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

Inclusion Criteria: * Documented diagnostic right heart catheterization (RHC) at any time prior to screening confirming the diagnosis of World Health Organization (WHO) pulmonary arterial hypertension (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 functional class (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 Echocardiogram (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