This purpose of this study is to understand the differences between people who have a good response to deferasirox (exjade) compared to people who have a poor response to this medication when used for transfusion-dependent iron overload.

The hypothesis is that patients with poor responses have physiologic barriers to deferasirox that may include absorption, pharmacokinetics of drug metabolism, hepatic clearance and/or genetic factors.

The purpose of this trial is to examine three potential mechanisms of inadequate response to Exjade® in patients with transfusion dependent iron overload including patients with thalassemia syndromes, sickle cell disease and bone marrow failure.

Hypothesis: Patients have physiologic barriers to adequately respond to deferasirox that may include absorption, pharmacokinetics of drug metabolism, hepatic clearance and/or genetic factors.

Study objectives Primary objective

• To evaluate three potential mechanisms for inadequate response to deferasirox in a small cohort of patients with hemoglobinopathies.
• Oral pharmacokinetics measured with Cmax and AUC following standard dose deferasirox.
• Hepatobiliary excretory function
• Accessibility of chelatable iron pool by deferoxamine challenge Secondary objective(s)
• To identify risk factors that can predict adequate response including demographics, disease status, presence and severity of liver disease, trough levels of deferasirox at outpatient visits and pharmacogenomics.
• To investigate usefulness of potential surrogate measures of response including serum deferasirox levels, Hepatobiliary Iminodiacetic Acid (HIDA)nuclear medicine scan to evaluate hepatic excretory function and urinary iron excretion by deferoxamine challenge.

This is an investigator-initiated, pilot-scale, open-label physiological assessment of patients who respond poorly to deferasirox compared with patients who respond well. We plan to study 2 groups of patients: a)10 patients who have demonstrated poor responses and b) 5 control patients with good responses as defined further in the protocol. The study has two parts.

Part I: Both groups of patients will have inpatient physiological assessments with a dose of 35mg/kg of deferasirox.

Part II: Inadequate responders eligible to continue on deferasirox will continue on a dose of 35 mg/kg for three months during which time serial pharmacokinetic levels will be studied. The control patients will resume their previous clinically appropriate dosing (likely less than 35 mg/kg) and for three months have serial pharmacokinetic levels drawn as well.

The study will begin with an outpatient screening visit when demographics and historical information as well as a physical examination will be obtained and reviewed for eligibility. At that visit patients will be able to sign informed consent. Shortly thereafter patients will be admitted to the GCRC at Children's Hospital Boston for part I of the study, a 2-3 day stay during which PK and nuclear medicine studies will be performed as well as the deferoxamine urinary iron excretion challenge. Patients who are eligible will continue on to part II of the study, and for 3 months and will be monitored for compliance, PK and ferritin changes on appropriate deferasirox doses.

Part I: Inclusion criteria for Inadequate responders

• Male or female patients with transfusion dependent iron overload including patients with thalassemia syndromes, sickle cell disease and bone marrow failure.
• Patients currently on Desferal (desferrioxamine) therapy will require a one day wash out prior to the first dose of study drug.
• Dose of deferasirox: >30 mg/kg/day of deferasirox for at least 3 months
• No improvement or worsening of liver iron content (LIC) if this has been evaluated on deferasirox in the 3 months preceding the baseline studies.
• Age greater than 6 years
• Serum Ferritin: Ferritin >1500 ng/ml and rising over three month period while on deferasirox.
• Patients had to achieve 'failure' as described above previously and may or may not currently be on deferasirox and may currently be having adequate responses on doses greater than or equal to 35 mg/kg/day of deferasirox.
• Life expectancy ≥ 6 months
• Written informed consent by the patient or for pediatric patients consent of the patient's legal guardian. The definition of the term 'pediatric' for enrollment and study conduct will be in accordance with Children's Hospital IRB. Parents or the legal guardians will be fully informed by the investigator as to the requirements of the study. Pediatric patients themselves will be informed according to their capabilities in a language and in terms that they are able to understand. Written informed consent will be obtained from their legal guardian on the patient's behalf in accordance with national legislation. If capable, all patients should also personally sign their written informed consent.

Part I: Inclusion criteria for good responders:

• Male or female patients with transfusion dependent iron overload including patients with thalassemia syndromes, sickle cell disease and bone marrow failure.
• Patients currently on Desferal (desferrioxamine) therapy will require a one day wash out prior to the first dose of study drug.
• Serum ferritin less than or equal to 1000 ng/ml or declining over a 3 month period on a dose of less than 30 mg/kg of deferasirox.
• Age greater than 6 years
• Life expectancy ≥ 6 months
• Written informed consent by the patient or for pediatric patients consent of the patient's legal guardian. The definition of the term 'pediatric' for enrollment and study conduct will be in accordance with Children's Hospital IRB. Parents or the legal guardians will be fully informed by the investigator as to the requirements of the study. Pediatric patients themselves will be informed according to their capabilities in a language and in terms that they are able to understand. Written informed consent will be obtained from their legal guardian on the patient's behalf in accordance with national legislation. If capable, all patients should also personally sign their written informed consent.

Exclusion criteria for Part I:

• Pregnancy (as documented in required screening laboratory test) or breast feeding
• History of non-compliance to medical regimens or patients who are considered potentially unreliable and/or not cooperative
• Patients with transfusion requirements equal to or more frequent than every three weeks.
• AST or ALT > 400 U/L during screening
• Patients with uncontrolled systemic hypertension
• Severe cardiac insufficiency (NYHA III or IV), with uncontrolled and/or unstable cardiac or coronary artery disease not controlled by standard medical therapy
• Patients who received treatment with systemic investigational drug within the past 4 weeks or topical investigational drug within the past 7 days or are planning to receive other investigational drugs while participating in the study
• Allergy to deferoxamine
• Known contraindication to having a nuclear medicine study
• Any other condition which in the opinion of the investigator would prevent completion of the trial.
• Prior possible toxicity is not an exclusion criteria for Part I because patients require a chelating agent of which there are only two Patients who are found to be ineligible after screening procedures will have this documented on the screening log. No further data will be collected in the CRF for these patients.

Exclusion criteria for Part II:

• Patients with unacceptable toxicity to deferasirox such as renal failure or worsening cardiac function
• Patients who have failed to achieve negative iron balance at the maximum tolerated dose of deferasirox
• Patients who require an alternative chelator for specific reasons
• Patients who are currently enrolled on conflicting therapeutic trials
• Patients with serum ferritin less than 500 ng/ml at screening
• Any other condition which in the opinion of the investigator would prevent completion of the trial

Adverse event are reported for at least 28 days following the last dose of study drug.