Phase I, Open-Label, Dose-Escalation/Dose-Expansion Study of Lifirafenib (BGB-283), an RAF Family Kinase Inhibitor, in Patients With Solid Tumors.

PURPOSE: Lifirafenib is an investigational, reversible inhibitor of B-RAFV600E, wild-type A-RAF, B-RAF, C-RAF, and EGFR. This first-in-human, phase I, dose-escalation/dose-expansion study evaluated the safety, tolerability, and efficacy of lifirafenib in patients with B-RAF- or K-RAS/N-RAS-mutated solid tumors. METHODS: During dose escalation, adult patients with histologically/cytologically confirmed advanced solid tumors received escalating doses of lifirafenib. Primary end points were safety/tolerability during dose escalation and objective response rate in preselected patients with B-RAF and K-RAS/N-RAS mutations during dose expansion. RESULTS: The maximum tolerated dose was established as 40 mg/d; dose-limiting toxicities included reversible thrombocytopenia and nonhematologic toxicity. Across the entire study, the most common grade ≥ 3 treatment-emergent adverse events were hypertension (n = 23; 17.6%) and fatigue (n = 13; 9.9%). One patient with B-RAF-mutated melanoma achieved complete response, and 8 patients with B-RAF mutations had confirmed objective responses: B-RAFV600E/K melanoma (n = 5, including 1 patient treated with prior B-RAF/MEK inhibitor therapy), B-RAFV600E thyroid cancer/papillary thyroid cancer (PTC; n = 2), and B-RAFV600E low-grade serous ovarian cancer (LGSOC; n = 1). One patient with B-RAF-mutated non-small-cell lung cancer (NSCLC) had unconfirmed partial response (PR). Patients with K-RAS-mutated endometrial cancer and K-RAS codon 12-mutated NSCLC had confirmed PR (n = 1 each). No responses were seen in patients with K-RAS/N-RAS-mutated colorectal cancer (n = 20). CONCLUSION: Lifirafenib is a novel inhibitor of key RAF family kinases and EGFR, with an acceptable risk-benefit profile and antitumor activity in patients with B-RAFV600-mutated solid tumors, including melanoma, PTC, and LGSOC, as well as K-RAS-mutated NSCLC and endometrial carcinoma. Future comparisons with first-generation B-RAF inhibitors and exploration of lifirafenib alone or as combination therapy in patients with selected RAS mutations who are resistant/refractory to first-generation B-RAF inhibitors are warranted.

The Selective Late Sodium Current Inhibitor Eleclazine, Unlike Amiodarone, Does Not Alter Defibrillation Threshold or Dominant Frequency of Ventricular Fibrillation.

INTRODUCTION: We examined the effects of the selective late INa inhibitor eleclazine on the 50% probability of successful defibrillation (DFT50) before and after administration of amiodarone to determine its suitability for use in patients with implantable cardioverter defibrillators (ICDs). METHODS AND RESULTS: In 20 anesthetized pigs, transvenous active-fixation cardiac defibrillation leads were fluoroscopically positioned into right ventricular apex through jugular vein. ICDs were implanted subcutaneously. Dominant frequency of ventricular fibrillation was analyzed by fast Fourier transform. The measurements were made before drug administration (control), and at 40 minutes after vehicle, eleclazine (2 mg/kg, i.v., bolus over 15 minutes), or subsequent/single amiodarone administration (10 mg/kg, i.v., bolus over 10 minutes). Eleclazine did not alter DFT50, dominant frequency, heart rate, or mean arterial pressure (MAP). Subsequent amiodarone increased DFT50 (P = 0.006), decreased dominant frequency (P = 0.022), and reduced heart rate (P = 0.031) with no change in MAP. Amiodarone alone increased DFT50 (P = 0.005; NS compared to following eleclazine) and decreased dominant frequency (P = 0.003; NS compared to following eleclazine). CONCLUSION: Selective late INa inhibition with eleclazine does not alter DFT50 or dominant frequency of ventricular fibrillation when administered alone or in combination with amiodarone. Accordingly, eleclazine would not be anticipated to affect the margin of defibrillation safety in patients with ICDs.

The HARMONY Trial: Combined Ranolazine and Dronedarone in the Management of Paroxysmal Atrial Fibrillation: Mechanistic and Therapeutic Synergism.

