of treatment effects is a patients' metabolizer status for the use of clopidogrel. The aim of the study was to (1) assess clinicians' knowledge of and attitudes toward managing patients with CYP2C19 mutations, (2) identify barriers to implementation of CYP2C19 testing and management policies, and (3) reach consensus for CYP2C19 testing and management strategies for patients with PAD who undergo peripheral vascular interventions (PVI). METHODS: A modified Delphi method was used to establish consensus amongst PAD interventionalists around CYP2C19 testing. All practicing Yale New Haven Hospital PAD interventionalists with backgrounds in interventional cardiology, vascular surgery, or interventional radiology were approached by email for participation. Round 1 included the collection of baseline demographic questions, knowledge questions, and three statements for consensus. Knowledge questions were rated on a 0-10 Likert scale with the following anchors: 0 ("Not at all"), 5 ("Neutral), and 10 ("Very Much"). Participants were asked to rate the importance of the three consensus statements on a 9-point Likert scale from 1 ("Strongly Disagree") to 10 ("Strongly Agree"). In Round 2, participants were shown the same consensus statements, the median response of the group from the previous round, and their previous answers. Participants were instructed to revise their rating using the results from the previous round. This process was repeated for Round 3. RESULTS: Of the 28 experts invited to participate, 13 agreed (46%). Participants were predominantly male (92.3%) and white (61.5%) with representation from interventional cardiology (46.2%) and vascular surgery (53.8%). Most participants reported more than 10+ years in practice (61.5%). PAD interventionalists felt they would benefit from more education regarding CYP2C19 mutations (median score 8.0, interquartile range 5.0-8.5). They indicated some familiarity with CYP2C19 mutations (7.0, 6.0-9.5) but did not feel strongly that CYP2C19 was important to their practice (6.0, 5.5-7.5). In each round, the median responses for the three consensus statements were 5, 6, and 9, respectively. With each successive round the interquartile range narrowed indicative of evolving consensus but did not reach the prespecified interquartile range for consensus of 1 for any of the statements. CONCLUSIONS: PAD interventionalists practicing at an academic health system recognize the heterogenous response of their patients to clopidogrel therapy but are unsure when to leverage genetic testing to improve outcomes for their patients. Our study identified gaps regarding PAD interventionalists' knowledge, perceived barriers, and attitudes toward CYP2C19 testing in PAD. This information highlights the need for randomized data on genetic testing for clopidogrel responsiveness in peripheral vascular disease following intervention to help guide antiplatelet management.

Safety and efficacy outcomes of the Pioneer Plus catheter in endovascular revascularization of lower extremity chronic total occlusions.

OBJECTIVE: Our aim was to evaluate the efficacy and safety outcomes of the Pioneer Plus catheter (Philips, San Diego, Calif) and report the in-hospital and 30-day outcomes of lower extremity chronic total occlusion (CTO) interventions assisted by the Pioneer Plus catheter. In addition, we explored the factors associated with procedural success. METHODS: We conducted a retrospective review of 135 consecutive procedures in 116 patients from July 2011 to September 2018 performed by eight operators with various levels of experience at a high-volume center where the Pioneer Plus catheter was used for lower extremity CTO. The patient demographics, preprocedural symptoms, preprocedural testing results, procedural setting, and angiography findings were abstracted. The outcomes were divided into device-related and procedure-related outcomes. Device-related efficacy outcome included procedural success. Device-related safety outcomes included device-related complications. Procedure-related outcomes included procedure-related complications, 30-day major adverse cardiovascular events, and 30-day major adverse limb events. We conducted univariate comparisons of the provider, patient, and procedural characteristics stratified by procedural success. RESULTS: Procedural success was observed in 118 procedures overall (87.4%), and success rates ≤95.8% were observed for operators with an experience level of >25 devices deployed. No device-related complications, such as pseudoaneurysm formation, vessel perforation, or arteriovenous fistula formation, were observed. The Pioneer Plus catheter was mostly often used for CTO in the superficial femoral and popliteal arteries. Overall, the procedure-related complications included access site hematoma (5.2%), major bleeding (0.7%), pseudoaneurysm formation (0.7%), distal embolization (1.5%), and acute arterial thrombosis (1.5%). The 30-day major adverse limb events included index limb unplanned amputation (0.7%), index limb reintervention (4.4%), and index limb acute limb ischemia (0.7%) and occurred in 5.9% of the procedures. The only factor associated with procedural success was operator experience (P < .0001). CONCLUSIONS: The results from the present study have shown that Pioneer Plus catheter use is safe and effective when used to cross lower extremity CTO. However, further investigation is needed to identify patient- and provider-level factors to optimize patient outcomes.

