ABSTRACT
Relaxin is a 6-kDa peptide in the insulin superfamily of hormones. In addition to its effects on reproductive and musculoskeletal ligaments, relaxin has demonstrated beneficial effects on cardiac, renal, and vascular systems in preclinical models. The mouse intrapubic ligament ex vivo bioassay is the current standard for measuring in vivo relaxin bioactivity. However, this bioassay necessitates euthanasia and dissection of large cohorts to measure the intrapubic ligament at specified time points. We hypothesized that µCT imaging could be used to reduce the number of animals necessary for the intrapubic ligament bioassay by enabling a single animal to be followed longitudinally throughout the study rather than euthanizing different cohorts at established time points. Female CD1 mice were used to compare µCT imaging with the current standard. Both protocols revealed significant differences in intrapubic ligament length, with the µCT data having greater power when corrected for baseline imaging. From these data, we concluded that using µCT to measure the intrapubic ligament in mice primed with estrogen and dosed with relaxin is a viable refinement and will allow the use of fewer animals in longitudinal studies and provide more robust data, because animals can serve as their own controls.
Subject(s)
Biological Assay/methods , Ligaments/drug effects , Ligaments/diagnostic imaging , Relaxin/administration & dosage , X-Ray Microtomography , Administration, Intravenous , Animals , Estradiol/administration & dosage , Female , Infusion Pumps, Implantable , Infusions, Subcutaneous , Injections, Subcutaneous , Mice , Predictive Value of Tests , Time FactorsABSTRACT
INTRODUCTION: Despite the widespread use of the mouse transverse aortic constriction heart failure model, there are no reports on the characterization of the standard-of-care agent carvedilol in this model. METHODS: Left ventricular pressure overload was produced in mice by transverse aortic constriction between the innominate and left common carotid arteries. Carvedilol was administered at multiple dose levels (3, 10 and 30 mg/kg/day per os; yielding end-study mean plasma concentrations of 0.002, 0.015 and 0.044 µM, respectively) in a therapeutic design protocol with treatment initiated after the manifestation of left ventricular remodeling at 3 weeks post transverse aortic constriction and continued for 10 weeks. RESULTS: Carvedilol treatment in transverse aortic constriction mice significantly decreased heart rate and left ventricular dP/dt (max) at all dose levels consistent with ß-adrenoceptor blockade. The middle dose of carvedilol significantly decreased left ventricular weight, whereas the higher dose decreased total heart, left and right ventricular weight and wet lung weight compared to untreated transverse aortic constriction mice. The higher dose of carvedilol significantly increased cardiac performance as measured by ejection fraction and fractional shortening and decreased left ventricular end systolic volume consistent with the beneficial effect on cardiac function. End-study plasma sST-2 and Gal-3 levels did not differ among sham, transverse aortic constriction control and transverse aortic constriction carvedilol groups. Plasma brain natriuretic peptide concentrations were elevated significantly in transverse aortic constriction control animals (~150%) compared to shams in association with changes in ejection fraction and heart weight and tended to decrease (~30%, p = 0.10-0.12) with the mid- and high-dose carvedilol treatment. CONCLUSION: A comparison of carvedilol hemodynamic and structural effects in the mouse transverse aortic constriction model versus clinical use indicates a strong agreement in effect profiles preclinical versus clinical, providing important translational validation for this widely used animal model. The present plasma brain natriuretic peptide biomarker findings support the measurement of plasma natriuretic peptides in the mouse transverse aortic constriction model to extend the translational utility of the model.
ABSTRACT
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.
