Patent Application
20120046299
This invention relates to a method of treating cardiac arrhythmias, comprising administration of compounds that modulate the activity of specific cardiac ion channels while minimizing undesirable side effects.
The heart is, in essence, a pump that is responsible for circulating blood throughout the body. In a normally functioning heart such circulation is caused by the generation of electrical impulses that, for example, increase or decrease the heart rate and/or the force of contraction in response to the demands of the circulatory system.
The electrical impulses of the heart can be electrically sensed and displayed (the electrocardiogram, EKG), and the electrical waveform of the EKG is characterized by accepted convention as the “PQRST” complex. The PQRST complex includes the P-wave, which corresponds to the atrial depolarization wave; the QRS complex, corresponding to the ventricular depolarization wave; and the T-wave, which represents the re-polarization of the cardiac cells. Thus, the P wave is associated with activity in the heart's upper chambers, and the QRS complex and the T wave both reflect activity in the lower chambers.
If the electrical signal becomes disturbed in some way, the efficient pumping action of the heart may deteriorate, or even stop altogether. Disturbance in the regular rhythmic beating of the heart is one of the most common disorders seen in heart disease. Irregular rhythms (arrhythmia) can be a minor annoyance, or may indicate a serious problem. For example, arrhythmias may indicate an underlying abnormality of the heart muscle, valves or arteries, and includes the situation where the heart is beating too slowly (bradycardia) and also where the heart is beating too rapidly (tachycardia).
Tachycardias come in two general varieties: supraventricular tachycardias and ventricular tachycardias.
Supraventricular tachycardias include paroxysmal supraventricular tachycardia (PSVT), atrial fibrillation, atrial flutter, AV node reentry, and Wolff-Parkinson White syndrome (WPW). Supraventricular tachycardia (SVT)) is a condition in which electrical impulses traveling through the heart are abnormal because of a cardiac problem somewhere above the lower chambers of the heart. SVT can involve heart rates of 140 to 250 beats per minute (normal is about 70 to 80 beats per minute).
The ventricular tachycardias include ventricular tachycardia itself, as well as ventricular fibrillation, and Torsade de Pointes (TdP). Ventricular tachycardia (VT) is a rapid heart rhythm originating within the ventricles. VT tends to disrupt the orderly contraction of the ventricular muscle, so that the ventricle's ability to eject blood is often significantly reduced. That, combined with the excessive heart rate, can reduce the amount of blood actually being pumped by the heart during VT to dangerous levels. Consequently, while patients with VT can sometimes feel relatively well, often they experience—in addition to the ubiquitous palpitations—extreme lightheadedness, loss of consciousness, or even sudden death. As a general rule, VT does not occur in patients without underlying cardiac disease. For people who have underlying cardiac disease, it is generally true that the worse the left ventricular function, the higher the risk of developing life-threatening ventricular tachycardias.
Ventricular tachycardias can arise in myocardial ischemia situations such as unstable angina, chronic angina, variant angina, myocardial infarction, acute coronary syndrome and, additionally in heart failure, both acute and chronic.
There is a condition known as abnormal prolongation of repolarization, or long QT Syndrome (LQTS), which is reflected by a longer than average interval between the Q wave and the T wave as measured by an EKG. Prolongation of the QT interval renders patients vulnerable to a very fast, abnormal heart rhythm (an “arrhythmia”) known as Torsade de Pointes. When an arrhythmia occurs, no blood is pumped out from the heart, and the brain quickly becomes deprived of blood, causing sudden loss of consciousness (syncope) and potentially leading to sudden death.
LQTS is caused by dysfunction of the ion channels of the heart or by drugs. These channels control the flow of potassium ions, sodium ions, and calcium ions, the flow of which in and out of the cells generate the electrical activity of the heart. Patients with LQTS usually have no identifiable underlying structural cardiac disease. LQTS may be inherited, with the propensity to develop a particular variety of ventricular tachycardia under certain circumstances, for example exercise, the administration of certain pharmacological agents, or even during sleep. Alternatively, patients may acquire LQTS, for example by exposure to certain prescription medications.
The acquired faun of LQTS can be caused by pharmacological agents. For example, the incidence of Torsade de Pointes (TdP) in patients treated with quinidine is estimated to range between 2.0 and 8.8%. DL-sotalol has been associated with an incidence ranging from 1.8 to 4.8%. A similar incidence has been described for newer class III anti-arrhythmia agents, such as dofetilide and ibutilide. In fact, an ever-increasing number of non-cardiovascular agents have also been shown to aggravate and/or precipitate TdP. Over 50 commercially available drugs have been reported to cause TdP. This problem appears to arise more frequently with newer drugs and a number have been withdrawn from the market in recent years (e.g. prenylamine, terodiline, and in some countries terfenadine, astemizole and cisapride). Drug-induced TdP has been shown to develop largely as a consequence of an increase in dispersion of repolarization secondary to augmentation of the intrinsic electrical heterogeneities of the ventricular myocardium.
The majority of pharmacological agents that are capable of producing prolonged repolarization and acquired LQTS can be grouped as acting predominantly through one of four different mechanisms (1) a delay of one or both K currents IKs and IKr. Examples are quinidine, N-acetylprocainamide, cesium, sotalol, bretylium, clofilium and other new Class III antiarrhythmic agents (this action could possibly be specifically antagonized by drugs that activate the K channel, such as pinacidil and cromakalin); (2) suppression of Ito, as in the case of 4-aminopyridine, which was shown to prolong repolarization and induce EADs preferentially in canine subepicardial M cells, which are reported to have prominent Ito; (3) an increase in ICa, as in the case of Bay K 8644 (this action could be reversed by Ca channel blockers); (4) a delay of INa inactivation, as in the case of aconitine, veratridine, batrachotoxin, DPI, and the sea anemone toxins (ATX) anthopleurin-A (AP-A) and ATX-II (this action could be antagonized by drugs that block INa, and/or slowly inactivate Na current, such as lidocaine and mexiletine). Because these drugs (e.g., lidocaine and mexiletine) can shorten prolonged repolarization, they can also suppress EADs induced by the first two mechanisms.
The list of drugs causing LQTS and TdP is continually increasing. Literally, any pharmacological agent that can prolongate QT can induce LQTS. The incidence of TdP has not been correlated with the plasma concentrations of drugs known to precipitate this arrhythmia. However, high plasma concentrations, resulting from excessive dose or reduced metabolism of some of these drugs, may increase the risk of precipitating TdP. Such reduced metabolism may result from the concomitant use of other drugs that interfere with cytochrome P450 enzymes. Medications reported to interfere with the metabolism of some drugs associated with TdP include systemic ketoconazole and structurally similar drugs (fluconazole, itraconazole, metronidazole); serotonin re-uptake inhibitors (fluoxetine, fluvoxamine, sertraline), and other antidepressants (nefazodone), human immunodeficiency virus (HIV) protease inhibitors (indinavir, ritonavir, saquinavir); dihydropyridine calcium channel blockers (felodipine, nicardipine, nifedipine) and erythromycin, and other macrolide antibiotics. Grapefruit and grapefruit juice may also interact with some drugs by interfering with cytochrome P450 enzymes. Some of the drugs have been associated with TdP, not so much because they prolong the QT interval, but because they are inhibitors primarily of P4503A4, and thereby increase plasma concentration of other QT prolonging agents. The best example is ketoconazole and itraconazole, which are potent inhibitors of the enzyme and thereby account for TdP during terfenadine, astemizole, or cisapride therapy. On the other hand, the incidence of drug associated TdP has been very low with some drugs: diphyhydramine, fluconazole, quinine, lithium, indapamide, and vasopressin. It should also be noted that TdP may result from the use of drugs causing QT prolongation in patients with medical conditions, such as hepatic dysfunction or congenital LQTS, or in those with electrolyte disturbances (particularly hypokalemia and hypomagnesemia).
However, there are anti-arrhythmic drugs that are known to prolong the QT interval but do not induce TdP. It has been discovered that a property common to such drugs is the ability to concurrently inhibit other ion currents such as INa channels, and/or the ICa channel.
The inherited form of LQTS occurs when a mutation develops in one of several genes that produce or “encode” one of the ion channels that control electrical repolarization. There are at least five different forms of inherited LQTS, characterized as LQT1, LQT2, LQT3, LQT4, and LQTS. They were originally characterized by the differing shape of the EKG trace, and have subsequently been associated with specific gene mutations. The LQT1 form, from KCNQ1 (KVLQT1) or KCNE1 (MinK) gene mutations, is the most frequent, accounting for approximately 55-60% of the genotyped patients. LQT2, from BERG or KCNE2 (MiRP1) mutations, is next at about 35-40%, and LQT3, from SCN5A mutations accounts for about 3-5%. Patients with two mutations seem to account for less than 1% of all patients, but this may change as more patients are studied with the newer genetic techniques.
The mutant gene causes abnormal channels to be formed, and as these channels do not function properly, the electrical recovery of the heart takes longer, which manifests itself as a prolonged QT interval. For example, an inherited deletion of amino-acid residues 1505-1507 (KPQ) in the cardiac Na+ channel, encoded by SCN5A, causes the severe autosomal dominant LQT3 syndrome, associated with fatal ventricular arrhythmias. Fatal arrhythmias occur in 39% of LQT3 patients during sleep or rest, presumably because excess late Na+ current abnormally prolongs repolarization, particularly at low heart rates, and thereby favors development of early afterdepolarizations (EADs) and ectopic beats. Preferential slowing of repolarization in the mid-myocardium might further enhance transmural dispersion of repolarization and cause unidirectional block and reentrant arrhythmias. In another 32% of LQT3 patients, fatal cardiac events are triggered by exercise or emotion.
It was recently reported that a variant of the cardiac sodium channel gene SCN5A was associated with arrhythmia in African-Americans. Single-strand conformation polymorphism (SCCP) and DNA sequence analyses revealed a heterozygous transversion of C to A in codon 1102 of SCN5A causing a substitution of serine (S1102) with tyrosine (Y1102). S1102 is a conserved residue located in the intracellular sequences that link domains II and III of the channel. These researchers found that the Y1102 allele increased arrhythmia susceptibility. The QTc (corrected QT) was found to be markedly prolonged with amiodarone, leading to Torsade de Pointes ventricular tachycardia.
There is a need for an agent to treat or prevent inherited or acquired LQTS in a manner that reduces the risk of arrhythmia and TdP. Ranolazine has previously been demonstrated to be an effective agent for the treatment of angina causing no or minimal effects on heart rate or blood pressure. Now, surprisingly, we have discovered that ranolazine and related compounds are effective agents for the prophylaxis and/or treatment of inherited or acquired arrhythmia.
Surprisingly, we have discovered that compounds that inhibit IKr, IKs, and late INa ion channels exhibit this preferred spectrum of activity. Such compounds prolong the ventricular action potential duration, increase the ventricular effective refractory period, decrease TDR, increase APD, and do not produce EADs. For example, ranolazine, which is known to be useful in the treatment of angina and congestive heart failure, has been found to be useful in the treatment of ventricular tachycardia by virtue of its ability to inhibit IKr, IKs, and late INa ion channels at dose levels that do not block calcium channels. This is particularly surprising, in that U.S. Pat. No. 4,567,264, which is incorporated by reference herein in its entirety, discloses that ranolazine is a cardioselective drug that inhibits calcium ion channels, and suggests that as a consequence of its effect to block calcium channels it might be useful in the treatment of a multitude of disease states including arrhythmia. However, we have discovered that ranolazine acts as an effective anti-arrhythmic agent at levels that have little or no effect on the calcium channel. The lack of or minimal effect on calcium channel activity at therapeutic dose levels is beneficial in that it obviates the well-known effects of calcium ion channel inhibitors (e.g., changes in blood pressure) that are undesirable when treating arrhythmia in a patient. We have also discovered that ranolazine is effective in suppressing EADs and triggered activity that are a side effect of administration of drugs such as quinidine and sotalol.
Accordingly, a novel and effective method of treating VT is provided that restores sinus rhythm while being virtually free of undesirable side effects, such as changes in mean arterial pressure, blood pressure, heart rate, or other adverse effects.
