To evaluate the efficacy and safety of S 303 treated red blood cells (RBCs) in subjects who require chronic transfusion support due to thalassemia major.

To evaluate the efficacy and safety of S 303 treated red blood cells (RBCs) in subjects who require chronic transfusion support due to thalassemia major.

Inclusion Criteria:

• Age ≥10 years, of either gender
• Diagnosed with thalassemia major and currently participating in a chronic transfusion program
• At least a one year history of chronic RBC transfusion support with a stable transfusion requirement (per treating physician)
• Intervals of at least 14 days between RBC transfusions
• All RBC components are given on one day for each transfusion episode
• Negative direct antiglobulin tests (DAT)
• Stable iron chelation regimen
• Available for measurement of hemoglobin level at one hour post transfusion
• Signed and dated informed consent form

Exclusion Criteria:

• Baseline antibody specific to S 303 treated RBC (positive test, as defined in Section 8.4.1)
• Evidence of splenic hyper function defined as a transfusion requirement >180 cc/kg/year (at 100% hematocrit)
• Splenic enlargement: spleen palpable ≥4 cm below costal margin OR ≥18 cm in longitudinal diameter by ultrasound (chosen at the Investigator's discretion according to the data available with ultrasound data being preferable)
• Any subject for whom a transition in the number of RBC units transfused is anticipated within 12 months of study entry due to growth of the subject (e.g. a transition from 1 RBC component per transfusion cycle to 2 OR a transition from 2 to 3 is anticipated based on weight change alone)
• Alloimmunization to high frequency blood group antigens to the extent that the ready provision of compatible blood may not be feasible for the study (alloimmunization alone is not an automatic exclusion)
• Current specialized treatment with washed or frozen RBC
• Requirement for gamma irradiated RBC components (would present blinding difficulty due to blood component labeling regulations
• Treatment with any medication that is known to adversely affect RBC viability
• HIV infection (defined as RNA positive)
• HCV (hepatitis C)infection (defined as RNA positive) if treated with concomitant medications known to suppress the bone marrow
• Pregnant or breast feeding female, or female of child bearing potential not using a medically approved form of contraception
• Acute or chronic medical disorder other than thalassemia that, in the opinion of the Investigator or medical monitor, may prevent the subject from completing participation in the study
• Participation in another clinical study, either concurrently or within the previous 28 days, in which the study drug or device may influence red blood cell viability