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).

Prior treatment

• Prior participation in another interventional clinical study with medicinal products within 30 days or 5 half-lives prior to Screening, whichever is longer. Sites in France, check section A7-1.1.
• Has pulmonary function tests (PFTs) at Screening or within 180 days prior to the Screening with evidence of significant obstructive or parenchymal lung disease.
• Prior heart or heart-lung transplants, active on the lung transplant list, or life expectancy of < 12 months per Investigator assessment.
• Initiation or discontinuation of an exercise program for cardiopulmonary rehabilitation within 90 days prior to baseline or planned initiation during the study.
• Prior participation in a KER-012 study, or prior treatment with a therapy targeting TGF-β (e.g., sotatercept).

Other illness

• Evidence or history of left ventricular dysfunction and/or clinically significant cardiac disease.
• Evidence of thromboembolic disease assessed by ventilation perfusion (V/Q) lung scan or other local standard of care diagnostic evaluation at the time of PAH diagnosis or after.
• Has uncontrolled systemic hypertension as evidenced by sitting systolic blood pressure (BP) > 160 mmHg or sitting diastolic BP > 100 mmHg at Screening.
• Diagnosis of pulmonary veno-occlusive disease or pulmonary capillary hemangiomatosis.

Lab values

• Hemoglobin < 9 g/dL at Screening.

• Adult participants ≥ 18 years of age.
• Symptomatic World Health Organization (WHO) Group 1 Pulmonary Hypertension (PAH) classified by one of the following subgroups: a. Idiopathic pulmonary arterial hypertension (IPAH) b. Hereditary pulmonary arterial hypertension (HPAH) c. Associated with drugs and toxins d. PAH associated with: i. Connective tissue disease (CTD), ii. Congenital systemic-pulmonary intracardiac shunt (must have surgical correction or repair with closure device at least 1 year prior to Screening, AND have no, or clinically insignificant, shunt fraction in the opinion of Investigator [1.0 ≤ pulmonary-systemic flow ratio ≤ 1.5]).
• Has the following hemodynamic parameters that are consistent with the diagnosis of PAH: a. Mean pulmonary arterial pressure (mPAP) > 20 mmHg at rest, AND b. Pulmonary artery wedge pressure (PAWP) ≤ 15 mmHg, AND c. PVR ≥ 5 Wood units (400 dyn·sec·cm−5). Note: RHC to assess eligibility performed within 6 weeks from Visit 1 (Day 1).
• Has WHO/New York Heart Association (NYHA) Functional Class (FC) II or III symptoms as assessed by the Investigator at Screening and Day 1.
• Must be on a stable PAH background therapy with either an endothelin-receptor antagonist (ERA) and/or a phosphodiesterase-5 inhibitor (PDE5-I) or soluble guanylate cyclase (sGC) stimulator and/or prostacyclin analogue or receptor agonist (oral/inhaled/SC/intravenous): a. Stable therapy is defined as no change in dose/regimen for at least 90 days prior to baseline and would be expected to be maintained for the duration of the study.
• 6MWD ≥ 150 and ≤ 500 meters repeated twice at Screening (measured at least 4 hours apart but no longer than 1 week), and both values within 15% of each other (calculated from the highest value).
• Provide written (signed and dated) informed consent form before the initiation of any Screening tests or procedures. Sites in Germany, check section A7-1.2 of the study protocol.