Soluble Guanylate Cyclase Stimulator Research Articles

The effects of the soluble guanylate cyclase stimulator riociguat on memory performance in healthy volunteers with a biperiden-induced memory impairment

RationaleAfter stimulation with nitric oxide, soluble guanylate cyclase (sGC) produces cyclic guanosine monophosphate (cGMP), which stimulates an important signalling pathway for long-term potentiation (LTP). By upregulating cGMP, LTP could be stimulated and thereby enhancing memory processes. The present study investigated the effects of the sGC stimulator riociguat on cognition in healthy volunteers. Participants were pre-treated with and without biperiden, which impairs memory performance, to investigate the memory-enhancing effects of riociguat.MethodsTwenty volunteers participated in a double-blind placebo-controlled six-way crossover design with a cognitive test battery including the verbal learning task (VLT), n-back task, spatial memory test, the attention network test, and a reaction time task. Treatments were placebo and riociguat 0.5 mg, placebo and riociguat 1.0 mg, biperiden 2.0 mg and placebo, biperiden 2.0 mg and riociguat 0.5 mg and biperiden 2.0 mg and riociguat 1.0 mg.ResultsBlood pressure was found to be decreased and heart rate to be increased after administration of riociguat. Cognitive performance was not enhanced after administration of riociguat. Biperiden decreased episodic memory on the VLT, yet this deficit was not reversed by riociguat.ConclusionThis supports the notion that biperiden might be a valuable pharmacological model to induce episodic memory impairments as observed in AD/MCI.

Pulmonary Arterial Hypertension: Pathophysiology and Treatment

Pulmonary arterial hypertension (PAH), the first category of pulmonary hypertension, is a chronic and progressive disorder characterised by angioproliferative vasculopathy in the pulmonary arterioles, leading to endothelial and smooth muscle proliferation and dysfunction, inflammation and thrombosis. These changes increase pulmonary vascular resistance and subsequent pulmonary arterial pressure, causing right ventricular failure which leads to eventual death if untreated. The management of PAH has advanced rapidly in recent years due to improved understanding of the condition’s pathophysiology, specifically the nitric oxide, prostacyclin-thromboxane and endothelin-1 pathways. Five classes of drugs targeting these pathways are now available: phosphodiesterase-5 inhibitors, soluble guanylate cyclase stimulators, prostacyclin analogues, prostacyclin receptor agonists and endothelin receptor antagonists. These developments have led to substantial improvements in mortality rate in recent decades. Recently, long-term studies have demonstrated sustained progression-free survival and have created a new paradigm of initial combination therapy. Despite these targeted therapies, PAH is still associated with significant morbidity and mortality. As such, further research into broadening our understanding of PAH pathophysiology is underway with potential of increasing the repertoire of drugs available.

Acute stimulation of the soluble guanylate cyclase does not impact on left ventricular capacitance in normal and hypertrophied porcine hearts in vivo.

Experimental data indicate that stimulation of the nitric oxide-soluble guanylate cyclase(sGC)-cGMP-PKG pathway can increase left ventricular (LV) capacitance via phosphorylation of the myofilamental protein titin. We aimed to test whether acute pharmacological sGC stimulation with BAY 41-8543 would increase LV capacitance via titin phosphorylation in healthy and deoxycorticosteroneacetate (DOCA)-induced hypertensive pigs. Nine healthy Landrace pigs and 7 pigs with DOCA-induced hypertension and LV concentric hypertrophy were acutely instrumented to measure LV end-diastolic pressure-volume relationships (EDPVRs) at baseline and during intravenous infusion of BAY 41-8543 (1 and 3 μg·kg-1·min-1 for 30 min, respectively). Separately, in seven healthy and six DOCA pigs, transmural LV biopsies were harvested from the beating heart to measure titin phosphorylation during BAY 41-8543 infusion. LV EDPVRs before and during BAY 41-8543 infusion were superimposable in both healthy and DOCA-treated pigs, whereas mean aortic pressure decreased by 20-30 mmHg in both groups. Myocardial titin phosphorylation was unchanged in healthy pigs, but total and site-specific (Pro-Glu-Val-Lys and N2-Bus domains) titin phosphorylation was increased in DOCA-treated pigs. Bicoronary nitroglycerin infusion in healthy pigs ( n = 5) induced a rightward shift of the LV EDPVR, demonstrating the responsiveness of the pathway in this model. Acute systemic sGC stimulation with the sGC stimulator BAY 41-8543 did not recruit an LV preload reserve in both healthy and hypertrophied LV porcine myocardium, although it increased titin phosphorylation in the latter group. Thus, increased titin phosphorylation is not indicative of increased in vivo LV capacitance. NEW & NOTEWORTHY We demonstrate that acute pharmacological stimulation of soluble guanylate cyclase does not increase left ventricular compliance in normal and hypertrophied porcine hearts. Effects of long-term soluble guanylate cyclase stimulation with oral compounds in disease conditions associated with lowered myocardial cGMP levels, i.e., heart failure with preserved ejection fraction, remain to be investigated.