It is an object of this invention to provide an effective method of treating arrhythmia in a mammal. Accordingly, in a first aspect, the invention relates to a method of treating arrhythmia in a mammal comprising administration of a therapeutic amount of a compound of the Formula I:
wherein:
A preferred compound is ranolazine, which is named N-(2,6-dimethylphenyl)-4-[2-hydroxy-3-(2-methoxyphenoxy)propyl]-1-piperazineacetamide {also known as 1-[3-(2-methoxyphenoxy)-2-hydroxypropyl]-4-[(2,6-dimethylphenyl)-aminocarbonylmethyl]-piperazine], as a racemic mixture, or an isomer thereof, or a pharmaceutically acceptable salt thereof. It is preferably administered at dose levels that inhibit Ikr, Iks, and late INa ion channels but does not inhibit calcium channels or other ion channels. Ranolazine, as a racemic mixture or an isomer, may be formulated either as the free base or as a pharmaceutically acceptable salt. If formulated as a pharmaceutically acceptable salt, the dihydrochloride salt is preferred.
In a second aspect, the invention relates to a method of treating arrhythmias, comprising administering an effective amount of ranolazine, or an isomer thereof, or a pharmaceutically acceptable salt of the compound or its isomer, to a mammal in need thereof.
In a third aspect, the invention relates to a method of treating arrhythmia in a mammal comprising administration of ranolazine, or an isomer thereof, or a pharmaceutically acceptable salt of the compound or its isomer, at a dose level that inhibits late INa ion channels. Preferred is a therapeutic amount that inhibits IKr, IKs, and late INa ion channels More preferred is a therapeutic amount that inhibits IKr, IKs, and late INa ion channels but does not inhibit calcium channels.
In one preferred embodiment, the compounds of the invention are administered in a manner that provides plasma level of the compound of Formula I of at least 350±30 ng/mL for at least 12 hours.
In a second preferred embodiment, the compounds of the invention are administered as a sustained release formulation that maintains plasma concentrations of the compound of Formula I at less than a maximum of 4000 ng/mL, preferably between about 350 to about 4000 ng base/mL, for at least 12 hours.
In a third preferred embodiment, the compounds of the invention are administered in a formulation that contains between about 10 mg and 700 mg of a compound of Formula I. A preferred compound of Formula I is ranolazine, or an isomer thereof, or a pharmaceutically acceptable salt of the compound or an isomer thereof.
In a fourth preferred embodiment, the compounds of the invention are administered in a formulation that provides a dose level of about 1 to about 30 micromoles per liter of the formulation. Preferred is the administration of a formulation that provides a dose level of about 1 to about 10 micromoles per liter of the formulation.
In a fourth aspect, the invention relates a method of preventing arrhythmias in a mammal comprising administering an effective amount of ranolazine, or an isomer thereof, or a pharmaceutically acceptable salt of the compound or an isomer thereof, to a mammal in need thereof.
In a fifth aspect, the invention relates a method of treating arrhythmias in a mammal comprising administering an effective amount of ranolazine, or an isomer thereof, or a pharmaceutically acceptable salt of the compound or an isomer thereof, to a mammal in need thereof.
In a sixth aspect, the invention relates to a method of treating acquired arrhythmias (arrhythmias caused by prescription medications or other chemicals) comprising administering a therapeutically effective amount of ranolazine, or an isomer thereof, or a pharmaceutically acceptable salt of the compound or an isomer thereof, to a mammal in need thereof. Preferred is the administration of a formulation to a mammal with arrhythmias acquired by sensitivity to quinidine.
In a seventh aspect, the invention relates to a method of preventing acquired arrhythmias (arrhythmias caused by sensitivity to prescription medications or other chemicals) comprising administering a therapeutically effective amount of ranolazine, or an isomer thereof, or a pharmaceutically acceptable salt of the compound or an isomer thereof, to a mammal in need thereof.
In an eighth aspect, the invention relates to a method of treating inherited arrhythmias (arrhythmias caused by gene mutations) comprising administering an effective amount of ranolazine, or an isomer thereof, or a pharmaceutically acceptable salt of the compound or an isomer thereof, to a mammal in need thereof.
In a ninth aspect, the invention relates to a method of preventing inherited arrhythmias (arrhythmias caused by gene mutations) comprising administering an effective amount of ranolazine, or an isomer thereof, or a pharmaceutically acceptable salt of the compound or an isomer thereof, to a mammal in need thereof.
In a tenth aspect, the invention relates to a method of preventing arrhythmias in a mammal with genetically determined congenital LQTS comprising administering an effective amount or ranolazine, or an isomer thereof, or a pharmaceutically acceptable salt of the compound or an isomer thereof, to a mammal in need thereof.
In an eleventh aspect, the invention relates to a method of treating arrhythmias in a mammal with genetically determined congenital LQTS comprising administering an effective amount or ranolazine, or an isomer thereof, or a pharmaceutically acceptable salt of the compound or an isomer thereof, to a mammal in need thereof.
In a twelfth aspect, the invention relates to a method of preventing Torsade de Pointes comprising administering an effective amount of ranolazine, or an isomer thereof, or a pharmaceutically acceptable salt of the compound or an isomer thereof, to a mammal in need thereof.
In a thirteenth aspect, the invention relates to a method of preventing arrhythmias in mammals afflicted with LQT3 comprising administering an effective amount of ranolazine, or an isomer thereof, or a pharmaceutically acceptable salt of the compound or an isomer thereof, to a mammal in need thereof.
In a fourteenth aspect, the invention relates to a method of treating arrhythmias in mammals afflicted with LQT3 comprising administering an effective amount of ranolazine, or an isomer thereof, or a pharmaceutically acceptable salt of the compound or an isomer thereof, to a mammal in need thereof.
In a fifteenth aspect, the invention relates to a method of preventing arrhythmias in mammals afflicted with LQT1, LQT2, and LQT3 comprising administering an effective amount of ranolazine, or an isomer thereof, or a pharmaceutically acceptable salt of the compound or an isomer thereof, to a mammal in need thereof.
In a sixteenth aspect, the invention relates to a method of treating arrhythmias in mammals afflicted with LQT1, LQT2, and LQT3 comprising administering an effective amount of ranolazine, or an isomer thereof, or a pharmaceutically acceptable salt of the compound or an isomer thereof, to a mammal in need thereof.
In a seventeenth aspect, the invention relates to a method of reducing arrhythmias in mammals afflicted with LQT3 comprising administering an effective amount of ranolazine, or an isomer thereof, or a pharmaceutically acceptable salt of the compound or an isomer thereof, to a mammal in need thereof.
In an eighteenth aspect, the invention relates to a method of reducing arrhythmias in mammals afflicted with LQT1, LQT2, and LQT3 comprising administering an effective amount of ranolazine, or an isomer thereof, or a pharmaceutically acceptable salt of the compound or an isomer thereof, to a mammal in need thereof.
In a nineteenth aspect, the invention relates to a method of preventing arrhythmias comprising screening the appropriate population for SCN5A genetic mutation and administering an effective amount of ranolazine, or an isomer thereof, or a pharmaceutically acceptable salt thereof, to a patient afflicted with this genetic mutation. A preferred appropriate population for SCN5A genetic mutation is that portion of the population that does not have normal functions of the sodium channel.
In a twentieth aspect, this invention relates to a method of treating ventricular tachycardia in a mammal while minimizing undesirable side effects.
In a twenty-first aspect, this invention relates to a method of treating ventricular tachycardia in a mammal that arise as a consequence of drug treatment comprising administration of a therapeutic amount of a compound that inhibits IKr, IKs, and late INa ion channels before, after, or concurrently with the drug that causes TdP as a side effect of administration. Preferred is the administration of a formulation to a mammal with arrhythmias acquired by sensitivity to quinidine or sotalol.
In a twenty-second aspect, this invention relates to a method of treating ventricular tachycardia in a cardiac compromised mammal comprising administration of a therapeutic amount of a compound of Formula I at dose levels that inhibit IKr, IKs, and late INa ion channels but does not inhibit calcium channels.
In a twenty-third aspect, this invention relates to a method of treating arrhythmias or ventricular tachycardia by administration of a compound of Formula I as a bolus in a manner that provides a plasma level of the compound of Formula I of at least 350±30 ng/mL for at least 12 hours.
In a twenty-fourth aspect, this invention relates to a method of treating arrhythmias or ventricular tachycardia by administration of a compound of Formula I as a sustained release formulation in a manner that maintains a plasma level of the compound of Formula I of at a less than a maximum of 4000 ng/ml, preferably between about 350 to about 4000 ng base/mL for at least 12 hours.
In a twenty-fifth aspect, this invention relates to methods of treating arrhythmias wherein a compound of Formula I or an isomer thereof, or a pharmaceutically acceptable salt or ester of the compound or its isomer is administered by bolus or sustained release composition.
In a twenty-sixth aspect, this invention relates to methods of treating arrhythmias wherein a compound of Formula I or an isomer thereof, or a pharmaceutically acceptable salt or ester of the compound or its isomer is administered intravenously.
In a twenty-seventh aspect, this invention relates to use of a compound of Formula I or an isomer thereof, or a pharmaceutically acceptable salt or ester of the compound or its isomer for the treatment of arrhythmias in mammals.
In a twenty-eighth aspect, this invention relates to methods of treating ventricular tachycardias arising in myocardial ischemia situations such as unstable angina, chronic angina, variant angina, myocardial infarction, acute coronary syndrome and, additionally in heart failure, both acute and chronic.
The invention provides a means of treating, reducing, or preventing the incidence of arrhythmias.
Normal heart rhythm (sinus rhythm) results from action potentials (APs), which are generated by the highly integrated electrophysiological behavior of ion channels on multiple cardiac cells. Sodium, calcium and potassium channels are the most important channels for determining the shape and the duration of the cardiac action potential. Briefly, activation of sodium and calcium channels leads to the influx of positively charged ions into individual cardiac cells, causing depolarization of the membrane. Conversely, the opening of potassium channels allows the flow of positive charge out of the cells and, in large part, terminates the action potential and repolarizes the cell (
APs are propagated from their origin in the pacemaker, through the sinoatrial node, through the atrial muscle, then through the atrioventricular node (AV), through the Purkinje conduction system, and finally to the ventricle.
Arrhythmia, a disruption in the normal sequence of impulse initiation and propagation in the heart, may result from primary cardiovascular disease, pulmonary disorders, autonomic disorders, systemic disorders, drug-related side effects, inherited effects (mutations of genes), or electrolyte imbalances.
Normal sinus rhythm and arrhythmias are visualized on electrocardiograms (ECGs). An ECG is a graphic tracing of the variations in electrical potential caused by the excitation of the heart muscle and detected at the body surface. From the electrocardiograms heart rate, PR interval duration, a reflection of AV nodal conduction time, QRS duration, a reflection of conduction time in the ventricle, and QT interval, which is a measure of ventricular action potential duration, can be measured. A representation of the ECG generated during sinus rhythm is shown in
Ventricular tachycardias are caused by enhanced automaticity, afterdepolarizations and triggered automaticity and reentry. Enhanced automaticity occurs in cells that normally display spontaneous diastolic depolarization. B-adrenergic stimulation, hypokalemia, and mechanical stretch of cardiac muscle cells increase phase 4 slope and so accelerate pacemaker rate, whereas acetylcholine reduces pacemaker rate both by decreasing phase 4 slope and by hyperpolarization. When impulses propagate from a region of enhanced normal or abnormal automaticity to excite the rest of the heart arrhythmias result.
Afterdepolarizations and triggered automaticity occur under some pathophysiological conditions in which a normal cardiac action potential is interrupted or followed by an abnormal depolarization. If this abnormal depolarization reaches threshold, it may, in turn, give rise to secondary upstrokes, which then can propagate and create abnormal rhythms. These abnormal secondary upstrokes occur only after an initial normal, or “triggering,” upstroke and so are termed triggered rhythms. Two major forms of triggered rhythms are recognized: (1) delayed afterpolarization (DAD) that may occur under conditions of intracellular calcium overload (myocardial ischemia, adrenergic stress, etc). If this afterdepolarization reaches threshold, a secondary triggered beat or beats may occur and; (2) early afterdepolarizations (EADs) often occur when there is a marked prolongation of the cardiac action potential. When this occurs, phase 3 repolarization may be interrupted by an EAD. EAD-mediated triggering in vitro and clinical arrhythmias are most common when the underlying heart rate is slow, extracellular K+ is low, and certain drugs that prolong action potential duration are present. EADs result from an increase in net inward current during the repolarization phase of the action potential.
TdP is a common and serious side effect of treatment with many different types of drugs; and could be caused by EADs and the resultant triggering. However, there are other conditions that measure the risk of TdP, including hypokalemia, hypomagnesemia, hypocalcemia, high-grade AV block, congenital disorders and severe bradycardia.