Systematic review and meta-analysis of outcomes of lower extremity peripheral arterial interventions in patients with and without chronic kidney disease or end-stage renal disease.

OBJECTIVE: Patients with chronic kidney disease (CKD) have a greater risk of peripheral arterial disease (PAD). Although individual studies have documented an association between CKD and/or end-stage renal disease (ESRD) and adverse outcomes in patients undergoing PAD interventions in an era of technological advances in peripheral revascularization, the magnitude of the effect size is unknown. Therefore, we performed a meta-analysis to compare the outcomes of PAD interventions for patients with CKD/ESRD with those patients with normal renal function, stratified by intervention type (endovascular vs surgical), reflecting contemporary practice. METHODS: Five databases were analyzed from January 2000 to June 2019 for studies that had compared the outcomes of lower extremity PAD interventions for patients with CKD/ESRD vs normal renal function. We included both endovascular and open interventions, with an indication of either claudication or critical limb ischemia. We analyzed the pooled odds ratios (ORs) across studies with 95% confidence intervals (CIs) using a random effects model. Funnel plot and exclusion sensitivity analyses were used for bias assessment. RESULTS: Seventeen observational studies with 13,140 patients were included. All included studies, except for two, had accounted for unmeasured confounding using either multivariable regression analysis or case-control matching. The maximum follow-up period was 114 months (range, 0.5-114 months). The incidence of target lesion revascularization (TLR) was greater in those with CKD/ESRD than in those with normal renal function (OR, 1.68; 95% CI, 1.25-2.27; P = .001). The incidence of major amputations (OR, 1.97; 95% CI, 1.37-2.83; P < .001) and long-term mortality (OR, 2.28; 95% CI, 1.45-3.58; P < .001) was greater in those with CKD/ESRD. The greater TLR rates with CKD/ESRD vs normal renal function were only seen with endovascular interventions, with no differences for surgical interventions. The differences in rates of major amputations and long-term mortality between the CKD/ESRD and normal renal function groups were statistically significant, regardless of the intervention type. CONCLUSIONS: Patients with CKD/ESRD who have undergone lower extremity PAD interventions had worse outcomes than those of patients with normal renal function. When stratifying our results by intervention (endovascular vs open surgery), greater rates of TLR for CKD/ESRD were only seen with endovascular and not with open surgical approaches. Major amputations and all-cause mortality were greater in the CKD/ESRD group, irrespective of the indication. Evidence-based strategies to manage this at-risk population who require PAD interventions are essential.

Characterization of Ubrogepant: A Potent and Selective Antagonist of the Human Calcitonin Gene‒Related Peptide Receptor.

