sGC 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.

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.

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.

Soluble Guanylate Cyclase Stimulators and Activators Attenuate Placental Production of sFlt‐1

Preeclampsia (PE) is a pregnancy specific disorder associated with maternal hypertension due to widespread endothelial dysfunction. Placental ischemia leads to increases in the circulating anti‐angiogenic factor, sFlt‐1 and a PE‐like phenotype. PE and chronic sFlt‐1 excess is also associated with depletion of nitric oxide (NO), which, during normal pregnancy, binds to soluble guanylate cyclase (sGC), and synthesizes cGMP, to facilitate vasodilation.. In fact, studies in reduced uterine perfusion pressure (RUPP) model of placental ischemia demonstrate that restoring the angiogenic imbalance, administration of placental growth factor or VEGF abolishes hypertension. A novel drug, sGC stimulators and activators, which increase sGC activity independently of NO, are currently in clinical trials for the treatment of hypertension, however, whether this drug could be beneficial during PE is not known. We tested the hypothesis that sGC stimulators (Riociguat, Sigma‐Aldrich) and activators (Cinaciguat, Sigma‐Aldrich) attenuate sFlt‐1 production by the placenta. Placentas were isolated from normal pregnant rats on gestational day 19. Villous bundles were excised and plated in 24‐well plate coated with Matrix Matrigel Basement Membrane. Increasing concentrations of each the sGC stimulator and activator (0.1 μM, 1 μM, 10 μM, 30 μM) were added to the media for treatments. The explants were then exposed to a hypoxic environment (1% oxygen) to determine whether sFlt‐1 production, directly by the placenta, is attenuated by sGC stimulators and activators in a dose‐dependent manner. Interestingly, each of the doses administered significantly reduced sFlt‐1 production in response to hypoxia compared to the untreated group. However, the 30 μM sGC activator treatment produced the most profound effect (Untreated, n=6, 4699±942 pg/mL; 30 μM sGC stimulator‐treated, n=6, 3647±1385 pg/mL, 30 μM sGC activator‐treated, n=6, 3247±1402 pg/mL; P<0.01). The results of this study demonstrate that increasing sGC activity attenuates sFlt‐1 production from the placenta and could improve the angiogenic imbalance seen in this condition. In conclusion, these findings suggest there is a therapeutic potential for treating preeclampsia with sGC activatorsSupport or Funding InformationFunding source: NIH HL51971This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Influence of the Soluble Guanylate Cyclase Stimulator Riociguat on Myocardial Function and Proteome after Experimental Aortic Stenosis in Mice

BackgroundThe development and progression of heart failure (HF) involves endothelial and myocardial dysfunction as well as a dysregulation of different signaling pathways, including the nitric oxide – soluble guanylate cyclase – cyclic guanosine monophosphate signaling (NO‐sGC‐cGMP). Riociguat is a stimulator of sGC and could have beneficial effects in chronic HF with reduced left ventricular ejection fraction (LVEF) by preventing or even reversing the progression of hypertrophy and fibrosis.MethodsTransverse aortic constriction (TAC) was used to simulate arterial hypertension by an increased afterload in 8 week old male C57Bl6/N mice. Animals with sham surgery were used as controls. Three weeks after TAC either Riociguat (TAC/RIO; 3 mg/kg) or placebo (TAC/P) were administered by daily gavage for 5 more weeks (n = 12 per group). Sham animals were also treated with RIO (Sham/RIO) or placebo (Sham/P) in the same drug regime (n = 12 per group). Cardiac structure and function was evaluated weekly by small animal echocardiography. Eight weeks after TAC myocardial tissue sections were stained by sirius red to determine fibrosis levels (n = 6 per group), and proteomes of the left ventricles (LV) were analyzed by mass spectrometry (n = 6 per group). Significantly altered proteins were categorized using Ingenuity Pathway Analysis (IPA).ResultsTAC decreased left ventricular systolic function over time (LVEF week 1: sham: 54.6±2.2 vs. TAC: 42.8±3.1%; week 8: sham: 53.6±3.7 vs. TAC: 20.9±4.3%, p<0.001) and increased left ventricular mass to body weight ratios (LVM/BW) (week 1: sham: 4.1±0.2 vs. TAC: 5.7±0.3 mg/g; week 8: sham: 3.8±0.1 vs. TAC: 7.7±0.7 mg/g; p<0.001), whereas in sham mice no changes occurred. This hypertrophic response and the decreased heart function of TAC mice recovered significantly after Riociguat treatment (TAC/RIO), but did not completely achieve left ventricular systolic function of healthy sham placebo treated animals (LVEF week 4: TAC/P: 27.7±5.3 vs. TAC/RIO: 37.7±3.2%; week 8: TAC/P: 20.9±4.3 vs. TAC/RIO: 43.4±6.0%, p<0.001). Riociguat did not influence cardiac function in sham mice. Sirius red staining of myocardial tissue sections revealed a trend towards more fibrosis in TAC mice, which was also detected in the proteome (Collagen↑). Reverting effects due to Riociguat treatment were seen in the histologic and also proteomic analyses (Collagen↓). Furthermore, the proteome analyses showed that alterations of proteins assigned to the IPA category “cardiovascular diseases” due to TAC were partially reverted upon drug treatment in TAC/RIO, such as Myosin‐7. This HF marker was more than tenfold higher in TAC compared to the sham group, but much less abundant in TAC/RIO. Riociguat treatment did not influence the myocardial proteome in sham mice.ConclusionThis study revealed beneficial effects of sGC stimulation in a model of pressure overload induced HF. Riociguat treatment not only improved left ventricular systolic heart function, but also reduced the hypertrophic response due to TAC.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

