A Study of Sotatercept in Japanese Pulmonary Arterial Hypertension (PAH) Participants (MK-7962-020)

Inclusion Criteria: Documented diagnostic 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 connective tissue disease PAH associated with simple, congenital systemic-to-pulmonary shunts at least 1 year following repair PAH classified as WHO FC I or symptomatic PAH classified as WHO FC II to IV On stable doses of background PAH therapy and diuretics (if applicable) for at least 90 days prior to screening. 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 PAH with features of significant venous/capillary pulmonary veno-occlusive disease/pulmonary capillary hemangiomatosis (PVOD/PCH) involvement Is on the waiting list for lung transplant Pregnant or breastfeeding women. History of full or partial pneumonectomy. Pulmonary function test (PFT) values of forced vital capacity (FVC) < 60% predicted at the screening visit or within 6 months prior to the screening visit. Initiation of an exercise program for cardiopulmonary rehabilitation within 90 days prior to the screening visit or planned initiation during the study. History of more than mild obstructive sleep apnea that is untreated. 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. History of restrictive, constrictive, or congestive cardiomyopathy. History of atrial septostomy within 180 days prior to the screening visit. Personal or family history of long QT syndrome (LQTS) or sudden cardiac death. Left ventricular ejection fraction (LVEF) < 45% on historical ECHO within 6 months prior to the screening visit. Any symptomatic coronary disease events within 6 months prior to the screening visit. Cerebrovascular accident within 3 months prior to the screening visit. Significant (≥ 2+ regurgitation) mitral regurgitation or aortic regurgitation valvular disease, mitral stenosis and more than mild aortic valve stenosis. Prior exposure to sotatercept or luspatercept or history of allergic or anaphylactic reaction or hypersensitivity to recombinant proteins or excipients in investigational product. Received intravenous inotropes (e.g., dobutamine, dopamine, norepinephrine, vasopressin) within 30 days prior to the screening visit. Currently enrolled in or have completed any other investigational product study within 30 days. Weight at the screening is over 85 kg.