Molecular recognition and activation of the prostacyclin receptor by anti-pulmonary arterial hypertension drugs.

The prostacyclin (PGI2) receptor (IP) is a Gs-coupled receptor associated with blood pressure regulation, allergy, and inflammatory response. It is a main therapeutic target for pulmonary arterial hypertension (PAH) and several other diseases. Here we report cryo-electron microscopy (cryo-EM) structures of the human IP-Gs complex bound with two anti-PAH drugs, treprostinil and MRE-269 (active form of selexipag), at global resolutions of 2.56 and 2.41 angstrom, respectively. These structures revealed distinct features governing IP ligand binding, receptor activation, and G protein coupling. Moreover, comparison of the activated IP structures uncovered the mechanism and key residues that determine the superior selectivity of MRE-269 over treprostinil. Combined with molecular docking and functional studies, our structures provide insight into agonist selectivity, ligand recognition, receptor activation, and G protein coupling. Our results provide a structural template for further improving IP-targeting drugs to reduce off-target activation of prostanoid receptors and adverse effects.

Case report: apatinib plus selexipag as a novel therapy for pulmonary tumor thrombotic microangiopathy accompanied by pulmonary hypertension associated with gastric carcinoma.

RATIONALE: PTTM is a rare but fatal disease, characterized by endothelial intimal proliferation and pulmonary hypertension due to micro-vascular remodeling. In view of the poor prognosis, new effective strategies are urgently required. PATIENT CONCERNS AND DIAGNOSIS: A 51-year-old woman was admitted to hospital for acute progressive dyspnea and dry cough. Clinical tests revealed hypercoagulable state and signs of severe pulmonary hypertension, without evidence of pulmonary embolism on contrast-enhanced CT. CT showed interlobular septal thickening and diffuse ground-glass opacity. Lung perfusion scan indicated multiple segment defect. Further right heart catherization proved a significant increase in pulmonary vascular resistance. INTERVENTIONS: A combination therapy of apatinib and selexipag was administered for treatment of PTTM. The conventional therapies of ventilation, anticoagulation and diuretic medicines were initiated after admission. OUTCOMES: Symptoms of PTTM were ameliorated with a reduction in pulmonary artery pressure. The resolution of interlobular septal thickening and ground-glass opacity on CT constituted the clinical benefits from treatment. LESSONS: Patient with PTTM will benefit from the combination strategy of apatinib, a VEGF-receptor antagonist, and selexipag, an oral prostacyclin receptor agonist.

Efficacy and safety of selexipag, an oral prostacyclin receptor agonist for the treatment of pulmonary hypertension: A meta-analysis.

BACKGROUND AND OBJECTIVE: This meta-analysis was performed to evaluate the effect and safety of selexipag in the treatment of pulmonary hypertension and to explore the effect of selexipag on cardiac function indexes in PAH patients. METHODS: Electronic databases, including the Cochrane Library, EMBASE, and PubMed databases, were searched. Endnote software X9 was used for study selection, and the Cochrane Risk of Bias Tool was used for literature screening and quality assessment. Data analysis was performed using RevMan 5.3 software, and GRADE was used to assess the evidence level. RESULTS: Ten studies were finally selected in accordance with the standard. A total of 10 papers were included. A total of 1322 patients were included, including 723 in the trial group and 599 in the control group. Patients with PAH treated with selexipag were included in the trial group, and patients with PAH treated with placebo were included in the control group. The results of the study showed that selexipag was effective in reducing mortality in patients (WMD=0.70, 95% CI: 0.53-0.94, P = 0.02). Selexipag effectively increased the 6-min walk distance (WMD=33.79, 95% CI: 2.69-64.90, P=0.03). Selexipag also effectively increased the 6-min distance between baseline and follow-up (WMD = 15.28, 95% CI: 7.76-22.80, P < 0.0001). Selexipag effectively reduced PVR (WMD = -230.96, 95% CI: 445.94 to -15.97, P = 0.04). Selexipag significantly reduced PVR between baseline and follow-up (WMD = -139.62, 95% CI: 215.32 to -63.91, P = 0.0003). The adverse reactions of selexipag were mild with headache, diarrhea and nausea reported as the main symptoms. CONCLUSION: Selexipag is a new drug with mild adverse reactions and is safe for the treatment of PAH. This drug significantly prolongs the level of 6MWD in PAH patients, reduces the fatality rate, improves WHO FC and reduces PVR. The effects of this drug on CI, mPAP, MRAP, SvO2 and other indicators still need to be further confirmed. PROSPERO REGISTRATION: CRD42021245557.

