Selexipag Dosing Strategies for Pediatric Patients with Pulmonary Arterial Hypertension.

This retrospective chart review of patients less than 18 years old with pulmonary arterial hypertension (PAH) receiving selexipag was conducted to describe selexipag dosing practices, impact on concomitant PAH therapies, and the safety and efficacy of selexipag. Twenty-seven patients aged 1-17 years started a median dose of oral selexipag 100 µg twice daily. Therapy was increased by a median of 100 µg twice daily every 6 days to a maximally tolerated median dose of 800 µg twice daily. All 24 patients on another prostacyclin derivative were able to discontinue therapy at their maximum tolerated selexipag dose; other concomitant PAH therapies did not change. Changes in echocardiogram data and 6-MWT results were variable. No patients discontinued selexipag; four patients received decreased doses due to flushing (n = 1), drug interactions (n = 2), or increased frequency of nose bleeds (n = 1).

Effectiveness of a Prostacyclin IP Receptor Agonist in Patients With Pulmonary Arterial Hypertension in the Real-world Andalusian Setting: The RAMPHA Study.

PURPOSE: The pillar for therapeutic decisions in the evolution of pulmonary arterial hypertension (PAH) is the patients' prognostic stratification. METHODS: A retrospective cohort study was conducted in a Spanish real-world setting to assess the clinical improvement of PAH patients treated with selexipag measured as changes in the risk profile. Secondary objectives were to describe their baseline characteristics, initial risk status, and variables used to assess patient survival and adverse events. FINDINGS: Total 42 patients (mean age 52.36 [SD: 15.09] years) were included. All had received initial endothelin receptor antagonist treatment and 95.2% dual therapy with phosphodiesterase-5 inhibitor or riociguat. At 6 to 12 months from baseline, patients risk stratification tripled the percentage of patients with low risk, and a trend towards improved risk stratification (P = 0.122). World Health Organization functional class changed, with more patients in milder classes (P = 0.003), and symptom progression slowed down (P < 0.0001). At 3-years, survival was 85.7% and the estimated median survival time was 2.73 years (SD: 1.351; 95% CI: 2.51-2.95). IMPLICATIONS: Selexipag did not achieve a significant improvement in risk profile, although it did show an excellent survival rate, effectively improved functional class, and delayed symptom progression in real life. Selexipag was well tolerated and showed a favorable safety profile, supporting a clinical benefit for PAH patients.

Pulmonary Hypertension: Intensification and Personalization of Combination Rx (PHoenix): A phase IV randomized trial for the evaluation of dose-response and clinical efficacy of riociguat and selexipag using implanted technologies.

Approved therapies for the treatment of patients with pulmonary arterial hypertension (PAH) mediate pulmonary vascular vasodilatation by targeting distinct biological pathways. International guidelines recommend that patients with an inadequate response to dual therapy with a phosphodiesterase type-5 inhibitor (PDE5i) and endothelin receptor antagonist (ERA), are recommended to either intensify oral therapy by adding a selective prostacyclin receptor (IP) agonist (selexipag), or switching from PDE5i to a soluble guanylate-cyclase stimulator (sGCS; riociguat). The clinical equipoise between these therapeutic choices provides the opportunity for evaluation of individualized therapeutic effects. Traditionally, invasive/hospital-based investigations are required to comprehensively assess disease severity and demonstrate treatment benefits. Regulatory-approved, minimally invasive monitors enable equivalent measurements to be obtained while patients are at home. In this 2 × 2 randomized crossover trial, patients with PAH established on guideline-recommended dual therapy and implanted with CardioMEMS™ (a wireless pulmonary artery sensor) and ConfirmRx™ (an insertable cardiac rhythm monitor), will receive ERA + sGCS, or PDEi + ERA + IP agonist. The study will evaluate clinical efficacy via established clinical investigations and remote monitoring technologies, with remote data relayed through regulatory-approved online clinical portals. The primary aim will be the change in right ventricular systolic volume measured by magnetic resonance imaging (MRI) from baseline to maximal tolerated dose with each therapy. Using data from MRI and other outcomes, including hemodynamics, physical activity, physiological measurements, quality of life, and side effect reporting, we will determine whether remote technology facilitates early evaluation of clinical efficacy, and investigate intra-patient efficacy of the two treatment approaches.

