['cystic fibrosis']
['cavosonstat', 'placebo']

        Inclusion Criteria:

          -  Patients must have been treated with lumacaftor/ivacaftor for at least 8 weeks prior
             to Day 1 (start of dosing)

          -  A history of Sweat Chloride (SC) ≥ 60 mEq/L by quantitative pilocarpine iontophoresis
             test (QPIT) (either before or after starting lumacaftor/ivacaftor treatment)

          -  Body weight ≥ 40 kg

          -  ppFEV1 40 - 85 % predicted (inclusive) at screening

          -  Oxygen saturation ≥ 90% breathing ambient air at screening

        Exclusion Criteria:

          -  Any acute infection that requires treatment or hospitalization within 2 weeks of Study
             Day 1

          -  Colonization with organisms associated with more rapid decline in pulmonary status,
             such as Burkholderia cenocepacia, Burkholderia dolosa, and Mycobacterium abscessus

          -  Any change in the regimen for chronic therapies for CF lung disease (e.g., Pulmozyme®,
             hypertonic saline, Azithromycin, TOBI®, Cayston®) within 4 weeks of Study Day 1

          -  Are pregnant, planning a pregnancy, or breast-feeding at screening

          -  Blood hemoglobin < 10 g/dL at screening

          -  Serum albumin < 2.5 g/dL at screening

          -  Abnormal liver function defined as ≥ 3 x upper limit of normal (ULN)

          -  History of abnormal renal function within 3 months of screening

          -  History of ventricular tachycardia or other clinically significant ventricular
             arrhythmias

          -  History, including the screening assessment, of prolonged QT and/or QTcF (Fridericia's
             correction) interval

          -  History of solid organ or hematological transplantation

          -  History of alcohol abuse or drug abuse

          -  Ongoing participation in another therapeutic clinical trial

          -  Use of continuous (24 hr/day) or nocturnal supplemental oxygen
      