Use of the Prostacyclin Receptor Agonist Selexipag in Patients With Pulmonary Arterial Hypertension Associated With Eisenmenger Syndrome.

Eisenmenger syndrome is a multisystem disorder and the most severe form of pulmonary arterial hypertension in adult congenital heart disease. Pulmonary arterial hypertension represents a fatal disease, characterized by increased pulmonary vascular resistance, right heart failure, and death. Although therapeutic management has rapidly advanced in recent years, these patients were not included in randomized controlled trials for specific pulmonary arterial hypertension drugs, except for bosentan. However, in clinical practice we apply treatment strategies combining drugs targeting multiple pathobiological pathways. We present 3 patients with Eisenmenger syndrome and their improvement after starting treatment with selexipag, an oral selective IP prostacyclin receptor agonist.

Prostaglandin I2 (PGI2) inhibits Brucella abortus internalization in macrophages via PGI2 receptor signaling, and its analogue affects immune response and disease outcome in mice.

To date, the implications of prostaglandin I2 (PGI2), a prominent lipid mediator for modulation of immune responses, has not been clearly understood in Brucella infection. In this study, we found that cyclooxygenase-2 (COX-2) was significantly expressed in both infected bone marrow-derived macrophages (BMMs) and RAW 264.7 cells. Prostaglandin I2 synthase (PTGIS) expression was not significantly changed, and PGI2receptor (PTGIR) expression was downregulated in BMMs but upregulated in RAW 264.7 macrophages at late infection. Here, we presented that PGI2, a COX-derived metabolite, was produced by macrophages during Brucella infection and its production was regulated by COX-2 and IL-10. We suggested that PGI2 and selexipag, a potent PGI2 analogue, inhibited Brucella internalization through IP signaling which led to down-regulation of F-actin polymerization and p38α MAPK activity. Administration with selexipag suppressed immune responses and resulted in a notable reduction in bacterial burden in spleen of Brucella-challenged mice. Taken together, our study is the first to characterize PGI2 synthesis and its effect in evasion strategy of macrophages against Brucella infection.

Targeted Drugs for Treatment of Pulmonary Arterial Hypertension: Past, Present, and Future Perspectives.

Pulmonary arterial hypertension (PAH) is a devastating disease that can lead to right ventricular failure and premature death. Although approved drugs have been shown to be safe and effective, PAH remains a severe clinical condition, and the long-term survival of patients with PAH is still suboptimal. Thus, potential therapeutic targets and new agents to treat PAH are urgently needed. In recent years, a variety of related pathways and potential therapeutic targets have been found, which brings new hope for PAH therapy. In this perspective, not only are the marketed drugs used to treat PAH summarized but also the recently developed novel pharmaceutical therapies currently in clinical trials are discussed. Furthermore, the advances in natural products as potential treatment for PAH are also updated.

The selective PGI2 receptor agonist selexipag ameliorates Sugen 5416/hypoxia-induced pulmonary arterial hypertension in rats.

Pulmonary arterial hypertension (PAH) is a lethal disease characterized by a progressive increase in pulmonary artery pressure due to an increase in vessel tone and occlusion of vessels. The endogenous vasodilator prostacyclin and its analogs are used as therapeutic agents for PAH. However, their pharmacological effects on occlusive vascular remodeling have not been elucidated yet. Selexipag is a recently approved, orally available and selective prostacyclin receptor agonist with a non-prostanoid structure. In this study, we investigated the pharmacological effects of selexipag on the pathology of chronic severe PAH in Sprague-Dawley and Fischer rat models in which PAH was induced by a combination of injection with the vascular endothelial growth factor receptor antagonist Sugen 5416 and exposure to hypoxia (SuHx). Oral administration of selexipag for three weeks significantly improved right ventricular systolic pressure and right ventricular (RV) hypertrophy in Sprague-Dawley SuHx rats. Selexipag attenuated the proportion of lung vessels with occlusive lesions and the medial wall thickness of lung arteries, corresponding to decreased numbers of Ki-67-positive cells and a reduced expression of collagen type 1 in remodeled vessels. Administration of selexipag to Fischer rats with SuHx-induced PAH reduced RV hypertrophy and mortality caused by RV failure. These effects were probably based on the potent prostacyclin receptor agonistic effect of selexipag on pulmonary vessels. Selexipag has been approved and is used in the clinical treatment of PAH worldwide. It is thought that these beneficial effects of prostacyclin receptor agonists on multiple aspects of PAH pathology contribute to the clinical outcomes in patients with PAH.

