Patrick Hess

Promotion of sleep by targeting the orexin system in rats, dogs and humans

Orexins are hypothalamic peptides that play an important role in maintaining wakefulness in mammals. Permanent deficit in orexinergic function is a pathophysiological hallmark of rodent, canine and human narcolepsy. Here we report that in rats, dogs and humans, somnolence is induced by pharmacological blockade of both orexin OX1 and OX2 receptors. When administered orally during the active period of the circadian cycle, a dual antagonist increased, in rats, electrophysiological indices of both non-REM and, particularly, REM sleep, in contrast to GABAA receptor modulators; in dogs, it caused somnolence and increased surrogate markers of REM sleep; and in humans, it caused subjective and objective electrophysiological signs of sleep. No signs of cataplexy were observed, in contrast to the rodent, dog or human narcolepsy syndromes. These results open new perspectives for investigating the role of endogenous orexins in sleep-wake regulation.

A novel genomic signature with translational significance for human idiopathic pulmonary fibrosis.

The bleomycin-induced rodent lung fibrosis model is commonly used to study mechanisms of lung fibrosis and to test potential therapeutic interventions, despite the well recognized dissimilarities to human idiopathic pulmonary fibrosis (IPF). Therefore, in this study, we sought to identify genomic commonalities between the gene expression profiles from 100 IPF lungs and 108 control lungs that were obtained from the Lung Tissue Research Consortium, and rat lungs harvested at Days 3, 7, 14, 21, 28, 42, and 56 after bleomycin instillation. Surprisingly, the highest gene expression similarity between bleomycin-treated rat and IPF lungs was observed at Day 7. At this point of maximal rat-human commonality, we identified a novel set of 12 disease-relevant translational gene markers (C6, CTHRC1, CTSE, FHL2, GAL, GREM1, LCN2, MMP7, NELL1, PCSK1, PLA2G2A, and SLC2A5) that was able to separate almost all patients with IPF from control subjects in our cohort and in two additional IPF/control cohorts (GSE10667 and GSE24206). Furthermore, in combination with diffusing capacity of carbon monoxide measurements, four members of the translational gene marker set contributed to stratify patients with IPF according to disease severity. Significantly, pirfenidone attenuated the expression change of one (CTHRC1) translational gene marker in the bleomycin-induced lung fibrosis model, in transforming growth factor-β1-treated primary human lung fibroblasts and transforming growth factor-β1-treated human epithelial A549 cells. Our results suggest that a strategy focused on rodent model-human disease commonalities may identify genes that could be used to predict the pharmacological impact of therapeutic interventions, and thus facilitate the development of novel treatments for this devastating lung disease.

Short-Term Endothelin Receptor Blockade With Tezosentan Has Both Immediate and Long-Term Beneficial Effects in Rats With Myocardial Infarction

OBJECTIVES We investigated the effects of short-term tezosentan treatment on cardiac function, pulmonary edema and long-term evolution of heart failure (HF) in a rat model of myocardial infarction (MI). BACKGROUND Endothelin (ET) may play a major role in the progression from MI to HF. Tezosentan is a new dual ET(A)/ET(B) receptor antagonist. METHODS Rats were subjected to coronary artery ligation and were treated with either vehicle or tezosentan (10 mg/kg IV bolus) at 1 h and 24 h after MI. Cardiac hemodynamics and lung weight were measured at 48 h after MI. Survival was assessed over a five-month period. RESULTS At 48 h after ligation, vehicle-treated rats developed HF, as evidenced by a marked increase in left ventricular end-diastolic pressure (LVEDP), reduction in dP/dt(max) and mean arterial pressure (MAP), and development of pulmonary edema. Tezosentan treatment attenuated the increase in LVEDP and in lung weight and slightly reduced MAP without affecting dP/dt(max). Infarct size was not modified by tezosentan. Despite the fact that treatment with tezosentan was stopped after 24 h, the initial tezosentan administration significantly reduced cardiac hypertrophy (22%) and decreased mortality by 51% at five months (50% survival vs. 19% survival in vehicle-treated rats, p < 0.001). CONCLUSIONS Tezosentan administered during the first day after MI in rats, in addition to improving acutely hemodynamic conditions, markedly increases long-term survival. This increase is associated with a decrease of pulmonary edema and prevention of cardiac hypertrophy. Tezosentan could be a safe and useful therapeutic agent in the prevention and treatment of ischemic HF.