BACKGROUND: Atrial fibrillation (AF) requires arrhythmogenic changes in atrial ion channels/receptors and usually altered atrial structure. AF is commonly treated with antiarrhythmic drugs; the most effective block many ion channels/receptors. Modest efficacy, intolerance, and safety concerns limit current antiarrhythmic drugs. We hypothesized that combining agents with multiple anti-AF mechanisms at reduced individual drug doses might produce synergistic efficacy plus better tolerance/safety. METHODS AND RESULTS: HARMONY tested midrange ranolazine (750 mg BID) combined with 2 reduced dronedarone doses (150 mg BID and 225 mg BID; chosen to reduce dronedarone's negative inotropic effect-see text below) over 12 weeks in 134 patients with paroxysmal AF and implanted pacemakers where AF burden (AFB) could be continuously assessed. Patients were randomized double-blind to placebo, ranolazine alone (750 mg BID), dronedarone alone (225 mg BID), or one of the combinations. Neither placebo nor either drugs alone significantly reduced AFB. Conversely, ranolazine 750 mg BID/dronedarone 225 mg BID reduced AFB by 59% versus placebo (P=0.008), whereas ranolazine 750 mg BID/dronedarone 150 mg BID reduced AFB by 43% (P=0.072). Both combinations were well tolerated. CONCLUSIONS: HARMONY showed synergistic AFB reduction by moderate dose ranolazine plus reduced dose dronedarone, with good tolerance/safety, in the population enrolled. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov; Unique identifier: NCT01522651.

Combined actions of ivabradine and ranolazine reduce ventricular rate during atrial fibrillation.

INTRODUCTION: Ventricular rate during atrial fibrillation (AF) can be reduced by slowing atrioventricular (AV) node conduction and/or by decreasing dominant frequency of AF. We investigated whether combined administration of ivabradine and ranolazine reduces ventricular rate during AF. METHODS AND RESULTS: Ivabradine (maximum clinical dose, 0.25 mg/kg, and 0.10 mg/kg, i.v.) and ranolazine (2.4 mg/kg, i.v., bolus followed by 0.135 mg/kg/min) were studied in an anesthetized pig (N = 16) model of AF. Combined administration of 0.25 mg/kg ivabradine with ranolazine reduced ventricular rate during AF by 51.9 ± 9.7 beats/min (23%, P = 0.017) and dominant frequency of AF by 2.8 ± 0.5 Hz (32%, P = 0.005). It increased PR (P = 0.0002, P = 0.0007) and A-H intervals (P = 0.047, P = 0.002) during pacing at 130 and 180 beats/min, respectively, to a greater degree than additive effects of single agents. Combined administration of 0.1 mg/kg ivabradine with ranolazine exceeded additive effects of single agents on A-H intervals and dominant frequency of AF. Moreover, ranolazine potentiated low-dose ivabradine's reduction in ventricular rate, as combined administration more than doubled effects of the higher ivabradine dose alone and was similar to the combination with the higher dose. Neither drug nor their combination affected contractility (left ventricular [LV] dP/dt), QT or His-ventricular (H-V) intervals, or mean arterial pressure during sinus rhythm or AF. CONCLUSION: Combined administration of ivabradine and ranolazine at clinically safe levels decreases ventricular rate during AF by reducing AV node conduction and AF dominant frequency without QT prolongation or depression in contractility. Targeting these actions offers intrinsic advantages over conventional nodal agents, which can reduce contractility.

If inhibition in the atrioventricular node by ivabradine causes rate-dependent slowing of conduction and reduces ventricular rate during atrial fibrillation.

