A Study Evaluating the Efficacy and Safety of AG-348 in Regularly Transfused Adult Participants With Pyruvate Kinase Deficiency (PKD)

Inclusion Criteria: * Informed consent; * Male or female, aged 18 or older; * Presence of at least 2 mutant alleles in the Pyruvate Kinase Liver and RBC (PKLR) gene, of which at least 1 is a missense mutation; * History of a minimum of 6 transfusion episodes in the 52-week period prior to date of informed consent; * Complete records of transfusion history for the 52 weeks prior to the date of informed consent, including all transfusion dates, number of blood units transfused for all the transfusions, and Hb concentrations within 1 week prior to transfusion for at least 80% of the transfusions; * Have received at least 0.8 mg of oral folic acid daily for at least 21 days prior to the first dose of study drug, to be continued daily during study participation; * Have adequate organ function; * Negative serum pregnancy test for women of reproductive potential; * For women of reproductive potential as well as fertile men and their partners who are women of reproductive potential: be abstinent or agree to use 2 forms of contraception, 1 of which must be considered highly effective, from the time of giving informed consent, during the study, and for 28 days following the last dose of AG-348; * Willing to comply with all study procedures, in particular the individual transfusion trigger (TT) calculated based on 52 weeks of transfusion history, for the duration of the study. Exclusion Criteria: * Homozygous for the R479H mutation or have 2 non-missense mutations, without the presen…