Stimulation of nitric oxide-sensitive soluble guanylate cyclase in monocrotaline-induced pulmonary hypertensive rats

AimsIn this study, we examined whether a disruption in the balance between nitric oxide (NO)-sensitive and -insensitive soluble guanylate cyclase (sGC) is observed in pulmonary hypertension (PH) and whether treatment with NO-enhancing drugs can halt disease progression. Main methodsRats were injected subcutaneously with saline or 60 mg/kg monocrotaline (MCT). At 14 days after injection, the vascular reactivity of isolated extralobar pulmonary arteries was assessed by organ chamber technique. In a separate experiment, isosorbide mononitrate (0.3 or 1 g/L) or sodium nitrite (30 or 300 mg/L) was administered in drinking water for the last 14 days (from day 15 to day 28), and their therapeutic potential was evaluated. Key findingsThe NO-sensitive sGC stimulant BAY 41-2272 and the NO-insensitive sGC stimulant BAY 60-2770 both relaxed the pulmonary arteries, which was comparable between saline- and MCT-injected rats. Treatment with isosorbide mononitrate suppressed the MCT-induced right ventricular systolic pressure (RVSP) elevation and pulmonary arterial medial thickening but not right ventricular hypertrophy. However, the beneficial effects on RVSP and pulmonary vascular remodeling were not observed when a high dose was administered. The same results were obtained following the sodium nitrite treatment. Interestingly, NO-enhancing drugs did not increase plasma nitrite plus nitrate levels at a dose that provided the greatest therapeutic advantage. SignificanceThese findings suggest that the balance between NO-sensitive and -insensitive sGC is not disrupted in the early stage of MCT-induced PH. Furthermore, supplementation with an adequate amount of NO may be a useful therapy to prevent the progression of PH.

Pharmacological Characterization of IW-1973, a Novel Soluble Guanylate Cyclase Stimulator with Extensive Tissue Distribution, Antihypertensive, Anti-Inflammatory, and Antifibrotic Effects in Preclinical Models of Disease

Soluble guanylate cyclase (sGC), a key signal-transduction enzyme, increases the conversion of guanosine-5'-triphosphate to cGMP upon binding of nitric oxide (NO). Endothelial dysfunction and/or reduced NO signaling have been implicated in cardiovascular disease pathogenesis and complications of diabetes and have been associated with other disease states and aging. Soluble guanylate cyclase (sGC) stimulators are small-molecule drugs that bind sGC and enhance NO-mediated cGMP signaling. The pharmacological characterization of IW-1973 [1,1,1,3,3,3-hexafluoro-2-(((5-fluoro-2-(1-(2-fluorobenzyl)-5-(isoxazol-3-yl)-1H-pyrazol-3-yl) pyrimidin-4-yl)amino)methyl)propan-2-ol], a novel clinical-stage sGC stimulator under clinical investigation for treatment of heart failure with preserved ejection fraction and diabetic nephropathy, is described. In the presence of NO, IW-1973 stimulated sGC in a human purified enzyme assay and a HEK-293 whole cell assay. sGC stimulation by IW-1973 in cells was associated with increased phosphorylation of vasodilator-stimulated phosphoprotein. IW-1973, at doses of 1-10 mg/kg, significantly lowered blood pressure in normotensive and spontaneously hypertensive rats. In a Dahl salt-sensitive hypertension model, IW-1973 significantly reduced blood pressure, inflammatory cytokine levels, and renal disease markers, including proteinuria and renal fibrotic gene expression. The results were affirmed in mouse lipopolysaccharide-induced inflammation and rat unilateral ureteral obstruction renal fibrosis models. A quantitative whole-body autoradiography study of IW-1973 revealed extensive tissue distribution and pharmacokinetic studies showed a large volume of distribution and a profile consistent with predicted once-a-day dosing in humans. In summary, IW-1973 is a potent, orally available sGC stimulator that exhibits renoprotective, anti-inflammatory, and antifibrotic effects in nonclinical models.