Comparing the efficacy and safety of low, medium, and high dosages of selexipag for treating pulmonary hypertension: A systematic review and meta-analysis.

BACKGROUND: The maintenance dosage of selexipag is categorized as low, medium or high. In order to assess the efficacy and safety of different dosages of selexipag for the risk stratification of pulmonary arterial hypertension (PAH), we performed a systematic review and meta-analysis. METHODS: Studies assessing PAH risk stratification indices, such as the World Health Organization functional class (WHO-FC), six-minute walk distance (6MWD), N-terminal pro-B-type natriuretic peptide (NT-proBNP) level, right atrial pressure (RAP), cardiac index (CI) and mixed venous oxygen saturation (SvO2), were included. RESULTS: Thirteen studies were included. Selexipag led to improvements in the 6MWD (MD: 24.20 m, 95% CI: 10.74-37.67), NT-proBNP (SMD: -0.41, 95% CI: -0.79-0.04), CI (MD: 0.47 L/min/m2, 95% CI: 0.17-0.77) and WHO-FC (OR: 0.564, 95% CI: 0.457-0.697). Subgroup analysis demonstrated that all three dosages improved the 6MWD. A moderate dosage led to improvements in the CI (MD: 0.30 L/min/m2, 95% CI: 0.15-0.46) and WHO-FC (OR: 0.589, 95% CI: 0.376-0.922). Within 6 months of treatment, only the WHO-FC and CI were significantly improved (OR: 0.614, 95% CI: 0.380-0.993; MD: 0.30 L/min/m2, 95% CI: 0.16-0.45, respectively). More than 6 months of treatment significantly improved the 6MWD, WHO-FC and NT-proBNP (MD: 40.87 m, 95% CI: 10.97-70.77; OR: 0.557, 95% CI: 0.440-0.705; SMD: -0.61, 95% CI: -1.17-0.05, respectively). CONCLUSIONS: Low, medium, and high dosages of selexipag all exhibited good effects. When treatment lasted for more than 6 months, selexipag exerted obvious effects, even in the low-dosage group. This finding is important for guiding individualized treatments.

Inhibition of TRPM8 function by prostacyclin receptor agonists requires coupling to Gq/11 proteins.

BACKGROUND AND PURPOSE: The TRPM8 ion channel is involved in innocuous cold sensing and has a potent anti-inflammatory action. Its activation by lower temperature or chemical agonists such as menthol and icilin induces analgesic effects, reversing hypersensitivity and reducing chronic pain. On the other hand, prostacyclin (PGI2) enhances pain and inflammation by activating the IP receptors. Due to the critical roles of TRPM8 and IP receptors in the regulation of inflammatory pain, and considering their overlapping expression pattern, we analysed the functional interaction between human TRPM8 and IP receptors. EXPERIMENTAL APPROACH: We transiently expressed human TRPM8 channels and IP receptors in HEK293T cells and carried out intracellular calcium and cAMP measurements. Additionally, we cultured neurons from the dorsal root ganglia (DRGs) of mice and determined the increase in intracellular calcium triggered by the TRPM8 agonist, icilin, in the presence of the IP receptor agonist cicaprost, the IP receptor antagonist Cay10441, and the Gq/11 inhibitor YM254890. KEY RESULTS: Activation of IP receptors by selective agonists (cicaprost, beraprost, and iloprost) inhibited TRPM8 channel function, independently of the Gs-cAMP pathway. The potent inhibition of TRPM8 channels by IP receptor agonists involved Gq/11 coupling. These effects were also observed in neurons isolated from murine DRGs. CONCLUSIONS AND IMPLICATIONS: Our results demonstrate an unusual signalling pathway of IP receptors by coupling to Gq/11 proteins to inhibit TRPM8 channel function. This pathway may contribute to a better understanding of the role of TRPM8 channels and IP receptors in regulating pain and inflammation.