A growing body of evidence has implicated the calcitonin gene-related peptide (CGRP) receptors in migraine pathophysiology. With the recent approval of monoclonal antibodies targeting CGRP or the CGRP receptor, the inhibition of CGRP-mediated signaling has emerged as a promising approach for preventive treatments of migraine in adults. However, there are no small-molecule anti-CGRP treatments available for treating migraine. The current studies aimed to characterize the pharmacologic properties of ubrogepant, an orally bioavailable, CGRP receptor antagonist for the acute treatment of migraine. In a series of ligand binding assays, ubrogepant exhibited a high binding affinity for native (K i=0.067 nM) and cloned human (K i=0.070 nM) and rhesus CGRP receptors (K i=0.079 nM), with relatively lower affinities for CGRP receptors from rat, mouse, rabbit and dog. In functional assays, ubrogepant potently blocked human α-CGRP stimulated cAMP response (IC50 of 0.08 nM) and exhibited highly selective antagonist activity for the CGRP receptor compared with other members of the human calcitonin receptor family. Furthermore, the in vivo CGRP receptor antagonist activity of ubrogepant was evaluated in a pharmacodynamic model of capsaicin-induced dermal vasodilation (CIDV) in rhesus monkeys and humans. Results demonstrated that ubrogepant produced concentration-dependent inhibition of CIDV with a mean EC50 of 3.2 and 2.6 nM in rhesus monkeys and humans, respectively. Brain penetration studies with ubrogepant in monkeys showed a CSF/plasma ratio of 0.03 and low CGRP receptor occupancy. In summary, ubrogepant is a competitive antagonist with high affinity, potency, and selectivity for the human CGRP receptor. SIGNIFICANCE STATEMENT: Ubrogepant is a potent, selective, orally delivered, small-molecule competitive antagonist of the human calcitonin generelated peptide receptor. In vivo studies using a pharmacodynamic model of capsaicin-induced dermal vasodilation (CIDV) in rhesus monkeys and humans demonstrated that ubrogepant produced concentration-dependent inhibition of CIDV, indicating a predictable pharmacokinetic-pharmacodynamic relationship.

Combining an in silico proarrhythmic risk assay with a tPKPD model to predict QTc interval prolongation in the anesthetized guinea pig assay.

Human-based in silico models are emerging as important tools to study the effects of integrating inward and outward ion channel currents to predict clinical proarrhythmic risk. The aims of this study were 2-fold: 1) Evaluate the capacity of an in silico model to predict QTc interval prolongation in the in vivo anesthetized cardiovascular guinea pig (CVGP) assay for new chemical entities (NCEs) and; 2) Determine if a translational pharmacokinetic/pharmacodynamic (tPKPD) model can improve the predictive capacity. In silico simulations for NCEs were performed using a population of human ventricular action potential (AP) models. PatchXpress® (PX) or high throughput screening (HTS) ion channel data from respectively n = 73 and n = 51 NCEs were used as inputs for the in silico population. These NCEs were also tested in the CVGP (n = 73). An M5 pruned decision tree-based regression tPKPD model was used to evaluate the concentration at which an NCE is liable to prolong the QTc interval in the CVGP. In silico results successfully predicted the QTc interval prolongation outcome observed in the CVGP with an accuracy/specificity of 85%/73% and 75%/77%, when using PX and HTS ion channel data, respectively. Considering the tPKPD predicted concentration resulting in QTc prolongation (EC5%) increased accuracy/specificity to 97%/95% using PX and 88%/97% when using HTS. Our results support that human-based in silico simulations in combination with tPKPD modeling can provide correlative results with a commonly used early in vivo safety assay, suggesting a path toward more rapid NCE assessment with reduced resources, cycle time, and animal use.

Drug-coated balloon versus plain old balloon angioplasty in femoropopliteal disease: An updated meta-analysis of randomized controlled trials.