A Hopeful Prospect of Riociguat as a Soluble Guanylate Cyclase Stimulator for Management of Pressure Ulcers.

Pressure ulcer remains as a common problem, especially developed in disabled patients and hence, subjected to continuous pressure for prolonged periods of time. Most of the studies investigating the preventive and therapeutic approaches have focused on wound cleansing, dressing and supportive strategies, as well as pharmacological therapy including zinc sulphate, vitamin A or phenytoin. Despite such efforts, pressure ulcer continues to impair the life quality and expectancy. Thus involving in the paradigm shift in biomedical studies, the recent ones focus on biological signaling pathways involving nitric oxide (NO)- soluble guanylatecyclase (sGC)- cyclic guanosine monophosphate (cGMP) contributing in vasodilation, reperfusion and oxygen delivery. Literatures review focusing on NO/sGC/cGMP pathway was performed as well as seeking themolecular biology aspects inKyoto Encyclopedia of genes and genomes (KEGG). NO is an important signaling molecule activating sGC and cGMP production, which is a mediator of vasodilation and platelet inhibition. Considering the subject, it could be hypothesized that the application of sGC stimulators and activators is a very curious strategy for pressure ulcer healing. It is well known that pressure and shear forces usually produce the blood vessel obstruction, inducing ischemia and tissue necrosis and in pathologic states, damaged endothelium leads to a reduced synthesis of NO and inadequate oxygen supply contributing to delayed wound healing. Riociguat is the first FDA approved agent of new class of sGC stimulators, involving in activation of sGC both in presence and absence of NO. The findings of this review confirm that Riociguat could start a new therapeutic approach for pressure ulcer treatment even with dysfunctional endothelium.

The soluble guanylate cyclase stimulator IWP‐550 inhibits neuroinflammation in vitro and in vivo

ObjectiveIWP‐550 is a brain‐penetrant soluble guanylate cyclase (sGC) stimulator. The objective of this work was to evaluate the effects of IWP‐550 on neuroinflammation in vitro in rat primary neurons, mouse microglial cells, rat brain 3D microtissues (MT, InSphero™), and in an in vivo quinolinic acid (QA)‐induced neuroinflammation rat model.MethodsMouse microglial SIM‐A9 cells, rat primary neurons and rat brain MT were stimulated with IWP‐550 for 30 min at 37°C. cGMP levels were measured by LC/MS. Phosphorylation of vasodilator‐stimulated phosphoprotein (VASP) and CREB was assayed using CisBio HTRF kits. For cytokine studies, cells or brain MT were treated with LPS and IWP‐550 for 24 h at 37°C. IL‐6 and TNFα levels in SIM‐A9 cells were determined by ELISA. Cytokines from isolated rat primary neurons and brain MT were measured by MSD multiplex assay. Neuroinflammation was induced in vivo by injecting QA in the rat striatum followed by treatment with IWP‐550 (10 mg/kg, p.o. QD) for 7 days. In the striatum, expression of ionized calcium‐binding adapter molecule 1 (Iba1), a marker of microglial activation, and glial fibrillary acidic protein (GFAP), a marker of astrogliosis, was quantified by IHC staining. Gene expression of TNFα, CD40, and MIP1α was determined by QuantiGene MultiPlex Assay (Affymetrix).ResultsIWP‐550 dose‐dependently stimulated cGMP formation (EC50 = 16 nM) and phosphorylation of CREB in isolated rat primary neurons. IWP‐550 also stimulated cGMP formation and phosphorylation of VASP in SIM‐A9 cells in synergy with the nitric oxide donor, DETA‐NONOate (DETA). In rat primary neurons, IWP‐550 decreased secreted proinflammatory cytokines, including IL‐1β, TNFα and MCP‐1 that were elevated by LPS treatment (1 μg/ml). In SIM‐A9 cells, IWP‐550 dose‐dependently decreased LPS‐mediated IL‐6 and TNFα elevation. In brain MT containing a mix of neurons, astrocytes, microglial cells and oligodendrocytes, IWP‐550 stimulated cGMP formation and phosphorylation of CREB. Moreover, IWP‐550 (1 and 10 μM) in the presence of DETA (10 μM) reduced LPS‐induced elevation of IL‐6, IFNγ, TNFα, IL‐1β, IL‐13 and CXCL1. In rat, QA administered unilaterally in the striatum caused local brain tissue injury and led to the activation of microglia and astrocytes, as demonstrated by increases in IHC staining for Iba1 and GFAP compared to the control side of striatum. Gene expression of pro‐inflammatory cytokines TNFα, CD40 and MIP1α were also increased following QA injection. Treatment with IWP‐550 (10 mg/kg) for 7 days significantly reduced Iba1 and GFAP staining, as well as gene expression of TNFα, CD40 and MIP1α, indicating a reduction of QA‐induced astrogliosis and inflammation in vivo.ConclusionIWP‐550 suppressed neuroinflammation in vitro in primary neurons, microglial cells, and brain microtissues, as well as in vivo in QA‐treated rats. These data suggest that sGC stimulation may provide potential neuroprotective effect by reducing neuroinflammation, a hallmark of neurodegenerative diseases.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Downregulation of Guanylate Cyclase Enzyme in Human Asthma model to Investigate NO‐sGc‐ cGMP as a Therapeutic Pathway in Asthma