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]).

Selexipag para el tratamiento de la Hipertensión Pulmonar / Selexipag for the treatment of pulmonary hypertension

CONTEXTO: La HAP es una condición crónica progresiva de baja incidencia, estimada en 2,4/1mill./año y una prevalencia de 15casos /mill.hab/año por lo que se la considera una enfermedad rara. Los síntomas más comunes son disnea, dolor torácico, fatiga y síncope. Presenta una elevada mortalidad y su sobrevida alcanza 2,8 años en adultos sin tratamiento. El objetivo terapéutico del abordaje de la enfermedad es mejorar la función pulmonar, alcanzando una clase funcional I, ya que las clases funcionales III y IV se asocian con un riesgo medio y elevado de muerte. Los datos de incidencia en Argentina provienen de un estudio realizado en base a datos del Censo 2001 y proyecciones en el que se identificó una tasa de mortalidad de 1.39 y 2.39 muertes/millón habitantes (promedio 76 muertes/año); con un predominio sexo femenino (1.76 a 3.16/millon) en comparación con los varones (0.9 a 2.11/millón). los tratamientos disponibles los mismos abarcan medidas terapéuticas generales, fármacos inespecíficos (diuréticos, anticoagulantes, oxigenoterapia y fármacos específicos como Bloqueantes de los canales del Ca, Antagonistas de los receptores de endotelina, Inhibidores de la Fosfodiesterasa-5(IP-5), Análogos de Prostaciclina. Selexipag (ATC: B01AC27), es un agonista del receptor IP de prostaciclina, activa la vía IP2, produciendo relajación de las Células del Músculo Liso Arterial Pulmonar. Se administra una dosis inicial de 200 mcg dos veces al día, hasta un máximo de 1600 mcg dos veces al día, en escalonamiento semanales. METOLODOGÍA: El objetivo del presente fue analizar la evidencia disponible sobre eficacia, seguridad de Selexipag en el tratamiento de Hipertensión Arterial Pulmonar (HAP)y emitir una recomendación de cobertura. Se realizó una búsqueda bibliográfica sistematizada, la que permitió hallar 33 documentos de los que se seleccionaron por criterio (completos, diseño) 17 para su análisis. Paralelamente se evaluó el impacto presupuestario para el Ministerio de Salud, y los impactos en la equidad y en la salud pública. La calidad de la evidencia disponible para la droga es moderada (ensayos clínicos vs placebo, no existen comparaciones directas, desenlaces combinados). La magnitud de los beneficios en el paciente tales como mejora en la Clase funcional, mortalidad y sobrevida es ESCASO ó nulos, según la evidencia analizada. Emitir una recomendación de cobertura para pacientes de la provincia de Mendoza. RESULTADOS: Se incluyeron 4 Ensayos clínicos, una Revisión sistemática y un metaanálisis en red. CONCLUSIONES: Escaso beneficio clínico de Selexipag en el tratamiento de la HAP I, Clase funcional II-III, (sección 9-f) junto a impactos negativos en demás aspectos valorados, no permiten recomendar la inclusión a la cobertura del Ministerio de Salud. Asegurar la continuidad de los tratamientos como ARE, Bloq.Calcio, IP-5 como el resto de las medidas de apoyo a los pacientes para evitar la progresión de la enfermedad, resulta clave. Se establece revisar la evidencia para la droga en el término de un año, ante nueva información disponible o al requerimiento de profesionales, pacientes, productores y/o gestores.

Experience in Transitioning From Parenteral Prostacyclins to Selexipag in Pulmonary Arterial Hypertension.

