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

This Phase 3, 2-part, open-label, multicenter study aims to demonstrate the safety and tolerability of L606 in patients with PAH or PH-ILD. The study will determine the short-term and long-term safety and tolerability of L606 in this patient population; also evaluate the steady-state pharmacokinetics (PK) of L606 as compared to Tyvaso, effects on exercise ability, quality of life, and treatment satisfaction with L606.

This Phase 3, 2-part, open-label, multicenter study aims to demonstrate the safety and tolerability of repeated doses of L606 in patients with PAH or PH-ILD. The current Phase 3 study will help determine the short-term and long-term safety and tolerability of L606 in this patient population. The study will also evaluate the steady-state pharmacokinetics (PK) of L606 as compared to Tyvaso, effects on exercise ability (6-minute walk distance \[6MWD\] and Borg Dyspnea Score), quality of life (QoL), and treatment satisfaction with L606.

Subjects who meet all the inclusion criteria and none of the exclusion criteria will be enrolled to one of the 2 cohorts:

Cohort A: Subjects with PAH or PH-ILD receiving prior stable doses of Tyvaso (4 times daily) and willing to switch to L606 (twice daily).

Cohort B: Subjects with PAH (not initially on prostacyclin therapy) who are likely to receive clinical benefit from inhaled treprostinil based on the opinion of the investigator.

Cohort A subjects will sequentially participate in the MSP for 2 weeks and the OEP for 46 weeks. A subset of up to 15 subjects from Cohort A will also participate in a PK substudy. Cohort B subjects will sequentially participate in the MSP for 12 weeks and the OEP for 36 weeks.

Eligibility Criteria:
Key Inclusion Criteria:

1. Able to understand and complete study requirements and provide written informed consent.
2. Males and females ≥18 and ≤80 years of age at the time of informed consent. All sexually active male subjects and female subjects of childbearing potential must use an acceptable, highly effective method of contraception.
3. Diagnosed with

   1. PAH belonging to at least 1 of the following subgroups of Group 1 pulmonary hypertension (PH) per European Society of Cardiology/European Respiratory Society Guidelines for the diagnosis and treatment of PH at least 1 year prior to screening. or
   2. PH-ILD Group 3 European Society of Cardiology/European Respiratory Society Guidelines for the diagnosis and treatment of PH. Subjects with Group 3 PH that is not related to underlying ILD are not eligible.
4. Subjects with PAH: Documentation of having PAH as confirmed by RHC within 12 months prior to screening and meeting the following criteria:

   i. Mean PAP \>20 mmHg. ii. Pulmonary arterial wedge pressure ≤15 mmHg. iii. Pulmonary vascular resistance \>3 Wood units. Subjects with PH-ILD: Confirmation of the underlying ILD must be based on HRCT imaging conducted within the past 12 months prior to randomization with demonstration of diffuse parenchymal lung disease and documented by the Investigator or radiology report. Subjects may have any form of ILD or CPFE.
5. NYHA functional class II, III, or IV at the screening visit.
6. Can complete a screening 6MWD of ≥150 meters
7. For subjects with PAH: \>65% of predicted and FEV1/FVC ratio \>65% at screening. For subjects 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 to aortic or mitral valve disease, pericardial constriction, restrictive or congestive cardiomyopathy, or coronary artery disease) per investigator's discretion.
3. Experienced an acute exacerbation of disease or hospitalization for any reason within 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 or knee joint replacement) or any disease that would likely be the primary limit to ambulation or subject is connected to a machine that is not portable enough to allow for a 6MWT.
7. Alanine aminotransferase or aspartate aminotransferase levels \>3 × upper limit of normal reference range, clinically significant liver disease/dysfunction, or known Child-Pugh Class C hepatic disease.
8. Estimated glomerular filtration rate \<30 mL/min/1.73 m2 or requires dialysis.