Asthma is characterized by airway smooth muscle hypersensitivity. Common treatments include β‐adrenergic agonist therapy, such as budesonide, to induce airway smooth muscle relaxation via increased cAMP. However, 70% of patients develop resistance to such therapies. Nitric oxide is a locally produced smooth muscle relaxant that operates via stimulation of soluble guanylate cyclase (sGc) to increase cGMP production. In this study, the NO‐sGc‐cGMP pathway was investigated as an alternate pharmacologic pathway for asthma therapy. Previous studies have found that asthma patients are insensitive to NO signaling and have used sGc drugs to directly stimulate the enzyme. The objective of this study was to examine the expression of the two sGc subunits, α and β, within smooth muscle cells isolated from asthma patients in order to understand how NO‐sGC‐cGMP signaling may be disrupted. Further, we examined how budesonide treatment altered sGc expression. RNA sequencing data showed increased mRNA for both sGc subunits in asthmatic patients and that budesonide downregulated the gene expression of both subunits. We hypothesized that this increased gene expression was in part due to a lack of cGMP signaling due to decreased protein levels that is further impaired with steroids such as budesonide. To examine sGc, we measured the protein levels of both the α and β subunits of sGC by western blot in cultured smooth muscle cells. Fatal asthma and non‐asthma donor derived primary airway smooth muscle cells were cultured with and 24 hours of budesonide treatment. Statistical analysis of western blotting was performed by ANOVA. Densitometry of sGC western blots indicated a 2‐fold downregulation of the α (p<0.0001) and 1.5 fold downregulation of the β (p<0.05) subunits in asthmatic compared to normal patients. No significant changes were observed with normal or asthmatic patients with budesonide treatment (p>0.05), indicating no effect of steroids on the NO‐sGc‐cGMP pathway. A downregulation of sGc protein levels in asthmatic patients would lower cGMP production, which could explain the lack of NO responsiveness in these patients and would contribute to increased airway constriction in fatal asthma. These results indicate the NO‐sGc‐cGMP pathway as a potential new therapeutic pathway in asthma, and future work will examine cGMP levels.Support or Funding InformationSupported by R25ES020721 and ASPET SURF Intern ProgramThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

FRI-081 - Stimulation of soluble guanylate cyclase inhibited fibrosis and inflammation in human liver microtissues and in an animal model of liver disease

FRI-081 - Stimulation of soluble guanylate cyclase inhibited fibrosis and inflammation in human liver microtissues and in an animal model of liver disease

Activation of soluble guanylyl cyclase with inhibition of multidrug resistance protein inhibitor-4 (MRP4) as a new antiplatelet therapy

The intracellular levels of cyclic GMP are controlled by its rate of formation through nitric oxide-mediated stimulation of soluble guanylate cyclase (sGC) and its degradation by phosphodiesterases. Multidrug resistance protein 4 (MRP4) expressed in human platelets pumps cyclic nucleotides out of cells. In search for new antiplatelet strategies, we tested the hypothesis that sGC activation concomitant with MRP4 inhibition confers higher antiplatelet efficacy compared with monotherapy alone. This study was undertaken to investigate the pharmacological association of the sGC activator BAY 60-2770 with the MRP4 inhibitor MK571 on human washed platelets. Collagen- and thrombin-induced platelet aggregation and ATP-release reaction assays were performed. BAY 60-2770 (0.001–10 µM) produced significant inhibitions of agonist-induced platelet aggregation accompanied by reduced ATP-release. Pre-incubation with 10 µM MK571 alone had no significant effect on platelet aggregation and ATP release, but it produced a left displacement by about of 10–100-fold in the concentration-response curves to BAY 60-2770. Pre-incubation with MK571increased and decreased, respectively, the intracellular and extracellular levels of cGMP to BAY 60-2770, whereas the cAMP levels remained unchanged. The increased VASP-serine 239 phosphorylation in BAY 60-2770-treated platelets was enhanced by MK571. In Fluo-4-loaded platelets, BAY 60-2770 reduced the intracellular Ca2+ levels, an effect significantly potentiated by MK571. Flow cytometry assays showed that BAY 60-2770 reduces the αIIbβ3 integrin activation, which was further reduced by MK571 association. Blocking the MRP4-mediated efflux of cGMP may be a potential mechanism to enhance the antiplatelet efficacy of sGC activators.

