Cardiovascular action of mesoionic compounds, 3-substituted sydnonimines

A mechanochemical approach to the synthesis of sydnones and derivatives

Sydnones are heterocyclic compounds which display important biological activities, including their abilities to react in 1,3-dipolar additions for applications in the development of new prodrugs. Capitalizing on our preliminary work on the mechanosynthesis of sydnones, an extension of this work to two related families of molecules, diarylsydnones and iminosydnones is reported. A ball-milling approach towards the synthesis of diaryl sydnones was developed, a necessary step for the synthesis of potential sydnone-based ligands of metal complexes. A mechanochemistry-based synthesis of iminosydnones was optimized, including the preparation of active pharmaceutical ingredients (API) related to feprosidnine, linsidomine, mesocarb and molsidomine. This work demonstrated that the ball-milling procedures were efficient and time saving through avoiding purification steps, and reduced the use of organic solvents.

Novel approaches for the prevention of restenosis

Restenosis, the re-narrowing of the lumen of the coronary artery, in the months following a successful percutaneous balloon angioplasty or stenting, remains the main limitation to percutaneous coronary revascularisation. Serial intravascular ultrasound studies have shown that restenosis after conventional balloon angioplasty represents a complex interplay between elastic recoil, smooth muscle proliferation and vascular remodelling, while restenosis after stent deployment is due almost entirely to smooth muscle hyperplasia and matrix proliferation. Despite intensive investigation in animal models and in clinical trials, most pharmacological agents have been found to be ineffective in preventing restenosis after percutaneous balloon angioplasty or stenting. Although studies frequently report success in the suppression of neointimal proliferation in animal models of balloon vascular injury, few of them have been successful in clinical trials. Lately, the advent of endovascular radiation, new antiproliferative agents, recombinant DNA, growth factor regulators and novel local drug delivery systems have shown promising results. In the past five years, intracoronary radiation with gamma- and beta-emitting sources has been evaluated intensively with very encouraging results. This is the first potent non-pharmacological approach that has been successful in a large number of patients in controlling excessive tissue proliferation. It is very likely that a combination of stents and pharmacological and/or non-pharmacological inhibition of neointimal hyperplasia will likely result in further reductions in the incidence if restenosis. The continued attractiveness of percutaneous coronary revascularisation, as an alternative to medical treatment or bypass surgery for patients with coronary artery disease, will depend upon our ability to control the restenotic process. Due to the vast literature on the subject, this review will focus mainly on clinical trials that show the most promise and will highlight those that warrant further investigation.

Effect of the direct nitric oxide donors linsidomine and molsidomine on angiographic restenosis after coronary balloon angioplasty. The ACCORD Study. Angioplastic Coronaire Corvasal Diltiazem

BACKGROUND

Nitric oxide (NO) donors, in addition to their vasodilator effect, decrease platelet aggregation and inhibit vascular smooth muscle cell proliferation. These actions could have beneficial effects on restenosis after coronary balloon angioplasty.

METHODS AND RESULTS

In a prospective multicenter, randomized trial, 700 stable coronary patients scheduled for angioplasty received direct NO donors (infusion of linsidomine followed by oral molsidomine) or oral diltiazem. Treatment was started before angioplasty and continued until 12 to 24 hours before follow-up angiography at 6 months. The primary study end point was minimal lumen diameter, assessed by quantitative coronary angiography, 6 months after balloon angioplasty. Clinical variables were well matched in both groups. However, despite intracoronary administration of isosorbide dinitrate, the reference diameter in the NO donor group was significantly greater than in the diltiazem group on the preangioplasty, postangioplasty, and follow-up angiograms. Pretreatment with an NO donor was associated with a modest improvement in the immediate angiographic result compared with pretreatment with diltiazem (minimum luminal diameter, 1.94 versus 1.81 mm; P = .001); this improvement was maintained at the 6-month angiographic follow-up (minimal lumen diameter, 1.54 versus 1.38 mm; P = .007). The extent of late luminal narrowing did not differ significantly between groups (loss index in the NO donor and diltiazam groups, 0.35 +/- 0.78 and 0.46 +/- 0.74, respectively; P = .103). Restenosis, defined as a binary variable (> or = 50% stenosis), occurred less often in the NO donor group (38.0% versus 46.5%; P = .026). Combined major clinical events (death, nonfatal myocardial infarction, and coronary revascularization) were similar in the two groups (32.2% versus 32.4%).

CONCLUSIONS

Treatment with linsidomine and molsidomine was associated with a modest improvement in the long-term angiographic result after angioplasty but had no effect on clinical outcome. The improved angiographic result related predominantly to a better immediate procedural result, because late luminal loss did not differ significantly between groups.

