A Phase 2, Multicenter, Open-Label Study to Evaluate the Intermediate/Long Term Safety and Efficacy of AIR001 in Subjects With WHO Group 1 Pulmonary Arterial Hypertension

The primary objective of this study is to evaluate the intermediate/long-term safety of
inhaled nebulized AIR001 administered according to 3 treatment arms (80 milligrams (mg) 4
times daily, 46 mg 4 times daily, or 80 mg once daily) in subjects with World Health
Organization (WHO) Group 1 Pulmonary Arterial Hypertension (PAH) who have completed the
16-week AIR001-CS05 study.

Inclusion Criteria:

1. Evidence of a personally signed and dated informed consent document indicating that
the subject (or a legally acceptable representative) has been informed of all
pertinent aspects of the study prior to initiation of any subject-mandated
procedures.

2. Is willing and able to comply with scheduled visits, treatment plan, laboratory
tests, and other study procedures.

3. Has completed the 16-week AIR001-CS05study as planned.

4. If on corticosteroids, has been receiving a stable dose of less than or equal to 20
mg/day of prednisone (or equivalent dose, if other corticosteroid) for at least 1
month (30 days) prior to the AIR001-CS05 study Baseline/Day 1 visit. If receiving
treatment for Connective Tissue Disease (CTD) with any other drugs, doses should
remain stable, if clinically feasible, for the duration of the AIR001-CS06 study.

5. Women of childbearing potential must be using at least one form of medically
acceptable contraception (i.e. either oral, topical, implanted hormonal
contraceptives, or an intrauterine device) or two barrier methods; have a negative
pregnancy test at Screening and Baseline/Day 1 and agree to use reliable methods of
contraception until at least 24-hours after the last dose of study drug. Women who
are surgically sterile (i.e. hysterectomy, bilateral oophorectomy, or tubal ligation)
or those who are post-menopausal for at least 2 years are not considered to be of
childbearing potential. Men who are not sterile (i.e. have not had a vasectomy) must
also agree to use contraception until at least 24-hours after the last dose of study
drug.

Exclusion Criteria:

1. Participation in a device or other interventional clinical studies (other than
AIR001-CS05), within 1 month (30 days) of Baseline/Day 1 and/or during study
participation.

2. Has uncontrolled systemic hypertension as evidenced by sitting systolic blood
pressure > 160 mmHg or sitting diastolic blood pressure > 100 mmHg during
Baseline/Day 1 visit.

3. Systolic blood pressure < 90 mmHg at Baseline/Day 1.

4. Diagnosis of Down syndrome.

5. Moderate to severe hepatic impairment classified as a Child-Pugh Class B or C at
Baseline/Day 1.

6. Has chronic renal insufficiency as defined by serum creatinine > 2.5 mg/dL or has an
estimated Glomerular Filtration Rate (eGFR) < 30 mL/min at Baseline/Day 1, or
requires dialytic support.

7. Has a hemoglobin (Hgb) concentration < 8.5 g/dL at Baseline/Day 1.

8. Personal or family history of the following:

1. Congenital or acquired methemoglobinemia;

2. RBC CYPB5 reductase deficiency.

9. History of glucose-6-phosphate dehydrogenase (G6PD) deficiency or any
contraindication to receiving methylene blue.

10. For subjects with Human immunodeficiency virus (HIV) associated PAH, requirement for
the use of inhaled pentamidine.

11. The use of oral or topical nitrates (nitroglycerin, glyceryl trinitrate (GTN),
isosorbide dinitrate, and isosorbide mononitrate) within 1 month (30 days) prior to
Baseline/Day 1 or throughout the AIR001-CS06 study until EOS or Termination visit.
Note: Intravenous GTN in an emergency setting may be administered by starting with a
low dose and titrating upward, while the subject is being monitored closely for
changes in blood pressure and heart rate.

12. Known or suspected hypersensitivity or allergic reaction to sodium nitrite or sodium
nitrate.

13. History of malignancy within 5-years prior to Baseline/Day 1 of the AIR001-CS05
study, with the exception of localized non-metastatic basal cell carcinoma of the
skin and in situ carcinoma of the cervix.

14. 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 subject inappropriate for entry into this study.

15. Has a psychiatric, addictive or other disorder that compromises the ability to give
informed consent for participating in this study. This includes subjects with a
recent history of abusing alcohol or illicit drugs 1 month (30 days) prior to study
Baseline/Day 1 of the AIR001-CS05 study and for the duration of the study.

16. Is currently pregnant or breastfeeding or intends to become pregnant during the
duration of the study.

17. Investigators, study staff or their immediate families.