In Endothelial Cells, the Activation or Stimulation of Soluble Guanylyl Cyclase Induces the Nitric Oxide Production by a Mechanism Dependent of Nitric Oxide Synthase Activation.

In endothelial cells, investigate if the soluble guanylate cyclase (sGC) activation or stimulation is able to potentiate the relaxation in vessels. Aortic and coronary rings with and without endothelium were placed in a myograph and cumulative concentration-effect curves for DETA-NO or ataciguat were performed. Nitric oxide (NO) were measured by fluorescence or by selective electrode in human umbilical endothelial cells (HUVECs) in response to some treatments, including ataciguat, 8-Br-cGMP and A23187. The presence of the endothelium potentiated the relaxation induced by DETA-NO in aortic and coronary rings. In addition, in aortic rings the endothelium potentiated the relaxation induced by ataciguat. In the presence of nitric oxide synthase (NOS) inhibitor, the endothelium effect was abolished to DETA-NO or ataciguat, in both vessels. Ataciguat, 8-Br-cGMP and A23187 were able to induce NO production in HUVECs cells. In the presence of NOS inhibitor, the NO production induced by ataciguat and 8-Br-cGMP was abolished. Our results suggest that in aortic and coronary rings the endothelium potentiates the relaxation induced by activation or stimulation of sGC through a mechanism dependent of NOS activation.This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.

From molecules to patients: exploring the therapeutic role of soluble guanylate cyclase stimulators.

Nitric oxide (NO) signaling represents one of the major regulatory pathways for cardiovascular function. After the discovery of NO, awarded with the Nobel Prize in 1998, this signaling cascade was stepwise clarified. We now have a good understanding of NO production and NO downstream targets such as the soluble guanylyl cyclases (sGCs) which catalyze cGMP production. Based on the important role of NO-signaling in the cardiovascular system, intense research and development efforts are currently ongoing to fully exploit the therapeutic potential of cGMP increase. Recently, NO-independent stimulators of sGC (sGC stimulators) were discovered and characterized. This new compound class has a unique mode of action, directly binding to sGC and triggering cGMP production. The first sGC stimulator made available to patients is riociguat, which was approved in 2013 for the treatment of different forms of pulmonary hypertension (PH). Besides riociguat, other sGC stimulators are in clinical development, with vericiguat in phase 3 clinical development for the treatment of chronic heart failure (HF). Based on the broad impact of NO/cGMP signaling, sGC stimulators could have an even broader therapeutic potential beyond PH and HF. Within this review, the NO/sGC/cGMP/PKG/PDE-signaling cascade and the major pharmacological intervention sites are described. In addition, the discovery and mode of action of sGC stimulators and the clinical development in PH and HF is covered. Finally, the preclinical and clinical evidence and treatment approaches for sGC stimulators beyond these indications and the cardiovascular disease space, like in fibrotic diseases as in systemic sclerosis (SSc), are reviewed.

Modulation of BAY 41-2272-induced-relaxation in normotensive and hypertensive rat aorta by perivascular adipose tissue