Efficacy and safety of non-prostanoid prostacyclin receptor agonist for pulmonary hypertension: A meta-analysis.

BACKGROUND: Oral non-prostanoid prostacyclin receptor agonists therapies have been recommended for pulmonary arterial hypertension in many countries. OBJECTIVE: We aimed to evaluate the specific impact of non-prostanoid prostacyclin receptor agonists on pulmonary hypertension and to explore the influence of study characteristics on results. METHODS: PubMed, Embase, and ClinicalTrials.gov were systematically searched from inception to July 12, 2022. Randomized controlled trials comparing non-prostanoid prostacyclin receptor agonists administration with placebo for treating pulmonary hypertension were included. Two researchers independently selected eligible studies, assessed the bias risk and extracted related data. RevMan5.1 was used for performing the statistical analysis and the assessment of bias risk of the enrolled studies. PROSPERO registered number CRD42022304172. RESULTS: Seven trials involving 1727 patients were included. Pooled analyses indicated non-prostanoid prostacyclin receptor agonists significantly reduced clinical worsening events (risk ratio [RR], 0.63; 95% confidence interval [CI], 0.54 to 0.74), increased 6-min walk distance (mean difference [MD], 10 m; 95% CI, 3-17 m), decreased pulmonary vascular resistance (MD, -121 dyn s/cm5; 95% CI, -172 to -69 dyn s/cm5) and increased cardiac index (MD, 0.38 L/min/m2; 95% CI, 0.26-0.50 L/min/m2) compared with the control. No significant differences in all-cause mortality (RR, 0.86; 95% CI, 0.26 to 2.78), NYHA/WHO functional class (RR, 1.16; 95% CI, 0.61 to 2.18), mean pulmonary artery pressure (MD, -0.88 mmHg; 95% CI, -2.20 to 0.44 mmHg), right atrial pressure (MD, 0.66 mmHg; 95% CI, -0.59 to 1.90 mmHg) and total adverse events (RR, 1.05; 95% CI, 0.99 to 1.10) were found between non-prostanoid prostacyclin receptor agonists group and control group. CONCLUSION: Non-prostanoid prostacyclin receptor agonists treatment exerted benefits on clinical worsening, pulmonary vascular resistance, and cardiac index in pulmonary hypertension patients, without increasing the incidence of total adverse events.

Pharmacological counseling in hepatotoxicity induced by macitentan and selexipag: a case report.

BACKGROUND: Pulmonary arterial hypertension is a progressive, debilitating condition characterized by increased resistance in the pulmonary arterial circulation. Current treatments for pulmonary arterial hypertension include endothelin receptor antagonists such as bosentan, sitaxentan, ambrisentan, macitentan, and oral prostacyclin receptor agonists such as selexipag. Endothelin receptor antagonists have been associated with liver injury, while hepatotoxicity was not reported for selexipag. Although genetic variability has been indisputably associated with variability in drug response, no study has been designed until now to assess its effects on the pharmacokinetics of endothelin receptor antagonists or selexipag. CASE PRESENTATION: We report the case of a 58-year-old female Caucasian patient with a dramatic increase in plasma levels of transaminases after treatment with macitentan and selexipag, drugs whose risk of causing liver injury has so far been considered limited. After therapy discontinuation, plasma levels of transaminases returned to baseline, thus suggesting a role of these drugs in the observed hepatotoxicity. After pharmacological counseling, we decided to introduce ambrisentan for the patient's treatment. After 7 months of treatment, no liver injury has been reported. To evaluate the role of genetic factors in the observed hepatotoxicity, we genotyped the patient for single-nucleotide polymorphisms previously associated with macitentan, ambrisentan, or selexipag metabolism. We found a genetic profile associated with a poor metabolizer (PM) phenotype for CYP2C8 and CYP2C9, key enzymes for elimination of both macitentan and selexipag. The reported results suggest that an allelic profile associated with low activity for CYP2C8 and CYP2C9 enzyme could be a potential risk factor for macitentan and selexipag-induced liver injury and could provide a possible marker for early identification of subjects at higher risk of developing hepatotoxicity. CONCLUSIONS: A multidisciplinary approach based on clinical evaluation, as well as pharmacological counseling and evaluation of the patient's genetic profile, might be useful for identification of patients with a high chance of drug-induced liver injury, avoiding unnecessary risks in therapy selection and prescription.