Parenteral prostacyclin therapies remain first-line therapy for patients with pulmonary arterial hypertension (PAH) with class IV symptoms. In selected patients who have been clinically stabilized, switching to selexipag, a chemically distinct prostacyclin receptor agonist, may alleviate risks associated with long-term parenteral therapy. We report our experience with transition of patients from parenteral prostacyclin therapy to selexipag. From January 2016 to July 2017, patients with PAH at the Duke University Pulmonary Vascular Disease Center with functional class II symptoms on stable parenteral prostacyclin therapy were offered the opportunity to transition to selexipag. A standardized protocol was developed to guide titration of therapies. Patients underwent pre- and post-transition assessments of hemodynamics, echocardiography, laboratory biomarkers, and functional status. We studied 14 patients with PAH (11 women; median age 53 years) in total. Overall, 13 patients tolerated the switch to selexipag and remained on the drug at study completion, and 1 patient passed away due to progressive liver failure. Surrogate markers including NT-proBNP, 6MWD, RV function, and TAPSE, and right heart catheterization hemodynamics were similar before and after transition. The transition from parenteral prostanoid therapy to oral selexipag was overall well-tolerated in patients with stable PAH and functional class II symptoms. Finally, doses of selexipag up to 3200 µg twice daily were well-tolerated in patients who had been treated with prior parenteral prostacyclins.

Efficacy and safety of ralinepag, a novel oral IP agonist, in PAH patients on mono or dual background therapy: results from a phase 2 randomised, parallel group, placebo-controlled trial.

PURPOSE: This phase 2 study was designed to assess the efficacy, safety and tolerability of immediate-release orally administered ralinepag, a selective, non-prostanoid prostacyclin receptor agonist with a 24-h terminal half-life, compared to placebo in adult patients with symptomatic pulmonary arterial hypertension (PAH). METHODS: 61 PAH patients who were receiving standard care, including mono or dual PAH-targeted background therapy were randomised 2:1 to ralinepag (n=40) or placebo (n=21). The starting dose of ralinepag was 10 µg twice daily. Dosage was then up-titrated as tolerated over the course of the 9-week dose-titration period, to a maximum total daily dose of 600 µg (300 µg twice daily). The primary efficacy end-point was the absolute change in pulmonary vascular resistance (PVR) from baseline to week 22. Additional end-points included percentage change in PVR from baseline, other haemodynamic parameters, 6-min walk distance (6MWD) and safety and tolerability. RESULTS: Ralinepag significantly decreased PVR by 163.9 dyn·s·cm-5 compared to an increase of 0.7 dyn·s·cm-5 with placebo (p=0.02); the least-squares mean change from baseline PVR was -29.8% compared with placebo (p=0.03). 6MWD increased from baseline by 36.2 m with ralinepag and 29.4 m with placebo (p=0.90). Serious adverse events occurred in 10% of ralinepag patients and 29% of placebo patients. Study discontinuations occurred in 13% of ralinepag patients and 10% of placebo patients. SUMMARY: Ralinepag reduced PVR compared with placebo in PAH patients on mono (41%) or dual combination (59%) background therapy.