BACKGROUND: Drug-coated balloon (DCB) angioplasty has emerged as a mainstay of therapy for the treatment of peripheral arterial disease (PAD) involving the superficial femoral and popliteal arteries. We performed a meta-analysis including all available randomized controlled trials (RCTs) to date which compare DCB to plain balloon angioplasty (POBA) in femoropopliteal disease (FPD). METHODS: Five databases were analyzed including EMBASE, PubMed, Cochrane, Scopus, and Web-of-Science from January 2000 to September 2018 for RCTs comparing DCB to POBA in patients with FPD. Heterogeneity was determined using Cochrane's Q-statistics. Random effects model was used. RESULTS: Twenty-two RCTs, including five trials of in-stent restenosis (ISR) intervention, with 3,217 patients were included in the analysis. Mean follow-up was approximately 21.6 ± 14.4 months. Overall, DCB use was associated with a 51% reduction in target vessel revascularization (TLR) when compared to POBA at follow-up (relative risk [RR]: 0.49, 95% confidence interval [CI]: 0.40-0.61, P < 0.0001). Rates of TLR were 45% lower in the DCB group when compared to POBA in patients with ISR (RR: 0.55, 95% CI: 0.37-0.81, P = 0.002). DCB was associated with lower rates of binary stenosis, late lumen loss and higher primary safety endpoints. Major amputation and mortality were not different between DCB and POBA. CONCLUSIONS: Use of DCBs is associated with improved vessel patency and a lower risk of TLR when compared to POBA in patients with FPD, especially in the setting of ISR. There was no difference in mortality between DCB and POBA in our meta-analysis. Extended follow-up of the available RCT data will be essential to analyze long-term device-related mortality.

Reducing emergency department visits utilizing a primary care asthma specialty clinic in a high-risk patient population.

OBJECTIVE: Asthma is a leading cause of pediatric emergency department (ED) use. Optimizing asthma outcomes is a goal of Nationwide Children's Hospital (NCH) and its affiliated Accountable Care Organization. NCH's Primary Care Network, comprised of 12 offices serving a predominantly Medicaid population, sought to determine whether an Asthma Specialty Clinic (ASC) operated within a single primary care office could reduce ED asthma rates and improve quality measures, relative to all other network offices. METHODS: An ASC was piloted with four components: patient monitoring, provider continuity, standardized assessment, and multi-disciplinary education. A registry was established to contact patients at recommended intervals. At extended-length visits, a general pediatrician evaluated patients and a multi-disciplinary team provided education. Novel educational tools were utilized, guideline-based templates recorded and spirometry obtained. ED asthma rate, spirometry utilization, and controller fills by intervention office patients were compared to all other network offices before and after ASC initiation. RESULTS: At baseline, asthma ED visits by intervention and usual care populations were similar (p = 0.43). After, rates were significantly lower for intervention office patients versus usual care office patients (p < 0.001), declining in the intervention population by 26.2%, 25.2%, and 31.8% in 2013, 2014, and 2015, respectively, from 2012 baseline, versus increases of 3.8%, 16.2%, and 9.5% in the usual care population. Spirometry completion, controller fills, and patients with favorable Asthma Medication Ratios significantly increased for intervention office patient relative to the usual care population. CONCLUSIONS: A primary care-based asthma clinic was associated with a significant and sustainable reduction in ED utilization versus usual care. What's new: This study describes a comprehensive, multi-disciplinary, and innovative model for an asthma management program within the medical home that demonstrated a significant reduction in ED visits, an increase in spirometry utilization, and an increase in controller fills in a high-risk asthma population versus comparison group.

Assessment of the clinical cardiac drug-drug interaction associated with the combination of hepatitis C virus nucleotide inhibitors and amiodarone in guinea pigs and rhesus monkeys.