Prostacyclin Synthesis and Prostacyclin Receptor Expression in the Porcine Myometrium: Prostacyclin Potential to Regulate Fatty Acid Transporters, Cytokines and Contractility-Related Factors.

Although prostacyclin (PGI2) has been well described as a regulator of smooth muscle activity, limited data are available concerning its role in the myometrium of pigs. The present research aimed to examine profiles of PGI2 synthase (PTGIS) and PGI2 receptor (PTGIR) expression and 6-keto PGF1α (a PGI2 metabolite) concentrations in the myometrium of gilts throughout the estrous cycle and during early pregnancy using qPCR, Western blot, and/or ELISA methods. Furthermore, myometrial explants were exposed to iloprost (a stable PGI2 analog) to investigate the effect of PGI2 on the mRNA expression of factors engaged in smooth muscle contraction, nutrient transport, prostaglandin synthesis and action, and inflammatory response. PTGIS mRNA expression was greater in cyclic than in pregnant gilts on days 11-12 after estrus and was accompanied by greater concentrations of 6-keto PGF1α detected in cyclic than in pregnant animals on days 11-20. Iloprost stimulated fatty acid transporters and contractility-related calponin 1 and caldesmon 1 mRNA expression and decreased interleukin 1ß and tumor necrosis factor transcript abundance. The obtained results indicate a physiologically relevant role of PGI2 during the estrous cycle in the porcine myometrium with its importance for regulating the expression of contractility-, nutrient transport- and inflammatory response-related factors.

Inhibition of the Proliferation of Human Lung Fibroblasts by Prostacyclin Receptor Agonists is Linked to a Sustained cAMP Signal in the Nucleus.

Idiopathic pulmonary fibrosis is a chronic and progressive fibrotic lung disease, and current treatments are limited by their side effects. Proliferation of human lung fibroblasts in the pulmonary interstitial tissue is a hallmark of this disease and is driven by prolonged ERK signalling in the nucleus in response to growth factors such as platelet-derived growth factor (PDGF). Agents that increase cAMP have been suggested as alternative therapies, as this second messenger can inhibit the ERK cascade. We previously examined a panel of eight Gαs-cAMP-coupled G protein-coupled receptors (GPCRs) endogenously expressed in human lung fibroblasts. Although the cAMP response was important for the anti-fibrotic effects of GPCR agonists, the magnitude of the acute cAMP response was not predictive of anti-fibrotic efficacy. Here we examined the reason for this apparent disconnect by stimulating the Gαs-coupled prostacyclin receptor and measuring downstream signalling at a sub-cellular level. MRE-269 and treprostinil caused sustained cAMP signalling in the nucleus and complete inhibition of PDGF-induced nuclear ERK and fibroblast proliferation. In contrast, iloprost caused a transient increase in nuclear cAMP, there was no effect of iloprost on PDGF-induced ERK in the nucleus, and this agonist was much less effective at reversing PDGF-induced proliferation. This suggests that sustained elevation of cAMP in the nucleus is necessary for efficient inhibition of PDGF-induced nuclear ERK and fibroblast proliferation. This is an important first step towards understanding of the signalling events that drive GPCR inhibition of fibrosis.