Subject(s)
Kv1.5 Potassium Channel/antagonists & inhibitors , Pyridines/pharmacology , Drug Discovery , Humans , Pyridines/pharmacokinetics , Structure-Activity RelationshipABSTRACT
INTRODUCTION: Mouse transverse aortic constriction (TAC) is a widely-used model of pressure overload-induced heart failure. An intrinsic limitation of the model is variability in the response to pressure overload even when employing a standard severity of stenosis. Few literature studies have explicitly reported the use of entry criteria or early predictors to mitigate variability and enrich outcomes in this model. METHODS: Eleven-week-old male C57BL/6J mice underwent TAC or sham surgery. Left ventricular (LV) function and dimensions were assessed by M-mode echocardiography at baseline (pre) and 3, 9 and 12weeks post-procedure (end-study). At 24h post-procedure, transverse aortic flow velocities were obtained for estimating trans-TAC pressure gradients. Invasive LV hemodynamic assessments were performed and terminal heart and lung weights obtained at end-study. RESULTS: TAC mice displayed early development of LV hypertrophy and wall thickening followed by the later development of LV chamber dilation, and progressive development of LV systolic and diastolic dysfunction. The use of a pre-defined trans-TAC pressure gradient criterion of 45-60mmHg did not affect end-study organ weight, echocardiographic and invasive hemodynamic outcomes. A post-hoc receiver operator characteristic (ROC) analysis identified early 3week echocardiographic measures of LVmass(echo) and ejection fraction, with threshold changes of ~+30% and -10% normalized to baseline respectively, as good predictors for multiple end-study organ weight, echocardiographic and invasive hemodynamic outcomes. DISCUSSION: This ROC analysis has identified early predictive threshold changes which may serve, alone or in combination, as entry criteria to enrich outcome in this model.
Subject(s)
Disease Models, Animal , Echocardiography/methods , Heart Failure/diagnostic imaging , Heart Failure/physiopathology , Animals , Constriction , Heart Failure/etiology , Hypertrophy, Left Ventricular/diagnostic imaging , Hypertrophy, Left Ventricular/etiology , Hypertrophy, Left Ventricular/physiopathology , Male , Mice , Mice, Inbred C57BL , Predictive Value of Tests , Random Allocation , Ventricular Function, Left/physiologyABSTRACT
The preclinical pharmacodynamic and pharmacokinetic properties of 4-methylbenzyl (3S, 4R)-3-fluoro-4-[(Pyrimidin-2-ylamino) methyl] piperidine-1-carboxylate (CERC-301), an orally bioavailable selective N-methyl-D-aspartate (NMDA) receptor subunit 2B (GluN2B) antagonist, were characterized to develop a translational approach based on receptor occupancy (RO) to guide CERC-301 dose selection in clinical trials of major depressive disorder. CERC-301 demonstrated high-binding affinity (K i, 8.1 nmol L(-1)) specific to GluN2B with an IC 50 of 3.6 nmol L(-1) and no off-target activity. CERC-301 efficacy was demonstrated in the forced swim test with an efficacy dose (ED 50) of 0.3-0.7 mg kg(-1) (RO, 30-50%); increase in locomotor activity was observed at ED 50 of 2 mg kg(-1), corresponding to an RO of 75%. The predicted 50% RO concentration (Occ50) in humans was 400 nmol L(-1), similar to that predicted for rat, dog, and monkey (300, 200, and 400 nmol L(-1), respectively). Safety pharmacology and neurotoxicity studies raised no specific safety concerns. A first-in-human study in healthy males demonstrated a dose-proportional pharmacokinetic profile, with T max of ~1 h and t 1/2 of 12-17 h. Based on the preclinical and pharmacodynamic data, doses of ≥8 mg in humans are hypothesized to have an acceptable safety profile and result in clinically relevant peak plasma exposure.
ABSTRACT
AIMS: Vernakalant is a newly developed antiarrhythmic drug against atrial fibrillation (AF). However, its electrophysiological actions on human myocardium are unknown. METHODS AND RESULTS: Action potentials (APs) and ion currents were recorded in right atrial trabeculae and cardiomyocytes from patients in sinus rhythm (SR) and chronic AF. Vernakalant prolonged early repolarization in SR and AF, but late only in AF. AP amplitude (APA) and dV/dtmax were reduced in a concentration- and frequency-dependent manner with IC50 < 10 µM at >3 Hz. Effective refractory period was increased more than action potential duration (APD) in SR and AF. INa was blocked with IC50s of 95 and 84 µM for SR and AF, respectively (0.5 Hz). Vernakalant did not reduce outward potassium currents compared with time-matched controls. However, area under the current-time curve was reduced due to acceleration of current decline with IC50s of 19 and 12 µM for SR and AF, respectively. Vernakalant had less effect on APD than the IKr blocker E-4031, blocked IK,ACh, and had a small inhibitory effect on IK1 at 30 µM. L-Type Ca(2+) currents (SR) were reduced with IC50 of 84 µM. CONCLUSION: Rate-dependent block of Na(+) channels represents the main antiarrhythmic mechanism of vernakalant in the fibrillating atrium. Open channel block of early transient outward currents and IK,ACh could also contribute.