Long QT Syndrome (LQTS) is caused by dysfunction of protein structures in the heart cells called ion channels. These channels control the flow of ions like potassium, sodium and calcium molecules. The flow of these ions in and out of the cells produces the electrical activity of the heart. Abnormalities of these channels can be acquired or inherited. The acquired form is usually caused by prescription medications.
The inherited form occurs when a mutation develops in one of several genes that produce or “encode” one of the ion channels that control electrical repolarization. The mutant gene produces abnormal channels to be formed, and as these abnormal channels are not as efficient as the normal channels, the electrical recovery of the heart takes longer. This is manifested on the electrocardiogram (ECG, EKG) by a prolonged QT interval. QT prolongation makes the heart vulnerable to polymorphic VTs, one kind of which is a fast, abnormal heart rhythm known as “Torsade de Pointes”.
The congenital LQTS is caused by mutations of at least one of six genes
The LQT diseases and ion channels listed in the table above are the same for acquired LQTS as they are for inherited LQTS.
It should be noted that if the inherited or acquired form of LQTS is present in a mammal, and symptoms of a VT have appeared, then administration of a compound of Formula I, especially ranolazine, reduces the occurrence and/or frequency of VT. If the inherited or acquired form of LQTS is present, but there are no symptoms of VT, then administration of a compound of Formula I, especially ranolazine, prevents the occurrence of VT.
Sodium pentobarbital is known to prolong QT interval, but also reduces the transmural dispersion of repolarization. It does this by inhibiting LKr, IKs and INa most prominently. Transmural dispersion reduction is shown by a greater prolongation of APD in epi and endo cells than in M cells. Sodium pentobarbital also suppresses d-sotalol-induced EAD activity in M cells. Thus, despite its actions to prolong QT, pentobarbital does not induce TdP.
Amiodarone is known to prolong QT and at low instances induce TdP. It was found that amiodarone reduces transmural dispersion of repolarization by exhibiting a greater prolongation of APD in epi and endo cells than in M cells. Amiodarone blocks the sodium, potassium and calcium channels in the heart. When administered chronically (30-40 mg/kg/day orally for 30-45 days) it also suppresses the ability of the IKr blocker, d-sotalol, to induce a marked dispersion of repolarization or EAD activity.
In arterially-perfused wedge preparations from the canine left ventricle ranolazine was found to preferentially prolong APD90 of epicardial (epc) cells. The reduction in transmural dispersion was found to be more pronounced at higher concentrations because ranolazine also abbreviates the APD90 of the M cells while prolonging that of the epi cells.
Tests also were carried out in isolated myocytes from canine left ventricle to determine if ranolazine induces EADs and whether ranolazine's action on late sodium current and calcium current can antagonize EAD induction by d-sotalol in Purkinje fibers. EADs were not observed in the presence of ranolazine. Ranolazine was found to suppress EADs induced by d-sotalol at concentrations as low as 5 micromolar/L.
It was also found that ranolazine blocks the calcium channel, but does so at a concentration (296 micromolar/L) very much higher than the therapeutic concentration of the drug (˜2 to 8 μM).
Thus, even if ranolazine exhibits a prolonged QT interval, it does not induce EADs or TdP.
Because ranolazine may cause a prolonged QT interval, ranolazine may increase the duration of APD of ventricular myocytes. The QT interval of surface EKG reflects the duration of ventricular repolarization.
It was found that ranolazine decreased the APD of guinea pig myocytes (reversible on washout). Ranolazine also was found to reduce APD in the presence of quinidine. Quinidine is known to trigger EADs and TdP. Ranolazine was found to suppress EADs and other triggered activity induced by quinidine
ATXII (a sea anemone toxin) slows the inactivation of the open state of the sodium channel, triggers EADs, prolongs QT interval, and causes a sharp rise in transmural dispersion of repolarization as a result of greater prolongation of APD in M cells. Data shows that ranolazine causes a decrease in APD in the presence of ATXII. Therefore, ranolazine suppresses EADs induced by ATXII. ATXII is a sodium ion activator that mimics LTQ3 syndrome (which leads to TdP). Thus, ranolazine does not lead to TdP, instead suppresses TdP caused by ATX.
As used in the present specification, the following words and phrases are generally intended to have the meanings as set forth below, except to the extent that the context in which they are used indicates otherwise.
“Aminocarbonylmethyl” refers to a group having the following structure:
where A represents the point of attachment.
“Halo” or “halogen” refers to fluoro, chloro, bromo or iodo.
“Lower acyl” refers to a group having the following structure:
where R is lower alkyl as is defined herein, and A represents the point of attachment, and includes such groups as acetyl, propanoyl, n-butanoyl and the like.
“Lower alkyl” refers to a unbranched saturated hydrocarbon chain of 1-4 carbons, such as methyl, ethyl, n-propyl, and n-butyl.
“Lower alkoxy” refers to a group —OR wherein R is lower alkyl as herein defined.
“Lower alkylthio” refers to a group —SR wherein R is lower alkyl as herein defined.
“Lower alkyl sulfinyl” refers to a group of the formula:
wherein R is lower alkyl as herein defined, and A represents the point of attachment.
“Lower alkyl sulfonyl” refers to a group of the formula:
wherein R is lower alkyl as herein defined, and A represents the point of attachment.
“N-Optionally substituted alkylamido” refers to a group having the following structure:
wherein R is independently hydrogen or lower alkyl and R′ is lower alkyl as defined herein, and A represents the point of attachment.
The term “drug” or “drugs” refers to prescription medications as well as over-the-counter medications and all pharmacological agents.
“Isomers” refers to compounds having the same atomic mass and atomic number but differing in one or more physical or chemical properties. All isomers of the compound of Formula I are within the scope of the invention.
“Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances in which it does not.
The term “therapeutically effective amount” refers to that amount of a compound of Formula I that is sufficient to effect treatment, as defined below, when administered to a mammal in need of such treatment. The therapeutically effective amount will vary depending upon the subject and disease condition being treated, the weight and age of the subject, the severity of the disease condition, the manner of administration and the like, which can readily be determined by one of ordinary skill in the art.
The term “treatment” or “treating” means any treatment of a disease in a mammal, including:
preventing the disease, that is, causing the clinical symptoms of the disease not to develop;
inhibiting the disease, that is, arresting the development of clinical symptoms; and/or
relieving the disease, that is, causing the regression of clinical symptoms.
Arrhythmia refers to any abnormal heart rate. Bradycardia refers to abnormally slow heart rate whereas tachycardia refers to an abnormally rapid heart rate. As used herein, the treatment of arrhythmia is intended to include the treatment of supra ventricular tachycardias such as atrial fibrillation, atrial flutter, AV nodal reentrant tachycardia, atrial tachycardia, and the ventricular tachycardias (VTs), including idiopathic ventricular tachycardia, ventricular fibrillation, pre-excitation syndrome, and Torsade de Pointes (TdP).
Sinus rhythm refers to normal heart rate.
The term “cardiac compromised mammal” means a mammal having cardiopathological disease state, for example angina, congestive heart failure, ischemia and the like.
In many cases, the compounds of this invention are capable of forming acid and/or base salts by virtue of the presence of amino and/or carboxyl groups or groups similar thereto. The teen “pharmaceutically acceptable salt” refers to salts that retain the biological effectiveness and properties of the compounds of Formula I, and which are not biologically or otherwise undesirable. Pharmaceutically acceptable base addition salts can be prepared from inorganic and organic bases. Salts derived from inorganic bases, include by way of example only, sodium, potassium, lithium, ammonium, calcium and magnesium salts. Salts derived from organic bases include, but are not limited to, salts of primary, secondary and tertiary amines, such as alkyl amines, dialkyl amines, trialkyl amines, substituted alkyl amines, di(substituted alkyl) amines, tri(substituted alkyl) amines, alkenyl amines, dialkenyl amines, trialkenyl amines, substituted alkenyl amines, di(substituted alkenyl) amines, tri(substituted alkenyl) amines, cycloalkyl amines, di(cycloalkyl) amines, tri(cycloalkyl) amines, substituted cycloalkyl amines, disubstituted cycloalkyl amine, trisubstituted cycloalkyl amines, cycloalkenyl amines, di(cycloalkenyl) amines, tri(cycloalkenyl) amines, substituted cycloalkenyl amines, disubstituted cycloalkenyl amine, trisubstituted cycloalkenyl amines, aryl amines, diaryl amines, triaryl amines, heteroaryl amines, diheteroaryl amines, triheteroaryl amines, heterocyclic amines, diheterocyclic amines, triheterocyclic amines, mixed di- and tri-amines where at least two of the substituents on the amine are different and are selected from the group consisting of alkyl, substituted alkyl, alkenyl, substituted alkenyl, cycloalkyl, substituted cycloalkyl, cycloalkenyl, substituted cycloalkenyl, aryl, heteroaryl, heterocyclic, and the like. Also included are amines where the two or three substituents, together with the amino nitrogen, form a heterocyclic or heteroaryl group.
Specific examples of suitable amines include, by way of example only, isopropylamine, trimethyl amine, diethyl amine, tri(iso-propyl) amine, tri(n-propyl) amine, ethanolamine, 2-dimethylaminoethanol, tromethamine, lysine, arginine, histidine, caffeine, procaine, hydrabamine, choline, betaine, ethylenediamine, glucosamine, N-alkylglucamines, theobromine, purines, piperazine, piperidine, morpholine, N-ethylpiperidine, and the like.
Pharmaceutically acceptable acid addition salts may be prepared from inorganic and organic acids. Salts derived from inorganic acids include hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid, and the like. Salts derived from organic acids include acetic acid, propionic acid, glycolic acid, pyruvic acid, oxalic acid, malic acid, malonic acid, succinic acid, maleic acid, fumaric acid, tartaric acid, citric acid, benzoic acid, cinnamic acid, mandelic acid, methanesulfonic acid, ethanesulfonic acid, p-toluene-sulfonic acid, salicylic acid, and the like.
As used herein, “pharmaceutically acceptable carrier” includes any and all solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents and the like. The use of such media and agents for pharmaceutically active substances is well known in the art. Except insofar as any conventional media or agent is incompatible with the active ingredient, its use in the therapeutic compositions is contemplated. Supplementary active ingredients can also be incorporated into the compositions.
The compounds of the invention are usually administered in the form of pharmaceutical compositions. This invention therefore provides pharmaceutical compositions that contain, as the active ingredient, one or more of the compounds of the invention, or a pharmaceutically acceptable salt or ester thereof, and one or more pharmaceutically acceptable excipients; carriers, including inert solid diluents and fillers; diluents, including sterile aqueous solution and various organic solvents; permeation enhancers; solubilizers; and adjuvants. The compounds of the invention may be administered alone or in combination with other therapeutic agents. Such compositions are prepared in a manner well known in the pharmaceutical art (see, e.g., Remington's Pharmaceutical Sciences, Mace Publishing Co., Philadelphia, Pa. 17th Ed. (1985) and “Modern Pharmaceutics”, Marcel Dekker, Inc. 3rd Ed. (G. S. Banker & C. T. Rhodes, Eds.).
The compounds of the invention may be administered in either single or multiple doses by any of the accepted modes of administration of agents having similar utilities, for example as described in those patents and patent applications incorporated by reference, including rectal, buccal, intranasal and transdermal routes, by intra-arterial injection, intravenously, intraperitoneally, parenterally, intramuscularly, subcutaneously, orally, topically, as an inhalant, or via an impregnated or coated device such as a stent, for example, or an artery-inserted cylindrical polymer.
One preferred mode for administration is parental, particularly by injection. The forms in which the novel compositions of the present invention may be incorporated for administration by injection include aqueous or oil suspensions, or emulsions, with sesame oil, corn oil, cottonseed oil, or peanut oil, as well as elixirs, mannitol, dextrose, or a sterile aqueous solution, and similar pharmaceutical vehicles. Aqueous solutions in saline are also conventionally used for injection, but less preferred in the context of the present invention. Ethanol, glycerol, propylene glycol, liquid polyethylene glycol, and the like (and suitable mixtures thereof), cyclodextrin derivatives, and vegetable oils may also be employed. The proper fluidity can be maintained, for example, by the use of a coating, such as lecithin, by the maintenance of the required particle size in the case of dispersion and by the use of surfactants. The prevention of the action of microorganisms can be brought about by various antibacterial and antifungal agents, for example, parabens, chlorobutanol, phenol, sorbic acid, thimerosal, and the like.
