Ten patients with PAH who are stable and eligible to initiate sotatercept therapy will participate in a 26 week study that consists of a 24-week intervention period where patients will receive complimentary sotatercept as prescribed, plus a tailored, progressive home exercise program with wrist-worn fitness tracker and oxygen saturation monitoring.

Inclusion Criteria:

• Age ≥ 18 years
• Documented diagnostic right heart catheterization (RHC) at any time prior to screening confirming the diagnosis of WHO PAH Group 1 in any of the following subtypes: Idiopathic PAH, Heritable PAH, Drug/toxin-induced PAH, PAH associated with CTD, PAH associated with simple, congenital systemic-to-pulmonary shunts at least 1 year following repair
• Symptomatic PH classified as WHO FC II or III
• Baseline RHC performed during the Screening Period documenting a minimum PVR of ≥ 5 WU and a pulmonary capillary wedge (PCWP) or left ventricular end-diastolic pressure of ≤ 15 mmHg
• Receiving stable background therapy for PAH for >90 days and will continue receiving throughout trial. Background treatments may consist of monotherapy, double therapy, or triple therapy with currently available medications for PAH.
• Initiation of Sotatercept is clinically indicated
• Willing and able to participate in a remotely-monitored home exercise program for 24 weeks
• Ability to adhere to study visit schedule and understand and comply with all protocol requirements
• Ability to understand and provide written informed consent

Exclusion Criteria:

• Diagnosis of PH WHO Groups 2, 3, 4, or 5
• Diagnosis of the following PAH Group 1 subtypes: human immunodeficiency virus (HIV)-associated PAH, PAH associated with portal hypertension, schistosomiasis-associated PAH and pulmonary veno-occlusive disease
• Hemoglobin at screening above gender-specific ULN
• Baseline platelet count < 50,000/mm3 (< 50.0 × 109/L) at screening
• Uncontrolled systemic hypertension as evidenced by sitting systolic BP > 160 mmHg or sitting diastolic BP > 100 mmHg during screening visit after a period of rest; Baseline systolic BP < 90 mmHg at screening
• Pregnant or breastfeeding females
• Clinical laboratory liver and kidney function tests outside of normal range
• Currently enrolled in or have completed any other investigational product study within 30 days for small-molecule drugs or within 5 half-lives for biologics prior to the date of signed informed consent
• Prior exposure to sotatercept (ACE-011) or luspatercept (ACE-536) or known allergic reaction to either one
• History of full pneumonectomy
• Initiation of a structured exercise program within 90 days prior or planned initiation during the study
• Known history of portal hypertension or chronic liver disease, including hepatitis B and/or hepatitis C (with evidence of recent infection and/or active virus replication), defined as mild to severe hepatic impairment (Child-Pugh Class A-C).
• Cardiac related history: History of restrictive, constrictive, or congestive cardiomyopathy; History of atrial septostomy within 180 days prior to the screening visit; ECG with Fridericia's corrected QT interval (QTcF) > 500 ms during the Screening Period; Personal or family history of long QT syndrome (LQTS) or sudden cardiac death; Left ventricular ejection fraction (LVEF) < 45% on historical ECHO within 12 months prior to the screening visit; Any symptomatic coronary disease events (prior myocardial infarction, percutaneous coronary intervention, coronary artery bypass graft surgery, or cardiac anginal chest pain) within 6 months prior to the screening visit. Note: Anginal pain can be ignored as an exclusion criterion if coronary angiography shows no obstructions
• Cerebrovascular accident within 3 months prior to the screening visit
• Acutely decompensated heart failure within 14 days prior to the screening visit, as per investigator assessment
• Significant (≥ 2+ regurgitation) mitral regurgitation or aortic regurgitation valvular disease
• Received intravenous inotropes (e.g., dobutamine, dopamine, norepinephrine, vasopressin) within 30 days prior to the screening visit