A Study of Sotatercept (MK-7962) in Japanese Children With Pulmonary Arterial Hypertension (PAH) (MK-7962-032)

The goal of this study is to learn about the safety of sotatercept and how well Japanese children tolerate it, when taken along with standard (usual) pulmonary arterial hypertension (PAH) treatment. Researchers also want to learn what happens to it in a person's body over time and whether it lowers resistance in blood vessels in the lungs.

Inclusion Criteria: The main inclusion criteria include but are not limited to the following: * Has pulmonary arterial hypertension (PAH, World Health Organization Group 1) confirmed by a prior right heart catheterization * Has idiopathic, heritable, drug- or toxin-induced PAH, connective tissue disease-associated PAH, repaired congenital heart disease-associated PAH, or PAH with coincidental shunt * Has PAH classified as World Health Organization Functional Class I, or symptomatic World Health Organization Functional Class II to IV * Has been receiving stable standard-of-care background therapy for PAH for at least 90 days * Is Japanese Exclusion Criteria: The main exclusion criteria include but are not limited to the following: * History of left-sided heart disease * Has severe congenital or developmental abnormalities of the lung, thorax, and/or diaphragm * History of Eisenmenger syndrome, Potts shunt, or recent atrial septostomy within 180 days * Has unrepaired or residual cardiac shunt with Qp/Qs \>1.5 * Has pulmonary veno-occlusive disease, pulmonary capillary hemangiomatosis, or overt signs of pulmonary capillary and/or venous involvement * PAH associated with portal hypertension * Known visceral arteriovenous malformations * History of full or partial pneumonectomy * Untreated more than mild obstructive sleep apnea * History of known pericardial constriction * Family history of sudden cardiac death or long QT syndrome * History of symptomatic coronary disease within 6 months or cerebrovascular accident within 3 months * Prior treatment with sotatercept or luspatercept