Comparison of pharmacological activity of macitentan and bosentan in preclinical models of systemic and pulmonary hypertension

AIMS The endothelin (ET) system is a tissular system, as the production of ET isoforms is mostly autocrine or paracrine. Macitentan is a novel dual ETA/ETB receptor antagonist with enhanced tissue distribution and sustained receptor binding properties designed to achieve a more efficacious ET receptor blockade. To determine if these features translate into improved efficacy in vivo, a study was designed in which rats with either systemic or pulmonary hypertension and equipped with telemetry were given macitentan on top of maximally effective doses of another dual ETA/ETB receptor antagonist, bosentan, which does not display sustained receptor occupancy and shows less tissue distribution. MAIN METHODS After establishing dose-response curves of both compounds in conscious, hypertensive Dahl salt-sensitive and pulmonary hypertensive bleomycin-treated rats, macitentan was administered on top of the maximal effective dose of bosentan. KEY FINDINGS In hypertensive rats, macitentan 30 mg/kg further decreased mean arterial blood pressure (MAP) by 19 mm Hg when given on top of bosentan 100 mg/kg (n=9, p<0.01 vs. vehicle). Conversely, bosentan given on top of macitentan failed to induce an additional MAP decrease. In pulmonary hypertensive rats, macitentan 30 mg/kg further decreased mean pulmonary artery pressure (MPAP) by 4 mm Hg on top of bosentan (n=8, p<0.01 vs. vehicle), whereas a maximal effective dose of bosentan given on top of macitentan did not cause any additional MPAP decrease. SIGNIFICANCE The add-on effect of macitentan on top of bosentan in two pathological models confirms that this novel compound can achieve a superior blockade of ET receptors and provides evidence for greater maximal efficacy.

Measurements of blood pressure and electrocardiogram in conscious freely moving guineapigs: a model for screening QT interval prolongation effects

The pro-arrhythmic risk inherent to a new drug must be assessed at an early preclinical stage. Telemetry system implantation is a method widely used in vivo in various species. The present study was designed to assess whether conscious freely moving guineapigs can be used to predict QT prolongation in vivo. The guineapig has three advantages over the dog and the primate. First, it has specific ion channels similar to man; second, a smaller amount of test article is required for the investigation and third, its housing is less expensive. Under sterile conditions and isoflurane anaesthesia, telemetry transmitters were implanted intraperitoneally in male Dunkin Hartley guineapigs. Blood pressure, heart rate and electrocardiographic intervals were measured from two days up to eight months. Chronic implantation of the telemetry device did not lead to anatomic or macroscopic alterations in the abdominal cavity and no inflammation of the peritoneum or infection was observed. Four reference compounds were used: three positive (sotalol, terfenadine and dofetilide) and one negative reference (enalapril). Single oral administration of all three positive references dose-dependently induced bradycardia and QT corrected (QTc) prolongation. In contrast, neither enalapril nor its vehicle prolonged the QTc. These results demonstrate that the guineapig is both a suitable model and a good alternative to dogs or primates to assess the potential of compounds for QT interval prolongation in the early stages of drug development.

Chronic endothelin receptor blockade prevents renal vasoconstriction and sodium retention in rats with chronic heart failure

OBJECTIVE Importance of endothelin in mediating the chronic renal alterations of chronic heart failure was studied in rats chronically treated with bosentan after myocardial infarction. METHODS Rats were subjected to coronary artery ligation and were treated for 8 weeks with placebo or bosentan, a dual ET(A) and ET(B) receptor antagonist, (approximately 100 mg/kg/day) as food admix. Sham-operated rats served as normal controls. Cardiac and renal functions were measured at the end of 8-week treatment. RESULTS Bosentan significantly reduced the elevated left ventricular end-diastolic pressure (from 26.6+/-3.3 to 11.4+/-2.2 mmHg, P<0.001) and the increased heart-to-body-weight ratio seen in untreated rats with myocardial infarction. Bosentan prevented the marked increase in renal vascular resistance (bosentan, 7.7+/-0.6; untreated, 15.6+/-2.5 mmHg/ml/min; P<0.001). This led to a significant increase in renal plasma flow resulting in a decrease in filtration fraction. Bosentan furthermore increased urinary sodium excretion. CONCLUSIONS Prolonged ET receptor blockade in rats with myocardial infarction has chronic renal vasodilatory effect and improves renal sodium excretory function. Thus, dual ET antagonists such as bosentan might be useful in the treatment of the progressive renal failure associated with human chronic heart failure.