BACKGROUND: If channels are functionally expressed in atrioventricular (AV) nodal tissue. OBJECTIVE: The purpose of this study was to address whether the prototypical If inhibitor, ivabradine, at clinically safe concentrations can slow AV node conduction to reduce ventricular rate (VR) during atrial fibrillation (AF). METHODS: Effects of ivabradine (0.1 mg/kg i.v. bolus) were studied in an anesthetized Yorkshire pig (N = 7) model of AF and in isolated guinea pig hearts (N = 7). RESULTS: Ivabradine reduced heart rate (P = .0001) without affecting mean arterial pressure during sinus rhythm. The agent lengthened PR intervals in a rate-dependent manner (P = .0009) by 14 ± 2.7 ms (P = .003) and 25 ± 3.0 ms (P = .0004) and increased atrial-His (A-H) intervals in a rate-dependent manner (P = .020) by 10 ± 1.7 ms and 17 ± 2.8 ms during pacing at 130 and 180 bpm, respectively (both P = .0008). Similar rate-dependent effects were observed in isolated guinea pig hearts. Ivabradine slowed VR during AF from 240 ± 21 bpm to 211 ± 25 bpm (P = .041). The ivabradine-induced increase in A-H interval was inversely correlated with VR (r = -0.85, P = .03, at 130 bpm; r = -0.95, P = .003, at 180 bpm). QT and HV intervals, AF dominant frequency (8.5 ± 0.9 to 8.7 ± 1.1 Hz, P = NS), mean arterial pressure, and left ventricular dP/dt (1672 ± 222 to 1889 ± 229 mm Hg/s, P = NS) during AF were unaffected. CONCLUSION: Ivabradine's rate-dependent increase in A-H interval is highly correlated with VR during AF. As dominant frequency was unaltered, AV node conduction slowing during high nodal activation rates appears to be the main mechanism of ivabradine's VR reduction. If inhibition in the AV node may provide a promising target to slow VR during AF without depression in contractility.

Ranolazine terminates atrial flutter and fibrillation in a canine model.

BACKGROUND: Ranolazine has been shown to have antiarrhythmic properties. OBJECTIVE: We tested the hypothesis that intravenous ranolazine would terminate induced atrial flutter (AFL) or atrial fibrillation (AF) in the canine sterile pericarditis model. METHODS: In 6 dogs with sterile pericarditis, we performed electrophysiological measurements of the atrial effective refractory period (AERP) and conduction time (CT) while pacing from the right atrial appendage, Bachmann bundle, and the posteroinferior left atrium at cycle lengths (CLs) of 400, 300, and 200 ms before and after the administration of ranolazine. In 13 induced episodes of AFL (n = 9) and AF (n = 4), ranolazine was administered intravenously as a 3.2 mg/kg bolus, followed by a maintenance infusion of 0.17 mg/(kg·min). Six episodes (4 AFL and 2 AF) were induced in the open-chest state to perform simultaneous, multisite (486 electrodes), epicardial mapping of the arrhythmia and its termination. RESULTS: Ranolazine terminated 7 of 9 AFL and 3 of 4 AF episodes. Ranolazine significantly prolonged the AFL CL by a mean of 43 ms (P < .001) and the AF CL by a mean of 34 ms (P < .01). The AERP was prolonged (P < .05 overall), and the atrial capture threshold increased minimally (P < .01 for all). Ranolazine prolonged CTs (P < .01 overall). During open-chest, multisite mapping, block in the region of slow conduction in the reentrant circuit terminated AFL and interruption of the regular driver terminated AF. CONCLUSION: Ranolazine terminated AFL/AF in our canine sterile pericarditis model by interrupting the regular driver. Ranolazine was found to significantly prolong the AERP, CT, and tachycardia CLs.

Blockade of A2B adenosine receptor reduces left ventricular dysfunction and ventricular arrhythmias 1 week after myocardial infarction in the rat model.

BACKGROUND: Remodeling occurs after myocardial infarction (MI), leading to fibrosis, dysfunction, and ventricular tachycardias (VTs). Adenosine via the A2B adenosine receptor (A2BAdoR) has been implicated in promoting fibrosis. OBJECTIVE: To determine the effects of GS-6201, a potent antagonist of the A2BAdoR, on arrhythmogenic and functional cardiac remodeling after MI. METHODS: Rats underwent ischemia-reperfusion MI and were randomized into 4 groups: control (treated with vehicle), angiotensin-converting enzyme inhibitor (treated with enalapril 1 day after MI), GS-6201-1d (treated with GS-6201 1 day after MI), GS-6201-1w (treated with GS-6201 administered 1 week after MI) . Echocardiography was performed at baseline and 1 and 5 weeks after MI. Optical mapping, VT inducibility, and histologic analysis were conducted at follow-up. RESULTS: Treatment with the angiotensin-converting enzyme inhibitor improved ejection fraction (57.8% ± 2.5% vs 43.3% ± 1.7% in control; P < .01), but had no effect on VT inducibility. Treatment with GS-6201 improved ejection fraction (55.6% ± 2.6% vs 43.3% ± 1.7% in control; P < .01) and decreased VT inducibility (9.1% vs 68.4% in control; P < .05). Conduction velocities were significantly higher at border and infarct zones in hearts of rats treated with GS-6201 than in those of other groups. The conduction heterogeneity index was also significantly lower in hearts of rats treated with GS-6201. Histologic analysis showed that while both GS-6201 and enalapril decreased fibrosis in the noninfarct zone, only GS-6201 reduced the heterogeneity of fibrosis at the border, which is consistent with its effect on VT reduction. CONCLUSIONS: Treatment with an A2BAdoR antagonist at 1 week results in the improvement in cardiac function and decreased substrate for VT. The inhibition of fibrogenesis by A2BAdoR antagonists may be a new target for the prevention of adverse remodeling after MI.