In 2015, European and U.S. health agencies issued warning letters in response to 9 reported clinical cases of severe bradycardia/bradyarrhythmia in hepatitis C virus (HCV)-infected patients treated with sofosbuvir (SOF) in combination with other direct acting antivirals (DAAs) and the antiarrhythmic drug, amiodarone (AMIO). We utilized preclinical in vivo models to better understand this cardiac effect, the potential pharmacological mechanism(s), and to identify a clinically translatable model to assess the drug-drug interaction (DDI) cardiac risk of current and future HCV inhibitors. An anesthetized guinea pig model was used to elicit a SOF+AMIO-dependent bradycardia. Detailed cardiac electrophysiological studies in this species revealed SOF+AMIO-dependent selective nodal dysfunction, with initial, larger effects on the sinoatrial node. Further studies in conscious, rhesus monkeys revealed an emergent bradycardia and bradyarrhythmia in 3 of 4 monkeys administered SOF+AMIO, effects not observed with either agent alone. Morever, bradycardia and bradyarrhythmia were not observed in rhesus monkeys when intravenous infusion of MK-3682 was completed after AMIO pretreatment. CONCLUSIONS: These are the first preclinical in vivo experiments reported to replicate the severe clinical SOF+AMIO cardiac DDI and provide potential in vivo mechanism of action. As such, these data provide a preclinical risk assessment paradigm, including a clinically relevant nonhuman primate model, with which to better understand cardiovascular DDI risk for this therapeutic class. Furthermore, these studies suggest that not all HCV DAAs and, in particular, not all HCV nonstructural protein 5B inhibitors may exhibit this cardiac DDI with amiodarone. Given the selective in vivo cardiac electrophysiological effect, these data enable targeted cellular/molecular mechanistic studies to more precisely identify cell types, receptors, and/or ion channels responsible for the clinical DDI. (Hepatology 2016;64:1430-1441).

Discovery of MK-1832, a Kv1.5 inhibitor with improved selectivity and pharmacokinetics.

Selective inhibition of Kv1.5, which underlies the ultra-rapid delayed rectifier current, IKur, has been pursued as a treatment for atrial fibrillation. Here we describe the discovery of MK-1832, a Kv1.5 inhibitor with improved selectivity versus the off-target current IKs, whose inhibition has been associated with ventricular proarrhythmia. MK-1832 exhibits improved selectivity for IKur over IKs (>3000-fold versus 70-fold for MK-0448), consistent with an observed larger window between atrial and ventricular effects in vivo (>1800-fold versus 210-fold for MK-0448). MK-1832 also exhibits an improved preclinical pharmacokinetic profile consistent with projected once daily dosing in humans.

Astrocyte overexpression of heme oxygenase-1 improves outcome after intracerebral hemorrhage.

BACKGROUND AND PURPOSE: Heme oxygenase-1 (HO-1) catalyzes the rate-limiting reaction of heme breakdown and may have both antioxidant and pro-oxidant effects. In previous studies, HO-1 overexpression protected astrocytes from heme-mediated injury in vitro. In the present study, we tested the hypothesis that selective astrocyte overexpression of HO-1 improves outcome after intracerebral hemorrhage. METHODS: Male and female transgenic mice overexpressing human HO-1 driven by the GFAP promoter (GFAP.HMOX1) and wild-type controls received striatal injections of autologous blood (25 µL). Blood-brain barrier disruption was assessed by Evans blue assay and striatal cell viability by methylthiazolyldiphenyl-tetrazolium bromide assay. Neurological deficits were quantified by digital analysis of spontaneous cage activity, adhesive removal, and elevated body swing tests. RESULTS: Mortality rate for wild-type mice was 34.8% and was similar for males and females; all GFAP.HMOX1 mice survived. Striatal Evans blue leakage at 24 hours was 23.4±3.2 ng in surviving wild-type mice, compared with 10.9±1.8 ng in transgenics. Perihematomal cell viability was reduced to 61±4% of contralateral at 3 days in wild-type mice, versus 80±4% in transgenics. Focal neurological deficits were significantly reduced and spontaneous cage activity was increased in GFAP.HMOX1 mice. CONCLUSIONS: Selective HO-1 overexpression in astrocytes reduces mortality, blood-brain barrier disruption, perihematomal cell injury, and neurological deficits in an autologous blood injection intracerebral hemorrhage model. Genetic or pharmacological therapies that acutely increase astrocyte HO-1 may be beneficial after intracerebral hemorrhage.

The first recorded outbreak of cryptosporidiosis due to Cryptosporidium cuniculus (formerly rabbit genotype), following a water quality incident.

