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.
Parallel
Mitapivat Matched Placebo
DrugTablets or Granules
Mitapivat
DrugTablets or Granules
Percentage of Participants Who Achieved Transfusion Reduction Response (TRR) Through Week 48
TRR is defined as ≥50 percent (%) reduction in transfused red blood cells (RBC) volume (normalized by weight) in any consecutive 12-week period through Week 48 compared with historical RBC transfusion volume (normalized by weight) and standardized to 12 weeks.
Percentage of Participants Who Achieved TRR2 From Week 13 to Week 24
TRR2 is defined as ≥50% reduction in transfused RBC volume (normalized by weight) from week 13 to week 24 compared with historical RBC transfusion volume (normalized by weight) and standardized to 12 weeks.
Percentage of Participants Who Achieved TRR3 From Week 25 to Week 36
TRR3 is defined as ≥50% reduction in transfused RBC volume (normalized by weight) from week 25 to week 36 compared with historical RBC transfusion volume (Normalized by Weight) and standardized to 12 weeks.
Percentage of Participants Who Achieved TRR4 From Week 37 to Week 48
TRR4 is defined as ≥50% reduction in transfused RBC volume (normalized by weight) from week 37 to week 48 compared with historical RBC transfusion volume (normalized by weight) and standardized to 12 weeks.
Percentage of Participants Who Achieved TRR5 From Week 25 to Week 48
TRR5 is defined as ≥50% reduction in transfused RBC volume (normalized by weight) from week 25 to week 48 compared with historical RBC transfusion volume (normalized by weight) and standardized to 24 weeks.
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