Inhibition of I(f) in the atrioventricular node as a mechanism for dronedarone's reduction in ventricular rate during atrial fibrillation.

BACKGROUND: In clinical trials, dronedarone lowers ventricular rate during atrial fibrillation (AF). This agent was recently demonstrated to inhibit If in the sinoatrial node. OBJECTIVE: The purpose of this study was to examine whether dronedarone inhibits If at the atrioventricular (AV) node to reduce ventricular rate during AF by slowing conduction at the AV node. METHODS: We studied the effects of dronedarone (1.0 mg/kg IV bolus) before and after administration of the If inhibitor ivabradine (0.5 mg/kg IV). Ventricular rate, mean arterial pressure, dominant frequency of AF, PR and QT intervals, and atrial (AERP) and ventricular effective refractory periods (VERP) were measured during atrial pacing at 150 bpm in an anesthetized pig model of AF induced by intrapericardial acetylcholine and burst pacing. RESULTS: Dronedarone reduced ventricular rate during AF by 22.1% (from 213 ± 11.1 bpm to 166 ± 8.3 bpm, P = .01) and increased PR interval by 8.7% (from 173 ± 5.6 ms to 188 ± 5.2 ms, P = .001), QT interval by 3.3% (from 272 ± 6.2 ms to 281 ± 4.9 ms, P = .05), and AERP and VERP by 6.2% and 11.7%, respectively. All other parameters remained unchanged. Dronedarone plasma levels were low (29 ± 4 nM), and concentration in tissue was 15- to 21-fold higher than in plasma. Ivabradine reduced ventricular rate during AF by 39.5% (from 200 ± 14.6 bpm to 121 ± 20.1 bpm, P = .005) and increased PR interval by 20.4% (from 157 ± 9.5 ms to 189 ± 7.4 ms, P <.05). Administration of dronedarone after ivabradine did not further alter these endpoints. CONCLUSION: Dronedarone, which is concentrated in myocardial tissue, reduces ventricular rate during AF by slowing AV conduction. Absence of this effect after ivabradine administration implicates If inhibition as a mechanism.

Adenosine A2B receptor and hyaluronan modulate pulmonary hypertension associated with chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death worldwide. The development of pulmonary hypertension (PH) in patients with COPD is strongly associated with increased mortality. Chronic inflammation and changes to the lung extracellular matrix (ECM) have been implicated in the pathogenesis of COPD, yet the mechanisms that lead to PH secondary to COPD remain unknown. Our experiments using human lung tissue show increased expression levels of the adenosine A2B receptor (ADORA2B) and a heightened deposition of hyaluronan (HA; a component of the ECM) in remodeled vessels of patients with PH associated with COPD. We also demonstrate that the expression of HA synthase 2 correlates with mean pulmonary arterial pressures in patients with COPD, with and without a secondary diagnosis of PH. Using an animal model of airspace enlargement and PH, we show that the blockade of ADORA2B is able to attenuate the development of a PH phenotype that correlates with reduced levels of HA deposition in the vessels and the down-regulation of genes involved in the synthesis of HA.

Dronedarone's inhibition of If current is the primary mechanism responsible for its bradycardic effect.