Molsidomine: alternative approaches to treat myocardial ischemia

The long-acting antianginal drug molsidomine has been shown experimentally to reduce myocardial infarct size when administered prior to or after cardiac insult. This is due to several drug actions. Dilation of postcapillary capacitance vessels diminishes venous return, preload, heart dimensions, and myocardial oxygen consumption. Relaxation of stenosed conductive coronary arteries increases the perfusion of myocardial areas at risk of infarction due to enhanced collateral circulation. Increased regional blood supply nourishes predominantly subendocardial cardiac muscles as a result of reduction of extravascular coronary pressure, and resistance. The stable heart rate and cardiac contractility favor improved heart performance. The inhibition of platelet aggregation in vivo by molsidomine or its active metabolites, SIN-1 and SIN-1A, is linked to the stimulation of prostacyclin synthesis, inhibition of thromboxane release with induction of thrombosis and vasoconstriction, and enhanced concentrations of cyclic guanosine monophosphate. Dilation of coronary arteries after intracoronary administration of SIN-1, with inhibition of platelet aggregation by restrained release of adenosine diphosphate and stabilization of platelet membranes, facilitates the recanalization of stenosed arteries and reduces coronary muscle tone at the site of thrombosis. Activation of the human fibrinolytic system and drug-induced release of a plasminogen activator favor dysaggregatory effects. The drug's inhibiting actions on lipoxygenase products of arachidonate (e.g., 12-hydroperoxy-eicosatetraenoic acid and leukotrienes) may shift prostaglandin catabolism to cyclooxygenase products (e.g., prostacyclin) that protect against the expansion of ischemia and the induction of coronary spasm. Experimentally, the hemodynamic effectiveness of molsidomine can be antagonized by catecholamines (afterload effects) and dihydroergotamine (preload and afterload effects) respectively. Further clinical investigations will clarify the application of these mechanisms for the therapeutic success of the drug in human myocardial infarction.

Long-term clinical and hemodynamic results of molsidomine treatment in patients with refractory heart failure

In this report we describe the clinical and hemodynamic response of refractory cardiac failure to molsidomine. In the first part of the study the hemodynamic effects of a single oral dose of 2 or 4 mg of molsidomine were compared with placebo control in 23 patients. In the second phase the dose 8 to 24 mg/24 hours was used in nine patients with functional class III or IV symptoms over an average period of 28 months (range 7 to 42 months); a hemodynamic control study was performed. These data demonstrate that molsidomine has a hemodynamic effect on pulmonary artery pressure for 5 to 6 hours, that the peak effect is reached between 1 and 1 1/2 hours after oral intake, and that the clinical and hemodynamic benefits of molsidomine may be maintained in the long term in patients with particularly severe cardiac failure. The conditions of seven patients were clinically improved with treatment; significant reductions in mean right atrial, pulmonary artery, and pulmonary capillary pressures were observed.

Effects of molsidomine on exercise tolerance in patients with coronary heart disease

We performed a double-blind crossover study with molsidomine in 10 patients with coronary heart disease. A single dose of molsidomine and placebo were given sublingually 1 hour before an exercise tolerance test. Molsidomine significantly reduced systolic blood pressure at rest and at all work-loads. There was also a significant reduction in electrocardiographic ST-segment depression at submaximal exercise. At maximal exercise the drug significantly increased symptom-limited oxygen consumption and total mechanical work. Molsidomine could prove useful in the treatment of angina pectoris. It has no adverse effects on pulmonary function.

Anti-ischemic effects of molsidomine in an experimental model of coronary artery stenosis

The effect of molsidomine, a novel antianginal agent, on the epicardial electrographic changes induced by reduced perfusion of the left anterior descending coronary artery (LAD) was investigated in the anesthetized dog. The LAD was cannulated and perfused at a constant volume with blood taken from a carotid artery. The perfusion volume was than reduced by approximately 75%. The sum of the ST-segment changes obtained from six unipolar epicardial leads was taken as a measure of myocardial hypoxia. Simultaneously, heart rate, blood pressure, left ventricular end-diastolic pressure, pulmonary arterial pressure, and heart contractility were also recorded. In control animals, reduction of the perfusion volume of the LAD resulted in a dramatic elevation of the ST segments lasting more than 4 hr. Molsidomine administered after the induction of the ischemia at a dose of 0.05 mg/kg i.v. resulted within 40 min in a complete normalization of the electrographic changes. This effect was evident for over 4 hr in spite of the continuous reduced perfusion of the LAD. The beneficial effect of molsidomine on the electrical changes paralleled the reduction of the left ventricular end-diastolic pressure. It is suggested that the effect of molsidomine on the ischemic electrographic changes is brought about by a reduction of the preload, resulting in a better perfusion of the ischemic zones.

[Effect of molsidomine on hemodynamics and myocardial ischemia in patients with acute myocardial infarction (author's transl)]

The effect of molsidomine on hemodynamics and myocardial ischemia were studied in 48 patients with acute myocardial infarction. Between 8 and 12 mg of orally and intravenously administered molsidomine led to a significant reduction in left ventricular filling pressure. In response to 2 x 4 mg p.o., diastolic pulmonary arterial pressure fell from 12.1 to 8.8 mm Hg in patients with filling pressure below 20 mm Hg. Patients with left heart failure and left ventricular filling pressure above 20 mm Hg (Group 2) displayed a decline in filling pressure from 23.8 to 17.4 mm Hg following 12 mg i.v. In addition, right atrial pressure dropped significantly across the entire range of dosages. Although patients without left ventricular failure (Group I) showed a decline in cardiac output (5.7 to 4.7 l/min), this parameter remained unchanged in Group 2. Heart rate in Group 2 fell from 85 to 81 per min. Arterial blood pressure was reduced by a mean of only 10 mm Hg at high dosages and remained unchanged at lower dosages. No change was observed in peripheral resistance. The maximum effect was seen 30 min after oral administration. Three hours later, the effect was reduced by half. Only minimal activity could be observed after 8 h. The incidence of side effects was low, with transient headaches occurring in 8% of the patients. An intraindividual comparison with 1.6 mg of sublingually administered nitroglycerin demonstrated no significant difference in hemodynamic effectiveness (n = 11). Molsidomine, not unlike nitroglycerin, exerts a favorable effect on hemodynamics and myocardial ischemia. It acts primarily to reduce preload. The additional moderate effect on afterload with a slight decline in arterial pressure at high dosages may also be considered advantageous.