The primary objective of this study is to compare the effect of mitapivat versus placebo on transfusion burden in pediatric participants with α- or β-transfusion-dependent thalassemia.
Written informed consent/assent from the participant (or their legally authorized representative, parent(s), or legal guardian) must be obtained before any study-related procedures are conducted and participants must be willing to comply with all study procedures for the duration of the study.
Aged 1 to <18 years and weighing at least 7 kilograms (kg) at the time of providing informed consent/assent.
Documented diagnosis of thalassemia (β-thalassemia with or without α-globin gene mutations, hemoglobin E (HbE)/β-thalassemia, or α-thalassemia/hemoglobin H (HbH) disease) based on Hemoglobin (Hb) electrophoresis, Hb high-performance liquid chromatography, and/or DNA analysis from the participant's medical record. If this information is not available from the participant's medical record, the test(s) can be performed by a local laboratory during the Screening Period. If a local laboratory is unable to perform the test(s), results from the comprehensive α- and β-globin genotyping performed by the study central laboratory can be used.
Transfusion dependent, defined as 6 to 20 transfusion episodes (also referred to as "transfusion events") and a ≤6-week transfusion-free period during the 24-week period before randomization.
Pregnant or breastfeeding.
Documented history of homozygous or heterozygous hemoglobin S (HbS) or hemoglobin C (HbC).
Prior exposure to gene therapy or prior bone marrow or stem cell transplantation, including any prior exposure to myeloablative chemotherapy.
Any conditions other than thalassemia expected to affect sexual maturation.