Subject(s)
Anisoles/pharmacology , Anti-Arrhythmia Agents/pharmacology , Arrhythmia, Sinus/drug therapy , Atrial Fibrillation/drug therapy , Heart Atria/drug effects , Pyrrolidines/pharmacology , Action Potentials/drug effects , Aged , Calcium Channels/drug effects , Chronic Disease , Female , Humans , Male , Middle Aged , Myocytes, Cardiac/drug effects , Myocytes, Cardiac/physiology , Potassium Channels/drug effects , Sodium Channels/drug effectsABSTRACT
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.
Subject(s)
Anisoles/pharmacology , Anti-Arrhythmia Agents/pharmacology , Arteries/drug effects , Flecainide/pharmacology , Heart Ventricles/drug effects , Pyrrolidines/pharmacology , Sodium Potassium Chloride Symporter Inhibitors/pharmacology , Vasodilator Agents/pharmacology , Cardiotonic Agents/pharmacology , Cardiotoxins/pharmacology , Humans , In Vitro Techniques , Myocardial Contraction/drug effects , Osmolar Concentration , Skin/blood supply , Vascular Resistance/drug effects , Vasodilation/drug effectsABSTRACT
BACKGROUND: We evaluated the viability of I(Kur) as a target for maintenance of sinus rhythm in patients with a history of atrial fibrillation through the testing of MK-0448, a novel I(Kur) inhibitor. METHODS AND RESULTS: In vitro MK-0448 studies demonstrated strong inhibition of I(Kur) with minimal off-target activity. In vivo MK-0448 studies in normal anesthetized dogs demonstrated significant prolongation of the atrial refractory period compared with vehicle controls without affecting the ventricular refractory period. In studies of a conscious dog heart failure model, sustained atrial fibrillation was terminated with bolus intravenous MK-0448 doses of 0.03 and 0.1 mg/kg. These data led to a 2-part first-in-human study: Part I evaluated safety and pharmacokinetics, and part II was an invasive electrophysiological study in healthy subjects. MK-0448 was well-tolerated with mild adverse experiences, most commonly irritation at the injection site. During the electrophysiological study, ascending doses of MK-0448 were administered, but no increases in atrial or ventricular refractoriness were detected, despite achieving plasma concentrations in excess of 2 µmol/L. Follow-up studies in normal anesthetized dogs designed to assess the influence of autonomic tone demonstrated that prolongation of atrial refractoriness with MK-0448 was markedly attenuated in the presence of vagal nerve simulation, suggesting that the effects of I(Kur) blockade on atrial repolarization may be negated by enhanced parasympathetic neural tone. CONCLUSIONS: The contribution of I(Kur) to human atrial electrophysiology is less prominent than in preclinical models and therefore is likely to be of limited therapeutic value for the prevention of atrial fibrillation.
Subject(s)
Atrial Fibrillation/prevention & control , Electrophysiological Phenomena/physiology , Kv1.5 Potassium Channel/antagonists & inhibitors , Potassium Channel Blockers/adverse effects , Potassium Channel Blockers/pharmacokinetics , Adult , Animals , Atrial Fibrillation/physiopathology , Delayed Rectifier Potassium Channels/antagonists & inhibitors , Delayed Rectifier Potassium Channels/drug effects , Delayed Rectifier Potassium Channels/physiology , Disease Models, Animal , Dogs , Dose-Response Relationship, Drug , Double-Blind Method , Electrophysiological Phenomena/drug effects , Female , Heart Conduction System/physiology , Heart Failure/physiopathology , Heart Failure/prevention & control , Humans , In Vitro Techniques , Kv1.5 Potassium Channel/drug effects , Kv1.5 Potassium Channel/physiology , Male , Potassium Channel Blockers/pharmacology , Pyridines/adverse effects , Pyridines/pharmacokinetics , Pyridines/pharmacology , Sinoatrial Node/physiology , Sulfonamides/adverse effects , Sulfonamides/pharmacokinetics , Sulfonamides/pharmacology , Vagus Nerve/physiologyABSTRACT