In spontaneously hypertensive rat (SHR), perivascular adipose tissue (PVAT) has been recently identified as the effector of vascular dysfunction. In order to restore this alteration, therapeutic strategies target the cGMP/PKG pathway which is involved in both vascular and adipose tissue functions. However, direct activation of soluble guanylate cyclase, a key enzyme of this signalling pathway has not been studied yet in arterial hypertension. This study was designed to determine whether relaxation induced by BAY 41-2272, a soluble guanylate cyclase stimulator agent, was modified in SHR aorta and whether PVAT modulates this effect. Aortic rings isolated from 12-week-old Wistar Kyoto (WKY) rats and SHR were mounted in organ baths and pre-constricted with phenylephrine. Cumulative concentration-response curves to BAY 41-2272 (0.1 nM to 30 μM) were constructed in different experimental conditions in the absence or presence of endothelium and PVAT. In the absence of PVAT, BAY 41-2272 produced concentration-dependent relaxation, which was inhibited by L-NAME (100 μM), a nitric oxide (NO) synthase inhibitor only in WKY rat aorta. Endothelium denudation enhanced the BAY 41-2272-induced-relaxation only in SHR aorta. In both rat strains, relaxant effect to BAY 41-2272 was attenuated by PVAT and this was associated with a decrease in tissue cGMP content. NO and cyclo-oxygenases (COX)-derived products do not appear to participate to this impairment since 100 μM L-NAME and 10 μM indomethacin, a non-specific COX inhibitor, do not modify the BAY 41-2272-induced-relaxation. We showed for the first time that BAY 41-2272 partially relaxes WKY rat aorta by NO-dependent-mechanism and that the endothelium negatively modulates the BAY 41-2272-induced-relaxation only in hypertensive rats. The decrease of BAY 41-2272-induced-relaxation in SHR aorta by PVAT suggests the release of adipose contracting factors that need further elucidation.

Prevention and treatment of the chronic thromboembolic pulmonary hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is an uncommon and late complication of pulmonary embolism resulting from misguided remodelling of residual pulmonary thromboembolic material and small-vessel arteriopathy. CTEPH is the only form of pulmonary hypertension (PH) potentially curable by pulmonary endarterectomy (PEA). Unfortunately, several patients have either an unacceptable risk-benefit ratio for undergoing the surgical intervention or develop persistent PH after PEA. Novel medical and endovascular therapies can be considered for them. The soluble guanylate cyclase stimulator riociguat is recommended for the treatment of patients with inoperable disease or with recurrent/persistent PH after PEA. Other drugs developed for the treatment of other forms of PH, as prostanoids, phosphodiesterase-5 inhibitors and endothelin receptor antagonists have been used in the treatment of CTEPH, with limited benefit. Balloon pulmonary angioplasty is a novel and promising technique and is progressively emerging from the pioneering phase. Highly specialized training level and complex protocols of postoperative care are mandatory to consolidate the technical success of the surgical and endovascular intervention.

Multiple Avenues of Modulating the Nitric Oxide Pathway in Heart Failure Clinical Trials.

This review discusses the integral role of the nitric oxide (NO) pathway in the pathophysiology of heart failure (HF). We emphasize potential therapeutic targets in the NO pathway and review contemporary clinical trials evaluating these novel therapeutic options. Nitrates, neprilysin inhibitors, and phosphodiesterase (PDE) inhibitors have all proven to be efficacious in HF patients with systolic dysfunction, with the former two classes of medications producing a net mortality benefit. However, neither PDE inhibitors nor nitrates have demonstrated significant clinical benefit in patients with HF with preserved ejection fraction (HFpEF), and neprilysin inhibitors have yet to be evaluated in this population. Soluble guanylate cyclase (sGC) stimulators have shown significant promise in all HF patients, leading to improvements in both quality of life scores and exercise capacity. Conversely, sGC activators have limited clinical utility in HF, owing largely to safety concerns of hypotension. Inorganic nitrates and nitrites, meanwhile, may be emerging as potential therapies for the HFpEF population. The advent of novel therapies targeting the NO pathway is beginning to create a paradigm shift in the treatment of the HF patient. These therapies offer a promising outlook for the future, with hopes of reducing HF-associated morbidity and mortality.

Soluble guanylate cyclase stimulators and phosphodiesterase-5 inhibitors in therapy of some groups of pulmonary hypertension

Pulmonary hypertension (PH) is a large group of diseases characterized by pulmonary artery pressure (PAP) > 25 mm Hg. Currently, specific medications are available for several groups of PH only. These are prostacyclin analogues, soluble guanylate cyclase (sGC) stimulators (sGCS), phosphodiesterase-5 inhibitors (iPDE-5), and endothelin receptor antagonists. Modern evidence-based pharmacological treatment of PH and therapeutic algorithm have been described in this review. Particular attention was paid to mechanisms of dysregulation of vascular tone including nitric oxide (NO-sGC-cGMP) pathway that is a target for sGCS and iPDE-5. A new class of sGCS principally differs from iPDE-5 and is very important for clinical practice. Safety, availability and benefit of switching from iPDE-5 to riociguat was investigated in the RESPITE trial. Results of main clinical trials of efficacy and safety of riociguat in patients with pulmonary arterial hypertension and thromboembolic PH were also discussed in this review.

Treatment Patterns and Associated Health Care Costs Before and After Treatment Initiation Among Pulmonary Arterial Hypertension Patients in the United States.