We report the first identified outbreak of cryptosporidiosis with Cryptosporidium cuniculus following a water quality incident in Northamptonshire, UK. A standardised, enhanced Cryptosporidium exposure questionnaire was administered to all cases of cryptosporidiosis after the incident. Stool samples, water testing, microscopy slides and rabbit gut contents positive for Cryptosporidium were typed at the Cryptosporidium Reference Unit, Singleton Hospital, Swansea. Twenty-three people were microbiologically linked to the incident although other evidence suggests an excess of 422 cases of cryptosporidiosis above baseline. Most were adult females; unusually for cryptosporidiosis there were no affected children identified under the age of 5 years. Water consumption was possibly higher than in national drinking water consumption patterns. Diarrhoea duration was negatively correlated to distance from the water treatment works where the contamination occurred. Oocyst counts were highest in water storage facilities. This outbreak is the first caused by C. cuniculus infection to have been noted and it has conclusively demonstrated that this species can be a human pathogen. Although symptomatically similar to cryptosporidiosis from C. parvum or C. hominis, this outbreak has revealed some differences, in particular no children under 5 were identified and females were over-represented. These dissimilarities are unexplained although we postulate possible explanations.

Characterization of ascending dose canine telemetry model supports its use in E14/S7B QT integrated risk assessments.

INTRODUCTION: Nonclinical evaluation of the cardiovascular effects of novel chemical or biological entities (NCE, NBEs) is crucial for supporting first-in-human clinical trials. One important aspect of these evaluations is the assessment of potential QT/QTc prolongation risk, as drug-induced QT prolongation can have catastrophic effects. The recent publication of E14/S7B Q&As allows for the situational incorporation of nonclinical QTc data as part of an integrated risk assessment for a Thorough QT (TQT) waiver application provided certain best practice criteria are met. Recent publications provided detailed characterization of nonclinical QTc telemetry data collected from the commonly used Latin square study design. METHODS: To understand whether data from alternate telemetry study designs were sufficient to serve as part of the E14/S7B integrated risk assessment, we report the performance and translational sensitivity to identify clinical risk of QTc prolongation risk for an ascending dose telemetry design. RESULTS: The data demonstrated low variability in QTci interval within animals from day to day, indicating a well-controlled study environment and limited concern for uncontrolled effects across dosing days. Historical study variances of the ascending dose design with n = 4 subjects, measured by least significant difference (LSD) and root mean square error (RMSE) values, were low enough to detect a + 10 ms QTci interval change, and the median minimum detectable difference (MDD) for QTci interval changes was <10 ms. Furthermore, concentration-QTci (C-QTci) assessments to determine +10 ms QTci increases for known hERG inhibitors were comparable to clinical CC values listed in the E14/S7B training materials, supporting the use of the ascending dose design in an E14/S7B integrated risk assessment. DISCUSSION: These findings suggest that the ascending dose design can be a valuable tool in nonclinical evaluation of QT/QTc prolongation risk and the support of TQT waiver applications.

Structure Guided Discovery of Novel Pan Metallo-ß-Lactamase Inhibitors with Improved Gram-Negative Bacterial Cell Penetration.

The use of ß-lactam (BL) and ß-lactamase inhibitor combination to overcome BL antibiotic resistance has been validated through clinically approved drug products. However, unmet medical needs still exist for the treatment of infections caused by Gram-negative (GN) bacteria expressing metallo-ß-lactamases. Previously, we reported our effort to discover pan inhibitors of three main families in this class: IMP, VIM, and NDM. Herein, we describe our work to improve the GN coverage spectrum in combination with imipenem and relebactam. This was achieved through structure- and property-based optimization to tackle the GN cell penetration and efflux challenges. A significant discovery was made that inhibition of both VIM alleles, VIM-1 and VIM-2, is essential for broad GN coverage, especially against VIM-producing P. aeruginosa. In addition, pharmacokinetics and nonclinical safety profiles were investigated for select compounds. Key findings from this drug discovery campaign laid the foundation for further lead optimization toward identification of preclinical candidates.