Sterile injectable solutions are prepared by incorporating the compound of the invention in the required amount in the appropriate solvent with various other ingredients as enumerated above, as required, followed by filtered sterilization. Generally, dispersions are prepared by incorporating the various sterilized active ingredients into a sterile vehicle which contains the basic dispersion medium and the required other ingredients from those enumerated above. In the case of sterile powders for the preparation of sterile injectable solutions, the preferred methods of preparation are vacuum-drying and freeze-drying techniques which yield a powder of the active ingredient plus any additional desired ingredient from a previously sterile-filtered solution thereof.
Oral administration is another route for administration of the compounds of Formula I. Administration may be via capsule or enteric coated tablets, or the like. In making the pharmaceutical compositions that include at least one compound of Formula I, the active ingredient is usually diluted by an excipient and/or enclosed within such a carrier that can be in the form of a capsule, sachet, paper or other container. When the excipient serves as a diluent, it can be a solid, semi-solid, or liquid material (as above), which acts as a vehicle, carrier or medium for the active ingredient. Thus, the compositions can be in the form of tablets, pills, powders, lozenges, sachets, cachets, elixirs, suspensions, emulsions, solutions, syrups, aerosols (as a solid or in a liquid medium), ointments containing, for example, up to 10% by weight of the active compound, soft and hard gelatin capsules, sterile injectable solutions, and sterile packaged powders.
Some examples of suitable excipients include lactose, dextrose, sucrose, sorbitol, mannitol, starches, gum acacia, calcium phosphate, alginates, tragacanth, gelatin, calcium silicate, microcrystalline cellulose, polyvinylpyrrolidone, cellulose, sterile water, syrup, and methyl cellulose. The formulations can additionally include: lubricating agents such as talc, magnesium stearate, and mineral oil; wetting agents; emulsifying and suspending agents; preserving agents such as methyl- and propylhydroxy-benzoates; sweetening agents; and flavoring agents.
The compositions of the invention can be formulated so as to provide quick, sustained, delayed release or any combination of these release means of the active ingredient after administration to the patient by employing procedures known in the art.
Controlled release drug delivery systems for oral administration include osmotic pump systems and diffusion/dissolution systems including polymer-coated reservoirs or drug-polymer matrix formulations. Examples of controlled release systems are given in U.S. Pat. Nos. 3,845,770; 4,326,525; 4,902,514; 5,616,345 and 6,303,607 (equivalent to WO 0013687), all U.S. patents of which are incorporated in their entireties herein by reference. Another formulation for use in the methods of the present invention employs transdermal delivery devices (“patches”). Such transdermal patches may be used to provide continuous or discontinuous infusion of the compounds of the present invention in controlled amounts. The construction and use of transdermal patches for the delivery of pharmaceutical agents is well known in the art. See, e.g., U.S. Pat. Nos. 5,023,252, 4,992,445 and 5,001,139, all of which are incorporated herein in their entireties by reference. Such patches may be constructed for continuous, pulsatile, or on demand delivery of pharmaceutical agents.
The compositions are preferably formulated in a unit dosage form. The term “unit dosage forms” refers to physically discrete units suitable as unitary dosages for human subjects and other mammals, each unit containing a predetermined quantity of active material calculated to produce the desired therapeutic effect, in association with a suitable pharmaceutical excipient (e.g., a tablet, capsule, ampoule). The compounds of Formula I are effective over a wide dosage range and is generally administered in a pharmaceutically effective amount. Preferably, for oral administration, each dosage unit contains from 10 mg to 2 g of a compound of Formula I, more preferably from 10 to 700 mg, and for parenteral administration, preferably from 10 to 700 mg of a compound of Formula I, more preferably about 50 to about 200 mg. It will be understood, however, that the amount of the compound of Formula I actually administered will be determined by a physician, in the light of the relevant circumstances, including the condition to be treated, the chosen route of administration, the actual compound administered and its relative activity, the age, weight, and response of the individual patient, the severity of the patient's symptoms, and the like.
For preparing solid compositions such as tablets, the principal active ingredient is mixed with a pharmaceutical excipient to form a solid pre-formulation composition containing a homogeneous mixture of a compound of the present invention. When referring to these pre-formulation compositions as homogeneous, it is meant that the active ingredient is dispersed evenly throughout the composition so that the composition may be readily subdivided into equally effective unit dosage forms such as tablets, pills and capsules.
The tablets or pills of the present invention may be coated or otherwise compounded to provide a dosage form affording the advantage of prolonged action, or to protect from the acid conditions of the stomach. For example, the tablet or pill can comprise an inner dosage and an outer dosage component, the latter being in the form of an envelope over the former. The two components can be separated by an enteric layer that serves to resist disintegration in the stomach and permit the inner component to pass intact into the duodenum or to be delayed in release. A variety of materials can be used for such enteric layers or coatings, such materials including a number of polymeric acids and mixtures of polymeric acids with such materials as shellac, cetyl alcohol, and cellulose acetate.
In one embodiment, the preferred compositions of the invention are formulated so as to provide quick, sustained or delayed release of the active ingredient after administration to the patient, especially sustained release formulations. The most preferred compound of the invention is ranolazine, which is named (±)-N-(2,6-dimethylphenyl)-4-[2-hydroxy-3-(2 methoxyphenoxy)propyl]-1-piperazine-acetamide. Unless otherwise stated, the ranolazine plasma concentrations used in the specification and examples refers to ranolazine free base.
Compositions for inhalation or insufflation include solutions and suspensions in pharmaceutically acceptable, aqueous or organic solvents, or mixtures thereof, and powders. The liquid or solid compositions may contain suitable pharmaceutically acceptable excipients as described supra. Preferably the compositions are administered by the oral or nasal respiratory route for local or systemic effect. Compositions in preferably pharmaceutically acceptable solvents may be nebulized by use of inert gases. Nebulized solutions may be inhaled directly from the nebulizing device or the nebulizing device may be attached to a face mask tent, or intermittent positive pressure breathing machine. Solution, suspension, or powder compositions may be administered, preferably orally or nasally, from devices that deliver the formulation in an appropriate manner.
The intravenous formulation of ranolazine is manufactured via an aseptic fill process as follows. In a suitable vessel, the required amount of Dextrose Monohydrate is dissolved in Water for Injection (WFI) at approximately 78% of the final batch weight. With continuous stirring, the required amount of ranolazine free base is added to the dextrose solution. To facilitate the dissolution of ranolazine, the solution pH is adjusted to a target of 3.88-3.92 with 0.1N or 1N Hydrochloric Acid solution. Additionally, 0.1N HCl or 1.0N NaOH may be utilized to make the final adjustment of solution to the target pH of 3.88-3.92. After ranolazine is dissolved, the batch is adjusted to the final weight with WFI. Upon confirmation that the in-process specifications have been met, the ranolazine bulk solution is sterilized by sterile filtration through two 0.2 μm sterile filters. Subsequently, the sterile ranolazine bulk solution is aseptically filled into sterile glass vials and aseptically stoppered with sterile stoppers. The stoppered vials are then sealed with clean flip-top aluminum seals.
Compounds of the invention may be impregnated into a stent by diffusion, for example, or coated onto the stent such as in a gel form, for example, using procedures known to one of skill in the art in light of the present disclosure.
The intravenous formulation of ranolazine is manufactured via an aseptic fill process as follows. In a suitable vessel, the required amount of Dextrose Monohydrate is dissolved in Water for Injection (WFI) at approximately 78% of the final batch weight. With continuous stirring, the required amount of ranolazine free base is added to the dextrose solution. To facilitate the dissolution of ranolazine, the solution pH is adjusted to a target of 3.88-3.92 with 0.1N or 1N Hydrochloric Acid solution. Additionally, 0.1N HCl or 1.0N NaOH may be utilized to make the final adjustment of solution to the target pH of 3.88-3.92. After ranolazine is dissolved, the batch is adjusted to the final weight with WFI. Upon confirmation that the in-process specifications have been met, the ranolazine bulk solution is sterilized by sterile filtration through two 0.2 μm sterile filters. Subsequently, the sterile ranolazine bulk solution is aseptically filled into sterile glass vials and aseptically stoppered with sterile stoppers. The stoppered vials are then sealed with clean flip-top aluminum seals.
The preferred sustained release formulations of this invention are preferably in the form of a compressed tablet comprising an intimate mixture of compound and a partially neutralized pH-dependent binder that controls the rate of dissolution in aqueous media across the range of pH in the stomach (typically approximately 2) and in the intestine (typically approximately about 5.5).
To provide for a sustained release of compound, one or more pH-dependent binders may be chosen to control the dissolution profile of the compound so that the formulation releases the drug slowly and continuously as the formulation passed through the stomach and gastrointestinal tract. The dissolution control capacity of the pH-dependent binder(s) is particularly important in a sustained release formulation because a sustained release formulation that contains sufficient compound for twice daily administration may cause untoward side effects if the compound is released too rapidly (“dose-dumping”).
Accordingly, the pH-dependent binders suitable for use in this invention are those which inhibit rapid release of drug from a tablet during its residence in the stomach (where the pH is-below about 4.5), and which promotes the release of a therapeutic amount of compound from the dosage form in the lower gastrointestinal tract (where the pH is generally greater than about 4.5). Many materials known in the pharmaceutical art as “enteric” binders and coating agents have the desired pH dissolution properties. These include phthalic acid derivatives such as the phthalic acid derivatives of vinyl polymers and copolymers, hydroxyalkylcelluloses, alkylcelluloses, cellulose acetates, hydroxyalkylcellulose acetates, cellulose ethers, alkylcellulose acetates, and the partial esters thereof, and polymers and copolymers of lower alkyl acrylic acids and lower alkyl acrylates, and the partial esters thereof.
Preferred pH-dependent binder materials that can be used in conjunction with the compound to create a sustained release formulation are methacrylic acid copolymers. Methacrylic acid copolymers are copolymers of methacrylic acid with neutral acrylate or methacrylate esters such as ethyl acrylate or methyl methacrylate. A most preferred copolymer is methacrylic acid copolymer, Type C, USP (which is a copolymer of methacrylic acid and ethyl acrylate having between 46.0% and 50.6% methacrylic acid units). Such a copolymer is commercially available, from Röhm Pharma as Eudragit® L 100-55 (as a powder) or L30D-55 (as a 30% dispersion in water). Other pH-dependent binder materials which may be used alone or in combination in a sustained release formulation dosage form include hydroxypropyl cellulose phthalate, hydroxypropyl methylcellulose phthalate, cellulose acetate phthalate, polyvinylacetate phthalate, polyvinylpyrrolidone phthalate, and the like. One or more pH-dependent binders are present in the dosage forms of this invention in an amount ranging from about 1 to about 20 wt %, more preferably from about 5 to about 12 wt % and most preferably about 10 wt %.
One or more pH-independent binders may be in used in sustained release formulations in oral dosage forms. It is to be noted that pH-dependent binders and viscosity enhancing agents such as hydroxypropyl methylcellulose, hydroxypropyl cellulose, methylcellulose, polyvinylpyrrolidone, neutral poly(meth)acrylate esters, and the like, do not themselves provide the required dissolution control provided by the identified pH-dependent binders. The pH-independent binders are present in the formulation of this invention in an amount ranging from about I to about 10 wt %, and preferably in amount ranging from about 1 to about 3 wt % and most preferably about 2.0 wt %.
As shown in Table 1, the preferred compound of the invention, ranolazine, is relatively insoluble in aqueous solutions having a pH above about 6.5, while the solubility begins to increase dramatically below about pH 6. In the following examples solutions of ranolazine in water or solutions with a pH above 6 are made up of ranolazine dihydrochloride. In the discussion portions of the following examples, concentrations of ranolazine found as a result of experiments are calculated as ranolazine free base.
Increasing the pH-dependent binder content in the formulation decreases the release rate of the sustained release form of the compound from the formulation at pH is below 4.5 typical of the pH found in the stomach. The enteric coating formed by the binder is less soluble and increases the relative release rate above pH 4.5, where the solubility of compound is lower. A proper selection of the pH-dependent binder allows for a quicker release rate of the compound from the formulation above pH 4.5, while greatly affecting the release rate at low pH. Partial neutralization of the binder facilitates the conversion of the binder into a latex like film which forms around the individual granules. Accordingly, the type and the quantity of the pH-dependent binder and amount of the partial neutralization composition are chosen to closely control the rate of dissolution of compound from the formulation.
