A Study to Evaluate the Efficacy and Safety of Mitapivat in Pediatric Participants With Pyruvate Kinase Deficiency (PKD) Who Are Not Regularly Transfused, Followed by a 5-Year Extension Period

Study ACTIVATE-Kids (AG348-C-023) will evaluate the efficacy and safety of orally administered mitapivat as compared with placebo in pediatric participants with pyruvate kinase deficiency (PKD) who are not regularly receiving blood transfusions. Participants will be randomized 2:1 to receive either mitapivat or matching placebo. Randomization will be stratified by age (1 to \< 6 years, 6 to \< 12 years, 12 to \< 18 years). Participants will be dosed by age and weight during a double-blind period consisting of an 8-week dose titration period followed by a 12-week fixed-dose period. Participants who complete the double-blind period will be eligible to receive mitapivat for up to 5 years in the open-label extension (OLE) period.

Inclusion Criteria: * Written informed consent from the participant, or the participant's legally authorized representative, parent(s), or legal guardian, and the participant's assent, where applicable (informed consent/assent) 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 \