Prostacyclin facilitates vascular smooth muscle cell phenotypic transformation via activating TP receptors when IP receptors are deficient.

AIM: By activating prostacyclin receptors (IP receptors), prostacyclin (PGI2 ) exerts cardiovascular protective effects such as vasodilation and inhibition of vascular smooth muscle cell (VSMC) proliferation. However, IP receptors are dysfunctional under pathological conditions, and PGI2 produces detrimental effects that are opposite to its physiological protective effects via thromboxane-prostanoid (TP) receptors. This attempted to investigate whether or not IP receptor dysfunction facilitates the shift of PGI2 action. METHODS: The effects of PGI2 and its stable analog iloprost on VSMC phenotypic transformation and proliferation were examined in A10 cells silencing IP receptors, in human aortic VSMCs (HAVSMCs) knocked down IP receptor by CRISPR-Cas9, or in HAVSMCs transfected with a dysfunctional mutation of IP receptor IPR212C . RESULTS: PGI2 /iloprost treatment stimulated cell proliferation, upregulated synthetic proteins and downregulated contractile proteins, suggesting that PGI2 /iloprost promotes VSMC phenotypic transformation in IP-deficient cells. The effect of PGI2 /iloprost was prevented by TP antagonist S18886 or TP knockdown, indicating that the VSMC detrimental effect of PGI2 is dependent on TP receptor. RNA sequencing and Western blotting results showed that RhoA/ROCKs, MEK1/2 and JNK signalling cascades were involved. Moreover, IP deficiency increased the distribution of TP receptors at the cell membrane. CONCLUSION: PGI2 induces VSMC phenotypic transformation when IP receptors are impaired. This is attributed to the activation of TP receptor and its downstream signaling cascades, and to the increased membrane distribution of TP receptors. The VSMC detrimental effect of PGI2 medicated by IP dysfunction and TP activation might probably exacerbate vascular remodelling, accelerating cardiovascular diseases.

Selexipag for Chronic Thromboembolic Pulmonary Hypertension in Japanese Patients　- A Double-Blind, Randomized, Placebo-Controlled, Multicenter Phase II Study.

BACKGROUND: Selexipag is an oral prostacyclin receptor (IP receptor) agonist with a non-prostanoid structure. This study examined its efficacy and safety in Japanese patients with non-operated or persistent/recurrent chronic thromboembolic pulmonary hypertension (CTEPH).Methods and Results:This Phase II study was a randomized, double-blind, placebo-controlled parallel-group comparison. The primary endpoint was a change in pulmonary vascular resistance (PVR) from baseline to week 17. The main analysis involved a per-protocol set group of 28 subjects. The change in PVR (mean±SD) after 17 weeks of treatment in the selexipag group was -104±191 dyn·s/cm5, whereas that in the placebo group was 26±180 dyn·s/cm5. Thus, the treatment effect after 17 weeks of selexipag treatment was calculated as -130±189 dyn·s/cm5(P=0.1553). Although the primary endpoint was not met, for the group not concomitantly using a pulmonary vasodilator the PVR in the selexipag group was significantly decreased compared with placebo group (P=0.0364). The selexipag group also showed improvement in total pulmonary resistance and cardiac index. CONCLUSIONS: Selexipag treatment improved pulmonary hemodynamics in Japanese patients with CTEPH, but PVR did not show a significant difference between the selexipag and placebo groups. (Trial registration: JAPIC Clinical Trials Information [JapicCTI-111667]).

Mannitol triggers mast cell-dependent contractions of human small bronchi and prostacyclin bronchoprotection.