The dosage forms of this invention should have a quantity of pH-dependent binders sufficient to produce a sustained release formulation from which the release rate of the compound is controlled such that at low pHs (below about 4.5) the rate of dissolution is significantly slowed. In the case of methacrylic acid copolymer, type C, USP (Eudragit® L 100-55), a suitable quantity of pH-dependent binder is between 5% and 15%. The pH dependent binder will typically have from about 1 to about 20% of the binder methacrylic acid carboxyl groups neutralized. However, it is preferred that the degree of neutralization ranges from about 3 to 6%. The sustained release formulation may also contain pharmaceutical excipients intimately admixed with the compound and the pH-dependent binder. Pharmaceutically acceptable excipients may include, for example, pH-independent binders or film-forming agents such as hydroxypropyl methylcellulose, hydroxypropyl cellulose, methylcellulose, polyvinylpyrrolidone, neutral poly(meth)acrylate esters (e.g. the methyl methacrylate/ethyl acrylate copolymers sold under the trademark Eudragit® NE by Röhm Pharma, starch,gelatin, sugars carboxymethylcellulose, and the like. Other useful pharmaceutical excipients include diluents such as lactose, mannitol, dry starch, microcrystalline cellulose and the like; surface active agents such as polyoxyethylene sorbitan esters, sorbitan esters and the like; and coloring agents and flavoring agents. Lubricants (such as tale and magnesium stearate) and other tableting aids are also optionally present.
The sustained release formulations of this invention preferably have a compound content of about 50% by weight to about 95% or more by weight, more preferably between about 70% to about 90% by weight and most preferably from about 70 to about 80% by weight; a pH-dependent binder content of between 5% and 40%, preferably between 5% and 25%, and more preferably between 5% and 15%; with the remainder of the dosage form comprising pH-independent binders, fillers, and other optional excipients. Some preferred sustained release formulations of this invention are shown below in Table 2.
The sustained release formulations of this invention are prepared as follows: compound and pH-dependent binder and any optional excipients are intimately mixed(dry-blended). The dry-blended mixture is then granulated in the presence of an aqueous solution of a strong base that is sprayed into the blended powder. The granulate is dried, screened, mixed with optional lubricants (such as talc or magnesium stearate),
and compressed into tablets. Preferred aqueous solutions of strong bases are solutions of alkali metal hydroxides, such as sodium or potassium hydroxide, preferably sodium hydroxide, in water (optionally containing up to 25% of water-miscible solvents such as lower alcohols).
The resulting tablets may be coated with an optional film-forming agent, for identification, taste-masking purposes and to improve ease of swallowing. The film forming agent will typically be present in an amount ranging from between 2% and 4% of the tablet weight. Suitable film-forming agents are well known to the art and include hydroxypropyl. methylcellulose, cationic methacrylate copolymers (dimethylaminoethyl methacrylate/methyl-butyl methacrylate copolymers—Eudragit® E—Röhm. Pharma), and the like. These film-forming agents may optionally contain colorants, plasticizers, and other supplemental ingredients.
The compressed tablets preferably have a hardness sufficient to withstand 8 Kp compression. The tablet size will depend primarily upon the amount of compound in the tablet. The tablets will include from 300 to 1100 mg of compound free base. Preferably, the tablets will include amounts of compound free base ranging from 400-600 mg, 650-850 mg, and 900-1100 mg.
In order to influence the dissolution rate, the time during which the compound containing powder is wet mixed is controlled. Preferably the total powder mix time, i.e. the time during which the powder is exposed to sodium hydroxide solution, will range from 1 to 10 minutes and preferably from 2 to 5 minutes. Following granulation, the particles are removed from the granulator and placed in a fluid bed dryer for drying at about 60° C.
It has been found that these methods produce sustained release formulations that provide lower peak plasma levels and yet effective plasma concentrations of compound for up to 12 hours and more after administration, when the compound used as its free base, rather than as the more pharmaceutically common dihydrochloride salt or as another salt or ester. The use of free base affords at least one advantage: The proportion of compound in the tablet can be increased, since the molecular weight of the free base is only 85% that of the dihydrochloride. In this manner, delivery of an effective amount of compound is achieved while limiting the physical size of the dosage unit.
The method is effective in the treatment of conditions that respond to concurrent inhibition of IKr, IKs, and late INa channels. Such conditions include VT, as exemplified by idiopathic ventricular tachycardia, ventricular fibrillation, pre-excitation syndrome, and Torsade de Pointes.
Activity testing is conducted as described in the Examples below, and by methods apparent to one skilled in the art.
The Examples that follow serve to illustrate this invention. The Examples are intended to in no way limit the scope of this invention, but are provided to show how to make and use the compounds of this invention. In the Examples, all temperatures are in degrees Centigrade.
The following examples illustrate the preparation of representative pharmaceutical formulations containing a compound of Formula I.
Hard gelatin capsules containing the following ingredients are prepared:
The above ingredients are mixed and filled into hard gelatin capsules.
A tablet formula is prepared using the ingredients below:
The components are blended and compressed to form tablets.
A dry powder inhaler formulation is prepared containing the following components:
The active ingredient is mixed with the lactose and the mixture is added to a dry powder inhaling appliance.
Tablets, each containing 30 mg of active ingredient, are prepared as follows:
The active ingredient, starch and cellulose are passed through a No. 20 mesh U.S. sieve and mixed thoroughly. The solution of polyvinylpyrrolidone is mixed with the resultant powders, which are then passed through a 16 mesh U.S. sieve. The granules so produced are dried at 50° C. to 60° C. and passed through a 16 mesh U.S. sieve. The sodium carboxymethyl starch, magnesium stearate, and talc, previously passed through a No. 30 mesh U.S. sieve, are then added to the granules which, after mixing, are compressed on a tablet machine to yield tablets each weighing 120 mg.
Suppositories, each containing 25 mg of active ingredient are made as follows:
The active ingredient is passed through a No. 60 mesh U.S. sieve and suspended in the saturated fatty acid glycerides previously melted using the minimum heat necessary. The mixture is then poured into a suppository mold of nominal 2.0 g capacity and allowed to cool.
Suspensions, each containing 50 mg of active ingredient per 5.0 mL dose are made as follows:
The active ingredient, sucrose and xanthan gum are blended, passed through a No. 10 mesh U.S. sieve, and then mixed with a previously made solution of the microcrystalline cellulose and sodium carboxymethyl cellulose in water. The sodium benzoate, flavor, and color are diluted with some of the water and added with stirring. Sufficient water is then added to produce the required volume.
A subcutaneous formulation may be prepared as follows:
An injectable preparation is prepared having the following composition:
A topical preparation is prepared having the following composition:
All of the above ingredients, except water, are combined and heated to 60) C with stirring. A sufficient quantity of water at 60) C is then added with vigorous stirring to emulsify the ingredients, and water then added q.s. 100 g.
The following examples demonstrate the utility of the compounds of the invention.
I. Electrophysiologic Effects of Ranolazine in Isolated Myocytes, Tissues and Arterially-Perfused Wedge Preparations from the Canine Left Ventricle
Dogs weighing 20-25 kg were anticoagulated with heparin (180 IU/kg) and anesthetized with pentobarbital (30-35 mg/kg, i.v.). The chest was opened via a left thoracotomy, the heart excised and placed in a cold cardioplegic solution ([K+]0=8 mmol/L, 4° C.). All protocols were in conformance with guidelines established by the Institutional Animal Care and Use Committee.
Myocytes were isolated by enzymatic dissociation from a wedge-shaped section of the left ventricular free wall supplied by the left circumflex coronary artery. Cells from the epicardial and midmyocardial regions of the left ventricle were used in this study.
Tyrode's solution used in the dissociation contained (in mM): 135 NaCl, 5.4 KCl, 1 MgCl2, 0 or 0.5 CaCl2, 10 glucose, 0.33 NaH2PO4, 10 N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid (HEPES), and the pH was adjusted to 7.4 with NaOH.
Inward rectifier potassium current (IK1), slow delayed rectifier potassium current (IKs), and rapid delayed rectifier potassium current (IKr) were recorded at 37° C. using conventional whole cell voltage clamp configuration. The composition of the external and pipette solutions used to isolate specific ionic currents is summarized in Table 3.
IK1 was measured using an external solution containing 3 μM ouabain and 5 μM nifedipine to block the sodium-potassium pump and L-type calcium current (ICa,L), respectively. IKs was measured in the presence of 5 μM E-4031 and 5 μM nifedipine to block IKr and ICa. 5 μM nifedipine was present in the external solution when IKr was being recorded.
Isolated myocytes were placed in a temperature controlled 0.5 ml chamber (Medical Systems, Greenvale, N.Y.) on the stage of an inverted microscope and superfused at a rate of 2 ml/min. An eight-barrel quartz micromanifold (ALA Scientific Instruments Inc., Westbury, N.Y.) placed 100 μm from the cell was used to apply ranolazine at concentrations of (in μM): 0.1, 0.5, 1.0, 5.0, 10 and 100.0. An Axopatch ID amplifier (Axon Instruments, Foster City, Calif.) was operated in voltage clamp mode to record currents. Whole cell currents were filtered with a 3-pole low-pass Bessel filter at 5 kHz, digitized between 2-5 kHz (Digidata 1200 A, Axon Instruments) and stored on a computer. Clampex 7 acquisition and analysis software (Axon Instruments) was used to record and analyze ionic currents. Pipette tip resistance was 1.0-2.0 MΩ and seal resistance was greater than 5 GΩ. Electronic compensation of series resistance averaged 76%. Voltages reported in the text were corrected for patch electrode tip potentials. The seal between cell membrane and patch pipette was initially formed in external solution containing 1 mM CaCl2. A 3 M KCl-agar bridge was used between the Ag/AgCl ground electrode and external solution to avoid development of a ground potential when switching to experimental solution.
IKs was elicited by depolarization to 40 mV for 3 sec from a holding potential of −50 mV followed by a repolarization step to 0 mV (4.5 sec). The time-dependent tail current elicited by the repolarization was termed IKs. This protocol was repeated 5 times every 20 sec. Ito was not blocked, but it had little influence on our measurement of IKs because of its fast and complete inactivation. All measurements were obtained 5-12 min after patch rupture since no significant run-down of IKs is observed during this interval.
IKr was measured as the time-dependent tail current elicited at a potential of −40 mV following a short 250 ms depolarizing pulse to 30 mV. Data are presented as mean±S.E.M. IK1 was recorded during 900 msec voltage steps applied from a holding potential of −40 mV to test potentials ranging from −100 mV to 0 mV, and was characterized as the 5 msec average of the steady state current at the end of the test pulse.
Epicardial and midmyocardial (M) cell preparations (strips approximately 1×0.5×0.15 cm) were isolated from the left ventricle. The tissue slices were placed in a tissue bath (5 ml volume with flow rate of 12 ml/min) and allowed to equilibrate for at least 4 hours while superfused with an oxygenated Tyrode's solution (pH=7.35, t0=37±0.5° C.) and paced at a basic cycle length (BCL) of 2 Hz using field stimulation. The composition of the Tyrode's solution was (in mM): NaCl 129, KCl 4, NaH2PO4 0.9, NaHCO3 20, CaCl2 1.8, MgSO4 0.5, and D-glucose 5.5.
Action potential recordings: Transmembrane potentials were recorded using standard glass microelectrodes filled with 2.7 M KCl (10 to 20 MΩ DC resistance) connected to a high input-impedance amplification system (World Precision Instruments, Sarasota, Fla., USA). Amplified signals were displayed on Tektronix (Beaverton, Oreg., USA) oscilloscopes and amplified (model 1903-4 programmable amplifiers [Cambridge Electronic Designs (C.E.D.), Cambridge, England]), digitized (model 1401 AD/DA system [C.E.D.]), analyzed (Spike 2 acquisition and analysis module [C.E.D.], and stored on magnetic media.
Study protocols: Action potentials were recorded from epicardial and M cell preparations. Control recordings were obtained after a 4-6 hour equilibrium period. The effects of ranolazine were determined at concentrations of 1, 5, 10, 50, and 100 μM, with recordings started 30 minutes after the addition of each concentration of the drug. Rate-dependence of ranolazine's actions were determined by recording transmembrane action potentials at basic pacing cycle lengths (BCL) of 300, 500, 800, 1000, 2000, 5000 msec. Data recorded at BCLs of 500 and 2000 msec are presented.