BACKGROUND: Several clinical trials have shown that vernakalant is effective in terminating recent onset atrial fibrillation (AF). The electrophysiological actions of vernakalant are not fully understood. METHODS AND RESULTS: Here we report the results of a blinded study comparing the in vitro canine atrial electrophysiological effects of vernakalant, ranolazine, and dl-sotalol. Action potential durations (APD(50,75,90)), effective refractory period (ERP), post repolarization refractoriness (PRR), maximum rate of rise of the action potential (AP) upstroke (V(max)), diastolic threshold of excitation (DTE), conduction time (CT), and the shortest S(1)-S(1) permitting 1:1 activation (S(1)-S(1)) were measured using standard stimulation and microelectrode recording techniques in isolated normal, non-remodeled canine arterially perfused left atrial preparations. Vernakalant caused variable but slight prolongation of APD(90) (P=not significant), but significant prolongation of APD(50) at 30 µmol/L and rapid rates. In contrast, ranolazine and dl-sotalol produced consistent concentration- and reverse rate-dependent prolongation of APD(90). Vernakalant and ranolazine caused rate-dependent, whereas dl-sotalol caused reverse rate-dependent, prolongation of ERP. Significant rate-dependent PRR developed with vernakalant and ranolazine, but not with dl-sotalol. Other sodium channel-mediated parameters (ie, V(max), CT, DTE, and S(1)-S(1)) also were depressed significantly by vernakalant and ranolazine, but not by dl-sotalol. Only vernakalant elevated AP plateau voltage, consistent with blockade of ultrarapid delayed rectified potassium current and transient outward potassium current. CONCLUSIONS: In isolated canine left atria, the effects of vernakalant and ranolazine were characterized by use-dependent inhibition of sodium channel-mediated parameters, and those of dl-sotalol by reverse rate-dependent prolongation of APD(90) and ERP. This suggests that during the rapid activation rates of AF, the I(Na) blocking action of the mixed ion channel blocker vernakalant takes prominence. This mechanism may explain vernakalant's anti-AF efficacy.
Subject(s)
Acetanilides/pharmacology , Anisoles/pharmacology , Heart Atria/drug effects , Piperazines/pharmacology , Pyrrolidines/pharmacology , Sodium Channels/drug effects , Sotalol/pharmacology , Action Potentials/drug effects , Action Potentials/physiology , Animals , Anti-Arrhythmia Agents/pharmacology , Dogs , Female , In Vitro Techniques , Male , Models, Animal , Ranolazine , Refractory Period, Electrophysiological/drug effects , Refractory Period, Electrophysiological/physiology , Sodium Channel Blockers/pharmacology , Sodium Channels/physiology , Time FactorsABSTRACT
BACKGROUND: Vernakalant (VER) is a relatively atrial-selective antiarrhythmic drug capable of blocking potassium and sodium currents in a frequency- and voltage-dependent manner. Ranolazine (RAN) is a sodium-channel blocker shown to exert antiarrhythmic effects in pulmonary vein (PV) sleeves. dl-Sotalol (SOT) is a ß-blocker commonly used in the rhythm-control treatment of atrial fibrillation. This study evaluated the electrophysiological and antiarrhythmic effects of VER, RAN, and SOT in canine PV sleeve preparations in a blinded fashion. METHODS: Transmembrane action potentials were recorded from canine superfused PV sleeve preparations exposed to VER (n = 6), RAN (n = 6), and SOT (n = 6). Delayed afterdepolarizations were induced in the presence of isoproterenol and high-calcium concentrations by periods of rapid pacing. RESULTS: In PV sleeves, VER, RAN, and SOT (3-30 µM) produced small (10-15 ms) increases in action potential duration. The effective refractory period, diastolic threshold of excitation, and the shortest S(1)-S(1) cycle length permitting 1:1 activation were significantly increased by VER and RAN in a rate- and concentration-dependent manner. VER and RAN significantly reduced V(max) in a concentration- and rate-dependent manner. SOT did not significantly affect the effective refractory period, V(max), diastolic threshold of excitation, or the shortest S(1)-S(1) cycle length permitting 1:1 activation. All 3 agents (3-30 µM) suppressed delayed afterdepolarization-mediated triggered activity induced by isoproterenol and high calcium. CONCLUSIONS: In canine PV sleeves, the effects of VER and RAN were similar and largely characterized by concentration- and rate-dependent depression of sodium-channel-mediated parameters, which were largely unaffected by SOT. All 3 agents demonstrated an ability to effectively suppress delayed afterdepolarization-induced triggers of atrial arrhythmia.