BACKGROUND: Clinical research supports that exercise-induced bronchoconstriction (EIB) is caused by hyperosmolar triggering of mast cells. The reaction can be mimicked by inhalation of mannitol, but it has paradoxically previously not been possible to replicate this mode of action of mannitol in isolated airways. OBJECTIVE: We sought to establish an ex vivo model of EIB in human small bronchi. METHODS: Small bronchi (inner diameter, 0.5-2 mm) from macroscopically healthy human lung tissue were obtained from 48 patients and mounted in organ baths. Contractions and mediator release were analyzed after challenge with hyperosmolar mannitol (850 mOsm). RESULTS: Ten minutes of exposure to mannitol caused a small initial contraction (12% ± 1% of maximum) that was followed by a second and much larger contraction (maximum effect [Emax], 47% ± 5%) when mannitol was washed out. The mast cell stabilizer cromolyn reduced the second contraction (Emax, 27% ± 3%). Furthermore, this main contraction was abolished by the combination of antagonists of histamine and cysteinyl leukotrienes in the presence of indomethacin. Mannitol increased the release of the mast cell mediators histamine (9.0-fold), cysteinyl leukotrienes (4.5-fold), and prostaglandin (PG) D2 (5.4-fold), as well as PGE2 (6.3-fold) and the prostacyclin metabolite 6-keto PGF1α (5.7-fold). In contrast, indomethacin alone enhanced the bronchoconstriction (Emax, 68% ± 6%). Likewise, receptor antagonists for PGE2 (EP2 and EP4) and prostacyclin (IP) also enhanced the mannitol-induced bronchoconstriction (Emax, 67% ± 5%, 66% ± 4%, and 68% ± 3%, respectively). In bronchi precontracted by carbachol, the IP receptor agonist cicaprost induced profound relaxation. CONCLUSION: This new protocol established an in vitro model for studies of EIB in isolated human bronchi. The IP receptor might be a new target for asthma treatment.

Association of N-Terminal Pro Brain Natriuretic Peptide and Long-Term Outcome in Patients With Pulmonary Arterial Hypertension.

BACKGROUND: NT-proBNP (N-terminal pro brain natriuretic peptide) levels are included in the multiparametric risk assessment approach for pulmonary arterial hypertension (PAH) outlined in PAH guidelines. However, data supporting the use of NT-proBNP risk thresholds in assessing prognosis in PAH are limited. The GRIPHON trial (Prostacyclin [PGI2] Receptor Agonist In Pulmonary Arterial Hypertension) provides an opportunity to assess the prognostic value of NT-proBNP thresholds in a controlled clinical trial and to evaluate the response to selexipag according to these thresholds. METHODS: The event-driven GRIPHON trial randomly assigned patients to selexipag or placebo. NT-proBNP was measured at regular intervals in GRIPHON. Here, patients were categorized post hoc into low, medium, and high NT-proBNP subgroups according to 2 independent sets of thresholds: (1) baseline tertiles: <271 ng/L; 271 to 1165 ng/L; >1165 ng/L; and (2) 2015 European Society of Cardiology/European Respiratory Society guidelines cutoffs: <300 ng/L; 300 to 1400 ng/L; >1400 ng/L. Hazard ratios (selexipag versus placebo) with 95% CIs were calculated for the primary end point (composite morbidity/mortality events) by NT-proBNP category at baseline using Cox proportional-hazards models, and at any time during the exposure period using a time-dependent Cox model. RESULTS: With both thresholds, baseline and follow-up NT-proBNP categories were highly prognostic for future morbidity/mortality events during the study ( P<0.0001). In the time-dependent analysis, the risk of experiencing a morbidity/mortality event was 92% and 83% lower in selexipag-treated patients with a low and medium NT-proBNP level, and 90% and 56% lower in placebo-treated patients with a low and medium NT-proBNP level, in comparison with patients with a high NT-proBNP level. Selexipag reduced the risk of morbidity/mortality events across all 3 NT-proBNP categories in both the baseline and time-dependent analyses, with a more pronounced treatment benefit of selexipag seen in the medium and low NT-proBNP subgroups (interaction P values 0.20 and 0.007 in the baseline and time-dependent analyses). CONCLUSIONS: These analyses further establish the prognostic relevance of NT-proBNP levels in PAH and provide first evidence for the association of NT-proBNP level and treatment response. Using 2 similar sets of thresholds, these analyses support the relevance of the low, medium, and high NT-proBNP categories as part of the multiparametric risk assessment approach outlined in the European Society of Cardiology/European Respiratory Society guidelines for the management of PAH patients. CLINICAL TRIAL REGISTRATION: URL: https://www.clinicaltrials.gov . Unique identifier: NCT01106014.