The following action potential parameters were measured:
Vmax was recorded under control conditions and in the presence of 10 and 100 μM of ranolazine. Vmax was measured at a BCL of 500 msec.
Because low extracellular K+ is known to promote drug-induced APD prolongation and early afterdepolarization, two separate sets of experiments were performed, one at normal [K+]o (4 mM) and the other with low [K+]o (2 mM).
Transmural left ventricular wedges with dimensions of approximately 12 mm×35 mm×12 mm were dissected from the mid-to-basal anterior region of the left ventricular wall and a diagonal branch of the left anterior descending coronary artery was cannulated to deliver the perfusate (Tyrode's solution). The composition of the Tyrode's solution was (in mM): NaCl 129, KCl4, NaH7PO4 0.9, NaHCO3 20, CaCl2 1.8, MgSO4 0.5, and D-glucose 5.5; pH=7.4. A separate set of experiments were performed using Tyrode's solution containing 2 mM KCl.
Transmembrane action potentials were recorded from epicardial (EPI) and Subendocardial regions (M) using floating microelectrodes. A transmural pseudo-electrocardiogram (ECG) was recorded using two K-Agar electrodes (1.1 mm, i.d.) placed at approx. 1 cm. from the epicardial (+) and endocardial (−) surfaces of the preparation and along the same axis as the transmembrane recordings. Ventricular wedges were allowed to equilibrate in the chamber for 2 hrs while paced at basic cycle lengths of 2000 msec using silver bipolar electrodes contacting the endocardial surface. A constant flow rate was set before ischemic to reach a perfusion pressure of 40-50 mmHg. The temperature was maintained at 37±0.5° C. by heating the perfusate and a contiguous water-chamber that surrounded the tissue-chamber with the same heater/circulating bath. The top-uncovered part of the tissue-chamber was covered in each experiment to ˜75% of its surface with plastic sheets to further prevent heat loss; the remainder 25% was kept uncovered to position and maneuver the ECG electrodes and the floating microelectrodes. The preparations were fully immersed in the extracellular solution throughout the course of the experiment.
The QT interval was defined as the time interval between the initial deflection of the QRS complex and the point at which a tangent drawn to the steepest portion of the terminal part of the T wave crossed the isoelectric line.
Experimental Series 1: To determine the changes in repolarization time (action potential duration at 50 and 90% repolarization [APD50 and APD90, respectively] and QT interval [ECG]) as well as the vulnerability of the tissues to arrhythmogenesis after perfusing the preparations with ranolazine at concentrations ranging from 1 to 100 μM. [K+]o=4 mM.
Transmembrane action potentials were recorded from epicardial (Epi), subendocardial regions (M region) using glass floating microelectrodes. A transmural ECG was recorded concurrently.
a. Steady-state stimulation: Basic cycle length (BCL) was varied from 300 to 2000 msec to examine the rate-dependent changes in repolarization time (APD and ECG) at the following concentrations of ranolazine: 1, 5, 10, 50 and 100 μM.
b. Programmed electrical stimulation (PES): Premature stimulation was applied to the epicardial surface before and after each concentration of drug in an attempt to induce arrhythmias. Single pulses (S2) were delivered once after every fifth or tenth basic beat (S1) at cycle lengths of 2000 msec. The S1-S2 coupling interval was progressively reduced until refractoriness was encountered (S2 stimuli were of 2-3 msec duration with an intensity equal to 3-5 times the diastolic threshold).
Experimental Series 2: To determine the changes in repolarization time (action potential duration at 50 and 90% repolarization [APD50 and APD90, respectively] and QT interval [ECG]) as well as the vulnerability of the preparation to arrhythmogenesis after perfusing the preparations with ranolazine at concentrations ranging from 1 to 100 μM. [K+]o=2 mM.
a. Steady-state stimulation: Performed at basic cycle lengths (BCL) of 500 and 2000.
b. Programmed electrical stimulation (PES): See above.
Drugs: Ranolazine dihydrochloride was diluted in 100% distilled water as a stock solution of 50 mM. The drug was prepared fresh for each experiment.
Statistics: Statistical analysis was performed using one way repeated measures analysis of variance (ANOVA) followed by Bonferroni's test.
Ranolazine inhibited IKr and IKs in a concentration-dependent manner, but did not alter IK1. IKr was measured as the time-dependent tail current at −40 mV, after a 250 msec activating pulse to 30 mV.
IKs was elicited by a 3 sec step to +40 mV and measured as the peak time-dependent tail current recorded after stepping back to 0 mV. Shown in
The inward rectifier, IK1, was recorded using perforated-patch voltage clamp techniques.
Ranolazine produced a concentration-dependent abbreviation of both APD50 and APD90 in M cell preparations at a [K+]o=4 mM and BCL=2000 msec (
At a BCL of 500 msec, ranolazine caused a concentration-dependent prolongation of APD in epicardial tissues and abbreviation in M cell preparations. At a concentration of 100 μM, epicardial APD exceeded that of the M cell. As a result, transmural dispersion of repolarization was reduced or eliminated. At the highest concentration of ranolazine (100 μM), the transmural repolarization gradient reversed. It is noteworthy that ranolazine induced a use-dependent prolongation of APD90 in epicardial preparations, i.e., prolongation was greater at faster rates (
To assess ranolazine actions on INa, the rate of rise of the upstroke of the action potential (Vmax) was measured. Ranolazine caused a reduction of Vmax. This effect was modest (n.s.) at 10 μM, but more substantial with 100 μM ranolazine (
At concentrations of up to 50 μM, ranolazine produced little to no effect on amplitude, overshoot, and resting membrane potential in M cell preparations (Table 4).
At the highest dose tested (100 μM), ranolazine caused a decrease in phase 0 amplitude. Overshoot of the action potential as well as a resting membrane potential were reduced, although these did not reach statistical significance.
In epicardial preparations, ranolazine produced little to no change in resting membrane potential, overshoot and phase 0 amplitude (Table 5).
In the presence of low [K+]o and slow rates (BCL=2000 msec), ranolazine caused no significant change in APD90 of the M cell, but a concentration-dependent abbreviation of APD50 (
At a BCL of 500 msec, ranolazine caused little change in repolarization of the M cell, but a prominent concentration-dependent prolongation of APD90 in epicardium (
Action Potential Studies in Arterially-Perfused Canine Left Ventricular Wedge Preparations
Each panel in
In the presence of 4 mM KCl, ranolazine did not significantly alter APD90, but significantly reduced APD50 at high concentrations of the drug (50 and 100 μM). In contrast, in the presence of 2 mM KCl, ranolazine significantly prolonged APD90 at concentrations of 5-100 μM, but did not significantly alter APD50 at any concentration (Table 6).
Ranolazine prolonged APD90 of epicardium more than that of M cells at [K+]o of 4 mM. As a consequence, transmural dispersion of repolarization was reduced, although this did not reach significance. At a [K+]o of 2 mM, ranolazine prolonged APD90 of M cells more than those of epicardium, resulting in an increase in transmural dispersion of repolarization, which also failed to reach significance (Table 7).
Table 8 highlights the fact that Torsade de Pointes arrhythmias are not observed to develop spontaneously, nor could they be induced by programmed electrical stimulation under any of the protocols involving the canine left ventricular wedge preparation. No arrhythmias were observed under control conditions or following any concentration of ranolazine.
Neither early nor delayed afterdepolarizations were observed in either tissue or wedge preparations pretreated with any concentration of ranolazine. Indeed, ranolazine proved to be effective in suppressing EADs induced by exposure of M cell preparations to other IKr blockers such as d-sotalol, as illustrated in
1. Voltage Clamp Studies in Isolated Canine Ventricular Myocytes
Adult male mongrel dogs were given 180 IU/kg heparin (sodium salt) and anesthetized with 35 mg/kg i.v. pentobarbital sodium, and their hearts were quickly removed and placed in Tyrode's solution. Single myocytes were obtained by enzymatic dissociation from a wedge-shaped section of the ventricular free wall supplied by the left circumflex coronary artery. Cells from the epicardial and midmyocardial regions of the left ventricle were used. All procedures were in accordance with guidelines established by the Institutional Animal Care and Use Committee.
Tyrode's solution used in the dissociation contained (mM): 135 NaCl, 5.4 KCl, 1 MgCl2, 0 or 0.5 CaCl2, 10 glucose, 0.33 NaH2PO4, 10 N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid (HEPES), and pH was adjusted to 7.4 with NaOH.
L-type calcium current (ICa), transient outward current (Ito), and sodium-calcium exchange current (INa—Ca) were recorded at 37° C. using standard patch electrodes. The composition of the external and pipette solutions is shown in Tables 9 and 10, respectively. Late INa was recorded using perforated patch techniques.
Dissociated cells were placed in a temperature controlled 0.5 ml chamber (Medical Systems, Greenvale, N.Y.) on the stage of an inverted microscope and superfused at 2 ml/min. A ten-barrel quartz micro-manifold (ALA Scientific Instruments Inc., Westbury, N.Y.) placed 100 μm from the cell was used to apply ranolazine, tetrodotoxin (TTX), or cadmium. An Axopatch 200 A amplifier (Axon Instruments, Foster City, Calif.) was operated in voltage clamp mode to record currents at 37° C. Whole cell currents were filtered with a 4-pole low-pass Bessel filter at 5 kHz, digitized between 2-5 KHz (Digidata 1200 A, Axon Instruments) and stored on a computer. pClamp 8.2 software (Axon Instruments) was used to record and analyze ionic currents. Pipette tip resistance was 1.0-1.5 MΩ and seal resistance was greater than 5 GΩ. Electronic compensation of series resistance averaged 76%. Voltages reported were corrected for patch electrode tip potentials. The seal between cell membrane and patch pipette was initially formed in Tyrode's solution containing 1 mM CaCl2. A 3 M KCl-agar bridge was used between the Ag/AgCl ground electrode and external solution to avoid development of a ground potential when switching to experimental solution.
Tetrodotoxin (FIX) was prepared in water and diluted 1:100 for a final concentration of 10 μM in external solution. Ranolazine was prepared in water at a concentration of 50 mM and diluted in external solution to final concentrations ranging from 1-800 μM.
ICa was defined as peak inward current minus the current at the end of the test pulse. External solution contained 10 μM TTX to block the steady state component of late INa. Cells were rested for 20 seconds at −90 mV before evoking an 800 ms ramp to −60 mV and a 15 ms step to −50 mV to inactivate sodium channels and maintain voltage control, immediately followed by a 500 ms step to 0 mV to record ICa in control solutions. This protocol was repeated 5 times at a rate of 0.5 Hz for each of the drug concentrations. The steady state effects of the Ranolazine were measured as the fractional change in ICa during the 5th pulse of the train. Changes in ICa were plotted against drug concentration on a semi-log scale and fitted to a logistic equation.
Late INa was defined as the average TTX-sensitive current measured in the final 5 ms of the test pulse to −30 mV. The transient loss of voltage control that occurred at the beginning of the 500 ms pulse did not affect currents measured at the end of the pulse3. A train of 500 ms pulses repeated at a rate of 1 Hz was used to determine steady state block. Reduction of late INa during the 10th pulse was plotted as a function of drug concentration on a semi-log scale and fitted to a logistic equation.
Ito was recorded in the presence of 300 μM CdCl2 to block ICa, and was defined as the peak outward current minus the steady state current at the end of the test pulse. Holding potential was −80 mV and a 5 ms pulse to −50 mV was taken before evoking 100 ms pulses to −10, 0, and 10 mV, which were repeated at a rate of 0.1 Hz. The effects of ranolazine were evaluated 4 min after addition of each drug concentration. Results were not plotted as a logistic function as ranolazine had a minimal effect on Ito. Instead, all results are presented as means±standard error. A two-tailed Student's t-test was used to determine differences among means.
To trigger INa—Ca by means of the normal calcium transient, a 3-ms pulse to −50 mV was followed by a 5 ms step to 0 mV to activate ICa and a calcium transient. This two step protocol was immediately followed by a pulse to −80 mV to record INa—Ca. INa—Ca was quantified as total charge transported (pA×ms). Voltage clamp protocols were preceded by a train of ten pulses to 20 mV delivered at a rate of 0.5 Hz followed by a rest of 6 sec to maintain calcium loading of the SR. Reduction of INa—Ca was plotted as a function of drug concentration on a semi-log scale and fitted to a logistic equation.
The effect of Ranolazine on Ito was determined at test potentials of −10, 0, and 10 mV. Ito was quite resistant to inhibition by ranolazine.