Comparison of the intrinsic vasorelaxant and inotropic effects of the antiarrhythmic agents vernakalant and flecainide in human isolated vascular and cardiac tissues.

This study explored the intrinsic vasorelaxant and inotropic effects of the mixed potassium and sodium channel blocker atrial antiarrhythmic vernakalant and the class IC antiarrhythmic agent flecainide in human isolated subcutaneous resistance artery and in ventricular trabecular muscle preparations. At test concentrations encompassing free plasma concentrations associated with clinical efficacy for conversion of atrial fibrillation, vernakalant (1-10 µM) displayed no significant direct effects on human resistance artery tone or ventricular contractility. In contrast, tested at equimolar concentrations, flecainide significantly reduced peak isometric contractile force (10 µM) and maximal rates of force development and decline (3 and 10 µM) in the human ventricular muscle preparation while displaying no significant effect on human resistance artery tone. The lack of effects of vernakalant on human resistance artery tone and ventricular muscle contractile function suggests that direct vasorelaxant and inotropic effects do not underlie the rare hypotensive events observed clinically with vernakalant, raising the possibility that secondary (eg, reflex) effects may mediate these events. The demonstration of negative inotropic effects with flecainide in the human ventricular muscle preparations in the absence of an effect on resistance artery tone suggests that the hemodynamic effects of flecainide observed clinically result primarily from direct negative inotropic effects.

A generalized canine transfer function accurately reconstructs central aortic pressure waveforms to enable enhanced pulse wave analysis.

Routine preclinical blood pressure evaluation is an important risk assessment tool. Although proximal aortic pressure is most relevant for key target organs, abdominal aortic pressures are more commonly recorded. Pulse pressure amplification and waveform distortion in abdominal waveforms make it inappropriate for central hemodynamic analytical methods without the use of a mathematical transfer function. Clinical transfer functions have been developed to estimate ascending aortic waveforms from brachial or radial artery waveforms in humans, but no preclinical analogues exist. The aim of this study was to develop a canine-specific transfer function to reconstruct thoracic aortic pressure waveforms from abdominal aortic data to enable the application of central hemodynamic analytical methods. Simultaneous abdominal and thoracic blood pressures were recorded from seven conscious, male beagle dogs administered 3 well-characterized pharmacologic standards and animals were appointed to a training (n = 3) or validation (n = 4) group at baseline and during dosing. A generalized transfer function was developed from the training group data and evaluated for its ability to synthesize thoracic pressure waves in the training and validation groups. Select hemodynamic parameters were evaluated in measured and synthesized thoracic data. There was a high degree of correlation between measured and synthesized thoracic parameters (r2 = 0.74-0.99). There was no difference between indices computed from synthesized or actual thoracic waveforms at baseline or after administration of pharmacologic standards. This work demonstrates that a generalized preclinical transfer function can reproduce thoracic pressure waves across a range of hemodynamic responses thus enabling the application of central hemodynamic analytical methods.

Development and characterization of canine-specific computational models to predict pulsatile arterial hemodynamics and ventricular-arterial coupling.

Pulsatile hemodynamics analyses provide important information about the ventricular-arterial system which cannot be inferred by standard blood pressure measurements. Pulse wave analysis (PWA), wave separation analysis (WSA), and wave power analysis (WPA) characterize arterial hemodynamics with limited preclinical applications. Integrating these tools into preclinical testing may enhance understanding of disease or therapeutic effects on cardiovascular function. We used a canine rapid ventricular pacing (RVP) heart failure model to: (1) Characterize hemodynamics in response to RVP and (2) assess analyses from flow waveforms synthesized from pressure compared to those derived from measured flow. Female canines (n = 7) were instrumented with thoracic aortic pressure transducers, ventricular pacing leads, and an ascending aortic flow probe. Data were collected at baseline, 1 week, and 1 month after RVP onset. RVP progressively reduced stroke volume (SV), the PWA SV estimator, and WSA and WPA pulsatility and wave reflection indices. Indices derived from synthesized flow exhibited similar directional changes and high concordance with measured flow calculations. Our data demonstrate the value of analytical hemodynamic methods to gain deeper insight into cardiovascular function in preclinical models. These approaches can provide complementary value to standard endpoints in evaluating potential effects of pharmaceutical agents intended for human use.