Despite multiple treatment options, the prognosis of pulmonary arterial hypertension (PAH) remains poor. PAH patients experience a high economic burden due to comorbidities, hospitalizations, and medication costs. Although combination therapy has been shown to reduce hospitalizations, the relationship between treatment, health care utilization, and costs remains unclear. To provide a characterization of health care utilization and costs in real-world settings by comparing periods before and after initiating PAH-specific treatment. This retrospective study identified PAH patients in the Truven Health MarketScan Commercial and Medicare Supplemental Databases between 2010 and 2014 who initiated treatment with endothelin receptor antagonists (ERAs), phosphodiesterase-5 inhibitors (PDE-5Is), or soluble guanylate cyclase (sGC) stimulators. The index date was the date of the first PAH pharmacy claim. We included patients with ≥ 2 medical claims with diagnoses for PAH (ICD-9-CM: 416.0, 416.8) or PAH-related conditions and continuous enrollment in medical and pharmacy benefits for the 6 months before and after the index date. Treatment patterns were assessed at the drug class level (ERAs, PDE-5Is, sGC stimulators, and prostacyclins) from outpatient pharmacy claims during the 6-month post-index period. All-cause and PAH-related utilization and costs were measured. McNemar's and paired t-tests were used to compare patients' health care resource utilization and costs in the 6-month pre- and posttreatment periods. A total of 3,908 patients met the selection criteria. The study sample was 63% female with a mean age of 63 ± 15 years. Only 5% of patients began initial combination therapy for PAH, defined as claims for ≥ 2 medication classes within the first 30 days of treatment. Treatment interruption (≥ 30-day gap in days supply) of any PAH-specific medication was observed in 38% of patients. Compared with the 6-month pre-index period, the proportion of patients in the 6-month post-index period with any inpatient admission decreased, 42% versus 30% (P < 0.001). In addition, PAH-related inpatient admissions decreased in the 6-month post-index period from 7% to 3% (P < 0.001). After treatment initiation, patients' nonpharmacy medical costs decreased from $48,200 (SD = $117,686) to $33,962 (SD = $90,294; P < 0.001), mainly attributable to reduced inpatient costs. However, total average medical costs including pharmacy costs remained comparable after treatment initiation (pre-index period = $51,455 vs. post-index period = $53,923; P = 0.213). This study found that while patients' PAH-related pharmacy costs increased after treatment initiation, the increase was offset by reduced inpatient utilization; therefore, total health care costs remained constant. While the majority of patients in this study were treated with monotherapy, the recently completed AMBITION study indicated that initial combination therapy with ambrisentan plus tadalafil reduced PAH-related hospitalizations compared with initial monotherapy with either of these agents. Future cost analyses of patients treated with combination therapy will be required to determine the economic effect of initial combination therapy. This study was sponsored and funded by Gilead Sciences. Ozbay is an employee of Gilead Sciences. At the time that this project and manuscript were developed, Lazarus was an employee of Gilead Sciences and may own stock/stock options. Riehle, Montejano, and Lenhart are employees of Truven Health Analytics, an IBM company, which received funding from Gilead Sciences to conduct this study. Burger and White do research with, and are paid consultants for, Gilead Sciences; they do not own equity and received no personal compensation for the work here. Burger also reports consultancy and advisory board work for Actelion Pharmaceuticals and grants from Gilead Sciences, Actelion Pharmaceuticals, Bayer, and United Therapeutics.

The soluble guanylate cyclase stimulator IW-1973 prevents inflammation and fibrosis in experimental non-alcoholic steatohepatitis.