INTRODUCTION: The mechanism(s) whereby dronedarone reduces sinus rate are not well understood, although L-type calcium channel antagonism, beta-adrenergic blockade, and inhibition of If are plausible. METHODS AND RESULTS: In anesthetized pigs, we compared the effects of dronedarone to the prototypical If inhibitor, ivabradine, and the L-type calcium channel antagonist diltiazem on heart rate, mean arterial blood pressure (MAP), and contractility. Dronedarone's effects on the phenylephrine-induced rise in MAP and on the chronotropic response to isoproterenol were also investigated. Cumulative doses of dronedarone (0.5 mg/kg, i.v., and 5.0 mg/kg, i.v.; plasma level: 80 ± 16.1 nM) progressively reduced heart rate (P < 0.02) without changes in MAP or contractility as assessed by LV dP/dt (N = 6). Ivabradine (0.5 mg/kg, i.v.) similarly reduced heart rate (P < 0.01) without change in MAP (N = 6). Diltiazem (0.8 mg/kg, i.v.) reduced heart rate and MAP and decreased contractility (N = 6). Dronedarone blunted phenylephrine's alpha-receptor-mediated increase in MAP but did not alter the marked beta-adrenergic receptor (BAR)-mediated increase in heart rate induced by isoproterenol. When dronedarone injection was preceded by ivabradine, no further decrease in heart rate or change in MAP was observed (N = 6). CONCLUSIONS: Dronedarone reduced heart rate without affecting MAP or contractility, effects that differ from L-type calcium channel blockade. Dronedarone did not antagonize BAR stimulation, and its heart-rate lowering effects were eliminated by prior administration of ivabradine. Thus, dronedarone's bradycardic action is likely due to inhibition of If and not to blockade of either L-type calcium channels or BAR.

Low doses of ranolazine and dronedarone in combination exert potent protection against atrial fibrillation and vulnerability to ventricular arrhythmias during acute myocardial ischemia.

BACKGROUND: Coronary artery disease carries dual risk for atrial tachyarrhythmias and sudden cardiac death. OBJECTIVE: To examine whether low-dose ranolazine and/or dronedarone can protect against vulnerability to atrial fibrillation (AF) and ventricular tachyarrhythmias. METHODS: In chloralose-anesthetized, open-chest Yorkshire pigs (n = 15), the proximal segment of left circumflex (LCx) coronary artery was occluded to reduce flow by 75%. An electrode catheter was positioned on the left atrial appendage to measure AF threshold (AFT) before and during LCx coronary artery stenosis before and at 1 hour after dronedarone (0.5 mg/kg intravenous bolus over 5 minutes) and/or ranolazine administration (0.6 mg/kg intravenous bolus followed by 0.035 mg/kg/min). RESULTS: Before drug administration, LCx coronary artery stenosis lowered AFT from 25.2 ± 1.7 mA control (mean ± SEM) to 4.9 ± 1.0 mA baseline (P<.01). At the low doses, neither ranolazine (plasma concentration 2.4 ± 0.6 µM) nor dronedarone (plasma concentration 20.9 ± 3.5 nM) alone blunted the ischemia-induced reduction in AFT but were effective together (from 25.2 ± 1.7 mA control to 22.0 ± 3.0 mA during stenosis; P = not significant). AF duration (P<.03) and AF inducibility (P = .012) were reduced by ranolazine and dronedarone together but not by either drug alone. Concurrently, combined but not separate administration blunted the ischemia-induced surge in T-wave heterogeneity, a marker of risk for ventricular tachyarrhythmias (from 43.1 ± 11.1 µV control to 149.7 ± 15.1 µV during stenosis, P<.001, compared to 61.7 ± 13.7 µV control to 83.7 ± 15.8 µV during stenosis, P = not significant). CONCLUSIONS: Combined administration of low doses of ranolazine and dronedarone exerts a potent antiarrhythmic action on ischemia-induced vulnerability to AF and ventricular tachyarrhythmias due to direct effects on myocardial electrical properties.

The risk of sudden cardiac death in patients with non-ST elevation acute coronary syndrome and prolonged QTc interval: effect of ranolazine.

