Resolution of Sickle Cell Leg Ulcers With Voxelotor

Inclusion Criteria: 1. Male or female participants with documented diagnosis of SCD (HbSS, HbS/β0 thalassemia) 2. Age 12 years and older 3. At least 1 cutaneous ulcer(s) on the lower extremity (leg, ankle, or dorsum of foot) that meets the following criteria: * Duration: ≥ 2 weeks and \< 6 months at Screening, and * Size: \> 2 cm2 prior to randomization 4. Written informed consent (≥ 18 years) or parental/guardian consent and participant assent (≥ 12-17 years) per IEC policy and requirements, consistent with ICH guidelines Exclusion Criteria: 1. Target ulcer(s) healed by ≥ 25% during the standard of care run-in period prior to randomization 2. Active infection/purulence at ulcer site, or exposed tendon or bone at the ulcer site, based on Investigator's clinical judgment 3. Current osteomyelitis at or near the ulcer site 4. Known vascular abnormalities that would preclude healing in the opinion of the Investigator (eg, pre-existing severe arterial insufficiency in the affected limb) 5. Serum albumin \< 2.0 g/dL 6. RBC transfusion within 60 days of initiation of study drug 7. Receiving regularly scheduled RBC transfusion therapy (also termed chronic, prophylactic, or preventive transfusion) during the study 8. Planned elective surgery within the next 6 months 9. Anemia due to bone marrow failure (eg, myelodysplasia) 10. Absolute reticulocyte count \< 100 × 109/L 11. Screening alanine aminotransferase (ALT) \> 4 × upper limit of normal (ULN) 12. Severe renal dysfunction (estimated glomerular filtration rate \[eGFR\] \< 30 mL/min/1.73 m2 by Schwartz formula) or is on chronic dialysis 13. Clinically significant bacterial, fungal, parasitic, or viral infection that requires therapy Other protocol-defined Eligibility Criteria that apply