Abstract:
The invention relates to perhexiline, or a pharmaceutically acceptable salt thereof, for use in the treatment of hypertrophic cardiomyopathy, as well as to a method of treating HCM, which comprises administering to an animal in need thereof an effective amount of perhexiline, or a pharmaceutically acceptable salt thereof, to treat said HCM. The invention further relates to a treatment programme for treating HCM, which involves the co-use or co-administration of perhexiline with one or more other compounds that are advantageous in treating HCM or the symptoms thereof.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the National Stage of International Application No. PCT/GB2010/050770, filed May 11, 2010, which claims the benefit of GB 0908193.6, filed May 13, 2009, the entire contents of which are incorporated by reference herein. 
     FIELD OF THE INVENTION 
     The invention relates to treatment of hypertrophic cardiomyopathy (HCM) in animal subjects, in particular humans. 
     BACKGROUND OF THE INVENTION 
     Hypertrophic cardiomyopathy, characterised by unexplained cardiac hypertrophy, is the commonest inherited cardiac condition (prevalence ˜0.2%). The clinical manifestations of HCM can range from the complete absence of symptoms to dyspnoea, chest pains, palpitations, and syncope; HCM&#39;s first presentation may even be as sudden cardiac death. Left ventricular outflow tract obstruction that accounts for some of these symptoms in a proportion of HCM patients, may be amenable to drug therapies and to interventions such as surgical septal myectomy or alcohol septal ablation. However, less progress has been made, in the treatment of the substantial number of patients with HCM without obstruction, in whom dyspnoea appears to be primarily due to diastolic dysfunction. Evidence supporting the benefit of the negative chrono-inotropes (eg, beta-blockers, verapamil, disopyramide), which are extensively used by these patients, is limited mandating a better understanding of the mechanisms underlying HCM with the intention of identifying novel therapies. 
     HCM is a disease of the perturbed sarcomere, with &gt;400 mutations having been identified in genes encoding cardiac contractile proteins (e.g. β-myosin heavy chain, cardiac myosin-binding protein-C, α-tropomyosin, cardiac troponin T and I). HCM-causing mutations increase sarcomeric Ca 2+  sensitivity, ATPase activity and the energetic “tension cost” of myocyte contraction. These biophysical considerations have led to the proposal that the pathophysiology of HCM is attributable, at least in part, to excessive sarcomeric energy use. Supporting this proposal, myocardial energy defects have been associated with HCM, in both animal and human disease. Indeed, consistent with a functional role for this energy deficiency, LV relaxation (an energy requiring process), has been observed to be aberrant in HCM. 
     Perhexiline (2-(2,2-dicyclohexylethyl) piperidine) is a known anti-anginal agent that operates principally by virtue of its ability to shift metabolism in the heart from free fatty acid metabolism to glucose, which is more energy efficient. 
     WO-A-2005/087233 discloses the use of perhexiline for the treatment of chronic heart failure (CHF) where the CHF is a result of an initial inciting influence of ischaemia or where the CHF is a result of an initial non-ischaemic inciting influence. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the present invention, there is provided a method of treating hypertrophic cardiomyopathy (HCM), which comprises administering to an animal in need thereof an effective amount of perhexiline, or a pharmaceutically acceptable salt thereof, to treat said HCM. The animal is preferably a mammal and most preferably a human. 
     The HCM treated may be obstructive HCM or non-obstructive HCM. 
     According to another aspect of the present invention, perhexiline, or a pharmaceutically acceptable salt thereof, is provided for use in the treatment of HCM. 
     According to a further aspect of the invention there is provided a treatment programme for treating HCM, which involves the co-use or co-administration of perhexiline or pharmaceutically acceptable salt thereof with one or more other compounds that are advantageous in treating HCM or the symptoms thereof, for example a calcium channel blocker such as verapamil, or a beta blocker. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a flow chart of a study carried out to establish a causative role for energy deficiency and to evaluate the impact of perhexiline on cardiac energy status in HCM. 
         FIGS. 2A-2D  represent the baseline data of HCM vs controls, more particularly: 
         FIG. 2A  represents the peak oxygen consumption (peak V O2 ) results; 
         FIG. 2B  represents the diastolic ventricular filling results (nTTPF, normalized for heart rate Time To Peak Filling) and shows that PCr/ATP ratio (a measure of cardiac energetic state) is lower in HCM patients versus controls; 
         FIG. 2C  is an example of  31 P cardiac spectra of a HCM patient in which Point C indicates centre of phosphorus coil, VOI; voxel of interest, 2,3-DPG indicates 2,3-diphosphoglycerate; PDE, phosphodiesters; PCr, phosphocreatine; α, β, γ indicate the three phosphorus nuclei of ATP, and shows that nTTPF (a measure of the rate of active relaxation of the LV) is essentially unchanged on exercise in the controls bu abnormally slows in the HCM patients; and 
         FIG. 2D  represent the myocardial energetic results (PCr/γ ATP ratio) and shows that exercise capacity (peak VO2) is lower in HCM patients versus controls. 