Ranolazine at a concentration of 50 μM reduced Ito by 10±2% at 10 mV (6 cells, p<0.001). The effects of ranolazine at −10 and 0 mV did not reach significance. Ranolazine at a concentration of 100 μM reduced Ito by 16±3% and 17±4% at test potentials of 0 and 10 mV, respectively (7 cells, p<0.001). Ranolazine had no effect at concentrations of 10 μM (9 cells) and 20 μM (9 cells) at any of the test voltages. Results presented in
The top panel of
Dogs weighing 20-25 kg were anticoagulated with heparin and anesthetized with pentobarbital (30-35 mg/kg, i.v.). The chest was opened via a left thoracotomy, the heart excised and placed in a cold cardioplegic solution ([K+]0=8 mmol/L, 4° C.). Free running Purkinje fibers were isolated from the left and right ventricles. The preparations were placed in a tissue bath (5 ml volume with flow rate of 12 ml/min) and allowed to equilibrate for at least 30 min while superfused with an oxygenated Tyrode's solution (pH=7.35, t0=37±0.5° C.) and paced at a basic cycle length (BCL) of 1 Hz using point stimulation. The composition of the Tyrode's solution was as following (in mM): NaCl 129, KCl 4, NaH2PO4 0.9, NaHCO3 20, CaCl2 1.8, MgSO4 0.5, and D-glucose 5.5. Action potential recordings: Transmembrane potentials were recorded using standard glass microelectrodes filled with 2.7 M KCl (10 to 20 MΩ DC resistance) connected to a high input-impedance amplification system (World Precision Instruments, Sarasota, Fla., USA). Amplified signals were displayed on Tektronix (Beaverton, Oreg., USA) oscilloscopes and amplified (model 19034 programmable amplifiers [Cambridge Electronic Designs (C.E.D.), Cambridge, England]), digitized (model 1401 AD/DA system [C.E.D.]), analyzed (Spike 2 acquisition and analysis module [C.E.D.], and stored on magnetic media (personal computer).
Control recordings were obtained after a 30 min equilibration period. Increasing concentrations of ranolazine (1, 5, 10, 50, and 100 μM) were evaluated, with recordings started 20 minutes after the addition of each concentration of the drug. The rate-dependence of ranolazine's actions were evaluated by recording action potentials at basic cycle lengths (BCL) of 300, 500, 800, 1000, 2000, and 5000 msec. In this report only BCLs of 500 and 2000 msec are presented as representative of relatively rapid and slow pacing rates.
The following action potential parameters were measured:
Because low extracellular K+ is known to promote drug-induced APD prolongation and early afterdepolarizations, we determined the effects of ranolazine in the presence of normal (4 mM) and low (3 mM) [K+]o.
In the final phase, we evaluate the effects of ranolazine on EADs induced by d-sotalol (100 μM), a fairly specific IKr blocker.
Ranolazine dihydrochloride was diluted in distilled water to make a stock solution of 50 mM. The drug was freshly prepared for each experiment.
Statistics. Statistical analysis was performed using one way repeated measures analysis of variance (ANOVA) followed by Bonferroni's test.
Ranolazine (1-100 μM) produced concentration- and rate-dependent effects on repolarization in Purkinje fibers (
To assess the effect of ranolazine on INa, we determined the effect of the drug on the rate of rise of the upstroke of the action potential (Vmax). Ranolazine caused a significant reduction of Vmax at concentrations of 50 and 100 μM (
Ranolazine, in concentrations of 1-50 μM, produced little to no effect on the amplitude, overshoot, or resting membrane potential (Table 11).
At the highest concentration tested (100 μM), ranolazine caused a statistically significant reduction of phase 0 amplitude and overshoot, consistent with the effect of the drug to reduce Vmax and INa.
Lowering extracellular K+ did not modify the effects of ranolazine substantially. The most obvious differences include the tendency of the drug to prolong APD90 at moderate concentrations and the induction of a smaller abbreviation of APD by highest concentration of the drug at a BCL of 2000 msec (
Concentrations greater than 5-10 μM significantly abbreviated APD50. As with the higher level of [K+]o, the amplitude of phase 0 and overshoot of the action potential were significantly reduced by high concentrations of ranolazine (50 and 100 μM). EADs were never observed.
Ranolazine Suppression of d-Sotalol-Induced EADs
The specific IKr blocker d-sotalol (100 μM) induced EAD activity in 4 out of 6 Purkinje fiber preparations. Ranolazine, in a concentration as low as 5 μM, promptly abolished the d-sotalol-induced EADs in 4 out of 4 Purkinje fibers (
IV. Effects of Ranolazine on QT Prolongation and Arrhythmia Induction in Anesthetized Dog: Comparison with Sotalol
Dogs were pretreated with Atravet (0.07 mg/kg sc) and then 15 minutes later anesthetized with ketamine (5.3 mg/kg iv) and valium (0.25 mg/kg iv) followed by isoflurane (1-2%), intubated and subjected to mechanical ventilation. They were then subjected to AV block with radiofrequency ablation. A median sternotomy was performed and catheters were inserted into a femoral artery for blood pressure (BP) recording and into both femoral veins for infusion of test drugs. Bipolar electrodes were inserted into both ventricles for programmed stimulation determination of refractory periods (extrastimulus technique), as well as for evaluation of QT interval and QRS duration at various controlled basic cycle lengths (BCLs). TdP was induced by challenges of phenylephrine, which were given as bolus intravenous doses of 10, 20, 30, 40 and 50 μg/kg. After each dose, the ECG was monitored continuously to detect arrhythmias. The BP always rose after phenylephrine, and sufficient time (at least 10 minutes) was allowed for BP to normalize before giving the next dose of phenylephrine. Test drug effects were evaluated as per protocols below.
Data are presented as the mean±S.E.M. Statistical comparisons were made with Student's t test. A 2-tailed probability<0.05 was taken to indicate statistical significance. In data tables, *denotes P<0.05, **P<0.01.
The test drug was infused as: Group 1 (5 dogs): Sotalol was administered iv at a loading dose of 8 mg/kg and a maintenance dose of 4 mg/kg/hr. Group 2 (6 dogs): Five dogs received ranolazine as a 0.5 mg/kg iv load followed by a first, a second and a third continuous iv infusion of 1.0, 3.0 and 15 mg/kg/hr, respectively. One dog received ranolazine as a 1.5 mg/kg iv load followed by infusions of 15 and 30 mg/kg/hr. Twenty minutes after starting the maintenance infusion (for sotalol) or 30 minutes after starting each iv infusion rate (for ranolazine) electrophysiological measurements (right and left ventricular ERP, QT and QRS) were obtained at BCLs of 300, 400, 600 and 1000 ms. The phenylephrine challenges were then given, with all doses given at each drug infusion rate, and any arrhythmias monitor.
Table 13 summarizes the proarrhythmic effects (bigeminy, trigeminy, torsades de pointes and torsades de pointes degenerating to ventricular fibrillation) of sotalol in the model.
Two of five dogs had proarrhythmia without phenylephrine challenge, and all 5 had proarrhythmia upon phenylephrine challenge. All the dogs eventually died from torsade de pointes degenerating to ventricular fibrillation induced by the combination of sotalol infusion and a phenylephrine bolus. Sotalol increased right ventricular (RV) and left ventricular (LV) effective refractory period in a reverse use-dependent fashion (Table 14 and
Results are available for the 5 dogs receiving the standard ranolazine infusion protocol. The high-dose dog died of pump failure during the 30 mg/kg/hr infusion, with no ventricular arrhythmias and electrophysiological study of this dog could not be performed. Table 16 summarizes arrhythmia occurrence in the presence of ranolazine, alone and in combination with phenylephrine boluses (10-50 μg/kg) according to an identical protocol as for sotalol above. We were unable to induce any torsades de pointes and/or ventricular fibrillation during ranolazine infusion with or without phenylephrine boluses.
Ranolazine slightly increased ERP (mean increases not larger than about 10%), with no reverse use-dependence (Table 17A and B and
Adult male mongrel dogs were given 180 IU/kg heparin (sodium salt) and anesthetized with 35 mg/kg i.v. pentobarbital sodium, and their hearts were quickly removed and placed in Tyrode's solution. Single myocytes were obtained by enzymatic dissociation from a wedge-shaped section of the ventricular free wall supplied by the left circumflex coronary artery. Cells from the midmyocardial region of the left ventricle were used. All procedures were in accordance with guidelines established by the Institutional Animal Care and Use Committee.
Tyrode's solution used in the dissociation contained (mMO: 135 NaCl, 5.4 KCl, 1 MgCl2, 0 or 0.5 CaCl2, 10 glucose, 0.33 NaH2PO4, 10 N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid (HEPES) and pH was adjusted to 7.4 with NaOH. The compositions of the external and internal solutions used are summarized in Table 19.
Late INa was recorded at 37° C. using standard patch electrodes. Dissociated cells were placed in a temperature controlled 0.5 ml chamber (Medical Systems, Greenvale, N.Y.) on the stage of an inverted microscope and superfused at 2 ml/min. A four-barrel quartz micro-manifold (ALA Scientific Instruments Inc., Westbury, N.Y.) placed 100 μm from the cell was used to apply ranolazine and tetrodotoxin (TTX). An inline heater (Harvard/Warner, Holliston, Mass.) was used to maintain temperatures of solutions within the quartz manifold. An Axopatch 700 A amplifier (Axon Instruments, Foster City Calif.) was operated in voltage clamp mode to record currents at 37° C. Whole cell currents were filtered with a 4-pole low-pass Bessel filter at 5 kHz, digitized between 2-5 kHz (Digidata 1200 A, Axon Instruments) and stored on a computer. pClamp 8.2 software (Axon Instruments) was used to record and analyze ionic currents. Pipette tip resistance was 1.0-1.5 MΩ and seal resistance was greater than 5 GΩ. Electronic compensation of series resistance averaged 76%. Voltages reported were corrected for patch electrode tip potentials. The seal between cell membrane and patch pipette was initially formed in Tyrode's solution containing 1 mM CaCl2. A 3 M KCl-agar bridge was used between the Ag/AgCl ground electrode and external solution to avoid development of a ground potential when switching to experimental solution.
Tetrodotoxin (TTX) was prepared in water and diluted 1:100 for a final concentration of 10 μM in external solution. Ranolazine dihydrochloride was prepared in water at a concentration of 5 mM and diluted in external solution to final concentrations ranging from 1-50 μM.
INa,late was recorded during a train of 30 pulses at repetition rates of 300 and 2000 ms. Currents during the last 5 pulses of the trains were averaged to reduce noise, and late INa was defined as the TTX-sensitive current. Protocols were repeated in drug-free solution, 2 to 4 minutes after adding ranolazine, and immediately after 10 μM TTX was added to completely block INa, late.
Action potentials, rather than square pulses were used to voltage clamp INa, late. At a BCL of 300 ms, measurements were made midway through the plateau at a voltage of 13 mV and during phase 3 repolarization at a voltage of −28 mV. At a BCL of 2000 ms, measurements were made at similar positions at voltages of 20 mV and −28 mV. Reduction of late INa was plotted as a function of drug concentration on a semi-log scale and fitted to a logistic equation.
Single ventricular myocytes were isolated from the hearts of adult, male guinea pigs (Harlan). In brief, the hearts were perfused with warm (35° C.) and oxygenated solutions in the following order: 1) Tyrode solution containing (in mmol/L) 140 NaCl, 4.6 KCl, 1.8 CaCl2, 1.1 MgSO4, 10 glucose and 5 HEPES, pH 7.4, for 5 minutes; 2) Ca2+-free solution containing (in mmol/L) 100 NaCl, 30 KCl, 2 MgSO4, 10 glucose, 5 HEPES, 20 taurine, and 5 pyruvate, pH 7.4, for 5 minutes; and 3) Ca2+-free solution containing sollagenase (120 units/ml) and albumin (2 mg/ml), for 20 minutes. At the end of the perfusion, the ventricles were removed, minced, and gently shaken for 10 minutes in solution #3. Isolated cells were harvested from the cell suspension.
