Comparative effectiveness of the new calpain inhibitor NPO-2270 versus enalapril in pressure overload-induced heart failure

Background

Studies performed in multiple preclinical models support the contribution of the Ca2+-dependent cysteine proteases calpains to ventricular remodelling and heart failure (HF). However, pharmacological calpain inhibition has not yet been tested in patients with HF mainly due to the limitations of available inhibitors.

Purpose

To determine the effect of NPO-2270 (NPO), a new ketoamide derivative calpain inhibitor, in a mouse model of pressure-overload and compare its effectiveness with that of enalapril.

Methods

C57BL6 mice were subjected to transverse aortic constriction (TAC) for 4 weeks. Mice were randomised to receive orally administered NPO or enalapril at the dose of 10 mg/kg/day once a day, or vehicle, starting at day 7 after TAC surgery. The combination of both drugs and the effect of NPO starting 1 day after surgery were tested in additional TAC mice. Echocardiographic data, markers of hypertrophy, fibrosis, calpain activity and cleavage of calpain substrates were measured at different time points.

Results

TAC increased calpain-1 and -2 expression and activity. Administration of NPO and enalapril prevented the progression of hypertrophy and interstitial fibrosis induced by TAC with no statistically significant differences between the two treatments. However, ongoing ventricular dysfunction was less severe in the NPO group than in the enalapril group (27% of LVEF reduction in control group, 6% in NPO group and 16% in the enalapril group after TAC, P=0.024 between NPO and enalapril groups). The combined treatment or the administration of NPO from the first day after TAC surgery was not superior to NPO alone starting 7 days after TAC. These differences in LVEF correlated with better preservation of cadherin-based cell adhesion complex in mice treated with NPO-2270. No adverse effects associated with long-term NPO administration were observed in a sham group.

Conclusions

The new calpain inhibitor NPO-2270 prevents the development of hypertrophy and fibrosis with similar efficacy than enalapril but prevents cardiac dysfunction more effectively in a preclinical model of pressure overload when given orally at equivalent doses.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Instituto de Salud Carlos III of the Spanish Ministry of Health

The Calcium Channel Blocker LAS 30538, Unlike Nifedipine, Verapamil, Diltiazem or Flunarizine, Potently Inhibits Insulin Secretion In-vivo in Rats and Dogs

The effects of a novel calcium channel blocker, LAS 30538 (1-[2-(2,6-dimethylphenoxy)ethyl]-α,α-bis-(p-fluorophenyl)-4-piperidine methanol), were studied on glucose tolerance and insulin secretion in rats and dogs in-vitro and in-vivo. Some comparisons were made with nifedipine, verapamil, diltiazem, flunarizine, diazoxide, cromakalim and minoxidil. LAS 30538, like a number of calcium channel blockers, was found to inhibit insulin secretion in-vitro, but was 1000-fold more potent than verapamil or diltiazem in this respect. LAS 30538 differed from the other calcium channel blockers studied in that it also potently inhibited insulin secretion and impaired glucose tolerance in-vivo. The evidence that LAS 30538 is more potent than diazoxide as a hyperglycaemic agent in-vivo suggests that this could be a useful drug for the treatment of hyperinsulinaemia in man.

Vascular effects of the new anti-migraine agent almotriptan on human cranial and peripheral arteries

This paper describes the vascular effects of almotriptan in comparison with sumatriptan in human vessels and tissues in vitro. The contractile properties of almotriptan and sumatriptan were evaluated in vitro in the following arteries: meningeal, temporal, basilar, internal carotid, ophthalmic, pulmonary and coronary. In addition, the effects of almotriptan on the pulmonary vein and on bronchial tissues were studied. Almotriptan showed selectivity of action for migraine-related arteries (i.e. contractile EC(50) of 30 and 700 nm for meningeal and temporal arteries, respectively), whereas the effect on arteries supplying blood to the brain was lower. The contractile effect of almotriptan was lower than that of sumatriptan in pulmonary arteries, whereas in bronchial preparations no clinically relevant contractile responses were observed for either almotriptan or sumatriptan. In ophthalmic arteries the contractile effects of almotriptan and sumatriptan were similar, whereas lower contractile effects were obtained with almotriptan than with sumatriptan in coronary arteries.

