Long-term Follow-up of Subjects With Transfusion-Dependent β-Thalassemia (TDT) Treated With Ex Vivo Gene Therapy

This is a multi-center, long-term safety and efficacy follow-up study for subjects with transfusion-dependent β-thalassemia (TDT) who have been treated with ex vivo gene therapy drug product in bluebird bio-sponsored parent clinical studies. After completing the parent clinical studies (approximately 2 years), eligible subjects will be followed for an additional 13 years for a total of 15 years post-drug product infusion. No investigational drug product will be administered in this study.

Inclusion Criteria: * Provision of written informed consent for this study by subjects, or as applicable, subject's parent(s)/legal guardian(s) * Treated with drug product for therapy of transfusion-dependent β-thalassemia in a bluebird bio-sponsored clinical study Exclusion Criteria: * There are no exclusion criteria for this study