AIMS: Clinical utility of QTc prolongation as a predictor for sudden cardiac death (SCD) has not been definitely established. Ranolazine causes modest QTc prolongation, yet it shows antiarrhythmic properties. We aimed to determine the association between prolonged QTc and risk of SCD, and the effect of ranolazine on this relationship. METHODS AND RESULTS: The relationship between baseline QTc and SCD was studied in 6492 patients with non-ST elevation acute coronary syndrome (NSTEACS) randomized to placebo or ranolazine in the MERLIN-TIMI 36 trial. In the placebo group, an abnormal QTc interval (≥450 ms in men, ≥470 ms in women) was associated with a two-fold increased risk of SCD (hazard ratio, HR, 2.3, P = 0.005) after adjustment for other risk factors (age ≥75 years, NYHA class III/IV, high TIMI risk score, ventricular tachycardia ≥8 beats, digitalis, and antiarrhythmics). In the ranolazine group, the association between abnormal QTc and SCD was similar to placebo, but not significant (HR 1.8, P = 0.074). There was no significant difference between placebo and ranolazine in the risk for SCD in patients with abnormal QTc (HR 0.78, P = 0.48). When QTc was used as a continuous variable, for every 10 ms increase in QTc, hazard rate for SCD increased significantly by 8% (P = 0.007) in the placebo group, and only by 2.9% (P = 0.412; P for interaction=0.25) in the ranolazine group. CONCLUSION: In NSTEACS patients treated with placebo, prolonged QTc was a significant independent predictor for SCD. Ranolazine, compared with placebo, was not associated with increased risk for SCD in patients with prolonged QTc.

GS-6201, a selective blocker of the A2B adenosine receptor, attenuates cardiac remodeling after acute myocardial infarction in the mouse.

Adenosine (Ado) is released in response to tissue injury, promotes hyperemia, and modulates inflammation. The proinflammatory effects of Ado, which are mediated by the A(2B) Ado receptor (AdoR), may exacerbate tissue damage. We hypothesized that selective blockade of the A(2B) AdoR with 3-ethyl-1-propyl-8-(1-(3-trifluoromethylbenzyl)-1H-pyrazol-4-yl)-3,7-dihydropurine-2,6-dione (GS-6201) during acute myocardial infarction (AMI) would reduce adverse cardiac remodeling. Male ICR mice underwent coronary artery ligation or sham surgery (n = 10-12 per group). The selective A(2B) AdoR antagonist GS-6201 (4 mg/kg) was given intraperitoneally twice daily starting immediately after surgery and continuing for 14 days. Transthoracic echocardiography was performed before surgery and after 7, 14, and 28 days. A subgroup of mice was killed 72 h after surgery, and the activity of caspase-1, a key proinflammatory mediator, was measured in the cardiac tissue. All sham-operated mice were alive at 4 weeks, whereas 50% of vehicle-treated mice and 75% of GS-6201-treated mice were alive at 4 weeks after surgery. Compared with vehicle, treatment with GS-6201 prevented caspase-1 activation in the heart at 72 h after AMI (P < 0.001) and significantly limited the increase in left ventricular (LV) end-diastolic diameter by 40% (P < 0.001), the decrease in LV ejection fraction by 18% (P < 0.01) and the changes in the myocardial performance index by 88% (P < 0.001) at 28 days after AMI. Selective blockade of A(2B) AdoR with GS-6201 reduces caspase-1 activity in the heart and leads to a more favorable cardiac remodeling after AMI in the mouse.

The A2B adenosine receptor modulates pulmonary hypertension associated with interstitial lung disease.

Development of pulmonary hypertension is a common and deadly complication of interstitial lung disease. Little is known regarding the cellular and molecular mechanisms that lead to pulmonary hypertension in patients with interstitial lung disease, and effective treatment options are lacking. The purpose of this study was to examine the adenosine 2B receptor (A(2B)R) as a regulator of vascular remodeling and pulmonary hypertension secondary to pulmonary fibrosis. To accomplish this, cellular and molecular changes in vascular remodeling were monitored in mice exposed to bleomycin in conjunction with genetic removal of the A(2B)R or treatment with the A(2B)R antagonist GS-6201. Results demonstrated that GS-6201 treatment or genetic removal of the A(2B)R attenuated vascular remodeling and hypertension in our model. Furthermore, direct A(2B)R activation on vascular cells promoted interleukin-6 and endothelin-1 release. These studies identify a novel mechanism of disease progression to pulmonary hypertension and support the development of A(2B)R antagonists for the treatment of pulmonary hypertension secondary to interstitial lung disease.

Ranolazine improves cardiac diastolic dysfunction through modulation of myofilament calcium sensitivity.