Background and PurposeNon‐alcoholic steatohepatitis (NASH) is the hepatic manifestation of metabolic syndrome and is characterized by steatosis, inflammation and fibrosis. Soluble guanylate cyclase (sGC) stimulation reduces inflammation and fibrosis in experimental models of lung, kidney and heart disease. Here, we tested whether sGC stimulation is also effective in experimental NASH.Experimental ApproachNASH was induced in mice by feeding a choline‐deficient, l‐amino acid‐defined, high‐fat diet. These mice received either placebo or the sGC stimulator IW‐1973 at two different doses (1 and 3 mg·kg−1·day−1) for 9 weeks. IW‐1973 was also tested in high‐fat diet (HFD)‐induced obese mice. Steatosis, inflammation and fibrosis were assessed by Oil Red O, haematoxylin–eosin, Masson's trichrome, Sirius Red, F4/80 and α‐smooth muscle actin staining. mRNA expression was assessed by quantitative PCR. Levels of IW‐1973, cytokines and cGMP were determined by LC‐MS/MS, Luminex and enzyme immunoassay respectively.Key ResultsMice with NASH showed reduced cGMP levels and sGC expression, increased steatosis, inflammation, fibrosis, TNF‐α and MCP‐1 levels and up‐regulated collagen types I α1 and α2, MMP2, TGF‐β1 and tissue metallopeptidase inhibitor 1 expression. IW‐1973 restored hepatic cGMP levels and sGC expression resulting in a dose‐dependent reduction of hepatic inflammation and fibrosis. IW‐1973 levels were ≈40‐fold higher in liver tissue than in plasma. IW‐1973 also reduced hepatic steatosis and adipocyte hypertrophy secondary to enhanced autophagy in HFD‐induced obese mice.Conclusions and ImplicationsOur data indicate that sGC stimulation prevents hepatic steatosis, inflammation and fibrosis in experimental NASH. These findings warrant further evaluation of IW‐1973 in the clinical setting.

Soluble guanylate cyclase stimulation reduces oxidative stress in experimental Chronic Obstructive Pulmonary Disease.

ObjectiveSoluble guanylate cyclase (sGC) is a key enzyme of the nitric oxide–cyclic guanosine 3′,5′-monophosphate (NO–cGMP) signaling pathway, and its pharmacological stimulation has been shown to prevent the development of emphysema and pulmonary vascular remodeling in animal models of chronic obstructive pulmonary disease (COPD). The aim of this study was to evaluate the effects of sGC stimulation on oxidative stress in the plasma of guinea pigs chronically exposed to cigarette smoke (CS).Methods and resultsGuinea pigs were exposed to CS or sham for three months, and received either the sGC stimulator BAY 41–2272 or vehicle. Body weight was measured weekly; and markers of oxidative stress in plasma, and airspace size and inflammatory cell infiltrate in lung tissue were analyzed at the end of the study. Compared to sham-exposed guinea pigs, CS-exposed animals gained less body weight and showed higher plasma levels of nitrated tyrosine residues (3-NT), 4-hydroxynonenal (4-HNE), and 8-hydroxydeoxyguanosine (8-OHdG). Treatment with the sGC stimulator led to a body weight gain in the CS-exposed guinea pigs similar to non-exposed and attenuated the increase in 3-NT and 4-HNE. Plasma levels of 3-NT correlated with the severity of inflammatory cell infiltrate in the lung.ConclusionStimulation of sGC prevents oxidative stress induced by CS exposure and is associated with an attenuated inflammatory response in the lung.

Soluble Guanylate Cyclase Stimulators and Activators.

When Furchgott, Murad, and Ignarro were honored with the Nobel prize for the identification of nitric oxide (NO) in 1998, the therapeutic implications of this discovery could not be fully anticipated. This was due to the fact that available therapeutics like NO donors did not allow a constant and long-lasting cyclic guanylyl monophosphate (cGMP) stimulation and had a narrow therapeutic window. Now, 20years later, the stimulator of soluble guanylate cyclase (sGC), riociguat, is on the market and is the only drug approved for the treatment of two forms of pulmonary hypertension (PAH/CTEPH), and a variety of other sGC stimulators and sGC activators are in preclinical and clinical development for additional indications. The discovery of sGC stimulators and sGC activators is a milestone in the field of NO/sGC/cGMP pharmacology. The sGC stimulators and sGC activators bind directly to reduced, heme-containing and oxidized, heme-free sGC, respectively, which results in an increase in cGMP production. The action of sGC stimulators at the heme-containing enzyme is independent of NO but is enhanced in the presence of NO whereas the sGC activators interact with the heme-free form of sGC. These highly innovative pharmacological principles of sGC stimulation and activation seem to have a very broad therapeutic potential. Therefore, in both academia and industry, intensive research and development efforts have been undertaken to fully exploit the therapeutic benefit of these new compound classes. Here we summarize the discovery of sGC stimulators and sGC activators and the current developments in both compound classes, including the mode of action, the chemical structures, and the genesis of the terminology and nomenclature. In addition, preclinical studies exploring multiple aspects of their in vitro, ex vivo, and in vivo pharmacology are reviewed, providing an overview of multiple potential applications. Finally, the clinical developments, investigating the treatment potential of these compounds in various diseases like heart failure, diabetic kidney disease, fibrotic diseases, and hypertension, are reported. In summary, sGC stimulators and sGC activators have a unique mode of action with a broad treatment potential in cardiovascular diseases and beyond.