| E.1 Medical condition or disease under investigation | 
| E.1.1 | Medical condition(s) being investigated  | 
| Pulmonary arterial hypertension (PAH) (idiopathic PAH, familial PAH, and PAH associated with collagen disease, corrected congenital vitium or anorexigen use | 
 
 
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| E.1.1.1 | Medical condition in easily understood language  | 
| Pulmonary Arterial Hypertension is an increase in blood pressure in the pulmonary arteries leading to shortness of breath, dizziness, fainting and other symptoms | 
 
 
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| E.1.1.2 | Therapeutic area  | Diseases [C] - Cardiovascular Diseases [C14] | 
| MedDRA Classification | 
| E.1.2 Medical condition or disease under investigation | 
| E.1.2 | Version  | 18.0 | 
 
| E.1.2 | Level  | PT | 
 
| E.1.2 | Classification code  | 10064911 | 
 
| E.1.2 | Term  | Pulmonary arterial hypertension | 
 
| E.1.2 | System Organ Class  | 10038738 - Respiratory, thoracic and mediastinal disorders | 
 
 
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| E.1.3 | Condition being studied is a rare disease  |  Yes  | 
| E.2 Objective of the trial | 
| E.2.1 | Main objective of the trial  | 
The primary objective of the study is to collect and evaluate long-term safety and tolerability data of selexipag treatment in subjects with pulmonary arterial hypertension (PAH). From Day 35 onward safety will be assessed every month for all patients. After Visit 5 (24 weeks) safety will be assessed every 3 months. | 
 
 
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| E.2.2 | Secondary objectives of the trial  | 
The secondary objectives of the open-extension study are the assessments of efficacy of selexipag regarding the following variable: 6-minute walk test (6MWT). Further objectives of the open-extension study are: assessments of efficacy of selexipag regarding the following variables: - time to aggravation of PAH - proportion of subjects with aggravation of PAH - Borg dyspnoea score - New York Heart Association (NYHA) functional class - Plasma brain natriuretic peptide (BNP) concentrations After Visit 5 (24 weeks) efficacy will be assessed every 6 months. | 
 
 
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| E.2.3 | Trial contains a sub-study  |  No  | 
| E.3 | Principal inclusion criteria  | 
1) Subjects who have completed the preceding double-blind study (NS-304/-02) 2) Subjects who have signed informed consent for participation in the open-extension study 3) Subjects who are willing and able to refrain from sunbathing, prolonged sun exposure and artificial sunlight exposure such as solarium use or UVA/UVB treatment, and to limit skin and eye exposure to sunlight using appropriate precautions (protective clothing, sunscreen and sunglasses) from the first dose until 14 days after study drug discontinuation. | 
 
 
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| E.4 | Principal exclusion criteria | 
1) Subjects with medically abnormal findings (ECG, physical examination, AEs) at the end of visit 7 of the preceding double-blind study that investigators considers not appropriate to enter this study 2) Females who are breast-feeding, pregnant or plan to become pregnant during the study and females who are not using a highly effective method of birth control (failure rate less than 1% per year) such as implants, injectables, combined oral contraceptives, some intrauterine devices, sexual abstinence or vasectomised partner. | 
 
 
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| E.5 End points | 
| E.5.1 | Primary end point(s) | 
| Safety assessment is the primary endpoint (vital signs: blood pressure, pulse rate; treatments-emergent AEs, clinical laboratory data: hematology, blood chemistry, and urinanalysis; physical examination and 12-lead electrocardiogramm (ECG) parameters). | 
 
 
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| E.5.1.1 | Timepoint(s) of evaluation of this end point | 
| After Visit 5, safety will be assessed every 3 months. | 
 
 
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| E.5.2 | Secondary end point(s) | 
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| E.5.2.1 | Timepoint(s) of evaluation of this end point | 
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| E.6 and E.7 Scope of the trial | 
| E.6 | Scope of the trial | 
| E.6.1 | Diagnosis |  No  | 
| E.6.2 | Prophylaxis |  No  | 
| E.6.3 | Therapy |  Yes  | 
| E.6.4 | Safety |  Yes  | 
| E.6.5 | Efficacy |  Yes  | 
| E.6.6 | Pharmacokinetic |  No  | 
| E.6.7 | Pharmacodynamic |  No  | 
| E.6.8 | Bioequivalence |  No  | 
| E.6.9 | Dose response |  No  | 
| E.6.10 | Pharmacogenetic |  No  | 
| E.6.11 | Pharmacogenomic |  No  | 
| E.6.12 | Pharmacoeconomic |  No  | 
| E.6.13 | Others |  No  | 
| E.7 | Trial type and phase | 
| E.7.1 | Human pharmacology (Phase I) |  No  | 
| E.7.1.1 | First administration to humans |  No  | 
| E.7.1.2 | Bioequivalence study |  No  | 
| E.7.1.3 | Other |  No  | 
| E.7.1.3.1 | Other trial type description |  | 
| E.7.2 | Therapeutic exploratory (Phase II) |  Yes  | 
| E.7.3 | Therapeutic confirmatory (Phase III) |  No  | 
| E.7.4 | Therapeutic use (Phase IV) |  No  | 
| E.8 Design of the trial | 
| E.8.1 | Controlled |  No  | 
| E.8.1.1 | Randomised |  No  | 
| E.8.1.2 | Open |  Yes  | 
| E.8.1.3 | Single blind |  No  | 
| E.8.1.4 | Double blind  |  No  | 
| E.8.1.5 | Parallel group |  No  | 
| E.8.1.6 | Cross over  |  No  | 
| E.8.1.7 | Other |  No  | 
| E.8.2 |  Comparator of controlled trial | 
| E.8.2.1 | Other medicinal product(s) |  No  | 
| E.8.2.2 | Placebo  |  No  | 
| E.8.2.3 | Other |  No  | 
| E.8.2.4 | Number of treatment arms in the trial | 1 | 
| E.8.3 | 
                                The trial involves single site in the Member State concerned
                             |  Yes  | 
| E.8.4 |  The trial involves multiple sites in the Member State concerned  |  No  | 
| E.8.5 | The trial involves multiple Member States |  Yes  | 
| E.8.5.1 | Number of sites anticipated in the EEA | 7 | 
| E.8.6 Trial involving sites outside the EEA | 
| E.8.6.1 | Trial being conducted both within and outside the EEA |  No  | 
| E.8.6.2 | Trial being conducted completely outside of the EEA |  No  | 
| E.8.7 | Trial has a data monitoring committee |  No  | 
| E.8.8 | 
                        Definition of the end of the trial and justification where it is not the last
                        visit of the last subject undergoing the trial
                     | 
| The overall study is considered completed when all patients have completed their safety follow-up visit or have died, withdrawn consent, or were lost to follow-up. | 
 
 
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| E.8.9 Initial estimate of the duration of the trial | 
| E.8.9.1 | In the Member State concerned years | 5 | 
| E.8.9.1 | In the Member State concerned months |  | 
| E.8.9.1 | In the Member State concerned days |  | 
| E.8.9.2 | In all countries concerned by the trial years | 5 |