Safety profile of almotriptan, a new antimigraine agent. Effects on central nervous system, renal function and respiratory dynamics

Almotriptan (3-[2-(dimethylamino) ethyl]-5-(pyrrolidin-1-ylsulfonylmethyl)-1H-indole, CAS 154323-57-6) is a new 5-HT1B/1D agonist whose clinical efficacy has been demonstrated in Phase III clinical trials. This study aimed to evaluate the safety of almotriptan with respect to the central nervous system, renal function and respiratory dynamics using preclinical animal models. The results indicate that almotriptan does not cross the blood-brain barrier, since no effects on/interaction with spontaneous locomotor activity, hexobarbital-induced sleeping time, caffeine-induced increase of spontaneous locomotor activity, or hypothermia (caused by stimulation of central 5-HT1D receptors) was observed following treatment. Almotriptan had a mild antiemetic effect and a slight, transient diuretic effect in dogs, although the latter effect is probably of no clinical relevance. In addition, no effect on the respiratory system of conscious guinea pigs was observed following almotriptan treatment. These results indicate that almotriptan has a favourable safety profile with respect to the central nervous, renal and respiratory systems.

Cardiovascular safety profile of almotriptan, a new indolic derivative for the treatment of migraine

Almotriptan is a new 5-HT(1B/1D) receptor agonist effective for treating acute migraine attacks with or without aura. As 3-5% of patients treated with sumatriptan experience chest symptoms thought to be of cardiac origin, we investigated the cardiovascular safety profile of almotriptan in comparison with that of sumatriptan in six animal models. Almotriptan did not modify blood pressure or heart rate in conscious telemetered normotensive Wistar rats (p.o.), in anaesthetised beagle dogs (i.v.), or in conscious beagle dogs (i.v.), and only produced transient increases when administered (s.c.) to telemetered cynomolgus monkeys. Almotriptan did not consistently affect the duration of the electrocardiogram (ECG) intervals in anaesthetised beagle dogs even when the drug was administered into the coronary artery, nor was ECG morphology altered in telemetered cynomolgus monkeys. In contrast, sumatriptan i.v. consistently increased mean blood pressure and heart rate in conscious beagle dogs. Finally, almotriptan did not modify coronary blood flow at a dose of up to 0.3 mg/kg i.v. in conscious beagle dogs. Thus, almotriptan has a favourable cardiovascular safety profile.

Functional profile of almotriptan in animal models predictive of antimigraine activity

Almotriptan is a new 5-HT(1B/1D) receptor agonist whose clinical efficacy for the treatment of migraine attacks has been demonstrated in Phase III clinical trials. We now compare the functional profile of almotriptan (assessed using animal models) with that of sumatriptan. Almotriptan selectively increased carotid vascular resistance in anaesthetised cats after intravenous or intraduodenal administration (ED(100)=11 microg/kg, i.v.; ED(50)=339 microg/kg, i. d.) and in anaesthetised beagle dogs following intravenous administration (ED(50)=116 microg/kg). A study in anaesthetised cats also demonstrated that almotriptan acts by selectively increasing the resistance of the carotid arteriovenous anastomoses without adversely affecting brain irrigation. In addition, almotriptan inhibited meningeal extravasation produced by electrical stimulation of the trigeminal ganglion in anaesthetised guinea pigs in the dose range of 0.3-3 mg/kg, i.v. In conclusion, almotriptan is both a selective constrictor affecting intracranial blood vessels and an inhibitor of neurogenically evoked plasma protein extravasation of the dura mater.

Pharmacological profile of LAS 31180, a new inotropic/vasodilator quinolone derivative

LAS 31180 (3-methylsulphonylamino-1-methyl-4(1H)-quinolone, CAS 137338-43-3) was found to have positive inotropic and vasodilator properties through its inhibitory action on type 3 phosphodiesterase. The inotropic effects of LAS 31180 were demonstrated in vitro both in isolated guinea-pig ventricular strips (EC50 of 1.2 mumol/l) and in isolated guinea-pig working hearts. In conscious chronically instrumented Beagle dogs, LAS 31180 administered either by intravenous or oral route, showed a dose-dependent, long-lasting positive inotropic effect with minimal effects on heart rate. In hypertensive Beagle dogs LAS 31180 elicited a potent and long-lasting fall in blood pressure.

