Phase I/II Pilot Study of Mixed Chimerism to Treat Hemoglobinopathies

Hematopoietic stem cell transplantation (HSCT) is emerging as a therapeutic alternative for patients with sickle cell disease. Conventional HSCT therapy has been limited to extremely high-risk hemoglobinopathy patients. Those patients who may be difficult to identify before end-organ damage develops.

Also, conventional HSCT is only available to the minority of candidates who have Histocompatibility Leukocyte Antigen (HLA) identical siblings to donate bone marrow or mobilized peripheral blood stem cells.

This study proposes two important improvements over conventional HSCT:

• Donor peripheral blood or bone marrow will be processed via a new technology, which will deplete mature immune cells while enriching hematopoietic stem cells (HSC) and graft facilitating cells (FC).
• A reduced intensity recipient conditioning regimen will be used to promote mixed allogeneic chimerism, as opposed to full donor chimerism, following HSCT.

These two elements may significantly improve the benefit:risk ratio of HSCT for patients with hemoglobinopathies. Stem cell transplantation may become a more feasible option for patients that do not have HLA-identical siblings that can donate stem cells. Also, transplantation may be offered to patients earlier in the disease progression, before end-organ damage occurs.

Inclusion criteria

The following criteria are established to identify subjects with sickle cell disease (SCD) who have a high predicted morbidity and are at risk for early mortality. Subjects with S/S disease, S/C disease, Hemoglobin H disease, Alpha Thalassemia Major, Thalassemia Major (also known as Cooley's anemia) or S/B* thalassemia and one or more of the following medical complications will be eligible:

• History of impaired neurological function and/or findings on Magnetic Resonance Image (MRI)/Magnetic Resonance Angiogram (MRA) that are associated with sickle cell disease
• More than 1 episode of acute chest syndrome with stage I or II pulmonary disease
• Osteonecrosis involving ≥ 2 joints
• Sickle cell nephropathy as evidenced by a glomerular filtration rate of 30% - 50% of the predicted normal
• Alloimmunization that is sufficient to interfere with the efficacy of chronic transfusion therapy
• Chronic or recurrent priapism
• Major visual impairment in one or both eyes with bilateral proliferative retinopathy
• Persistent disabling pain (≥ 2 episodes per year) despite trials of chronic transfusion and/or hydroxyurea at recommended doses for at least 6 months duration

Additional General Criteria:

Subjects must also meet all of the following general inclusion criteria:

• Subjects must have a related donor (identical or mismatched for 1, 2 or 3 HLA- A, HLA-B or HLA-DR loci).
• Subjects must have adequate cardiopulmonary function as documented by a left ventricular ejection fraction ≥ 50% (or within normal limits per Institutional criteria) or a left ventricular shortening fraction Within normal limits (WNL) per Institutional criteria, without inotropic support. If Ejection fraction is 40-50%, the patient may be considered for participation if cleared by a Cardiologist.
• Subjects must have adequate pulmonary function as documented by Diffusing capacity of the lung for carbon monoxide (DLCO) and Forced expiratory volume in 1 second (FEV1)

• 50% predicted for age and size. If DLCO and FEV1 are between 40-50%, patient may be considered for participation if cleared by a Pulmonologist.
• Subjects must have adequate hepatic function as demonstrated by a serum albumin ≥ 3.0 mg/dL, and serum glutamic pyruvic transaminase (SGPT) or serum glutamic oxaloacetic transaminase (SGOT) ≤ 2.5 times the upper limit of normal.
• Subjects must have adequate renal function as demonstrated by a serum creatinine ≤ 1.5 mg/dL. If serum creatinine is ≥ 1.5 mg/dL, then a creatinine clearance test must be done and the result 50% of normal.
• Subjects or legal guardians must give written informed consent, and subjects must assent where age and intellectually appropriate.
• There are no age limits for this protocol.

Exclusion criteria

• Uncontrolled infection or severe concomitant diseases, which in the judgment of the Principal Investigator, could not tolerate transplantation.
• Severe impairment of functional performance as evidenced by a Karnofsky (patients ≥16 years old) or Lansky (children <16 years old) score <70%
• Stage III or IV sickle cell pulmonary disease
• Renal insufficiency (GFR < 25% of predicted normal for age)
• Subjects with a positive human immunodeficiency virus (HIV) antibody test result
• Subjects who are pregnant, as indicated by a positive serum human chorionic gonadotrophin (HCG) test
• Subjects of childbearing potential who are not practicing adequate contraception as defined by the investigator at the site
• Subjects must not have had previous radiation therapy that would preclude total body irradiation (as determined by a radiation oncologist).