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.

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.

Prevention of PKG-1α Oxidation Suppresses Antihypertrophic/Antifibrotic Effects From PDE5 Inhibition but not sGC Stimulation.

Stimulation of sGC (soluble guanylate cyclase) or inhibition of PDE5 (phosphodiesterase type 5) activates PKG (protein kinase G)-1α to counteract cardiac hypertrophy and failure. PKG1α acts within localized intracellular domains; however, its oxidation at cysteine 42, linking homomonomers, alters this localization, impairing suppression of pathological cardiac stress. Because PDE5 and sGC reside in separate microdomains, we speculated that PKG1α oxidation might also differentially influence the effects from their pharmacological modulation. Knock-in mice expressing a redox-dead PKG1α (PKG1αC42S) or littermate controls (PKG1αWT) were subjected to transaortic constriction to induce pressure overload and treated with a PDE5 inhibitor (sildenafil), sGC activator (BAY602770 [BAY]), or vehicle. In PKG1αWT controls, sildenafil and BAY similarly enhanced PKG activity and reduced pathological hypertrophy/fibrosis and cardiac dysfunction after transaortic constriction. However, sildenafil failed to protect the heart in PKG1αC42S, unlike BAY, which activated PKG and thereby facilitated protective effects. This corresponded with minimal PDE5 activation in PKG1αC42S exposed to transaortic constriction versus higher activity in controls and little colocalization of PDE5 with PKG1αC42S (versus colocalization with PKG1αWT) in stressed myocytes. In the stressed heart and myocytes, PKG1α C42-disulfide formation contributes to PDE5 activation. This augments the pathological role of PDE5 and so in turn enhances the therapeutic impact from its inhibition. PKG1α oxidation does not change the benefits from sGC activation. This finding favors the use of sGC activators regardless of PKG1α oxidation and may help guide precision therapy leveraging the cyclic GMP/PKG pathway to treat heart disease.

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.

Protein kinases G are essential downstream mediators of the antifibrotic effects of sGC stimulators

Stimulators of soluble guanylate cyclase (sGC) are currently investigated in clinical trials for the treatment of fibrosis in systemic sclerosis (SSc). In this study, we aim to investigate the role of protein kinases G (PKG) as downstream mediators of sGC-cyclic guanosine monophosphate (cGMP) in SSc. Mice with combined knockout of PKG1 and 2 were challenged with bleomycin and treated with the sGC stimulator BAY 41-2272. Fibroblasts were treated with BAY 41-2272 and with the PKG inhibitor KT 5823. PKG1 and 2 are upregulated in SSc in a transforming growth factor-β1 (TGFβ1)-dependent manner, as an attempt to compensate for the decreased signalling through the sGC-cGMP-PKG pathway. Inhibition or knockout of PKG1 and 2 abrogates the inhibitory effects of sGC stimulation on fibroblast activation in a SMAD-independent, but extracellular signal-regulated kinase (ERK)-dependent manner. In vivo, sGC stimulation fails to prevent bleomycin-induced fibrosis in PKG1 and 2 knockout mice. Our data provide evidence that PKGs are essential mediators of the antifibrotic effects of sGC stimulators through interfering with non-canonical TGFβ signalling. TGFβ1 promotes its profibrotic effects through inhibition of sGC-cGMP-PKG signalling, sGC stimulation exerts its antifibrotic effects by inhibition of TGFβ1-induced ERK phosphorylation.