Selexipag en hipertensión pulmonar / Selexipag in pulmonary hypertension

CONTEXTO CLÍNICO: Actualmente la definición de hipertensión pulmonar (HP) comprende una presión arterial pulmonar media (PAPm) mayor a 20 milímetros de mercurio (mmHg) en reposos registrados por cateterismo cardíaco derecho y con resistencia pulmonar vascular mayor o igual a tres unidades de Wood. Hasta hace muy poco tiempo se definía como la elevación de la PAPm con valores iguales o superiores a 25 mmHg con el paciente en reposo. La Organización Mundial de la Salud (OMS) ha clasificado las etiologías de la HP en cinco grupos (ver Anexo III). El término hipertensión arterial pulmonar (HAP) se emplea solamente para describir a los incluidos en el grupo I, mientras que el término HP define a los cinco grupos. La prevalencia de la HP es desconocida debido sus diferentes clasificaciones y múltiples etiologías; sin embargo, el grupo más estudiado es el grupo I de la OMS (HAP, ver Anexo III) con 5 a 52 casos de HAP por millón para población europea. También de estima que la HAP de origen hereditario e idiopático (HAP) tiene una incidencia de entre 5 a 15 casos por millón de adultos. En Argentina se creó en 2014 el Primer Registro Colaborativo de HP (RECOPILAR) que mostrará el estado de la HP en nuestro país. La HAP suele ser más frecuente en jóvenes, y se observa más en mujeres frente a hombres con uma tasa de 1,7 a 4,8. TECNOLOGÍA: Selexipag (Uptravi®) es un agonista oral selectivo del receptor de prostaciclina no prostanoide que produce vasodilatación del lecho vascular pulmonar. Tanto el selexipag como su metabolito activo poseen una alta selectividad para el receptor de prostaciclina sobre otros receptores prostanoides que lo distinguen de la prostaciclina y los análogos de la prostaciclinas que se utilizan actualmente en el tratamiento de la HAP. MÉTODOS: Se realizó una búsqueda en las principales bases de datos bibliográficas, en buscadores genéricos de internet, y financiadores de salud. Se priorizó la inclusión de revisiones sistemáticas (RS), ensayos clínicos controlados aleatorizados (ECAs), evaluaciones de tecnologías sanitarias (ETS), evaluaciones económicas, guías de práctica clínica (GPC) y políticas de cobertura de diferentes sistemas de salud. RESULTADOS: Se incluyeron una RS con meta-análisis (MA), dos MA en red, cinco GPC, una evaluación económica, y trece informes de políticas de cobertura de selexipag en hipertensión arterial pulmonar. CONCLUSIONES: No se encontraron estudios que comparen selexipag frente a otros tratamientos habituales em pacientes con hipertensión arterial pulmonar (grupo I OMS). Evidencia indirecta sugiere que, en estos pacientes, selexipag en monoterapia como primera opción de tratamiento podría ser menos efectivo y presentar mayor mortalidad que los tratamientos habituales. Evidencia de moderada calidad proveniente de un estudio sugiere que en pacientes adultos con hipertensión arterial pulmonar con clase funcional II o III OMS y de origen idiopático, hereditario, o asociados a infección por el virus de la inmunodeficiencia humana, al uso de drogas o exposición a toxinas, a enfermedad del tejido conectivo o con derivaciones congénitas corregidas, el agregado de selexipag a la combinación de iPDE-5 y ARE mejora el tiempo a un desenlace combinado de mortalidad y complicaciones relacionadas a la hipertensión pulmonar frente a placebo al año y medio de seguimiento. El tratamiento con selexipag presentó más eventos adversos frente a placebo como dolor de cabeza, vasodilatación, dolor de mandíbula, diarrea, náuseas, vómitos, dolor de extremidades y mialgias. La mayoría de las guías de práctica clínica relevadas no recomiendan o no hacen mención sobre el uso de selexipag debido a la falta de evidencia. Solo una la menciona, junto a otras alternativas, en monoterapia o en terapia combinada con iPDE-5 y/o ARE en pacientes con hipertensión arterial pulmonar y clase funcional II-III OMS. El selexipag se encuentra en el Sistema Único de Reintegro de Argentina, mientras que en otros países de Latinoamérica relevados no lo cubren o no lo mencionan. De los países de altos ingresos relevados la mayoría reserva su uso como agregado al tratamiento en pacientes de riesgo intermedio que han progresado a la iPDE-5 y ARE, mientras que Australia explícitamente no lo cubre. Una evaluación económica proveniente de un país de altos ingresos sugiere que el selexipag en monoterapia o combinada con iPDE-5 y/o ARE versus iPDE-5 y/o ARE no es una opción costo-efectiva según los umbrales aceptados por ese país. El costo directo estimado para el tratamento con selexipag es menor frente al de los análogos de prostaciclinas, pero es mayor frente a los costos de los iPDE-5, ARE, bloqueadores del canal de calcio y riociguat.

Pharmacology of the single isomer, esuberaprost (beraprost-314d) on pulmonary vascular tone, IP receptors and human smooth muscle proliferation in pulmonary hypertension.