Myocytes were placed into a recording chamber and superfused with Tyrode solution at 35° C. Drugs were applied via the superfusate. Action potentials were measured using glass microelectrodes filled with a solution containing (in mmol/L) 120 K-aspartate, 20 KCl, 1 MgCl2, 4 Na2ATP, 0.1 Na3GTP, 10 glucose, 1 EGTA and 10 HEPES (pH 7.2). Microelectrode resistance was 1-3 MΩ. An Axopatch-200 amplifier, a DigiData-1200 A interface and pCLAMP6 software were used to perform electrophysiological measurements. Action potentials were induced by 5-ms depolarizing pulses applied at various frequencies as indicated. The duration of action potential was measured at 50% (APD50) and 90% (APD90) repolarization. Measurements were made when the response to a drug had reached a stable maximum.
1) Ventricular myocytes were electrically stimulated at a frequency of 0.5, 1 or 2 Hz. Each myocyte was treated with 3, 10 and 30 μmol/L ranolazine. The effect of ranolazine on action potential duration at each pacing frequency was determined from 4 myocytes.
2) Action potentials were elicited at a frequency of 0.25 Hz, and the effect of ranolazine (10 μmol/L) on action potential duration was examined in the presence of 5 μmol/L quinidine. Experiments were performed on 4 myocytes.
Data are expressed as mean±SEM. The paired Student's t-test was used for statistical analysis of paired data, and the one-way repeated measures ANOVA followed by Student-Newman-Keuls test was applied for multiple comparisons. A p value<0.05 was considered statistically significant.
In the absence of drug, the APD50 and APD90 measured at stimulation frequencies of 0.5 (n=4), 1 (n=4) and 2 (n=4) Hz were 250±20, 221±18, and 208±9 ms, and 284±22, 251±20 and 245±9 ms, respectively. Thus, increasing the pacing frequency resulted in a rate-dependent shortening of the action potential duration. Irrespective of the pacing frequency, ranolazine caused a moderate and concentration-dependent shortening of both the APD50 and APD90.
Quinidine, in addition to prolonging the action potential duration, is known to induce early afterdepolarizations (EADs), triggered activity and torsade de pointes. As shown in
Following the procedures and protocols of Example 21, guinea pig ventricular myocytes were electrically stimulated in the presence of ranolazine either alone or in the presence of ATX II [a sea anemone toxin known to mimic LQT3 syndrome by slowing Na+-channel inactivation from the open state and thereby increasing the peak and late Na+ current (INa) of cardiomyocytes]. ATXII is known to induce early afterdepolarizations (EADs) and triggered activity and ventricular tachycardia.
ATXII (10-40 nmol/L) was found to markedly increase the duration of action potentials measured at 50% repolarization (APD50) from 273±9 ms to 1,154±61 ms (n=20, p<0.001) as shown in
To study the effect of ranolazine on ATXII induced MAP (monophasic action potential) duration prolongation, EADs and ventricular tachyarrhythmia (VT), the K—H buffer perfused guinea pig isolated heart model was used.
ATXII (10-20 nM) was found to prolong MAPD90 by 6% in 4 hearts without rapid ventricular arrhythmia. ATXII markedly induced EADs and polymorphic VT in 10/14 guinea pig isolated hearts. Ranolazine at 5, 10 and 30 μM significantly suppressed EADs and VT, especially sustained VT, in the presence of ATXII. The protective effect of ranolazine was reversible upon washout of ranolazine. These results are shown in
To determine whether ranolazine suppressed ATX-II induced 1) EADs and triggered activity (TA), and 2) ventricular tachycardia (VT) guinea pig ventricular myocytes and isolated hearts, respectively, were used.
Action potentials were recorded using the whole-cell patch-electrode technique. Ventricular monophasic action potentials and electrograms were recorded from isolated hearts. ATX-II (10-20 nmol/L) increased the APD measured at 50% reporlarization (APD50) from 271±7 ms to 1,148±49 ms (n=24, p<0.001), and induced EADs in all cells. Multiple EADs and sustained depolarizations were frequently observed. Ranolazine at concentrations 1 μmol/L abolished ATX-II induced EADs and TA. Prolongation of the APD50 caused by ATX-II was significantly (p<0.001) reduced by ranolazine at concentrations of 0.1, 0.3, 1, 3, 10 and 30 μmol/L by 29±1% (n=5), 47±1% (n=5), 63±3% (n=11), 79±1% (n=10), 86±2% (n=12) and 99±1% (n=8), respectively. Ranolazine (10 μmol/L) also suppressed EADs and TA induced by 2.5 μmol/L quinidine (n=2). ATX-II (10-20 nmol/L) caused EADs and VT in 10 of 14 isolated hearts; ATX-II induced EADs were significantly reduced and VTs were terminated by 5-30 μmol/L ranolazine.
To determine whether an increase by ATX-II (which mimics SCN5A mutation) of the INa(L) facilitates the effects of E-4031 and 293B (potassium channel blockers of the rapid and slow components of the delayed rectifier (IK) to prolong the APD and to induce EADs, and whether ranolazine reverses the effects of ATX-II and the K+ blockers, guinea pig ventricular myocytes and isolated hearts were used.
The ventricular APD of guinea pigs isolated myocytes and hearts was measured, respectively, at 50% (APD50) and 90% (MAPD90) repolarization. ATX-II at a low concentration (3 nmol/L) only slightly increased the APD50 by 6±2%. However, when applied with either E-4031 or 293B, ATX-II greatly potentiated the effects of these K+ blockers to prolong the APD. In the absence and presence of ATX-II, the APD50 was increased by 11±2% and 104±41% by E-4031 (1 μmol/L), and 40±7% and 202±59% by 293B (30 μmol/L), respectively. Moreover, E-4031 and 293B induced EADs in the presence, but not in the absence, of ATX-II. Ranolazine (10 μmol/L) completely abolished the EADs and significantly reversed the prolongation of the APD50 by about 70% in the presence of ATX-II plus either E-4031 or 293B. ATX-II (7 nmol/L), E-4031 (1 μmol/L) and 293B (1 μmol/L) alone increased the MAPD90 by 32±0.1%, 30.1±0.1% and 6.3±0.2%, respectively. When applied with ATX-II, E-4031 and 293B increased the MAPD90 by 127.1±0.4% and 31.6±0.1%, respectively. Ranolazine (10 μmol/L) significantly decreased the MAPS90 by 24.5±0.1% in the presence of ATX-II plus E-4031 and by 8.3±0.1% in the presence of ATX-II plus 293B.
One form of the hereditary long QT-syndrome, LQT3-ΔKPQ, is associated with sustained inward sodium current during membrane depolarization. This study was undertaken to determine if ranolazine would have favorable electro-mechanical effects in patients with this genetic disorder.
Subjects were drawn from the U.S. portion of the international LQTS Registry. Eligibility criteria for enrollment in the study were genotype confirmed LQT3-ΔKPQ mutation with QTc>0.47 sec, males or females age 18-55 years of age, and signed informed consent to participate in this study. Patients already taking beta-blocking medication were continued on the drug. Patients with an implanted pacemaker or defibrillator or those with prior cervical-thoracic sympathetic ganglionectomy were not excluded. Exclusion criteria included significant comorbility that would preclude the patient's safe participation in this study, pregnancy or women of child-bearing age not receiving appropriate contraceptive therapy with any other sodium-channel blocker, use of medications that inhibit CYP-3A4 hepatic enzymes, (including diltiazem or verapamil) and psycho-social problems that could compromise compliance with the protocol. Thirteen patients with the LQT3-ΔKPQ mutation from two unrelated families met the eligibility criteria without exclusion, and of eight contacted patients five agreed to participate in the study.
Each patient had clinical and laboratory assessment including ultrasound evaluation on Day-2. Baseline studies off drug began at 8:00 am on Day-1: 12-lead ECG recorded at 8:00 am and every 0.5 hour for 8 hours and then at 2, 4, and 16 hours thereafter; a continuous 12-lead Holter was recorded for 24 hours. The 8-hour infusion of intravenous ranolazine was started at 8:00 am on Day 1 with time-matched ECG recordings at the same times as on Day-1. The second echocardiogram was obtained just before completion of the 8-hour of ranolazine infusion on Day 1. Blood samples for plasma ranolazine concentrations were drawn at hourly intervals during the ranolazine infusion, and at 2, 4, and 16 hours following completion of ranolazine infusion on Day 1.
Five patients with LQT3-ΔKPQ mutation were prospectively investigated during 8-hour intravenous infusions of ranolazine with electrocardiographic and echocardiographic evaluation before and during ranolazine administration. Ranolazine was infused at a rate of 40 mg/hr for 3 hours, with doubling of the infusion rate during the subsequent 5 hours while obtaining hourly ranolazine blood levels.
Changes in electrocardiographic parameters from before to during ranolazine infusion were evaluated by time-matched, paired t-test analyses, with repeated measures analysis of variance (ANOVA) where appropriate. The primary pre-specified electrocardiographic QTc analysis utilized a mixed-effects linear model of the change from time-matched baseline in QTc during ranolazine infusion with a fixed effect for time and a random effect for subject. A linear regression equation relating ranolazine blood level to QTc was developed using an analysis of covariance with effects for ranolazine level, subject and the interaction of subject with ranolazine level. The echocardiographic analyses involved evaluation of baseline parameters relative to normal standards for the laboratory as well as statistical comparisons of change in specific quantitative parameters between baseline and the peak ranolazine infusion. Two-sided p-values<0.05 were considered significant.
12-lead ECGs and 24-hour 12-lead Holter ECGs were obtained to evaluate ventricular repolarization before, during, and after ranolazine infusion. The QT interval and the Fridericia corrected QT interval for heart rate (QTc) were measured according to standard criteria. QT was measured from the beginning of QRS complex to the end of T wave determined by an intersection of T wave and isoelectric line or to the nadir between T and U waves. U waves were not incorporated in the measurement of QT interval. Measurement of T-wave patterns included QT peak (ms), T-wave duration (ms), T peak-T end (ms), and T-wave amplitude (mv). The ECG parameters were measured on 3 consecutive beats in lead II, with lead aVF or V5 used if lead II was technically unsatisfactory. Digital 24-hour Holter recordings with 1000 Hz sampling rate were obtained on the day before and day of ranolazine infusion. Holter repolarization parameters similar to those recorded on the 12-lead ECG were measured, and the recordings were scrutinized for atrial or ventricular arrhythmias. All electrocardiographic analyses were interpreted in a blinded manner regarding subject and sequence of before versus ranolazine infusion.
Echocardiographic tissue Doppler recordings were obtained on two occasions, before ranolazine infusion and just before completion of the 8-hour ranolazine infusion. Images were digitized and stored to optical disk for analysis offline. Cardiac ultrasound analyses were made in a blinded manner regarding sequence of baseline versus ranolazine infusion. Echocardiographic and tissue Doppler measurements included left ventricular (LV) end-diastolic and end-systolic volumes, LV ejection fraction, LV stroke volume, LV dyssynchrony score, LV isovolumic relaxation time, mitral E wave and A wave velocity, mitral E/A ratio, mitral E wave deceleration time, and mitral peak annular velocity.
Over the entire 8-hour ranolazine infusion, the mean reduction in QTc from baseline was 26±3 ms (p<0.0001), i.e., from 558±55 ms at baseline to 532±46 ms during ranolazine. Evaluation of the QTc response by dosing time revealed QTc in a concentration-dependent manner with an average slope of QTc vs. ranolazine plasma concentration of −24 ms per 1000 ng/ml (p=0.008). At peak ranolazine infusion, there was significant 15% shortening in left ventricular isovolumic relaxation time, a significant 27% increase in mitral E-wave velocity, and a meaningful 18% decrease in mitral E-wave deceleration time compared to baseline. No adverse effects of ranolazine were observed in the study patients.
Ranolazine at the therapeutic concentrations improved measures of the electrical and mechanical phenotype (shortens the QTc interval and improved myocardial relaxation, respectively) of patients with the LQT3-ΔKPQ mutation that is known to cause an increase of late INa.
This application is a continuation-in-part of U.S. patent application Ser. No. 10/406,894, filed Apr. 3, 2003, which claims priority to U.S. Provisional Patent Application Ser. No. 60/370,150, filed Apr. 4, 2002, U.S. Provisional Patent Application Ser. No. 60/408,292, filed Sep. 5, 2002, and U.S. Provisional Patent Application Ser. No. 60/422,589, filed Oct. 30, 2002, the complete disclosures of which are hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60370150 | Apr 2002 | US | |
| 60408292 | Sep 2002 | US | |
| 60422589 | Oct 2002 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11932291 | Oct 2007 | US |
| Child | 13190300 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10406894 | Apr 2003 | US |
| Child | 11932291 | US |
