• Age ≥ 4 years.

• Patients who require or are expected to require a transfusion of RBC component(s), including red cell exchange transfusion

• Signed and dated informed consent form.

• Female patients of child-bearing potential must:

‣ Have negative serum or urine pregnancy tests prior to study treatment to rule out pregnancy, and

⁃ Agree to use to use at least one method of birth control that results in a low failure rate (i.e., less than 1% per year) when used consistently and correctly such as implants, injectables, combined oral contraceptives, some intrauterine devices (IUDs), sexual abstinence or vasectomized partner for the duration of study participation and an additional 28 days.

∙ For 28-day +6-month extension study in chronically transfused patients:

∙ • A diagnosis of a bone marrow failure syndrome requiring repeated RBC transfusion for congenital or acquired chronic anemia (e.g., sickle cell anemia, thalassemia, other hemoglobinopathies, myelodysplastic syndrome, aplastic anemia, chemotherapy or stem cell transplant etc.)

∙ For 28-day +6-month extension study in SCD patients requiring regular repeated RCE.

• Diagnosis of SCD, either HbSS, HbSC or HbSB0 thalassemia, confirmed by Hb electrophoresis, deoxyribonucleic acid (DNA) analysis or high-performance liquid chromatography (HPLC)

• Currently participating in an automated RCE transfusion program (for at least 3 months prior to enrollment) with 3-to-8 week intervals between RCE transfusion episodes