BACKGROUND AND PURPOSE: Beraprost is a prostacyclin analogue and IP receptor agonist which is approved to treat pulmonary arterial hypertension (PAH) in Asia. The beraprost-314d isomer (esuberaprost) is one of four stereoisomers contained within the racemic mixture of beraprost. The pharmacological profile of esuberaprost is now evaluated to determine how stereoisomer separation affects its potency and mode of action in functional assays. EXPERIMENTAL APPROACH: Vascular tone was assessed using wire myography in rat and human distal pulmonary arteries (PAs) pre-contracted with U46619 (100 nM). HEK-293 cells stably expressing the human IP receptor (HEK-293-IP) and pulmonary arterial smooth muscle cells (PASMCs) derived from PAH patients were used to assess cyclic AMP (cAMP) generation and cell proliferation, respectively. KEY RESULTS: Esuberaprost relaxed rat PAs with a 5-fold greater potency compared with beraprost, and effects were strongly inhibited by RO3244794 (IP receptor antagonist) or L-NAME (NO synthase inhibitor). Esuberaprost caused EP3 receptor-dependent vasoconstriction at high concentrations ≥ 1000 nM, but contractions were 50% lower compared to beraprost. In HEK-293-IP cells, esuberaprost was 26-fold more potent (EC50 0.4 nM) at increasing cAMP than beraprost. In human PASMCs, esuberaprost was 40-fold more potent than beraprost at inhibiting cell proliferation (EC50 3 nM versus 120 nM), contrasting the 5-fold potency difference for cAMP elevation. Antiproliferative effects of esuberaprost appeared more dependent on NO than on the IP receptor. In PAs from patients with pulmonary hypertension, esuberaprost, caused some relaxation whereas beraprost instead produced a weak contraction. CONCLUSIONS AND IMPLICATIONS: Stereoisomer separation of beraprost has a significant effect on the pharmacology of the individual isomer, esuberaprost, identified in vitro as a highly potent prostanoid IP receptor agonist.

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.

Apolipoprotein E favours the blunting by high-fat diet of prostacyclin receptor activation in the mouse aorta.

BACKGROUND AND PURPOSE: NO-mediated, endothelium-dependent relaxations of isolated arteries are blunted by ageing and high-fat diets, as well as by apolipoprotein E deletion. The present study was designed to test the hypothesis that apolipoprotein E deletion impairs endothelium-dependent responses to prostacyclin (IP) receptor activation. EXPERIMENTAL APPROACH: Five-week-old ApoE+/+ and ApoE-/- mice were fed normal chow or high-fat diet for 29 weeks. The aortae were isolated for the measurements of isometric tension in Halpern-Mulvany myographs. Levels of proteins were assessed by Western blotting and immunofluorescence, and cyclic nucleotide levels by elisa. KEY RESULTS: The IP receptor agonist, iloprost, induced endothelium-, NO-synthase- and IP-dependent relaxations in aortae of young ApoE+/+ mice. High-fat diet favoured activation of thromboxane receptors by iloprost, causing contraction. Apolipoprotein E was present in aortae of ApoE+/+ mice, especially in endothelium. Its presence was augmented by high-fat diet. Its deletion potentiated iloprost-induced relaxations in aortae of young mice and prevented the blunting of this response by high-fat diet. Levels of cAMP were higher, but those of cGMP were lower in the aorta of ApoE-/- than in ApoE+/+ mice of the same age. The levels of IP receptor protein were not different between ApoE+/+ and ApoE-/- mice. CONCLUSIONS AND IMPLICATIONS: Iloprost induced an endothelium-dependent relaxation in the aorta of young healthy mice which involved both the cGMP and cAMP pathways. This response was blunted by prolonged exposure to a high-fat diet. Apolipoprotein E deletion potentiated relaxations to IP receptor activation, independently of age and diet.

Selective Prostacyclin Receptor Agonist Selexipag, in Contrast to Prostacyclin Analogs, Does Not Evoke Paradoxical Vasoconstriction of the Rat Femoral Artery.

