A Study of Mitapivat in Participants With Sickle Cell Disease and Nephropathy

Key Inclusion Criteria: * Age of 16 years or older (except in France where participants must be aged 18 years or older); * Females must be post-menarche; * Documented diagnosis of sickle cell disease (Homozygosity for hemoglobin S \[HbSS\] or Hemoglobin S/Beta 0 \[HbS/β0\]-thalassemia); * Hemoglobin concentration ≥ 5.5 and ≤ 10.5 grams per deciliter (g/dL) during the Screening Period. If more than one measurement is collected during the Screening Period, the average must be ≥ 5.5 and ≤ 10.5 g/dL; * If taking hydroxyurea, the dose of hydroxyurea must have been stable for at least 90 days before Study Day 1 with no planned dose adjustment during the study and no sign of hematologic toxicity; * Discontinuation of hydroxyurea requires a 90-day washout before providing informed consent/assent; * Two urine ACR results collected during the Screening Period, both of which must be ≥ 100 and \< 2000 milligrams per gram (mg/g). One ACR result can be from an untimed urine sample collected as part of a clinic visit. The other ACR result must be from a urine sample that is the first (or second) morning void on another day; * One ACR result \> 100 mg/g within 24 weeks before providing informed consent/assent; * If taking Angiotensin-converting enzyme (ACE) inhibitor or Angiotensin receptor blockers (ARB) therapy, must have been on stable dose for at least 90 days before providing informed consent/assent with no planned dose adjustment during the study; * Women of childbearing potenti…