Actigraphy Improvement With Voxelotor (ActIVe) Study

All participants will receive Voxelotor as treatment. There will be approximately 13 sites in the US. Participant safety and tolerability will be monitored during the study using standard measures, including physical examinations, vital signs (including temperature, blood pressure, pulse rate, respiratory rate and peripheral oxygen saturation \[SpO2\]), clinical laboratory tests, and adverse event (AE) monitoring. Screening Period (up to 4 weeks in duration): During this period, participants will sign the informed consent form (ICF), after which they will complete the screening assessments as detailed in the Schedule of Assessments (SOA). Run-in Period (2 weeks in duration): During this period, participants will enter a 2-week run-in period (Day -14 to Day -1) during which baseline actigraphy measures of physical activity and sleep quality, overnight pulse oximetry assessments of oxygen saturation, and Patient-Reported Outcome (PRO) assessments will be collected before initiating treatment with voxelotor. Treatment Period (24 weeks in duration): After completion of the 14-day Run-in Period, participants will enter the open label treatment period and receive voxelotor 1500 mg once daily for 24 weeks. Repeat actigraphy assessments of physical activity and sleep quality, and overnight pulse oximetry will be performed during the treatment period (Weeks 10 to 12 and Weeks 22 to 24). PRO and Clinical Global Impression (CGI) assessments will be completed at scheduled study visits. The open-label treatment period is considered the continuous 24 weeks of voxelotor treatment from date of first dose (Day 1). Follow-up Period (4 weeks in duration): Immediately following the 24-week treatment period, participants will enter a 4-week Follow-up Period.