Cross-species comparison of the metabolism and excretion of selexipag.

1. The metabolism of the prostacyclin receptor agonist selexipag (NS-304; ACT-293987) and its active metabolite MRE-269 (ACT-333679) has been investigated in liver microsomes and hepatocytes of rats, dogs, and monkeys. MRE-269 formation is the main pathway of selexipag metabolism, irrespective of species. Some interspecies differences were evident for both compounds in terms of both metabolic turnover and metabolic profiles. The metabolism of MRE-269 was slower than that of selexipag in all three species. 2. The metabolism of selexipag was also studied in bile-duct-cannulated rats and dogs after a single oral and intravenous dose of [14C]selexipag. MRE-269 acyl glucuronide was found in both rat and dog bile. Internal acyl migration reactions of MRE-269 glucuronide were identified in an experiment with the synthetic standard MRE-6001. 3. MRE-269 was the major component in the faeces of rats and dogs. In ex vivo study using rat and dog faeces, selexipag hydrolysis to MRE-269 by the intestinal microflora is considered to be a contributory factor in rats and dogs. 4. A taurine conjugate of MRE-269 was identified in rat bile sample. Overall, selexipag was eliminated via multiple routes in animals, including hydrolysis, oxidative metabolism, conjugation, intestinal deconjugation, and gut flora metabolism.

The Antifibrotic Activity of Prostacyclin Receptor Agonism Is Mediated through Inhibition of YAP/TAZ.

Idiopathic pulmonary fibrosis is a life-threatening progressive disease characterized by loss of alveolar epithelial cells, inflammation, and aberrant fibroblast activation. The two currently approved therapies do not halt or reverse tissue remodeling, and therefore novel disease-modifying mechanisms are needed. Our results describe YAP/TAZ inhibition through prostacyclin (IP) receptor activation as a novel mechanism that suppresses profibrotic (myo)fibroblast activity. We investigated the antifibrotic properties of the selective IP receptor agonist ACT-333679 using primary human lung fibroblasts. ACT-333679 prevented transforming growth factor ß1-induced fibroblast-to-myofibroblast transition, proliferation, extracellular matrix synthesis, and IL-6 and PAI-1 secretion, and exerted relaxant effects in cell contraction assays. ACT-333679 treatment also reverted an established myofibroblast phenotype. Unbiased analysis of ACT-333679-induced whole-genome expression changes in transforming growth factor ß1-treated fibroblasts identified significant attenuation of genes regulated by YAP/TAZ, two transcriptional cofactors that are essential for fibrosis. We then demonstrated that ACT-333679, via elevation of cAMP, caused YAP/TAZ nuclear exclusion and subsequent suppression of YAP/TAZ-dependent profibrotic gene transcription. In summary, we offer a rationale for further exploring the potential of IP receptor agonists for the treatment of idiopathic pulmonary fibrosis.

Should we use the oral selective IP receptor agonist selexipag off-label in children with pulmonary arterial hypertension?

We discuss the currently available data on the use of the prostacyclin mimetic selexipag in children and adolescents with pulmonary arterial hypertension (PAH). Future indications may include transitioning from intravenous prostacyclin/prostacyclin analog to oral selexipag, and vice versa, or adding selexipag as a third oral PAH-targeted agent in children not responding well to dual PAH therapy.