Synthesis and pharmacological evaluation of 2, 3-dihydro-3-oxo-4H-thieno[3,4-e][1,2,4]thiadiazine 1,1-dioxides as voltage-dependent calcium channel blockers

The synthesis of a novel series of 2,3-dihydro-3-oxo-4H-thieno[3, 4-e][1,2,4]thiadiazine 1,1-dioxides and their pharmacological evaluation as drugs with effects on the rat cardiovascular system are described. The compounds under study were synthesized via Curtius rearrangement of appropriate sulfamoylacylazides which, in turn, were prepared from known starting materials. In isolated rat portal vein, these thienothiadiazines, like verapamil and diazoxide, inhibited the spontaneous motility produced by KCl (20 mM). In addition, the new compounds, like verapamil and unlike diazoxide, also exhibited inhibitory effects in the same preparation when the cell membrane was depolarized by an increased extracellular KCl concentration (80 mM) and, consequently, the membrane potential approached a level close to the K(+) equilibrium potential. Further characterization of this inhibitory activity led to the identification of a selective inhibitory effect of the new compounds on KCl (80 mM)-induced 45Ca(2+) uptake in the same vascular tissue. When tested in vivo (anaesthetized normotensive rats), acute administration of verapamil, diazoxide and some of the most in vitro potent compounds in 45Ca(2+) uptake experiments produced a gradual, dose-dependent and sustained decrease in diastolic arterial blood pressure, devoid of cardiac effects. These results suggest that, like verapamil, the cardiovascular effects produced by the new thienothiadiazines seem to be due, at least in part, to a blockade of transmembrane voltage-dependent calcium channels present in vascular smooth muscle cells and not to an activation of ATP-sensitive K(+) channels. Compounds 5b, 5e and 5i have been selected for further studies as antihypertensive agents.

Effects of H1 antihistamines on animal models of QTc prolongation

OBJECTIVE

The clinical use of some nonsedating H1 antihistamines (histamine H1 receptor antagonists) has been associated with a rare but life-threatening type of arrhythmia, torsade de pointes, especially when these drugs are coadministered with cytochrome P450 (CYP) 3A4 enzyme inhibitors. On the basis of the latter observation and the fact that most of these H1 antihistamines undergo extensive first-pass metabolism to active metabolites apparently devoid of cardiovascular adverse effects, this arrhythmogenicity has been attributed to the parent drug. The objective of this study was to find an animal model with the ability to predict the proclivity of drugs to produce torsade de pointes.

DESIGN

Two experimental approaches were used: (i) blockade of CYP3A4 metabolism by coadministration of ketoconazole to increase the plasma concentrations of the parent compound in the conscious guinea-pig, and (ii) administration of the compound directly into the coronary circulation of the anaesthetised dog in order to circumvent first-pass metabolism.

RESULTS

The first approach demonstrated that terfenadine administered in the presence of ketoconazole prolongs the corrected QT (QTc) interval of the electrocardiogram, whereas ebastine does not. Similarly, when terfenadine was administered through the coronary circulation, a statistically significant increase in the QTc interval was also seen, whereas ebastine and carebastine were without effect. Thus, it is clear that ebastine was much better tolerated than terfenadine from a cardiovascular standpoint, since ebastine and its metabolite are devoid of effects on cardiac repolarisation, as measured by the QTc interval in these animal models.