Selexipag [2-{4-[(5,6-diphenylpyrazin-2-yl)(isopropyl)amino]butoxy}-N-(methylsulfonyl)acetamide] is a selective nonprostanoid prostacyclin (PGI2) receptor (IP receptor) agonist that is approved for the treatment of pulmonary arterial hypertension (PAH). In contrast to selexipag, PGI2 analogs used in the clinic are nonselective agonists at prostanoid receptors and can also activate contractile prostaglandin E receptor 3 (EP3) receptors. Leg pain is a common side effect in patients receiving treatment with PGI2 analogs and peripheral vasoconstriction can be responsible for side effects related to muscular ischemia. This study tested the hypothesis that PGI2 analogs could cause paradoxical vasoconstriction of the femoral artery via EP3 receptor activation but that only vasorelaxation would be observed in response to selexipag and its active metabolite ACT-333679 [{4-[(5,6-diphenylpyrazin-2-yl)(isopropyl)amino]butoxy}acetic acid]. Selexipag and ACT-333679 relaxed rings of the isolated rat femoral artery contracted with either prostaglandin F2α (PGF2α ) or the α1 adrenoceptor (α1AR) agonist phenylephrine. ACT-333679 also inhibited contraction of the femoral artery to sympathetic nerve stimulation. In contrast, PGI2 analogs (iloprost, beraprost, and treprostinil) caused additional contraction of arterial rings precontracted with phenylephrine, which was reverted to relaxation by antagonism of EP3 receptors. Treprostinil augmented contraction of the femoral artery to sympathetic nerve stimulation in an EP3 receptor-dependent manner. Mechanistically, concomitant EP3 and α1AR receptor activation synergistically constricted femoral arteries. It is concluded that selexipag and ACT-333679 are vasorelaxants of the rat femoral artery and, unlike PGI2 analogs, do not cause paradoxical vasoconstriction via activation of EP3 receptors. EP3 receptor-mediated vasoconstriction may contribute to the well documented peripheral muscle pain reported in patients with PAH receiving PGI2 analogs. Leg pain may be less in patients treated with selexipag.

Temporary treatment interruptions with oral selexipag in pulmonary arterial hypertension: Insights from the Prostacyclin (PGI2) Receptor Agonist in Pulmonary Arterial Hypertension (GRIPHON) study.

BACKGROUND: Parenteral prostacyclin analogs that target the prostacyclin pathway have been used to treat pulmonary arterial hypertension (PAH) since the 1990s. Abrupt discontinuation of parenteral prostacyclin analogs can be associated with acute deterioration of PAH. Less is known about temporary interruption of oral therapies that target the prostacyclin pathway, such as selexipag. METHODS: We evaluated the frequency, duration, reasons, and consequences of temporary selexipag interruptions among PAH patients enrolled in the Prostacyclin (PGI2) Receptor Agonist in Pulmonary Arterial Hypertension (GRIPHON) study. In GRIPHON, patients were randomized to selexipag or placebo and titrated to an individualized highest tolerated dose (200 to 1,600 µg twice daily) over 12 weeks, after which patients entered the maintenance phase. Treatment interruptions were allowed; if the interruption was < 3 days, treatment was restarted at the previous highest tolerated dose; if the interruption was ≥ 3 days, retitration from 200 µg twice daily was required. Descriptive analyses were performed. RESULTS: At least 1 treatment interruption occurred in 111 of 574 patients (19.3%) in the selexipag group and in 58 of 582 (10.0%) in the placebo group. Baseline characteristics were similar between patients with and without an interruption. Of the 111 patients in whom selexipag was temporarily interrupted, 94 (85%) were receiving background PAH therapy. Adverse events were the most common reason for selexipag interruption. Selexipag interruptions and reinstitution of treatment were well tolerated. There were no episodes of acute deterioration during treatment interruption. CONCLUSIONS: Based on observations from GRIPHON, selexipag interruptions can be expected in clinical practice. However, temporarily interrupting selexipag was well tolerated and manageable.

Prostaglandin I2 suppresses the development of diet-induced nonalcoholic steatohepatitis in mice.