         FIGS. 3A and 3B  respectively represent the effect of Placebo and Perhexiline on peak oxygen consumption (peak V O2 ), p=0.003 and myocardial energetic (PCr/γATP ratio), p=0.003, where the p value represents the significant difference between perhexiline and placebo response. Peak VO2 (exercise capacity) increases with Perhexiline ( FIG. 3A ). Perhexiline improves PCr/ATP ratio (energetic status of heart), but this was unchanged in the placebo group ( FIG. 3B ). 
         FIGS. 3C and 3D  respectively represent nTTPF changes in the placebo group ( 3 C) and the perhexiline group ( 3 D), p=0.03, where the p value represents the significant difference between perhexiline and placebo response. In the placebo group nTTPF (a measure of the rate of LV active relaxation) abnormally lengthened at baseline and on treatment. The response in healthy controls is shown in dotted lines. Perhexiline ( FIG. 3D ) normalises the response to similar to that seen in healthy controls (also shown in dotted lines). 
         FIG. 3E and 3F  illustrate that NYHA score (of breathlessness) falls (improves) with perhexiline ( 3 E) and Minnesota living with heart failure questionnaire score falls (=improved quality of life) on perhexiline ( 3 F). 
         FIG. 4  illustrate the causative role for energy deficiency in the pathophysiology of HCM. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In aspects of the present invention, the perhexiline exists in the form of a salt of perhexiline, preferably the maleate salt. The perhexiline may be used at doses titrated to achieve therapeutic but non-toxic plasma perhexiline levels (Kennedy J A, Kiosoglous A J, Murphy G A, Pelle M A, Horowitz J D. “Effect of perhexiline and oxfenicine on myocardial function and metabolism during low-flow ischemia/reperfusion in the isolated rat heart”, J Cardiovasc Pharmacol 2000; 36(6):794-801). Typical doses for a normal patient would be 100 mg to 300 mg daily, although smaller doses may be appropriate for patients who are slow metabolisers of perhexiline. 
     Physiologically acceptable formulations, such as salts, of the compound perhexiline, may be used in the invention. Additionally, a medicament may be formulated for administration in any convenient way and the invention therefore also includes within its scope use of the medicament in a conventional manner in a mixture with one or more physiologically acceptable carriers or excipients. Preferably, the carriers should be “acceptable” in the sense of being compatible with the other ingredients of the formulation and not deleterious to the recipient thereof. The medicament may be formulated for oral, buccal, parental, intravenous or rectal administration. Additionally, or alternatively, the medicament may be formulated in a more conventional form such as a tablet, capsule, syrup, elixir or any other known oral dosage form. 
     Perhexiline exists as two enantiomers, (+)-perhexiline and (−)- perhexiline which are known to be metabolized differently based on patient genotype. It has further been proposed that the atypical kinetics observed in the inhibition of both cardiac and liver derived CPT-1 may have been due to different inhibition affinities of each enantiomer of perhexiline for both the muscle and liver isoforms of CPT-1, and that (+)- and (−)-perhexiline may exhibit differential selectivity for target enzymes in cardiac and hepatic tissues. 
     In accordance with the invention, perhexiline may be used as a racemic mixture (typically a 50:50 mixture of the enantiomers), or as one or other of the (+)-perhexiline and (−)- perhexiline enantiomers, or as a mixture of the two enantiomers in any ratio. 
     Based on relative pharmacodynamic activities of the individual enantiomers, therapeutic drug monitoring may be employed based on specific enantiomer target concentration ranges in plasma for the racemic preparation of perhexiline, or by developing a target concentration for a chiral preparation. 
     As indicated, the preferred subject for treatment is a human. However, the treatment may be a veterinary one. For example, treatment of cats suffering from feline HCM is contemplated. 
     The invention is illustrated by the following non-limiting examples. 
     EXAMPLE 
     A study was carried out to establish a causative role for energy deficiency and to evaluate the impact of perhexiline on cardiac energy status in HCM. 
