A Study of Immune Suppression Treatment for People With Sickle Cell Disease or β-Thalassemia Who Are Going to Receive an Allogeneic Hematopoietic Cell Transplantation (HCT)

Inclusion Criteria: Age > 12 and < 35 years. Patients of age 2-12 and 35-50 years will be included after 8 patients reach day 100 without TRM and if ≥ 4 of the first 8 patients reach day 100 without graft failure or grade III-IV acute GvHD. Suitable haploidentical donor. Performance score ≥ 70% by Karnofsky Performance Scale or 0 to 1 by ECOG (age > 16 years), or Lansky Play-Performance Scale ≥ 70% (age ≤ 16 years). Adequate major organ system function as demonstrated by: For patients ≥ 18 years of age: eGFR ≥ 50 mL/min by Cockcroft-Gault formula For patients < 18 years of age: Serum creatinine clearance: glomerular filtration rate [GFR]) must be >50 mL/min/1.73 m2 as calculated by the Schwartz formula Conjugated (direct) bilirubin less than 2x upper limit of normal. ALT or AST ≤ 3 times institutional upper limit of normal. Left ventricular ejection fraction ≥ 50%. Diffusing capacity for carbon monoxide (DLCO) ≥ 50% predicted, corrected for hemoglobin. For children < 7 years of age who are unable to perform PFT, oxygen saturation > 92% on room air by pulse oximetry. For SCD patients: HbSS, HbSC, HbS/β° with one or more of the following complications: Acute chest syndrome: 2 or more episodes in the 2 years preceding enrollment Vaso-occlusive episodes: 3 or more episodes in the 2 years preceding enrollment Recurrent priapism: 2 or more episodes in the 2 years preceding enrollment History of osteomyelitis or osteonecrosis Cerebrovascular disease: Imaging evidence of prior overt or silent stroke History of a neurologic event resulting in focal neurologic deficits lasting > 24 hours Abnormal transcranial Doppler: Timed average maximum mean velocity ≥ 200 cm/sec in terminal portion of the carotid or proximal portion of the middle cerebral artery or > 185 cm/sec plus evidence of intracranial vasculopathy if imaging TCD is used Pulmonary hypertension: Confirmed by right heart catheterization with mean pulmonary arterial pressure ≥ 25 mmHg or mean pulmonary vascular resistance > 2 Wood units Red blood cell alloimmunization (> 3 alloantibodies) For thalassemia patients: Any genotype, with all of the following: Onset of red blood cell transfusion dependence during the first 3 years of life RBC transfusion history > 225 mL/kg/year or > 15 lifetime RBC transfusions Pre-transfusion hemoglobin ≤ 7 g/dL Hepatosplenomegaly Patient or the patient's legal representative, parent(s) or guardian should be able to provide written informed consent. Assent of a minor if participant's age is at least seven and less than eighteen years. For sexually active men and women of childbearing potential, must agree to use a form of contraception considered effective and medically acceptable by the Investigator. Exclusion Criteria: Prior myeloablative allogeneic HCT. Overt stroke or CNS instrumentation (e.g. for Moyamoya disease) within 6 months of enrollment. Liver cirrhosis. Mild fibrosis will be permitted, i.e. fine reticulin or grade 1 of 4, with bridging fibrosis. Hepatic iron content ≥ 3 mg Fe/g liver dry weight HIV positive Active hepatitis B or C. Other uncontrolled infections. BMI > 40. Other malignancy/cancer diagnosis unless in remission after definitive therapy for a minimum of 2 years. Exceptions: Ductal carcinoma in situ, basal cell carcinoma, cervical intraepithelial neoplasia. Positive pregnancy test in a woman with child-bearing potential, defined as not post-menopausal for 12 months or no previous surgical sterilization. Inability to comply with medical therapy or follow-up. Known history of allergic reactions to any constituents of the cell product, including a known history of allergic reactions to DMSO.