A Phase 3 Study to Evaluate the Safety and Tolerability of L606 in Subjects With PAH or PH-ILD

Key Inclusion Criteria:

1. Able to understand and complete study requirements and provide written informedconsent.

2. Males and females ≥18 and ≤80 years of age at the time of informed consent. Allsexually active male subjects and female subjects of childbearing potential must usean acceptable, highly effective method of contraception.

3. Diagnosed with

4. PAH belonging to at least 1 of the following subgroups of Group 1 pulmonaryhypertension (PH) per European Society of Cardiology/European RespiratorySociety Guidelines for the diagnosis and treatment of PH at least 1 year priorto screening. or

5. PH-ILD Group 3 European Society of Cardiology/European Respiratory SocietyGuidelines for the diagnosis and treatment of PH. Subjects with Group 3 PH thatis not related to underlying ILD are not eligible.

6. Subjects with PAH: Documentation of having PAH as confirmed by RHC within 12 monthsprior to screening and meeting the following criteria: i. Mean PAP >20 mmHg. ii. Pulmonary arterial wedge pressure ≤15 mmHg. iii. Pulmonaryvascular resistance >3 Wood units. Subjects with PH-ILD: Confirmation of theunderlying ILD must be based on HRCT imaging conducted within the past 12 monthsprior to randomization with demonstration of diffuse parenchymal lung disease anddocumented by the Investigator or radiology report. Subjects may have any form ofILD or CPFE.

7. NYHA functional class II, III, or IV at the screening visit.

8. Can complete a screening 6MWD of ≥150 meters

9. For subjects with PAH: >65% of predicted and FEV1/FVC ratio >65% at screening. Forsubjects with PH-ILD: >40% of predicted and FEV1/FVC ratio >70% at screening.

Key Exclusion Criteria:

1. LVEF of ≤45% on a historical echocardiogram within 6 months of screening.

2. History of sleep apnea, or left-sided heart disease (including but not limited toaortic or mitral valve disease, pericardial constriction, restrictive or congestivecardiomyopathy, or coronary artery disease) per investigator's discretion.

3. Experienced an acute exacerbation of disease or hospitalization for any reasonwithin 30 days of signing the ICF or prior to baseline.

4. Systolic blood pressure <90 mmHg or ≥160 mmHg at baseline.

5. Screening electrocardiogram (ECG) with QTcF >525 ms.

6. Musculoskeletal disorder (eg, arthritis affecting the lower limbs, recent hip orknee joint replacement) or any disease that would likely be the primary limit toambulation or subject is connected to a machine that is not portable enough to allowfor a 6MWT.

7. Alanine aminotransferase or aspartate aminotransferase levels >3 × upper limit ofnormal reference range, clinically significant liver disease/dysfunction, or knownChild-Pugh Class C hepatic disease.

8. Estimated glomerular filtration rate <30 mL/min/1.73 m2 or requires dialysis.