Cardiotoxicity of histamine and the possible role of histamine in the arrhythmogenesis produced by certain antihistamines

Since 1990 it has repeatedly been reported that some histamine H1 receptor antagonists (e.g. terfenadine and astemizole) are able to produce ventricular arrhythmias (e.g. torsade de pointes) when they are given at dosages above the therapeutic range and/or administered together with cytochrome P-450 3A4 inhibitors, such as ketoconazole or erythromycin. Although the mechanism by which these arrhythmias are produced remains unclear, the recently reported ability of these drugs to block outward K+ currents has been suggested as the cause of their arrhythmogenic effects. Alternatively, we have observed that some H1 antihistamines, including terfenadine and astemizole, are able to release histamine from guinea-pig cardiac mast cells. Thus, we have proposed that the liberated histamine, acting through an H2 receptor-stimulating mechanism, can prolong the action potential duration and hence induce arrhythmogenic effects. This paper describes experimental observations supporting the hypothesis that some H1 antihistamines can induce severe cardiac arrhythmias via the local release of histamine.

Clinical anti-inflammatory efficacy of arofylline, a new selective phosphodiesterase-4 inhibitor, in dogs with atopic dermatitis

Forty atopic dogs were studied for 28 days after the oral administration of four randomised treatments: (A) arofylline (1 mg/kg) twice daily for four weeks; (B) prednisone (0.5 mg/kg) twice daily for the first week, once a day during the second week and every 48 hours for the remaining two weeks; (C) prednisone following the same protocol but at a dose of 0.25 mg/kg; or (D) arofylline (1 mg/kg) twice daily for four weeks plus prednisone (0.25 mg/kg) following the same protocol as in (B) and (C). The degree of pruritus and skin lesions and the side effects were evaluated and graded from 0 to 3 before and weekly during the treatments. In all cases there was a progressive clinical improvement in the clinical signs, with no statistical differences among the four treatments. However, many of the dogs treated with arofylline vomited and had adverse gastrointestinal signs.

Arylimino-1,2,4-thiadiazolidinones: a new family of potassium channel openers

A series of arylimino-1,2,4-thiadiazolidines were prepared using an efficient synthesis starting from thiadiazolopyridinium chlorides. All the compounds showed smooth muscular relaxant properties in rat portal veins. The different behaviour under highly depolarized conditions and the reduction of the biological effect by glyburide suggests that the arylimino-1,2,4-thiadiazolidin-3-ones may act, at least in part, via K+-induced hyperpolarization of vascular smooth cells.

The role of ketoconazole in the QTc interval prolonging effects of H1-antihistamines in a guinea-pig model of arrhythmogenicity

We have carried out experiments to re-evaluate the influence of ketoconazole (400 mg kg-1,p.o.) on the effects of ebastine, terfenadine and loratadine on the QTc interval in conscious guinea-pigs. Following a previously described protocol of oral drug administration, but using telemetric recording of the ECG, we have found that the prolongation of the QTc interval attributed to ebastine and terfenadine is in fact entirely due to ketoconazole, and that neither terfenadine, ebastine nor loratadine produce any additional effects on subsequent administration.

Inhibition of lipopolysaccharide-induced bowel erythrocyte extravasation in rats, and of mesenteric hypoperfusion in dogs, by phosphodiesterase inhibitors

Sepsis is intricately associated with mesenteric ischemia. The remote complications of mesenteric ischemia are essentially those of sepsis, whether as a cause or as a consequence. Experimental endotoxic shock induces bowel hypoperfusion, erythrocyte extravasation and intestinal necrosis. The effects of pentoxifylline, rolipram and denbufylline, three phosphodiesterase inhibitors, were studied on endotoxin-induced bowel erythrocyte extravasation and intestinal and renal hypoperfusion, in conscious rats and anaesthetized dogs, respectively. Two hours after lipopolysaccharide i.v. injection in rats, erythrocyte extravasation was evident throughout the intestinal musculature and mucosa, apparently without affecting lungs, heart, kidneys, liver or pancreas. Pretreatment with the non-selective phosphodiesterase inhibitor, pentoxifylline, or selective phosphodiesterase IV inhibitors such as denbufylline or rolipram reduced intestinal haemoconcentration. In the anaesthetized dog, pentoxifylline and denbufylline both inhibited the E. coli lipopolysaccharide-induced mesenteric blood flow fall, without affecting renal blood flow or cardiac index. In conclusion, phosphodiesterase inhibitors protected from intestinal damage and bowel hypoperfusion after lipopolysaccharide challenge. This action may thus play a role in the protective effects against endotoxin-induced lethal toxicity previously described for phosphodiesterase inhibitors.

