A Study to Investigate the Safety and Efficacy of KER-012 in Combination With Background Therapy in Adult Participants With Pulmonary Arterial Hypertension (PAH) (TROPOS Study).

Inclusion Criteria:

• Adult participants ≥ 18 years of age

• Symptomatic World Health Organization (WHO) Group 1 Pulmonary Hypertension (PH)(PAH)classified by one of the following subgroups:

• Idiopathic pulmonary arterial hypertension (IPAH);

• Heritable pulmonary arterial hypertension (HPAH);

• Associated with drugs and toxins;

• PAH associated with:

• Connective tissue disease

• Congenital systemic-pulmonary intracardiac shunt

• Has the following hemodynamic parameters that are consistent with the diagnosis ofPAH:

• Mean pulmonary arterial pressure (mPAP) > 20 mmHg at rest, AND

• Pulmonary artery wedge pressure (PAWP) ≤ 15 mmHg, AND

• PVR ≥ 5 Wood Units (400 dyn·sec·cm-5)

• Has WHO/New York Heart Association (NYHA) Functional Class (FC) II or III symptomsas assessed by the Investigator

• Must be on a stable PAH background therapy with either an endothelin-receptorantagonist (ERA) and/or a phosphodiesterase-5 inhibitor (PDE5-I) or solubleguanylate cyclase (sGC) stimulator and/or prostacyclin analogue or receptor agonist (oral/inhaled/SC/intravenous)

• 6MWD ≥ 150 and ≤ 500 meters at screening

• Provide written (signed and dated) informed consent form before the initiation ofany Screening tests or procedures

Exclusion Criteria:

• Evidence or history of left ventricular dysfunction and/or clinically significantcardiac disease

• Has pulmonary function tests (PFTs) with evidence of significant obstructive orparenchymal lung disease

• Evidence of thromboembolic disease assessed by ventilation perfusion (V/Q) lung scanor other local standard of care diagnostic evaluation at the time of PAH diagnosisor after

• Has uncontrolled systemic hypertension

• Hemoglobin < 9 g/dL at Screening

• Prior heart or heart-lung transplants, active on the lung transplant list, or lifeexpectancy of < 12 months per Investigator assessment

• Diagnosis of pulmonary veno-occlusive disease or pulmonary capillary hemangiomatosis

• Initiation or discontinuation of an exercise program for cardiopulmonaryrehabilitation within 90 days prior to Baseline or planned initiation during thestudy

• Prior participation in a KER-012 study or prior treatment with a therapy targetingTGF-β superfamily (e.g. sotatercept)

• Prior participation in another interventional clinical study with medicinal productswithin 30 days or 5 half-lives prior to Screening, whichever is longer