Subject(s)
Acetanilides , Anisoles , Atrial Fibrillation/drug therapy , Piperazines , Pulmonary Veins , Pyrrolidines , Sodium Channels , Sotalol , Acetanilides/pharmacokinetics , Action Potentials/drug effects , Adrenergic beta-Agonists/pharmacokinetics , Animals , Anisoles/pharmacokinetics , Anti-Arrhythmia Agents/pharmacokinetics , Atrial Fibrillation/metabolism , Biological Availability , Cardiac Electrophysiology/methods , Cell Membrane/drug effects , Cell Membrane/metabolism , Dogs , Heart Rate/drug effects , Humans , Isoproterenol/pharmacokinetics , Membrane Potentials/drug effects , Piperazines/pharmacokinetics , Pulmonary Veins/metabolism , Pulmonary Veins/pathology , Pyrrolidines/pharmacokinetics , Ranolazine , Sodium Channels/drug effects , Sodium Channels/metabolism , Sotalol/pharmacokineticsABSTRACT
Although the S3 pocket of the thrombin active site is lined with lipophilic amino acid residues, the accommodation of polarity within the lipophilic P3 moiety of small molecule inhibitors is possible provided that the polar functionality is capable of pointing away from the binding pocket outwards toward solvent while simultaneously allowing the lipophilic portion of the P3 ligand to interact with the S3 amino acid residues. Manipulation of this motif provided the means to effect optimization of functional potency, in vivo antithrombotic efficacy and oral bioavailability in a series of 3-aminopyrazinone thrombin inhibitors which contained non-charged groups at the P1 position.
Subject(s)
Anticoagulants/chemical synthesis , Blood Coagulation Disorders/drug therapy , Drug Design , Pyrazines/chemical synthesis , Thrombin/antagonists & inhibitors , Administration, Oral , Animals , Anticoagulants/chemistry , Anticoagulants/pharmacology , Binding Sites , Biological Availability , Dogs , Molecular Structure , Pyrazines/chemistry , Pyrazines/pharmacology , Rats , Structure-Activity RelationshipABSTRACT
A novel 1,3,5-trisubstituted benzamide thrombin inhibitor template was designed via hybridization of a known aminopyridinoneacetamide and a known 1,3,5-trisubstituted phenyl ether. Optimization of this lead afforded a novel potent series of biaryl 1,3,5-trisubstituted benzenes with excellent functional anticoagulant potency.
Subject(s)
Antithrombins/chemical synthesis , Benzene/chemical synthesis , Drug Design , Thrombin/antagonists & inhibitors , Antithrombins/chemistry , Antithrombins/pharmacology , Benzene/chemistry , Benzene/pharmacology , Humans , Models, Molecular , Molecular Structure , Structure-Activity RelationshipABSTRACT
The effects of calcitonin gene-related peptide (CGRP) receptor antagonism with CGRP 8-37 on blood pressure changes evoked by the intravenous administration of the vasoactive modulators angiotensin II, phenylephrine, adenosine, nitroglycerine, and sodium nitroprusside were assessed in conscious rats. The effects of sumatriptan and dihydroergotamine on the blood pressure responses evoked by these vasomodulators also were assessed. The intravenous test dose of CGRP 8-37 was validated through block of depressor responses to intravenous CGRP in conscious rats, whereas the intravenous test doses of sumatriptan and dihydroergotamine were validated by reductions in carotid blood flow in anesthetized rats. CGRP 8-37 had no significant effects on blood pressure dose-response profiles and individual dose blood pressure responses to any of the vasomodulators tested. In contrast, sumatriptan altered the blood pressure dose-response profiles to angiotensin II and sodium nitroprusside (P < 0.03) and dihydroergotamine altered the blood pressure dose-response profile to sodium nitroprusside (P < 0.02) and tended to alter that of phenylephrine (P = 0.06). Both sumatriptan and dihydroergotamine displayed frequent alterations of individual dose blood pressure responses to all vasomodulators. These findings are consistent with concerns for sumatriptan and dihydroergotamine to alter systemic hemodynamics, whereas CGRP receptor antagonism did not display the same hemodynamic liability.
