An Open-label Extension Study to Evaluate Long-term Efficacy and Safety of Odevixibat (A4250) in Children with Biliary Atresia. Detailed Description: This is a Phase 3, multi-center, open-label extension study to evaluate the long-term efficacy and safety of odevixibat in patients with Biliary Atresia (BA). Patients who completed treatment in the A4250-011 BOLD study and meet eligibility criteria for Study A4250-016 (BOLD-EXT) can participate. The duration of the treatment period is 104 weeks, followed by a 4-week Safety Follow-up Period. Patients who wish to continue receiving odevixibat after 104 weeks can remain on treatment in the optional extension period (OEP). Up to 180 patients will be enrolled at approximately 70 sites in the North America, Europe, the Middle East and Asia-Pacific.