     The study was approved by the South Birmingham Research Ethics Committee and the investigation conforms with the principles outlined in the Declaration of Helsinki. All study participants provided written informed consent. The study was a randomized, double blind, placebo-controlled parallel-group design of minimum 3 months duration.  FIG. 1  represents a flow chart of the study. The pre-defined primary end point was peak oxygen consumption (peak VO2). Pre-defined secondary end points were symptomatic status, resting myocardial energetics (PCr/γ-ATP ratio) and diastolic function at rest and during exercise (nTTPF). 33 controls of similar age and gender distribution were recruited for comparison with baseline data of HCM patients. All controls had no history or symptoms of any cardiovascular disease with normal ECG and echocardiogram (LVEF≧55%). 
     Patients were recruited from dedicated cardiomyopathy clinics at The Heart Hospital, University College London Hospitals, London and Queen Elizabeth Hospital, Birmingham, UK between 2006 and 2008. Inclusion criteria were 18 to 80 years old symptomatic HCM patients (predominant symptom breathlessness) in sinus rhythm with reduced peak VO2 (&lt;75% of predicted for age and gender) and no significant LVOT obstruction at rest (gradient&lt;30 mmHg). Exclusion criteria were presence of epicardial coronary artery disease, abnormal liver function test, concomitant use of amiodarone or selective serotonin reuptake inhibitors (due to potential drug interactions with perhexiline), peripheral neuropathy and women of childbearing potential. Diabetic patients were also excluded to maintain the blindness of the study as Perhexiline may lead to a reduction in plasma glucose in such patients necessitating a reduction in anti-diabetic therapy. 46 consecutive consenting patients who met these entry criteria were recruited into the study. 
     Patients were subjected to a number of tests and assessments as follows. 
     Cardiopulmonary Exercise Test 
     This was performed using a Schiller CS-200 Ergo-Spiro exercise machine which was calibrated before every study. Subjects underwent spirometry and this was followed by symptom-limited erect treadmill exercise testing using a standard ramp protocol with simultaneous respiratory gas analysis (Bruce R A, McDonough J R. Stress testing in screening for cardiovascular disease. Bull N Y Acad Med 1969; 45(12):1288-1305.; Davies N J, Denison D M. The measurement of metabolic gas exchange and minute volume by mass spectrometry alone. Respir Physiol 1979;36(2):261-267). Peak oxygen consumption (peak VO2) was defined as the highest VO2 achieved during exercise and was expressed in ml/min/kg. 
     Symptomatic Status Assessment 
     All HCM patients filled in Minnesota Living with heart failure questionnaire and were also assessed for NHYA class. 
     Transthoracic Echocardiography 
     Echocardiography was performed with participants in the left lateral decubitus position with a Vivid 7 echocardiographic machine (GE Healthcare) and a 2.5-MHz transducer. Resting scans were acquired in standard apical 4-chamber and apical 2-chamber. LV volumes were obtained by biplane echocardiography, and LVEF was derived from a modified Simpson&#39;s formula (Lang R M, Bierig M, Devereux R B et al. Recommendations for chamber quantification: a report from the American Society of Echocardiography&#39;s Guidelines and Standards Committee and the Chamber Quantification Writing Group, developed in conjunction with the European Association of Echocardiography, a branch of the European Society of Cardiology. J Am Soc Echocardiogr 2005;18(12):1440-1463.) Pulse wave doppler sample volume was used to assess resting LVOTO gradient. 
     Radionuclide Ventriculography 
     Diastolic filling were assessed by equilibrium R-wave gated blood pool scintigraphy using a standard technique at rest and during graded semi erect exercise on a cycle ergometer (Atherton J J, Moore T D, Lele S S et al. Diastolic ventricular interaction in chronic heart failure. Lancet 1997;349 (9067):1720-1724; Lele S S, Macfarlane D, Morrison S, Thomson H, Khafagi F, Frenneaux M. Determinants of exercise capacity in patients with coronary artery disease and mild to moderate systolic dysfunction. Role of heart rate and diastolic filling abnormalities. Eur Heart J 1996;17(2):204-212). Peak left ventricular filling rate in terms of end-diastolic count per second (EDC/s) and time to peak filling normalised for R-R interval (nTTPF) in milliseconds were measured at rest and during exercise (50% of heart rate reserve). The validity of these radionuclide measures of diastolic filling at high heart rates has been established previously (Atherton et al. and Lele et al., see above). 