Dioxides of bicyclic thiadiazines: a new family of smooth muscle relaxants

The synthesis of dioxides of bicyclic thiadiazine related to diazoxide has been achieved. In a preliminary test, some of these compounds show smooth muscle relaxation similar to that obtained with the reference standard diazoxide.

Investigation into the role of phosphodiesterase IV in bronchorelaxation, including studies with human bronchus

1. We have investigated the role of cyclic nucleotide phosphodiesterase IV (PDE IV) in the relaxation of human bronchus and guinea-pig trachea in vitro and in guinea-pigs in vivo. 2. Functional studies showed that the selective PDE IV inhibitors, rolipram and denbufylline, relaxed human and guinea-pig preparations in vitro. 3. Two clinically used xanthine non-selective PDE inhibitors, theophylline and pentoxifylline, were also effective in these preparations, but were much less potent than the selective agents used. 4. The rank order of potency for the four PDE inhibitors in both species was similar. 5. Biochemical studies indicated that PDE IV was the major PDE isoform present in the human bronchial tissue. PDEs I, II and V were also identified. 6. Theophylline and pentoxifylline were, as expected, non-selective inhibitors of the human enzymes, but there was a good correlation between PDE IV inhibitory and bronchorelaxation potencies, suggesting that PDE IV inhibition is important for the clinical bronchodilator activities of the two xanthine compounds. 7. We have confirmed the ability of selective PDE IV inhibitors to cause bronchodilatation in guinea-pigs in vivo. 8. We conclude that our study has provided further evidence that selective PDE IV inhibitors could act as bronchodilators in the clinic.

Cardiovascular effects of LAS 30538, a new vascular selective Ca(2+)-channel blocker

A new compound, 1-[2-(2,6-dimethylphenoxy)ethyl]-alpha,alpha-bis-(p-fluorphenyl)-4 -piperidine methanol (LAS 30538), was found to have potent vasodilator effects. Its vasorelaxant activity was demonstrated in rat perfused hindlimbs contracted with 80 mM K+, having an IC50 value of 40 nM. In conscious spontaneously hypertensive rats, LAS 30538 administered orally, caused dose-dependent sustained falls in systolic blood pressure with an ED30 value of 11 mg kg-1. In pithed rats, LAS 30538, strongly inhibited vasoconstriction induced by the alpha 2-adrenoceptor agonist B-HT 933 and the calcium agonist compound Bay K8644 with ED50 values of 4 mg kg-1 p.o. and 1.3 mg kg-1 i.v., respectively. Results from electrophysiological studies carried out using guinea-pig papillary muscles partially depolarized by 22 mM K+ are consistent with LAS 30538 acting as a Ca(2+)-channel blocker. When compared with verapamil, in guinea-pig and rabbit isolated heart preparations, LAS 30538 caused less cardiodepression and bradycardia. The results suggest that LAS 30538 may have some advantages over other Ca(2+)-channel blockers such as verapamil in causing less myocardial depression for a given level of vasodilatation.

Studies on the cardiac actions of flosequinan in vitro

1. We have investigated the in vitro cardiac actions of flosequinan and of its major metabolite in man, BTS 53554. 2. Positive inotropic activity was seen with flosequinan in guinea-pig isolated ventricles, the threshold concentration for effect being less than 1 x 10(-5) M. BTS 53554 was approximately half as potent as the parent compound. 3. In guinea-pig working whole hearts flosequinan increased left ventricular dp/dtmax, indicating a positive inotropic action. This effect was accompanied by increases in heart rate, cardiac output and stroke volume. 4. The virtual complete inhibition of inotropic responses to flosequinan and BTS 53554 by carbachol suggests that these responses are adenosine 3':5'-cyclic monophosphate (cyclic AMP)-mediated. 5. Flosequinan was shown to increase calcium inward current in guinea-pig ventricle, an action consistent with a cyclic AMP involvement in the response. 6. The inotropic activity of flosequinan was not potentiated by the selective phosphodiesterase (PDE) III inhibitor SK&F 94120, a result which indicates that flosequinan does not increase cyclic AMP concentrations via stimulation of adenylate cyclase. 7. Flosequinan inotropic responses were potentiated by rolipram, a selective PDE IV inhibitor, a result consistent with flosequinan being itself a PDE III inhibitor. 8. Biochemical studies with purified enzymes confirmed that flosequinan and BTS 53554 are relatively selective inhibitors of PDE III. 9. A comparison of pharmacological and biochemical data for both flosequinan and BTS 53554 indicates that their PDE III inhibitory potency is sufficient to account for their inotropic activity.

