Study to Assess the Effect of Long-term Treatment With Voxelotor in Participants Who Have Completed Treatment in Study GBT440-031

Open Label Extension Study of Voxelotor Clinical Trial Participants with Sickle Cell Disease Who Participated in Voxelotor Clinical Trials

This open label extension (OLE), multi-center study will be conducted at approximately 100 clinical sites globally and will be available to eligible participants from study GBT440-031. The study will enroll participants from GBT440-031 (approximately 435) under any of the following conditions: * Participant has completed 72 weeks of treatment regardless of dose selection for GBT440-031 * Dose selection has occurred for GBT440-031 and participant is on non-selected dose on GBT440-031 * GBT440-031 study interim data analysis and/or study modifications have occurred * GBT440-031 study has completed The objective of this open-label extension (OLE) study is to assess the long-term safety and treatment effect of voxelotor in participants who have completed treatment in study GBT440-031, using the following parameters: 1. Safety based upon AEs, clinical laboratory tests, physical examinations (PE) and other clinical measures. 2. Frequency of sickle cell disease (SCD)-related complications. 3. Hemolytic anemia as measured by hematological laboratory parameters (e.g. hemoglobin, reticulocytes and unconjugated bilirubin). All participants will receive daily voxelotor treatment. Participants may receive study drug as long they continue to receive clinical benefit which outweighs risk as determined by the Investigator and/or until the participant has access to voxelotor from an alternative source (i.e., commercialization or through a managed access program).