     31P Cardiac Magnetic Resonance Spectroscopy (MRS) 
     In vivo myocardial energetics were measured using a MRS at 3-Tesla Phillips Achieva 3T scanner (Shivu G N, Abozguia K, Phan T T, Ahmed I, Henning A, Frenneaux M. (31)P magnetic resonance spectroscopy to measure in vivo cardiac energetics in normal myocardium and hypertrophic cardiomyopathy: Experiences at 3T. Eur J Radiol 2008). A java magnetic resonance user interface v3.0 (jMRUI) was used for analysis (see Naressi A, Couturier C, Castang I, de Beer R, Graveron-Demilly D. Java-based graphical user interface for MRUI, a software package for quantitation of in vivo/medical magnetic resonance spectroscopy signals. Comput Biol Med 2001;31(4):269-286)). PCr and γ-ATP peaks was used to determine the PCr/γ-ATP ratio which is a measure of the cardiac energetic state (Neubauer S, Krahe T, Schindler R et al. 31P magnetic resonance spectroscopy in dilated cardiomyopathy and coronary artery disease. Altered cardiac high-energy phosphate metabolism in heart failure. Circulation 1992;86(6):1810-1818). Data were analyzed by an investigator who was blinded to the participants&#39; clinical status. Carmeo-Rao ratio was used to assess signal to noise ratio. A typical example of cardiac 31 P MRS spectra from a patient with HCM is shown in  FIG. 2C . 
     Intervention 
     Following baseline studies, patients were randomized in a double-blind fashion to receive either perhexiline (n=25) or placebo (n=21) 100 mg OD. Serum perhexiline levels were obtained at 1 and 4 weeks after initiation of the drug. Dose adjustments were advised by an unblinded physician according to serum level to achieve therapeutic level and to avoid drug toxicity. Identical dosage adjustments were also made for randomly allocated placebo-treated patients by the unblinded observer to ensure that blinding of the investigators was maintained. At the end of study, patients were re-evaluated as described earlier. 
     Statistical Analysis 
     Data were analyzed using SPSS ver. 15.0 for Window and Microsoft Office Excel 2007, and expressed as Mean±Standard Deviation (SD). Comparison of continuous variables between Perhexiline and Placebo baseline data were determined by unpaired Student&#39;s t-test (2-tail) if variables were normally distributed and the Mann-Whitney U-test if the data were non-normally distributed. ANCOVA with baseline values as covariates was performed to test for the significance of differences in the perhexiline versus placebo group after treatment. For the primary end point, the sample size required to detect a change in peak Vo2 of 3 ml/kg/min versus placebo group with a power of 90% and probability of 5% is 44. 30 patients will be required to identify a 5% change in cardiac PCr/ATP ratio with a power of 90% and a p value of &lt;0.05. 40 patients will be required to detect a change ≧25% in nTTPF with power of 0.99 with probability of 5%. Therefore, we aimed to study 50 patients including the drop-outs, 32 of them will take part in the MRS study. 
     The characteristics and treatment of participants are shown in Table 1 below. Vo 2 : refers to peak oxygen consumption, ACE: refers to angiotensin-converting enzyme, and ARB refers to angiotensin II receptor blockers. 
                                                                                 TABLE 1                   The clinical characteristics of HCM patients and controls.                            HCM   HCM   P           HCM   Controls   P value   (Perhexiline)   (Placebo)   value                        Age [years]   55 ± 0.26   52 ± 0.46   0.2   56 ± 0.46   54 ± 0.64   0.42       Number (Male)   46 (34)   33 (20)   0.64   25 (19)   21 (17)   0.69       Heart Rate [bpm]   69 ± 0.27   82 ± 0.47   &lt;0.001*   69 ± 0.53   69 ± 0.52   0.97       Systolic BP [mmHg]   126 ± 0.64    126 ± 0.44    0.93   123 ± 0.84    130 ± 0.92    0.2       Diastolic BP [mmHg]   76 ± 0.25   78 ± 0.34   0.33   74 ± 0.45   78 ± 0.57   0.24       Peak Vo 2     23 ± 0.12   38 ± 0.24   &lt;0.0001*   22.2 ± 0.2     23.56 ± 0.27     0.42       [ml/kg/min]       Resting nTTPF   0.17 ± 0.002    0.18 ± 0.003    0.44   0.19 ± 0.003    0.17 ± 0.004    0.52       (sec)       PCr/γATP ratio   1.28 ± 0.01     2.26 ± 0.02     &lt;0.0001*   1.27 ± 0.02     1.29 ± 0.01     0.86       Drug therapy - no.       Beta-blocker   17   0   —   10   7   0.21       CC-blocker   24   0   —   11   8   0.53       Diuretic   10   0   —   4   5   0.49       ACE inhibitor   6   0   —   3   2   0.84       ARB   4   0   —   3   1   0.41       Warfarin   5   0   —   2   3   0.48       Statin   15   0   —   7   7   0.9               *indicates statistical significance            
Baseline Data (HCM Versus Controls)
 
     The clinical characteristics and cardiopulmonary exercise test results of all the HCM patients and controls are shown in Table 1. The groups were well matched with respect to age and gender. Heart rate was lower in the HCM group compared to controls due to medication use (beta blockers and/or calcium channel blockers). 