Subject(s)
Blood Pressure/drug effects , Calcitonin Gene-Related Peptide Receptor Antagonists , Calcitonin Gene-Related Peptide/pharmacology , Hemodynamics/drug effects , Peptide Fragments/pharmacology , Vasoconstrictor Agents/pharmacology , Vasodilator Agents/pharmacology , Animals , Carotid Arteries/drug effects , Carotid Arteries/physiology , Dihydroergotamine/pharmacology , Dose-Response Relationship, Drug , Male , Rats , Rats, Sprague-Dawley , Regional Blood Flow/drug effects , Sumatriptan/pharmacologyABSTRACT
A series of triarylethanolamine inhibitors of the Kv1.5 potassium channel have been prepared and evaluated for their effects in vitro and in vivo. The structure-activity relationship (SAR) studies described herein led to the development of potent, selective and orally active inhibitors of Kv1.5.
Subject(s)
Ethanolamines/pharmacology , Potassium Channel Blockers/pharmacology , Potassium Channels, Voltage-Gated/antagonists & inhibitors , Animals , Dose-Response Relationship, Drug , Drug Discovery , Drug Evaluation, Preclinical , Ethanolamines/chemistry , Humans , Potassium Channel Blockers/chemistry , Structure-Activity RelationshipABSTRACT
Studies were conducted in human isolated coronary arteries to explore the vascular effects of the calcitonin gene-related peptide (CGRP) receptor antagonist telcagepant and to compare its coronary vasoconstrictive potential to that of zolmitriptan. KCl precontracted coronary vessels were shown to relax to human alphaCGRP, with the CGRP-mediated vasorelaxation completely blocked with 30 microM telcagepant. In coronary vessels at basal tone, zolmitriptan caused a concentration-dependent contraction (pEC50 = 6.9 +/- 0.1; slope 0.94), with the greatest contraction obtained between 1 and 10 microM in most tissues. In contrast, telcagepant at concentrations up to 30 microM evoked no change in contractile tone. These findings suggest the potential for CGRP receptor antagonists to exert antimigraine efficacy in the absence of adverse effects on coronary tone.
Subject(s)
Azepines/pharmacology , Calcitonin Gene-Related Peptide Receptor Antagonists , Coronary Vessels/drug effects , Imidazoles/pharmacology , Oxazolidinones/pharmacology , Tryptamines/pharmacology , Vasoconstriction/drug effects , Adult , Azepines/adverse effects , Azepines/therapeutic use , Coronary Vessels/metabolism , Dose-Response Relationship, Drug , Humans , Imidazoles/adverse effects , Imidazoles/therapeutic use , In Vitro Techniques , Middle Aged , Migraine Disorders/drug therapy , Oxazolidinones/adverse effects , Oxazolidinones/therapeutic use , Tryptamines/adverse effects , Tryptamines/therapeutic use , Vasodilation/drug effects , Vasodilator Agents/pharmacologyABSTRACT
Calcitonin gene-related peptide (CGRP) has long been hypothesized to play a key role in migraine pathophysiology, and the advent of small-molecule antagonists has clearly demonstrated a clinical link between blocking the CGRP receptor and migraine efficacy. 2-[(8R)-8-(3,5-Difluorophenyl)-10-oxo-6,9-diazaspiro[4.5]dec-9-yl]-N-[(2R)-2'-oxo-1,1',2',3-tetrahydrospiro[indene-2,3'-pyrrolo[2,3-b]pyridin]-5-yl]acetamide (MK-3207) represents the third CGRP receptor antagonist to display clinical efficacy in migraine trials. Here, we report the pharmacological characterization of MK-3207, a potent and orally bioavailable CGRP receptor antagonist. In vitro, MK-3207 is a potent antagonist of the human and rhesus monkey CGRP receptors (K(i) = 0.024 nM). In common with other CGRP receptor antagonists, MK-3207 displays lower affinity for CGRP receptors from other species, including canine and rodent. As a consequence of species selectivity, the in vivo potency was assessed in a rhesus monkey pharmacodynamic assay measuring capsaicin-induced changes in forearm dermal blood flow via laser Doppler imaging. MK-3207 produced a concentration-dependent inhibition of dermal vasodilation, with plasma concentrations of 0.8 and 7 nM required to block 50 and 90% of the blood flow increase, respectively. The tritiated analog [3H]MK-3207 was used to study the binding characteristics on the human CGRP receptor. [3H]MK-3207 displayed reversible and saturable binding (K(D) = 0.06 nM), and the off-rate was determined to be 0.012 min(-1), with a t(1/2) value of 59 min. In vitro autoradiography studies on rhesus monkey brain slices identified the highest level of binding in the cerebellum, brainstem, and meninges. Finally, as an index of central nervous system penetrability, the in vivo cerebrospinal fluid/plasma ratio was determined to be 2 to 3% in cisterna magna-ported rhesus monkeys.
