Iron Balance Study of DFO and GT56-252 in Patients With Transfusional Iron Overload Secondary to Beta-Thalassemia

Inclusion Criteria: * Beta-thalassemia patients, 18 years of age or older, currently undergoing chronic blood transfusion therapy and iron chelation therapy who weigh more than 40 kg. * No clinically significant findings on physical exam, medical history, or screening laboratories. * Serum ferritin greater than 500 ng/mL, serum creatine creatinine within the normal range and platelet count greater than 100,000/mm3. * Willing and able to discontinue DFO or L1 for the period of study. * Woman of child-bearing potential must have a negative serum pregnancy test at screening and use a medically acceptable form of birth control during the study and for 1 month afterward. Male patients must also use barrier contraceptives during the study and for 1 month afterward. * Have a level of understanding and willingness to cooperate with the confinement and all procedures. Able to provide voluntary signed/dated written informed consent. Exclusion Criteria: * Serious medical condition unrelated to Beta-Thalassemia. * Participation in a previous investigational drug study within 30 days preceding screening. * Patients with a known allergy to DFO that prevents chronic administration.