['idiopathic pulmonary fibrosis', 'hypoxemia']
['gbt440', 'placebo']

        Inclusion Criteria:

          -  Documented diagnosis of IPF.

          -  Oxygen desaturation with exercise.

          -  Completion of the baseline 6MWT

          -  Weight ≥ 50 kg

          -  Male or female of child bearing potential willing and able to use highly effective
             methods of contraception from study start to 3 months after the last dose of study
             drug.

        Exclusion Criteria:

          -  FEV1/FVC < 70%.

          -  Subjects on supplemental oxygen therapy at rest.

          -  History of other interstitial lung diseases.

          -  Significant polycythemia.

          -  Female who is breast-feeding or pregnant.

          -  Known current malignancy or history of malignancy within the last 2 years prior to
             screening.

          -  Use of cytotoxic and/or immunosuppressant medications within 30 days screening.

          -  Hospitalization due to an exacerbation of IPF within 30 days of screening

          -  Subject plans to begin or has commenced pulmonary rehabilitation within 30 days of
             screening

          -  Corticosteroids (> 10 mg per day of prednisone or an equivalent) within 30 days of
             screening.

          -  Current smoker or history of smoking within 3 months of screening.

          -  Currently or, in the opinion of the investigator, soon to be listed for lung
             transplant.

          -  History of unstable or deteriorating cardiac or pulmonary disease (other than IPF)
             within 6 months of screening.

          -  Any condition possibly affecting drug absorption.

          -  Participated in another clinical trial of an investigational drug (or medical device)
             within 30 days or 5-half-lives, whichever is longer, prior to screening, or is
             currently participating in another trial of an investigational drug (or medical
             device).

          -  Subject who, for any reason, is deemed by the investigator to be inappropriate for
             this study.
      