Subject(s)
Bridged Bicyclo Compounds, Heterocyclic/pharmacology , Calcitonin Gene-Related Peptide Receptor Antagonists , Spiro Compounds/pharmacology , ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism , Animals , Autoradiography , Binding, Competitive , Biological Transport , Brain/metabolism , Bridged Bicyclo Compounds, Heterocyclic/blood , Bridged Bicyclo Compounds, Heterocyclic/cerebrospinal fluid , Cell Line , Chlorocebus aethiops , Female , Humans , Kinetics , Macaca mulatta , Male , Mice , Radioligand Assay , Receptors, Adrenomedullin , Receptors, Calcitonin/metabolism , Receptors, Calcitonin Gene-Related Peptide/physiology , Receptors, Islet Amyloid Polypeptide , Receptors, Peptide/metabolism , Spiro Compounds/blood , Spiro Compounds/cerebrospinal fluid , Vasodilation/drug effectsABSTRACT
Incorporation of polar functionality into a series of highly potent calcitonin gene-related peptide (CGRP) receptor antagonists was explored in an effort to improve pharmacokinetics. This strategy identified piperazinone analogues that possessed improved solubility at acidic pH and increased oral bioavailability in monkeys. Further optimization led to the discovery of the clinical candidate 2-[(8R)-8-(3,5-difluorophenyl)-10-oxo-6,9-diazaspiro[4.5]dec-9-yl]-N-[(2R)-2'-oxo-1,1',2',3-tetrahydrospiro[indene-2,3'-pyrrolo[2,3-b]pyridin]-5-yl]acetamide (MK-3207) (4), the most potent orally active CGRP receptor antagonist described to date.
ABSTRACT
The triptans, serotonin 5-HT(1B/1D) receptor agonists exemplified by sumatriptan, are a mainstay migraine therapy but have class labeling contraindicating their use in patients with coronary artery disease. Triptans constrict human coronary artery in vitro, and there are case reports of myocardial infarction in patients using sumatriptan. However, preclinical studies with sumatriptan in normal dogs have failed to demonstrate effects on resting coronary flow. Calcitonin gene-related peptide (CGRP) receptor antagonism, exemplified by the prototype CGRP receptor antagonist peptide CGRP(8-37), is a new antimigraine mechanism which also has been reported to have no effect on coronary flow in normal, non-stressed animals. The goal of the present studies was to compare the effects of sumatriptan (10microg/kg/min i.v.) and CGRP(8-37) (30microg/kg/min i.v.) on systemic and coronary hemodynamics in conscious dogs under resting conditions and during myocardial reactive hyperemia following a brief 15s of coronary artery occlusion. Neither CGRP(8-37) nor sumatriptan affected resting coronary flow. However, whereas CGRP(8-37) had no effect on myocardial reactive hyperemic response, sumatriptan reduced peak reactive hyperemic coronary artery blood flow (baseline vs treatment: 75.4+/-12.7 vs 60.0+/-10.3ml/min, P<0.05), reactive hyperemic flow (16.7+/-5.2 vs 11.6+/-3.3ml, P<0.05) and the repayment of coronary blood flow debt following coronary artery occlusion (484+/-76 vs 369+/-57%, P<0.05), indicating an impairment in coronary blood flow reserve. The positive control nitric oxide synthase inhibitor L-NNA (30mg/kg/30min i.v.) likewise significantly attenuated myocardial reactive hyperemic response. These findings provide evidence for a differentiation between CGRP receptor antagonism and triptan effects on coronary vascular function.
