Study AG348-C-010 is a multicenter study to evaluate the efficacy, safety, pharmacokinetics, and pharmacodynamics of treatment with AG-348 in adult participants with non-transfusion-dependent thalassemia (NTDT). This study includes a core period (up to 24 weeks) followed by an extension period (up to 10 years) for eligible participants. 20 participants with NTDT were enrolled. The initial dose of AG-348 was 50 milligrams (mg) twice daily (BID) with one potential dose-level increase to 100 mg BID at the Week 6 visit based on the participant's safety and hemoglobin (Hb) concentrations.