• Patients with a diagnosis of transfusion dependent beta or alpha thalassemia (3 or 4 gene deletion) between the age of 1-18 years.

• Thalassemia genotype must be confirmed by molecular genetic testing.

• Patients with thalassemia must have at least one of the high-risk features:

‣ Age \>7 years

⁃ Hepatomegaly (2 cm below costal margin)

⁃ Inadequate iron chelation (liver iron content \>7mg/g dry weight)

⁃ Severe alloimmunization

⁃ Unable to tolerate iron chelation

∙ 3\. Patients must have had a complete evaluation of their iron status including measurement of serum ferritin, MRI of the heart and liver (within the previous 6 months prior to referral). Liver elastography (within the preceding 3 months) will be also obtained but not required.

∙ 4\. Ability to take oral medication and be willing to adhere to the study regimen.

∙ 5\. Patients who have a performance status of at least 70% Karnofsky or Lansky status prior to transplantation.

∙ 6\. Patients who are acceptable candidates for marrow transplantation based on their pre-BMT evaluation.

∙ 7\. Patients who have histocompatibility sibling or HLA haplo identical family member and have been medically approved as hematopoietic progenitor cell donors.

∙ 8\. Patients who are not candidates for gene therapy.

∙ 9\. Patients/legal guardians who sign informed consent for the protocol approved by the Research Ethical Board of the Hospital for Sick Children/University of Toronto.