Study to Evaluate the Safety and Tolerability of GBT440 Administered to Subjects With IPF

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.