Subject(s)
Calcitonin Gene-Related Peptide Receptor Antagonists , Calcitonin Gene-Related Peptide/pharmacology , Coronary Circulation/drug effects , Hyperemia/drug therapy , Peptide Fragments/pharmacology , Serotonin 5-HT1 Receptor Agonists , Serotonin Receptor Agonists/pharmacology , Sumatriptan/pharmacology , Animals , Calcitonin Gene-Related Peptide/administration & dosage , Catheters, Indwelling , Consciousness/physiology , Coronary Artery Disease/complications , Coronary Occlusion/physiopathology , Cross-Over Studies , Dogs , Hemodynamics , Infusions, Intra-Arterial , Migraine Disorders/complications , Migraine Disorders/drug therapy , Peptide Fragments/administration & dosage , Serotonin Receptor Agonists/administration & dosage , Serotonin Receptor Agonists/blood , Sumatriptan/administration & dosage , Sumatriptan/blood , Time FactorsABSTRACT
The triptans, serotonin 5-HT 1B/1D agonists exemplified by sumatriptan, are an effective class of migraine therapy but have class labeling contraindicating their use in patients with coronary artery disease. Triptans have been shown to constrict human coronary artery in vitro, and there have been case reports of myocardial infarction in patients using sumatriptan. However, preclinical in vivo studies with sumatriptan in normal dogs have failed to demonstrate an effect on coronary flow. The present studies were conducted in a canine model in which regional myocardial ischemia was evoked by atrial pacing in the presence of a 40% stenosis of the left anterior descending coronary artery. Ischemic severity was quantified by changes in local epicardial electrograms (EGs) recorded in the ischemic zone. The intra-atrial administration of 10 microg x kg x min sumatriptan variably but not significantly increased the severity of regional ischemia (pre- vs. posttreatment: Delta EG: 2.00 +/- 0.17 vs. 3.05 +/- 1.15 mV). Sumatriptan at 30 microg x kg x min significantly increased ischemic severity (Delta EG: 1.88 +/- 0.19 vs. 3.32 +/- 0.58 mV, P < 0.05) concomitant with a significant reduction in coronary blood flow (8.9 +/- 0.5 vs. 7.2 +/- 0.8 mL/min, P < 0.05). These results demonstrate that a reduction in coronary flow with proischemic consequence can be modeled preclinically with sumatriptan in a canine model of cardiac stress.
Subject(s)
Coronary Stenosis/physiopathology , Myocardial Ischemia/physiopathology , Serotonin 5-HT1 Receptor Agonists , Sumatriptan/adverse effects , Vasoconstrictor Agents/adverse effects , Animals , Cardiac Pacing, Artificial , Coronary Circulation/drug effects , Coronary Stenosis/complications , Disease Models, Animal , Dogs , Female , Heart Atria/physiopathology , Hemodynamics/drug effects , Male , Myocardial Ischemia/etiology , Sumatriptan/therapeutic use , Vasoconstrictor Agents/therapeutic useABSTRACT
INTRODUCTION: The accurate assessment of blood pressure is often a key component of preclinical cardiovascular disease/efficacy models and of screening models used to determine the effects of test agents on cardiovascular physiology. Of the many methods utilized in large animals, telemetry is becoming more widely used throughout preclinical testing, and non-human primates are playing an ever increasing role as a large animal model to evaluate the cardiovascular effect of novel test agents. Therefore, we sought to characterize pressure transducer drift of a telemetry implant in primates over an extended duration. METHODS: We instrumented ten rhesus monkeys with a Konigsberg T27F implant and a chronic indwelling arterial catheter and cross calibrated the diastolic pressure recorded by the implant to the diastolic pressure that was simultaneously recorded through the arterial catheter using a calibrated external transducer/amplifier system. RESULTS: While all implanted pressure transducers experienced drift to some degree, magnitude of drift varied across animals (range of average drift 0.7-20.5 mmHg/month). Specifically, we found that all implants could be calibrated within the voltage range of the instrument up to 6 months after implantation despite the drift observed. Between 6 and 12 months, 3 of the 10 implants studied drifted outside the defined voltage range and were unusable, two more drifted off scale within 2 years, while the remainder remained within the operating voltage range. DISCUSSION: Given that pressure transducer drift was not consistent across implants or time, these data suggest careful assessment and quantitative correction for in vivo drift of telemetry blood pressure transducers implanted for extended duration should be considered.