• Adult subjects aged 18 to 75 years.

• Body mass index (BMI) ≥ 15 kg/m\^2 and ≤ 40 kg/m\^2.

• Diagnosis of PAH classified by one of the following:

∙ Idiopathic PAH (IPAH) or heritable PAH (HPAH).

‣ PAH associated with connective tissue disease (CTD-APAH); PAH associated with anorexigen or PAH associated with methamphetamine use.

‣ Congenital heart disease with simple systemic to pulmonary shunt at least 1 year after surgical repair.

• 6MWDs ≥ 150 meters and ≤ 475 meters during Screening prior to randomization.

• WHO FC II or III.

• US Registry to Evaluate Early and Long-term PAH Disease Management (REVEAL) Lite 2 Risk Score ≥ 5 OR NT-proBNP ≥ 300 ng/L OR PVR ≥ 800 dyne s/cm\^5.

• Cardiac catheterization within the screening period, or a standard of care right heart catheterization (RHC) (with pressure wave forms available for review) up to 48 weeks prior to Screening.

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

‣ Pulmonary vascular resistance (PVR) ≥ 400 dyne·s/cm\^5, AND

‣ Pulmonary capillary wedge pressure (PCWP) or left ventricle end-diastolic pressure (LVEDP) ≤ 15 mmHg.

• Treatment with at least one allowed background PAH disease-specific medication prior to Screening.

∙ Subjects receiving treatment with endothelin receptor antagonists, phosphodiesterase type 5 inhibitors, guanylate cyclase stimulators, and/or prostacyclin analogues or prostacyclin receptor agonists are eligible only if on a stable dose for at least 12 weeks prior to and throughout Screening.

‣ Subjects receiving treatment with sotatercept are eligible only if on a stable dose of sotatercept for at least 24 weeks prior to and throughout Screening, with a RHC performed during Screening (or within 2 weeks prior to Screening).

• Pulmonary function tests (PFTs) at Screening or completed no more than 12 weeks prior to Screening.

⁃ Women of childbearing potential (WOCBP) must have a negative pregnancy test at Screening and on Day 1 before first administration of Investigational Product (IP).

⁃ WOCBP who are not abstinent and intend to be sexually active with a non-sterilized male partner must be willing to use a highly effective method of contraception from consent through 30 days following the last administration of IP.

⁃ Male subjects: Non-sterilized male subjects who are not abstinent and intend to be sexually active with a female partner of childbearing potential must use a male condom from consent through 90 days after the last dose of IP.