Combination of non-hypotensive doses of valsartan and enalapril improves survival of spontaneously hypertensive rats with endothelial dysfunction

There is increasing evidence to suggest endothelial dysfunction as a critical factor in vascular diseases. Genetically predisposed spontaneously hypertensive rats (SHR) treated with inhibitors of nitric oxide (NO) synthase, develop a severe hypertensive nephrosclerosis without the necessity for surgical reduction in renal mass, nephrectomy, renal infarction or nephrotoxic drugs. In these animals, endothelial dysfunction is considered a valid model for assessment of the efficacy of cardiovascular therapy. SHR were treated with either the angiotensin-converting enzyme inhibitor enalapril or the angiotensin II (Ang II) AT1-receptor antagonist (AIIA) valsartan at sub-hypotensive doses and the effects on survival rates, cardiac and renal changes were monitored. Rats treated with valsartan, alone or in combination with enalapril, showed markedly higher survival rates (67—85%, respectively) than untreated animals (37%) or those treated with enalapril alone (55%). Valsartan at a dose which attenuated blood pressure increase led to even greater survival rates (95%). Despite these improved survival rates, at non-hypotensive doses the drugs had no effect on histological appearance, nor was kidney function improved. Plasma creatinine levels were reduced by valsartan, alone or in combination with enalapril, but proteinuria persisted with all treatments over the 12 weeks of the study. Aldosterone levels were significantly reduced by all treatments. The results suggest a beneficial role for endothelium in hypertension. Reduced renal perfusion pressure probably underlies the beneficial renal effects of high-dose valsartan.

Macitentan Does Not Interfere with Hepatic Bile Salt Transport

Treatment of pulmonary arterial hypertension with the endothelin receptor antagonist bosentan has been associated with transient increases in liver transaminases. Mechanistically, bosentan inhibits the bile salt export pump (BSEP) leading to an intrahepatic accumulation of cytotoxic bile salts, which eventually results in hepatocellular damage. BSEP inhibition by bosentan is amplified by its accumulation in the liver as bosentan is a substrate of organic anion-transporting polypeptide (OATP) transport proteins. The novel endothelin receptor antagonist macitentan shows a superior liver safety profile. Introduction of the less acidic sulfamide moiety and increased lipophilicity yield a hepatic disposition profile different from other endothelin receptor antagonists. Passive diffusion rather than OATP-mediated uptake is the driving force for macitentan uptake into the liver. Interaction with the sodium taurocholate cotransporting polypeptide and BSEP transport proteins involved in hepatic bile salt homeostasis is therefore limited due to the low intrahepatic drug concentrations. Evidence for this conclusion is provided by in vitro experiments in drug transporter-expressing cell lines, acute and long-term studies in rats and dogs, absence of plasma bile salt changes in healthy human volunteers after multiple dosing, and finally the liver safety profile of macitentan in the completed phase III morbidity/mortality SERAPHIN (Study with an Endothelin Receptor Antagonist in Pulmonary Arterial Hypertension to Improve Clinical Outcome) trial.

Piperidine-based renin inhibitors: upper chain optimization.

The optimization of the 4-position of recently described new 3,4-disubstituted piperidine-based renin inhibitors is reported herein. The synthesis and characterization of compounds leading to the discovery of 11 (ACT-178882, MK-1597), a renin inhibitor with a suitable profile for development is described.

Design and optimization of new piperidines as renin inhibitors

The discovery of a new series of piperidine-based renin inhibitors is described herein. SAR optimization upon the P3 renin sub-pocket is described, leading to the discovery of 9 and 41, two bioavailable renin inhibitors orally active at low doses in a transgenic rat model of hypertension.