The study was conducted as a placebo-controlled, randomized, 22-week double-blind study which included a dose titration period. An additional transition period occurred for those patients who elected to enroll into the open-label extension study, APD811-007. A total of 61 patients with PAH were enrolled.

Study APD811-003 was a 22-week, randomized, double-blind, parallel-group, placebo-controlled study in subjects with symptomatic WHO Group 1 PAH. The study consisted of a dose titration period of up to 9 weeks, a 13-week maintenance period, and a follow-up visit that was to occur approximately 3 weeks after the end of the maintenance period (Week 25). The transition period of 3 weeks (±1 week) was to occur for those subjects who elected to enroll into the open-label extension (OLE) Study APD811-007.

Approximately 60 subjects with PAH were planned to be enrolled (61 actual). After screening, eligible subjects were randomized 2:1 to ralinepag (APD811) or to placebo. Randomization was stratified by baseline WHO/NYHA functional class (II versus III or IV). Subjects randomized to active therapy were given ralinepag at a starting dose of 0.01 mg BID. Subjects randomized to the placebo arm received matching placebo capsules to preserve the blind. Subjects were instructed to take the study drug (ralinepag or placebo) with food. Dosage was then uptitrated, as tolerated, over the course of the 9-week dose-titration period to a maximum dose of 0.3 mg BID. Although doses could be reduced based on tolerability, the final dosage reached was required to be stable during the 13-week treatment period prior to evaluation at Week 22.

Subjects could receive concomitant oral disease-specific PAH therapy consisting of an ERA and/or an agent acting on the nitric oxide pathway, a PDE-5 inhibitor or a sGC stimulator, provided the dose had remained stable for at least 3 months prior to the start of screening. It was recommended that subjects continue the same dose and regimen of these medications for the duration of the study. With the exception of prostanoids, the use of other supporting therapies, which may affect PAH, was also permitted.

During the study, assessments of efficacy were performed including PVR and other hemodynamic parameters as determined by RHC, the 6MWT, assessment of clinical worsening, BNP and NT-proBNP levels, WHO/NYHA functional class assessment of PAH. Safety assessments included standard evaluations of AEs, clinical laboratory values, vital signs, and ECG measurements.

At the end of the maintenance period, subjects who did not choose to participate in the OLE study were to discontinue study drug (ralinepag or placebo). All subjects that chose to continue in the OLE study were to remain on study drug until the follow-up visit at Week 25. This visit served as the baseline visit for the OLE study if the subject was eligible and chose to participate.

Inclusion Criteria:

• Males or females aged 18-75 years, inclusive

• Symptomatic WHO Group 1 PAH classified by one of the following subgroups:

  • Idiopathic pulmonary arterial hypertension (IPAH);
  • Heritable pulmonary arterial hypertension (HPAH);
  • Drugs and toxins induced;
  • Associated pulmonary arterial hypertension (APAH); specifically connective tissue diseases, HIV infection and congenital heart disease.

• Has had the diagnosis of PAH confirmed by cardiac catheterization

• Has WHO/NYHA functional class II- IV symptomatology

• Previously diagnosed with PAH and on stable oral disease-specific PAH therapy with either an ERA and/or an agent acting on the nitric oxide pathway, i.e. a PDE5 inhibitor or a soluble guanylate cyclase stimulator. Stable is defined as no change in dose within 3 months of the start of Screening and for the duration of the study

• Has 6MWT distances of 100-500 m, and within 15% of each other on 2 consecutive tests done on different days at Screening

• Has pulmonary function tests (PFTs) within 6 months prior to the start of Screening with no evidence of significant parenchymal lung disease

• Has a ventilation-perfusion (V/Q) lung scan or pulmonary angiogram within 5 years prior to Screening and concomitant with or following diagnosis of PAH that shows no evidence of thromboembolic disease

• If on vasodilators (including calcium channel blockers), digoxin, spironolactone, or L-Arginine supplementation; the patient must be on a stable dose for at least 1 month prior to the start of Screening

Exclusion Criteria:

• Newly diagnosed with PAH and on no disease-specific PAH therapy
• Previous participation in any clinical study with an investigational drug, biologic, or device within 2 months prior to the Screening visit
• Acutely decompensated heart failure within 1 month prior to start of Screening
• Systolic blood pressure <90 mm Hg at Screening
• Evidence or history of left-sided heart disease and/or clinically significant cardiac disease
• Use or chronic administration (defined as >30 days) of a prostacyclin or prostacyclin analogue within 3 months of Screening
• Any previous use of a prostacyclin or prostacyclin analogue that was stopped for safety or tolerability issues associated with pharmacology/mechanism of action
• Other severe acute or chronic medical or laboratory abnormality that may increase the risk associated with study participation or investigational product administration or may interfere with the interpretation of study results and, in the judgment of the investigator, would make the patient inappropriate for entry into this study