Treatment of pulmonary hypertension caused by left heart failure with pulmonary arterial hypertension-specific therapies: lessons from the right and LEPHT

Olinciguat, an Oral sGC Stimulator, Exhibits Diverse Pharmacology Across Preclinical Models of Cardiovascular, Metabolic, Renal, and Inflammatory Disease

Nitric oxide (NO)-soluble guanylate cyclase (sGC)-cyclic 3',5' GMP (cGMP) signaling plays a central role in regulation of diverse processes including smooth muscle relaxation, inflammation, and fibrosis. sGC is activated by the short-lived physiologic mediator NO. sGC stimulators are small-molecule compounds that directly bind to sGC to enhance NO-mediated cGMP signaling. Olinciguat, (R)-3,3,3-trifluoro-2-(((5-fluoro-2-(1-(2-fluorobenzyl)-5-(isoxazol-3-yl)-1H-pyrazol-3-yl)pyrimidin-4-yl)amino)methyl)-2-hydroxypropanamide, is a new sGC stimulator currently in Phase 2 clinical development. To understand the potential clinical utility of olinciguat, we studied its pharmacokinetics, tissue distribution, and pharmacologic effects in preclinical models. Olinciguat relaxed human vascular smooth muscle and was a potent inhibitor of vascular smooth muscle proliferation in vitro. These antiproliferative effects were potentiated by the phosphodiesterase 5 inhibitor tadalafil, which did not inhibit vascular smooth muscle proliferation on its own. Olinciguat was orally bioavailable and predominantly cleared by the liver in rats. In a rat whole body autoradiography study, olinciguat-derived radioactivity in most tissues was comparable to plasma levels, indicating a balanced distribution between vascular and extravascular compartments. Olinciguat was explored in rodent models to study its effects on the vasculature, the heart, the kidneys, metabolism, and inflammation. Olinciguat reduced blood pressure in normotensive and hypertensive rats. Olinciguat was cardioprotective in the Dahl rat salt-sensitive hypertensive heart failure model. In the rat ZSF1 model of diabetic nephropathy and metabolic syndrome, olinciguat was renoprotective and associated with lower circulating glucose, cholesterol, and triglycerides. In a mouse TNFα-induced inflammation model, olinciguat treatment was associated with lower levels of endothelial and leukocyte-derived soluble adhesion molecules. The pharmacological features of olinciguat suggest that it may have broad therapeutic potential and that it may be suited for diseases that have both vascular and extravascular pathologies.

Pulmonary hypertension caused by pulmonary venous hypertension

The effect of pulmonary venous hypertension (PVH) on the pulmonary circulation is extraordinarily variable, ranging from no impact on pulmonary vascular resistance (PVR) to a marked increase. The reasons for this are unknown. Both acutely reversible pulmonary vasoconstriction and pathological remodeling (especially medial hypertrophy and intimal hyperplasia) account for increased PVR when present. The mechanisms involved in vasoconstriction and remodeling are not clearly defined, but increased wall stress, especially in small pulmonary arteries, presumably plays an important role. Myogenic contraction may account for increased vascular tone and also indirectly stimulate remodeling of the vessel wall. Increased wall stress may also directly cause smooth muscle growth, migration, and intimal hyperplasia. Even long-standing and severe pulmonary hypertension (PH) usually abates with elimination of PVH, but PVH-PH is an important clinical problem, especially because PVH due to left ventricular noncompliance lacks definitive therapy. The role of targeted PH therapy in patients with PVH-PH is unclear at this time. Most prospective studies indicate that these medications are not helpful or worse, but there is ample reason to think that a subset of patients with PVH-PH may benefit from phosphodiesterase inhibitors or other agents. A different approach to evaluating possible pharmacologic therapy for PVH-PH may be required to better define its possible utility.

New insights into the role of soluble guanylate cyclase in blood pressure regulation

PURPOSE OF REVIEW

Nitric oxide (NO)-soluble guanylate cyclase (sGC)-dependent signaling mechanisms have a profound effect on the regulation of blood pressure (BP). In this review, we will discuss recent findings in the field that support the importance of sGC in the development of hypertension.

RECENT FINDINGS

The importance of sGC in BP regulation was highlighted by studies using genetically modified animal models, chemical stimulators/activators and inhibitors of the NO/sGC signaling pathway, and genetic association studies in humans. Many studies further support the role of NO/sGC in vasodilation and vascular dysfunction, which is underscored by the early clinical success of synthetic sGC stimulators for the treatment of pulmonary hypertension. Recent work has uncovered more details about the structural basis of sGC activation, enabling the development of more potent and efficient modulators of sGC activity. Finally, the mechanisms involved in the modulation of sGC by signaling gases other than NO, as well as the influence of redox signaling on sGC, have been the subject of several interesting studies.

SUMMARY

sGC is fast becoming an interesting therapeutic target for the treatment of vascular dysfunction and hypertension, with novel sGC stimulating/activating compounds as promising clinical treatment options.

Additional use of a phosphodiesterase 5 inhibitor in patients with pulmonary hypertension secondary to chronic systolic heart failure: a meta-analysis

AIMS

Increased indiscriminate use of pulmonary artery hypertension-targeted drugs has been observed in patients with pulmonary hypertension (PH) secondary to heart failure. We performed a meta-analysis to evaluate the chronic effects of using phosphodiesterase 5 (PDE5) inhibitors to treat patients with PH secondary to chronic systolic heart failure.

METHODS AND RESULTS

PubMed, EMBASE, and the Cochrane Library were searched up to October 2013 for randomized controlled trials (RCTs) assessing PDE5 inhibitor treatments in PH patients secondary to chronic heart failure. Six RCTs involving 206 chronic systolic heart failure patients with PH complications were included. Sildenafil was used in all trials. Sildenafil treatment resulted in fewer hospital admissions compared with the placebo treatment (3.15% vs. 12.20%; risk ratio 0.29; 95% confidence interval 0.11-0.77). Various haemodynamic parameters were improved with additional sildenafil treatment, including reduced mean pulmonary artery pressure [weighted mean difference (WMD) -5.71 mmHg, P<0.05] and pulmonary vascular resistance (WMD -81.5 dynes/cm(-5), P<0.00001), increased LVEF (WMD 3.95%, P<0.01), and unchanged heart rate and blood pressure. The exercise capacity improved (oxygen consumption at peak exercise, WMD 3.20 mL/min(-1)/kg(-1), P<0.00001; ventilation to CO2 production slope, WMD -5.89, P<0.00001), and the clinical symptoms were relieved based on the breathlessness (WMD 7.72, P<0.00001), fatigue (WMD 2.28, P<0.05), and emotional functioning (WMD 5.92, P<0.00001) scores.

CONCLUSIONS

Additional sildenafil treatment is a potential therapeutic method to improve pulmonary exercise capacity and quality of life by ameliorating PH in patients with chronic systolic heart failure.