RATIONALE: Previously, we demonstrated that a deoxycorticosterone acetate (DOCA)-salt hypertensive mouse model produces cardiac oxidative stress and diastolic dysfunction with preserved systolic function. Oxidative stress has been shown to increase late inward sodium current (I(Na)), reducing the net cytosolic Ca(2+) efflux. OBJECTIVE: Oxidative stress in the DOCA-salt model may increase late I(Na), resulting in diastolic dysfunction amenable to treatment with ranolazine. METHODS AND RESULTS: Echocardiography detected evidence of diastolic dysfunction in hypertensive mice that improved after treatment with ranolazine (E/E':sham, 31.9 ± 2.8, sham+ranolazine, 30.2 ± 1.9, DOCA-salt, 41.8 ± 2.6, and DOCA-salt+ranolazine, 31.9 ± 2.6; P=0.018). The end-diastolic pressure-volume relationship slope was elevated in DOCA-salt mice, improving to sham levels with treatment (sham, 0.16 ± 0.01 versus sham+ranolazine, 0.18 ± 0.01 versus DOCA-salt, 0.23 ± 0.2 versus DOCA-salt+ranolazine, 0.17 ± 0.0 1 mm Hg/L; P<0.005). DOCA-salt myocytes demonstrated impaired relaxation, τ, improving with ranolazine (DOCA-salt, 0.18 ± 0.02, DOCA-salt+ranolazine, 0.13 ± 0.01, sham, 0.11 ± 0.01, sham+ranolazine, 0.09 ± 0.02 seconds; P=0.0004). Neither late I(Na) nor the Ca(2+) transients were different from sham myocytes. Detergent extracted fiber bundles from DOCA-salt hearts demonstrated increased myofilament response to Ca(2+) with glutathionylation of myosin binding protein C. Treatment with ranolazine ameliorated the Ca(2+) response and cross-bridge kinetics. CONCLUSIONS: Diastolic dysfunction could be reversed by ranolazine, probably resulting from a direct effect on myofilaments, indicating that cardiac oxidative stress may mediate diastolic dysfunction through altering the contractile apparatus.

Antiadrenergic and hemodynamic effects of ranolazine in conscious dogs.

Effects of ranolazine alone and in the presence of phenylephrine (PE) or isoproterenol (ISO) on hemodynamics, coronary blood flow and heart rate (HR) in the absence and presence of hexamethonium (a ganglionic blocker) were studied in conscious dogs. Ranolazine (0.4, 1.2, 3.6, and 6 mg/kg, intravenous) alone caused transient (<1 minute) and reversible hemodynamic changes. PE (0.3-10 µg/kg) caused a dose-dependent increase in blood pressure and decrease in HR. ISO (0.01-0.3 µg/kg) caused a dose-dependent decrease in blood pressure and an increase in HR. Ranolazine at high (11-13 mM), but not at moderate (4-5 mM) concentrations partially attenuated changes in mean arterial blood pressure and HR caused by either PE or ISO in normal conscious dogs. However, in dogs treated with hexamethonium (20 mg/kg) to cause autonomic blockade, ranolazine (both 4-5 and 11-13 µM) significantly attenuated both the PE- and ISO-induced changes in mean arterial blood pressure. The results suggest that a potential antiadrenergic effect of ranolazine was masked by autonomic control mechanisms in conscious dogs but could be observed when these mechanisms were inhibited (eg, in the hexamethonium-treated dog). Ranolazine, at plasma concentrations <10 µM and in conscious dogs with intact autonomic regulation, had minimal antiadrenergic (α and ß) effects.

Effect of body mass index on the efficacy, side effect profile, and plasma concentration of fixed-dose regadenoson for myocardial perfusion imaging.

BACKGROUND: There are limited data on the effect of body mass index (BMI) on the actions of fixed-dose regadenoson. The purpose of this study was to determine the effect of BMI on the efficacy, side effects, and plasma concentration of regadenoson for Myocardial Perfusion Imaging (MPI). METHODS AND RESULTS: The study included 2,015 subjects from the ADVANCE MPI trials. Initial adenosine MPI was followed by randomization to regadenoson (400-µg bolus injection) or adenosine (6-minute infusion) MPI. Subjects were classified according to BMI into six categories from underweight (<20 kg/m(2)) to extremely obese (≥40 kg/m(2)). PK modeling was used to predict the effect of BMI on plasma regadenoson concentration (PRC). Adenosine-regadenoson agreement rates for the presence and extent of reversibility were similar across BMI categories (P > .05). The incidence of side effects was also similar across BMIs (P ≥ .06). Subjects were less likely to feel very or extremely uncomfortable after regadenoson vs adenosine in all groups with BMI ≥ 25 kg/m(2), but this trend was not statistically significant in subjects with BMI 20-24 kg/m(2) (P > .05). PRC was inversely related to BMI with 19% higher PRC in the underweight and 36% lower PRC in the extremely obese compared with a normal weight subject. CONCLUSIONS: BMI does not alter the efficacy of regadenoson MPI despite lower PRC in high BMI subjects, or its side effect profile despite higher PRC in low BMI subjects. Regadenoson is better tolerated than adenosine but this benefit seems to lose statistical significance in subjects with BMI < 25 kg/m(2).