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.

Treatment Selection in Pulmonary Arterial Hypertension: Phosphodiesterase Type 5 Inhibitors versus Soluble Guanylate Cyclase Stimulator.

Pulmonary arterial hypertension is a chronic and life-threatening disease that if left untreated is fatal. Current therapies include stimulating the nitric oxide-soluble guanylate cyclase (sGC)-cyclic guanosine monophosphate axis, improving the prostacyclin pathway and inhibiting the endothelin pathway. Phosphodiesterase type 5 inhibitors, such as sildenafil, and the sGC stimulator riociguat are currently used in the treatment of pulmonary arterial hypertension. This article discusses the similarities and differences between phosphodiesterase type 5 inhibitors and sGC stimulator based on pharmacological action and clinical trials, and considers which is better for the treatment of pulmonary arterial hypertension.

Modern view on the place of riociguat in the treatment of pulmonary hypertension.

Current research is aimed at studying the fundamental therapeutic targets and discovering new drugs acting on previously set targets. Until recently, the only therapeutic strategy to influence the molecular pathway of nitric oxide (NO) - soluble guanylate cyclase (sGC) - cyclic guanosine monophosphate (cGMP) was the use of phosphodiesterase type 5 inhibitors (PDE-5 inhibitors), such as sildenafil. In September 2014, the first member of sGC stimulators riociguat was licensed in Russia. In the paper, the results of 5 multicenter studies (CHEST-1 and PATENT-1, CHEST-2 and PATENT-2, RESPITE), which reflect the effectiveness and safety of mono - and combination therapy with riociguat in patients suffer from some forms of pulmonary arterial hypertension, and patients with inoperable or persistent/recurrent chronic thromboembolic pulmonary hypertension (CTPH), as well as the possibility of optimizing therapy in patients with PAH using iPDE-5 -> riociguat switching was reviewed. It also provides information on the recently launched international registries EXPERT CTEPH; new REPLACE study was announced.

Comparative Safety of Drugs Targeting the Nitric Oxide Pathway in Pulmonary Hypertension: A Mixed Approach Combining a Meta-Analysis of Clinical Trials and a Disproportionality Analysis From the World Health Organization Pharmacovigilance Database

Recent guidelines recommend riociguat, a soluble guanylate cyclase (sGC) stimulator, and the type 5 phosphodiesterase inhibitor (PDE5i) tadalafil or sildenafil as treatments for pulmonary arterial hypertension. We compared the safety profiles of sildenafil, tadalafil, and riociguat in pulmonary hypertension. We combined two approaches. First, we performed a meta-analysis of safety data extracted from randomized controlled trials. Second, we conducted a disproportionality analysis of data from VigiBase, the World Health Organization's global database of individual case safety reports, to compare the safety profiles with real-life data. In the meta-analysis, a significant difference between the three drugs was only detected for gastrointestinal disorders, in disfavor of riociguat (P< .01 for interaction). In the disproportionality analysis, the use of riociguat was associated with fewer reports of visual disorders but increased reporting of gastrointestinal, hemorrhagic, and musculoskeletal disorders compared with sildenafil and tadalafil. Pharmacovigilance signals of hearing/vestibular disorders were heterogeneous: vestibular disorders (dizziness) were reported more frequently for riociguat, whereas hearing disorders (deafness) were reported less frequently compared with PDE5is. The safety profiles of PDE5is and sGC stimulators significantly differ in pulmonary hypertension. Accordingly, there is a safety rationale in switching between PDE5is and sGC stimulators because of their different side effects. PROSPERO; No.: CRD42016051986; URL: https://www.crd.york.ac.uk/prospero/.