Additional Study Information: The purpose of this study is to find out if subjects can take the prescribed dose of GBT440 without problems, and whether GBT440 is safe and helps subjects with IPF. GBT440 is called an investigational or experimental drug because it has not been approved for use in people by the Food and Drug Administration (FDA), the branch of U.S. government which approves new drugs, or by any other regulatory agency in other countries. Participation in this clinical trial will not have any effect on your disease management. Your disease management and treatment decisions will be determined by you and your health care professional.