A Phase 3 Adaptive Study to Evaluate the Safety and Efficacy of Inhaled Treprostinil in Participants With Pulmonary Hypertension (PH) Due to Chronic Obstructive Pulmonary Disease (COPD)

Inclusion Criteria: Participants who meet the following criteria may be included in the study: 1. Participant voluntarily gives informed consent to participate in the study. 2. Males and females 18 years of age and above at the time of informed consent. 1. Women of childbearing potential (defined as less than 1 year post-menopausal and not surgically sterile) must agree to practice abstinence or use 2 highly effective methods of contraception (defined as a method of birth control that results in a low failure rate, \[\<1% per year\], such as approved hormonal contraceptives, barrier methods \[such as condom or diaphragm\] used with a spermicide, or an intrauterine device) for the duration of study treatment and for 48 hours after discontinuing study drug. Participants must have a negative pregnancy test at the Screening Visit 1 (urine \[prior to the first dose of study medication\] and serum) and Baseline Visit (Study Week 1) (urine). 2. Males with a partner of childbearing potential must agree to use a barrier method (condom) with a spermicide for the duration of treatment and for at least 48 hours after discontinuing study drug. 3. Diagnosis of PH-COPD (World Heath Organization \[WHO\] Group 3). 4. Clinical diagnosis of COPD will be made using the Global Initiative for Chronic Obstructive Lung Disease (GOLD) diagnostic criteria (GOLD Criteria 2020) and spirometry with the following documented parameters measured during Screening Visit 1 (prior to start of low-dose inhaled treprostinil): 1. Forced expiratory volume in 1 second (FEV1) \<80% predicted 2. FEV1/Forced vital capacity (FVC) \<70 5. The participant has a resting saturation peripheral capillary oxygenation (SpO2) greater than or equal to 90%, with or without supplemental oxygen, but not to exceed 10 liters (L)/min oxygen supplementation by any mode of delivery during Screening Visit 1. 6. During Screening Visit 1 prior to start of low-dose inhaled treprostinil, a 6MWD greater than or equal to 100 meters. 7. Have a right heart catheterization (RHC) performed during Screening Visit 1. (A previous RHC obtained within 12 months prior to the start of Screening Visit 1 is acceptable for determining eligibility, even if done without oxygen or vasodilator challenge, and a repeat RHC is not required.) The following parameters must be documented for eligibility: 1. Pulmonary vascular resistance (PVR) greater than or equal to 4 Wood units 2. A pulmonary artery wedge pressure (PAWP) or left ventricular end-diastolic pressure (LVEDP) of less than or equal to 15 millimeters of mercury (mmHg) 3. A Pulmonary artery pressure mean (PAPm) of greater than or equal to 30 mmHg 8. Participants must be on a stable and optimized dose of chronic COPD medications for greater than or equal to 30 days prior to start of Screening Visit 1 and remain on the same dose throughout the Screening Period. 9. In the opinion of the Investigator, the participant can communicate effectively with study personnel and is considered reliable, willing, and likely to be cooperative with protocol requirements, including attending all study visits. Exclusion Criteria: The following will exclude participants from the study: 1. The participant has a diagnosis of either pulmonary arterial hypertension (PAH) or pulmonary hypertension (PH) due to reasons other than COPD. This would include, but is not limited to, chronic thromboembolic PH or acute/recent deep vein thrombosis or pulmonary embolism, untreated or inadequately treated obstructive sleep apnea, connective tissue disease (including but not limited to systemic sclerosis/scleroderma or systemic lupus erythematosus), sarcoidosis, human immunodeficiency virus-1 infection, and other conditions under WHO Group 1, 2, 4, and 5 classifications. 2. Based on chest computed tomography (CT) imaging during Screening Visit 1, the participant has a confirmed diagnosis of WHO Group 3 PH, other than COPD, such as idiopathic pulmonary fibrosis, combined pulmonary fibrosis and emphysema, diffuse parenchymal lung disease or interstitial lung disease. A previous chest CT scan performed within the 6 months prior to the start of Screening Visit 1 is also acceptable, and a repeat assessment is not required. A redacted CT scan report (from Screening Visit 1 or dated within prior 6 months) should be provided to the Medical Monitor with the Pre-Baseline Review Form to confirm eligibility. 3. The participant has received any Food and Drug Administration (FDA)-approved medication for the treatment of PAH (that is, prostacyclin, prostacyclin receptor agonist, endothelin receptor antagonist \[ERA\], phosphodiesterase type 5 inhibitor \[PDE5-I\], or soluble guanylate cyclase \[sGC\] stimulator) at Screening Visit 1 and thereafter, except if received for acute vasoreactivity testing. 4. The participant has a previous diagnosis of homozygous alpha-1 antitrypsin deficiency. 5. The participant has any prior intolerance to inhaled prostanoid therapy. 6. Inability to tolerate low-dose (3 breaths, 18 mcg) study drug and/or inability to follow dosing regimen during the Screening Period (pre-randomization). 7. Unwilling or unable to use Sponsor-provided devices (actigraph, spirometer, or smart device). 8. The participant has evidence of clinically significant left-sided heart disease (including but not limited to left ventricular ejection fraction \<40%, left ventricular hypertrophy,) or clinically significant cardiologic conditions, such as congestive heart failure, coronary artery disease, or valvular heart disease. Note: Participants with abnormal left ventricular function attributable to the effects of right ventricular overload will not be excluded, but a discussion with and approval by the Sponsor Medical Monitor is needed. 9. Any exacerbation of COPD (including hospitalization or outpatient therapy) or active pulmonary or upper respiratory infection 60 days prior to start of Screening Visit 1 through the Baseline Visit. This is defined as worsening of respiratory symptoms that required treatment with corticosteroids and/or antibiotics. 10. Initiation of pulmonary rehabilitation within 12 weeks prior to start of Screening Visit 1 or, in the opinion of the Investigator, pulmonary rehabilitation is likely to be needed during the study Treatment Period. 11. The participant has any form of congenital heart disease (repaired or unrepaired; other than a patent foramen ovale). 12. The participant has any musculoskeletal disorder (severe arthritis of the lower limbs which limits ambulation, recent hip or knee joint replacement, artificial leg) or any other condition that would likely be the primary limitation to ambulation. 13. Use of any other investigational drug or device within 30 days prior to the start of Screening Visit 1. 14. Any other clinically significant illness or abnormal laboratory value(s) measured during the Screening Period that, in the opinion of the Investigator, might adversely affect the interpretation of the study data or safety of the participant.