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.

Effects of selexipag and its active metabolite in contrasting the profibrotic myofibroblast activity in cultured scleroderma skin fibroblasts.

BACKGROUND: Myofibroblasts contribute to fibrosis through the overproduction of extracellular matrix (ECM) proteins, primarily type I collagen (COL-1) and fibronectin (FN), a process which is mediated in systemic sclerosis (SSc) by the activation of fibrogenic intracellular signaling transduction molecules, including extracellular signal-regulated kinases 1 and 2 (Erk1/2) and protein kinase B (Akt). Selexipag is a prostacyclin receptor agonist synthesized for the treatment of pulmonary arterial hypertension. The study investigated the possibility for selexipag and its active metabolite (ACT-333679) to downregulate the profibrotic activity in primary cultures of SSc fibroblasts/myofibroblasts and the fibrogenic signaling molecules involved. METHODS: Fibroblasts from skin biopsies obtained with Ethics Committee (EC) approval from patients with SSc, after giving signed informed consent, were cultured until the 3rd culture passage and then either maintained in normal growth medium (untreated cells) or independently treated with different concentrations of selexipag (from 30 µM to 0.3 µM) or ACT-333679 (from 10 µM to 0.1 µM) for 48 h. Protein and gene expressions of α-smooth muscle actin (α-SMA), fibroblast specific protein-1 (S100A4), COL-1, and FN were investigated by western blotting and quantitative real-time PCR. Erk1/2 and Akt phosphorylation was investigated in untreated and ACT-333679-treated cells by western botting. RESULTS: Selexipag and ACT-333679 significantly reduced protein synthesis and gene expression of α-SMA, S100A4, and COL-1 in cultured SSc fibroblasts/myofibroblasts compared to untreated cells, whereas FN was significantly downregulated at the protein level. Interestingly, ACT-333679 significantly reduced the phosphorylation of Erk1/2 and Akt in cultured SSc fibroblasts/myofibroblasts. CONCLUSIONS: Selexipag and mainly its active metabolite ACT-333679 were found for the first time to potentially interfere with the profibrotic activity of cultured SSc fibroblasts/myofibroblasts at least in vitro, possibly through the downregulation of fibrogenic Erk1/2 and Akt signaling molecules.

Cefminox, a Dual Agonist of Prostacyclin Receptor and Peroxisome Proliferator-Activated Receptor-Gamma Identified by Virtual Screening, Has Therapeutic Efficacy against Hypoxia-Induced Pulmonary Hypertension in Rats.

Prostacyclin receptor (IP) and peroxisome proliferator-activated receptor-gamma (PPARγ) are both potential targets for treatment of pulmonary arterial hypertension (PAH). Expression of IP and PPARγ decreases in PAH, suggesting that screening of dual agonists of IP and PPARγ might be an efficient method for drug discovery. Virtual screening (VS) of potential IP-PPARγ dual-targeting agonists was performed in the ZINC database. Ten of the identified compounds were further screened, and cefminox was found to dramatically inhibit growth of PASMCs with no obvious cytotoxicity. Growth inhibition by cefminox was partially reversed by both the IP antagonist RO113842 and the PPARγ antagonist GW9662. Investigation of the underlying mechanisms of action demonstrated that cefminox inhibits the protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling pathway through up-regulation of the expression of phosphatase and tensin homolog (PTEN, which is inhibited by GW9662), and enhances cyclic adenosine monophosphate (cAMP) production in PASMCs (which is inhibited by RO113842). In a rat model of hypoxia-induced pulmonary hypertension, cefminox displayed therapeutic efficacy not inferior to that of the prostacyclin analog iloprost or the PPARγ agonist rosiglitazone. Our results identified cefminox as a dual agonist of IP and PPARγ that significantly inhibits PASMC proliferation by up-regulation of PTEN and cAMP, suggesting that it has potential for treatment of PAH.