PRIMEx - A Study of 2 Doses of Oral CXA-10 in Pulmonary Arterial Hypertension (PAH)

Inclusion Criteria: * Males and females between 18 to 80 years of age inclusive at Screening * Weight ≥40 kg * Must have a diagnosis of WHO Group 1 PH * Have a World Health Organization (WHO) Classification of Functional Status Class II or III of patients with PH * Must meet hemodynamic criteria by means of a right heart catheterization * Meet pulmonary function test parameters * A 6 MWD test of ≥125m and ≤550m at the visit * Subjects must have a resting arterial oxygen saturation (SaO2) ≥90%, with or without supplemental oxygen, as measured by pulse oximetry at Screening * Subjects enrolled in a prescribed exercise program for pulmonary rehabilitation must be in a stable program for 3 months prior to Screening (Visit 1) and must agree to maintain their current level of rehabilitation throughout the study. If subjects are not enrolled in a prescribed exercise training program for pulmonary rehabilitation, they cannot enroll during the Screening/Baseline Period or throughout the study * If receiving simvastatin-containing products: dose should not exceed 20 mg/day * Subjects must be receiving no more than three of the following previously approved PAH therapies: phosphodiesterase type 5 (PDE-5) inhibitors, endothelin receptor antagonist (ERA), soluble guanylate cyclase (sGC) stimulator, prostanoids, prostacyclin receptor agonists and must be on stable doses (≥3 months) at Screening (Visit 1) Exclusion Criteria: * Contraindications for CMRI imaging * WHO Groups 2, 3, 4 and 5 Pulmonary Hypertension * Unrepaired congenital heart defects and significant congenital heart defects (i.e., atrial septal defects, ventricular septal defects, and patent ductus arteriosus) repaired less than 1 year prior to Screening (Visit 1) (Group 1 classification of Pulmonary Hypertension) * QTcF \> 500 msec * Acute myocardial infarction or acute coronary syndrome within the last 90 days * Cerebrovascular accident/transient ischemic attack (CVA/TIA) within the last 90 days * Hospitalization for left heart failure within the last 90 days * Clinically significant aortic or mitral valve disease defined as greater than mild regurgitation or mild stenosis; pericardial constriction; restrictive or constrictive cardiomyopathy; left ventricular dysfunction (LVEF \< 50%); left ventricular outflow obstruction; symptomatic coronary artery disease; autonomic hypotension; or fluid depletion * Chronic atrial fibrillation and life-threatening cardiac arrhythmias * Personal or family history of congenital prolonged QTc syndrome or sudden or sudden unexpected death due to a cardiac reason * Clinically significant anemia * Severe hepatic impairment or active chronic hepatitis * Receiving intravenous inotropes within 2 weeks prior to Screening * History of angina pectoris or other condition that was treated with long or short acting nitrates \<12 weeks of Screening * Received prednisone doses \>15mg/day or changes in immunosuppressive medications \< 12 weeks prior to Screening (Visit 1) * Recent (within 1 year) history of abusing alcohol or illicit drugs. * History of any primary malignancy, with no evidence of disease for at least 5 years * Treatment with any investigational drug or device within 30 days or 5 half-lives