Trends and impact of intravascular ultrasound and optical coherence tomography on percutaneous coronary intervention for myocardial infarction.

Background: Intravascular imaging with either intravascular ultrasound (IVUS) or optical coherence tomography (OCT) during percutaneous coronary intervention (PCI) is associated with improved outcomes, but these techniques have previously been underutilized in the real world. We aimed to examine the change in utilization of intravascular imaging-guided PCI over the past decade in the United States and assess the association between intravascular imaging and clinical outcomes following PCI for myocardial infarction (MI). Methods: We surveyed the National Inpatient Sample from 2008 to 2019 to calculate the number of PCIs for MI guided by IVUS or OCT. Temporal trends were analyzed using Cochran-Armitage trend test or simple linear regression for categorical or continuous outcomes, respectively. Multivariable logistic regression was used to compare outcomes following PCI with and without intravascular imaging. Results: A total of 2,881,746 PCIs were performed for MI. The number of IVUS-guided PCIs increased by 309.9 % from 6,180 in 2008 to 25,330 in 2019 (P-trend < 0.001). The percentage of IVUS use in PCIs increased from 3.4 % in 2008 to 8.7 % in 2019 (P-trend < 0.001). The number of OCT-guided PCIs increased 548.4 % from 246 in 2011 to 1,595 in 2019 (P-trend < 0.001). The percentage of OCT guidance in all PCIs increased from 0.0 % in 2008 to 0.6 % in 2019 (P-trend < 0.001). Intravascular imaging-guided PCI was associated with lower odds of in-hospital mortality (adjusted odds ratio 0.66, 95 % confidence interval 0.60-0.72, p < 0.001). Conclusions: Although the number of intravascular imaging-guided PCIs have been increasing, adoption of intravascular imaging remains poor despite an association with lower mortality.

Selective activation of the M1 muscarinic acetylcholine receptor achieved by allosteric potentiation.

The forebrain cholinergic system promotes higher brain function in part by signaling through the M(1) muscarinic acetylcholine receptor (mAChR). During Alzheimer's disease (AD), these cholinergic neurons degenerate, therefore selectively activating M(1) receptors could improve cognitive function in these patients while avoiding unwanted peripheral responses associated with non-selective muscarinic agonists. We describe here benzyl quinolone carboxylic acid (BQCA), a highly selective allosteric potentiator of the M(1) mAChR. BQCA reduces the concentration of ACh required to activate M(1) up to 129-fold with an inflection point value of 845 nM. No potentiation, agonism, or antagonism activity on other mAChRs is observed up to 100 microM. Furthermore studies in M(1)(-/-) mice demonstrates that BQCA requires M(1) to promote inositol phosphate turnover in primary neurons and to increase c-fos and arc RNA expression and ERK phosphorylation in the brain. Radioligand-binding assays, molecular modeling, and site-directed mutagenesis experiments indicate that BQCA acts at an allosteric site involving residues Y179 and W400. BQCA reverses scopolamine-induced memory deficits in contextual fear conditioning, increases blood flow to the cerebral cortex, and increases wakefulness while reducing delta sleep. In contrast to M(1) allosteric agonists, which do not improve memory in scopolamine-challenged mice in contextual fear conditioning, BQCA induces beta-arrestin recruitment to M(1), suggesting a role for this signal transduction mechanism in the cholinergic modulation of memory. In summary, BQCA exploits an allosteric potentiation mechanism to provide selectivity for the M(1) receptor and represents a promising therapeutic strategy for cognitive disorders.