Additional Relevant Details This is a Phase 2, open label, two arm, multicenter, randomized, dose-ranging study during which adult patients with PK deficiency will receive multiple doses of AG-348 for up to 24 weeks. Up to 25 patients will be randomized to two doses of AG-348; a third arm (up to 25 patients) may be added, if required. AG-348 will be administered orally at various doses; if implemented, the dose of Arm 3 will be determined based on ongoing review. Data will be reviewed on a regular basis and study design, dose and schedule will be adapted based on these reviews. The study will evaluate the safety and tolerability of multiple doses of AG-348, pharmacokinetic (PK) and pharmacodynamic (PD) profile of AG-348 and early indicators of clinical efficacy