Inclusion Criteria:

• - Patients who have scleroderma ILD will be defined as having a total lung capacity of less than 80% predicted and CT evidence of fibrosis.

The degree of fibrosis will be scored by a radiologist using the CT comparative scoring method of Wells et al (13).

• - Pulmonary Hypertension (PH) as defined as resting mean pulmonary arterial pressure (mPAP) ≥ 25 mmHg with a wedge pressure of ≤ 15 mmHg during right heart catheterization.

• - Stable ILD as evident by a stable FEV1 and FVC for 3 months prior to the initiation of the study, and be pulmonary arterial hypertension (PAH)-targeted treatment naïve.

Exclusion Criteria:

• - Patients with a left ventricular ejection fraction <50% or clinical, echocardiographic, and/or catheterization data consistent with heart failure with preserved ejection fraction (HFpEF) and/or moderate-severe aortic or mitral valve abnormality.

• - Patients with severe restrictive lung disease (FVC<40% predicted) and/or obstructive lung disease (FEV1 <55% predicted and FEV1/FVC <70%).

• - Patients with radiographic combined pulmonary fibrosis/emphysema (CPFE) will also be excluded if imaging shows predominant emphysema and/or obstruction is moderately severe (FEV1<30%) - Patients with a history of pulmonary embolism within the last three months or evidence of chronic pulmonary embolism.

• - Patients with a known contraindication to right heart catheterization.

• - Patients whom have received active or previous pulmonary vasoactive medication within the previous 12 weeks.

• - Patients with a contraindication to exercise testing based on American Heart Association/American College of Cardiology (AHA/ACC) guidelines.

• - PAH associated with significant venous or capillary involvement (PCWP > 15 mmHg), known pulmonary veno-occlusive disease, and pulmonary capillary hemangiomatosis.

• - Persistent pulmonary hypertension of the newborn.

• - Pulmonary Hypertension belonging to groups 2 to 5 of the Venice classification.

• - Moderate to severe hepatic impairment, i.e., Child-Pugh Class B or C.

• - Estimated creatinine clearance < 30 mL/min.

• - Serum aspartate aminotransferase (AST) and/or alanine aminotransferase (ALT) > 1.5 times the upper limit of normal.

• - Hemoglobin < 75% of the lower limit of the normal range.

• - Systolic blood pressure < 100 mmHg.

• - Acute or chronic physical impairment (other than dyspnea), limiting the ability to comply with study requirements.

• - Pregnant or breast-feeding.

• - Known concomitant life-threatening disease with a life expectancy < 12 months.

• - Body weight < 40 kg.

• - Any condition that prevents compliance with the protocol or adherence to therapy.

• - Treatment with endothelin receptor antagonists (ERAs) within 3 months prior to randomization.

• - Systemic treatment within 4 week prior to randomization with cyclosporine A or tacrolimus, everolimus, sirolimus (calcineurin or mammalian target of rapamycin (mTOR) inhibitors).

• - Treatment with cytochrome P3A (CYP3A) inducers within 4 weeks prior to randomization.

• - Known hypersensitivity to drugs of the same class as the study drug, or any of their excipients.

- Planned treatment, or treatment, with another investigational drug within 1 month prior to randomization

The investigators aim to use pressure-volume loop derived right ventriculo-vascular coupling, pulmonary impedance, and invasive cardiopulmonary exercise testing (CPET) to: 1. Comprehensively phenotype patients with scleroderma ILD-PH and pulmonary vascular exercise limitation (PVL) relative to scleroderma ILD-PH without PVL. 2. Compare the efficacy of chronic Macitentan therapy in improving 1) right ventricular hemodynamics 2) exercise capacity and 3) symptoms in scleroderma ILD-PH patients with and without PVL.

Arms

Experimental: Opsumit

Opsumit 10 mg tablet by mouth once daily

Interventions

Drug: - Opsumit 10 Mg Tablet

Oral tablet taken once daily