Nonalcoholic steatohepatitis (NASH) is a hepatic manifestation of metabolic syndrome. Although the prostaglandin (PG)I2 receptor IP is expressed broadly in the liver, the role of PGI2-IP signaling in the development of NASH remains to be determined. Here, we investigated the role of the PGI2-IP system in the development of steatohepatitis using mice lacking the PGI2 receptor IP [IP-knockout (IP-KO) mice] and beraprost (BPS), a specific IP agonist. IP-KO and wild-type (WT) mice were fed a methionine- and choline-deficient diet (MCDD) for 2, 5, or 10 wk. BPS was administered orally to mice every day during the experimental periods. The effect of BPS on the expression of chemokine and inflammatory cytokines was examined also in cultured Kupffer cells. WT mice fed MCDD developed steatohepatitis at 10 wk. IP-KO mice developed steatohepatitis at 5 wk with augmented histologic derangements accompanied by increased hepatic monocyte chemoattractant protein-1 (MCP-1) and TNF-α concentrations. After 10 wk of MCDD, IP-KO mice had greater hepatic iron deposition with prominent oxidative stress, resulting in hepatocyte damage. In WT mice, BPS improved histologic and biochemical parameters of steatohepatitis, accompanied by reduced hepatic concentration of MCP-1 and TNF-α. Accordingly, BPS suppressed the LPS-stimulated Mcp-1 and Tnf-α mRNA expression in cultured Kupffer cells prepared from WT mice. PGI2-IP signaling plays a crucial role in the development and progression of steatohepatitis by modulating the inflammatory response, leading to augmented oxidative stress. We suggest that the PGI2-IP system is an attractive therapeutic target for treating patients with NASH.-Kumei, S., Yuhki, K.-I., Kojima, F., Kashiwagi, H., Imamichi, Y., Okumura, T., Narumiya, S., Ushikubi, F. Prostaglandin I2 suppresses the development of diet-induced nonalcoholic steatohepatitis in mice.

Pharmacokinetics of the selective prostacyclin receptor agonist selexipag in rats, dogs and monkeys.

1. This study examined the pharmacokinetics, distribution, metabolism and excretion of the selective prostacyclin receptor agonist selexipag (NS-304; ACT-293987) and its active metabolite MRE-269 (ACT-33679). The compounds were investigated following oral and/or intravenous administration to intact rats, dogs and monkeys, and bile-duct-cannulated rats and dogs. 2. After oral administration of [14C]selexipag, selexipag was well absorbed in rats and dogs with total recoveries of over 90% of the dose, mainly in the faeces. Biliary excretion was the major elimination pathway for [14C]MRE-269 as well as [14C]selexipag, while renal elimination was of little importance. [14C]Selexipag-related radioactivity was secreted into the milk in lactating rats. 3. Plasma was analysed for total radioactivity, selexipag and MRE-269 in rats and monkeys. Selexipag was negligible in rat plasma due to extensive metabolism, and MRE-269 was present in rat and monkey plasma. A species difference was clearly evident when selexipag was incubated in rat, dog and monkey plasma. 4. Total radioactivity was rapidly distributed to tissues. The highest concentrations were found in the bile duct and liver without significant accumulation or persistence, while there was limited melanin-associated binding, penetration of the blood-brain barrier and placental transfer of drug-related materials.

The metabolism and drug-drug interaction potential of the selective prostacyclin receptor agonist selexipag.

1. The metabolism of selexipag has been studied in vivo in man and the main excreted metabolites were identified. Also, metabolites circulating in human plasma have been structurally identified and quantified. 2. The main metabolic pathway of selexipag in man is the formation of the active metabolite ACT-333679. Other metabolic pathways include oxidation and dealkylation reactions. All primary metabolites undergo subsequent hydrolysis of the sulphonamide moiety to their corresponding acids. ACT-333679 undergoes conjugation with glucuronic acid and aromatic hydroxylation to P10, the main metabolite detected in human faeces. 3. The formation of the active metabolite ACT-333679 is catalysed by carboxylesterases, while the oxidation and dealkylation reactions are metabolized by CYP2C8 and CYP3A4. CYP2C8 is the only P450 isoform catalysing the aromatic hydroxylation to P10. CYP2C8 together with CYP3A4 are also involved in the formation of several minor ACT-333679 metabolites. UGT1A3 and UGT2B7 catalyse the glucuronidation of ACT-333679. 4. The potential of selexipag to inhibit or induce cytochrome P450 enzymes or drug transport proteins was studied in vitro. Selexipag is an inhibitor of CYP2C8 and CYP2C9 and induces CYP3A4 and CYP2C9 in vitro. Also, selexipag inhibits the transporters OATP1B1, OATP1B3, OAT1, OAT3, and BCRP. However, due to its low dose and relatively low unbound exposure, selexipag has a low potential for causing drug-drug interactions.