Synergistic interactions between piracetam and dihydroergocristine in some animal models of cerebral hypoxia and ischaemia

In pharmacological screening tests for activity against the cerebral insults of hypoxia and ischaemia induced by MgCl2 or decapitation in mice, the combination of piracetam and dihydroergocristine has been shown to produce synergistic effects in prolonging the survival time. This was not the case in the model of histiocytic anoxia induced by KCN. Using an optimal combination of piracetam and dihydroergocristine (533:1, Diemil) significant increases in cerebral resistance to hypercapnic anoxia and reductions in the duration of the ensuing electrical silence on the electrocorticogram have been demonstrated in the rat. The same combination was also effective in antagonizing the memory ablating effects of anoxia in rats subjected to electric footshocks during a standard passive avoidance response. The absence of clear effects on gross cerebral blood flow and metabolism, together with considerations of the known pharmacological properties of the two components of the combination and the effects of standard drugs in the models used, lead to the conclusion that the explanation of the observed synergism probably lies in complimentary actions at the level of the cerebral neurones and is independent of simple vasodilation.

Calcium entry blocking drugs, 'calcium antagonists' and vascular smooth muscle function

The group of drugs known as "calcium antagonists' is under extensive investigation in experimental animals and man and a re-evaluation of their pharmacological properties is overdue. Recent proposals to adopt the more specific nomenclature of calcium entry blockers for some of these compounds (Vanhoutte & Bohr, 1981) should be supported since there is much confusion in the literature with this class of compound. In this review, which concentrates on vascular smooth muscle, only nifedipine, verapamil, their close chemical analogues and diltiazem are recognised as being relatively selective calcium entry blocking drugs. Whilst definitive evidence for calcium entry blockade must include the demonstration of a selective inhibition of Ca2+-influx into a tissue over a range of concentrations also inhibiting contraction, it is nevertheless possible to define several simple pharmacological criteria which may aid in the identification of such activity. These criteria include the selective antagonism of K+ and Ca2+-induced contractions, relative to those of noradrenaline in suitable vascular smooth muscle preparations and a selective inhibition of alpha 2- as opposed to alpha 1-adrenoreceptor mediated pressor responses in, for example, pithed rat preparations. Recent pharmacological and biochemical studies have identified 3 major subgroups of "calcium antagonist' drugs but the compounds within each subgroup varies with the technique adopted. It is therefore suggested that a combination of both pharmacological and ligand-binding studies be used for purposes of classification. Which mechanism, if any, of inhibiting calcium entry is therapeutically most desirable remains an important question for future research.

A comparison of the effects of verapamil and cinnarizine upon responses elicited by selective alpha 1- and alpha 2-adrenoceptor agonists in the autoperfused canine hindlimb

In an attempt to extend the hypothesis that activation of vascular postsynaptic alpha 2-adrenoceptors requires an influx of Ca2+ ions, the effects of 2 calcium entry blocking drugs verapamil and cinnarizine have been examined as inhibitors of the pressor responses to methoxamine and B-HT 920 in autoperfused dog hindlimb preparations. Verapamil (0.1-1 mg i.a.) selectively antagonized responses to B-HT 920 and had little or no effect upon responses to methoxamine, thus supporting this hypothesis. However cinnarizine, over the dose range studied (0.1-1 mg/kg i.a.) produced quantitatively similar inhibitions of the hindlimb responses to B-HT 920 and methoxamine. These results suggest that cinnarizine may have a different site of action to verapamil in resistance vessels of the dog hindlimb.