Alterations in adenosine metabolism and signaling in patients with chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis.

BACKGROUND: Adenosine is generated in response to cellular stress and damage and is elevated in the lungs of patients with chronic lung disease. Adenosine signaling through its cell surface receptors serves as an amplifier of chronic lung disorders, suggesting adenosine-based therapeutics may be beneficial in the treatment of lung diseases such as chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF). Previous studies in mouse models of chronic lung disease demonstrate that the key components of adenosine metabolism and signaling are altered. Changes include an up-regulation of CD73, the major enzyme of adenosine production and down-regulation of adenosine deaminase (ADA), the major enzyme for adenosine metabolism. In addition, adenosine receptors are elevated. METHODOLOGY/PRINCIPAL FINDINGS: The focus of this study was to utilize tissues from patients with COPD or IPF to examine whether changes in purinergic metabolism and signaling occur in human disease. Results demonstrate that the levels of CD73 and A(2B)R are elevated in surgical lung biopsies from severe COPD and IPF patients. Immunolocalization assays revealed abundant expression of CD73 and the A(2B)R in alternatively activated macrophages in both COPD and IPF samples. In addition, mediators that are regulated by the A(2B)R, such as IL-6, IL-8 and osteopontin were elevated in these samples and activation of the A(2B)R on cells isolated from the airways of COPD and IPF patients was shown to directly induce the production of these mediators. CONCLUSIONS/SIGNIFICANCE: These findings suggest that components of adenosine metabolism and signaling are altered in a manner that promotes adenosine production and signaling in the lungs of patients with COPD and IPF, and provide proof of concept information that these disorders may benefit from adenosine-based therapeutics. Furthermore, this study provides the first evidence that A(2B)R signaling can promote the production of inflammatory and fibrotic mediators in patients with these disorders.

Discovery of a novel A2B adenosine receptor antagonist as a clinical candidate for chronic inflammatory airway diseases.

Recently, we have reported a series of new 1,3-symmetrically (R 1 = R 3) substituted xanthines ( 3 and 4) which have high affinity and selectivity for the human adenosine A 2B receptors (hA(2B)-AdoR). Unfortunately, this class of compounds had poor pharmacokinetic properties. This prompted us to investigate the effect of differential alkyl substitution at the N-1 and N-3 positions ( N 1-R not equal to N 3-R) on A(2B)-AdoR affinity and selectivity; we had the dual objectives of enhancing affinity and selectivity for the A(2B)-AdoR, as well as improving oral bioavailability. This effort has led to the discovery of compound 62, that displayed high affinity and selectivity for the hA(2B)-AdoR (K(i) = 22 nM). In addition, compound 62 showed high functional potency in inhibiting the accumulation of cyclic adenosine monophosphate induced by 5'- N-ethylcarboxamidoadenosine in HEK-A(2B)-AdoR and NIH3T3 cells with K(B) values of 6 and 2 nM, respectively. In a single ascending-dose phase I clinical study, compound 62 had no serious adverse events and was well tolerated.

Selective, high affinity A(2B) adenosine receptor antagonists: N-1 monosubstituted 8-(pyrazol-4-yl)xanthines.

A series of N-1 monosubstituted 8-pyrazolyl xanthines have been synthesized and evaluated for their affinity for the adenosine receptors (AdoRs). We have discovered two compounds 18 (CVT-7124) and 28 (CVT-6694) that display good affinity for the A(2B) AdoR (K(i)=6 nM and 7 nM, respectively) and greater selectivity for the human A(1), A(2A), and A(3) AdoRs (>1000-, >830-, and >1500-fold; >850-, >700-, and >1280-fold, respectively). CVT-6694 has been shown to block the release of interleukin-6 and monocyte chemotactic protein-1 from bronchial smooth muscle cells (BSMC), a process believed to be promoted by activation of A(2B) AdoR.