     The resting cardiac PCr/γATP ratio was lower in HCM patients than in controls (1.28±0.01 vs 2.26±0.02, p&lt;0.0001) (see  FIGS. 2A  and B), and this remained so after excluding patients taking beta blocker therapy (p&lt;0.0001). At rest, nTTPF, a sensitive marker of LV relaxation, was similar in HCM patients and controls (0.17±0.002 vs 0.18±0.003 sec, p=0.44). During submaximal exercise (at a workload that achieved 50% of heart rate reserve) it remained relatively constant in controls (from 0.18±0.003 sec to 0.16±0.002 sec, [δnTTPF=−0.02±0.003 sec]), but lengthened in patients (from 0.17±0.002 to 0.34±0.002 sec, [εnTTPF=+0.17±0.002 sec]) p&lt;0.0001, ( FIG. 2C ). This pattern persisted after exclusion of patients on beta blockers and remained significantly different from controls (p&lt;0.0001). Patients exhibited marked exercise limitation compared to controls (23±0.12 vs 38±0.24 ml/kg/min, p&lt;0.0001) ( FIG. 2D ). 
     Randomized, Double Blinded, Placebo-controlled Parallel-group 
     The perhexiline and placebo groups were well matched (see Table 1). Only one patient (on placebo) did not complete the study due to poor compliance. Side effects were restricted to transient nausea (n=3) and dizziness (n=2) in the perhexiline group and transient nausea (n=2) and headache (n=1) in the placebo group during the first week of treatment. There were no deaths during the study period. 
     Myocardial Energetics 
     The PCr/γATP ratio increased with perhexiline (1.27±0.02 to 1.73±0.02) as compared with placebo (1.29±0.01 to 1.23±0.01), p=0.003 (see  FIG. 3A ). The mean Cramer-Rao ratios for PCr and γATP were 7.5% and 10.8% respectively. The effect of perhexiline on PCr/γATP ratio remained significant after inclusion of the 3 patients with Cramer Rao ratios &gt;20 from the analysis (p=0.02). 
     Diastolic Ventricular Filling 
     Whereas the placebo group showed similar prolongation of nTTPF during exercise before and after therapy (0.17±0.004 to 0.35±0.005 [εnTTPF 0.18±0.006 sec] and 0.23±0.006 to 0.35±0.005 sec [εnTTPF 0.12±0.006 sec], respectively), in the perhexiline group there was a substantial improvement on therapy with nTTPF at rest and exercise similar (0.19±0.003 to 0.19±0.004 sec[εnTTPF 0.00±0.003 sec]) p=0.03 between the perhexiline and placebo response (see  FIGS. 3B and 3C ). 
     Symptomatic Status 
     More patients in the perhexiline group than in the placebo group had improvements in NYHA classification (67 percent vs. 30 percent) and fewer had worsening (8 percent vs. 20 percent) (p&lt;0.001). Minnesota Living with heart failure questionnaire score showed an improvement (fall in score) in the perhexiline group (from 36.13±0.94 to 28±0.75) but did not change in the placebo group (p&lt;0.001) (see  FIGS. 3D and 3E ). 
     Exercise Capacity (Peak Oxygen Consumption) 
     Peak V O2  at baseline was similar in the perhexiline and placebo groups (Table 1). After treatment, Peak V O2  fell by −1.23 ml/kg/min in the placebo group (from 23.56±0.27 to 22.32±0.27 ml/kg/min) but increased by 2.09 ml/kg/min in the perhexiline group (from 22.2±0.2 to 24.29±0.2 ml/kg/min), p=0.003 (see  FIG. 3F ). 
     Discussion of Results 
     The study indicates that patients with symptomatic HCM manifest a cardiac energy defect at rest (reduced PCr/γATP ratio). This defect was accompanied by a slowing of the energy-requiring early diastolic LV active relaxation during exercise (prolongation of nTTPF). The metabolic modulator perhexiline resulted in significant myocardial energy augmentation. Supporting a causative role for energy deficiency in the pathophysiology of HCM, this energy augmentation was accompanied by striking normalisation of HCM&#39;s characteristic “paradoxical” nTTPF-prolongation in exercise. These biochemical and physiological improvements translated into significant subjective (NYHA classification and QoL score) and objective (V O2 ) clinical benefits in symptomatic HCM patients already on optimal medical therapy (see  FIG. 4 ).