A Pilot Study of HSCT for Patients With High-Risk Hemoglobinopathy Using a Nonmyeloablative Preparative Regimen

Severe hemoglobinopathies such as sickle cell disease (SCD) and Thalassemia are associated
with considerable morbidity, organ damage and premature mortality. Allogeneic hematopoietic
stem cell transplantation (HSCT) is the only therapy that can cure a hemoglobinopathy. The
applicability of HSCT for hemoglobinopathies is limited by the paucity of suitable donors,
and risk of early regimen-related toxicity and the late effects. Reduction of the dose of
myelotoxic drugs in preparative regimens prior to HSCT has the potential to increase the
applicability of this curative option for patients with hemoglobinopathies. We hypothesize
that a preparative regimen that maximizes host immunosuppression without myeloablation will
be well tolerated and sufficient for engraftment of donor hematopoietic stem cells in
patients with severe hemoglobinopathies. The long term objective of this research is to
develop novel, less toxic approaches to HSCT for patients with severe hemoglobinopathies.
Specific aims: 1. To evaluate the safety and efficacy of a novel nontoxic nonmyeloablative
approach to hematopoietic stem cell transplantation for hemoglobinopathies. 2. To optimize
the immunosuppressive regimen for HSCT patients through a thorough understanding of the
pharmacokinetics of Busulfan (BU) and Mycophenolic acid (MPA) 3. To determine the effect of
partial or complete donor chimerism on cerebral vasculopathy in patients with SCD. 4. To
determine the rate of T cell immune reconstitution in children with sickle cell disease
following myeloablative compared to nonmyeloablative stem cell transplantation, using
immunophenotyping assays, CDR3 spectratyping TREC analysis, and measurement of T cell
specific donor engraftment. Subjects meeting eligibility criteria in whom an human leukocyte
antigen matched, partially mismatched related or unrelated donor of bone marrow or umbilical
cord blood will receive a HSCT after a nonmyeloablative preparative regimen consisting of
BU, Fludarabine (FLU), total lymphoid radiation and Anti-Thymocyte globulin followed by
prophylaxis against graft versus host disease with cyclosporine A and MMF. Patients will be
studied for survival, cure of hemoglobinopathy, absence of severe regimen related toxicity
and graft versus host disease. The relationship of engraftment, survival and Graft versus
host disease to kinetics of lineage specific donor chimerism and area under the curve for
Mycophenolic acid and Busulfan will be studied.

Inclusion Criteria:

- Patients with SCD 0-35 years of age with an HLA-identical or 1 HLA antigen mismatched
bone marrow or up to 2 HLA antigen mismatched umbilical cord blood (UCB) donor with
one or more of the following:

- Stroke, CNS hemorrhage or a neurologic event lasting longer than 24 hours, or
abnormal cerebral MRI or cerebral arteriogram or MRI angiographic study and
impaired neuropsychological testing,

- Acute chest syndrome with a history of recurrent hospitalizations or exchange
transfusions,

- Recurrent vaso-occlusive pain 3 or more episodes per year for 3 years or more
years or recurrent priapism,

- Impaired neuropsychological function and abnormal cerebral MRI scan,

- Stage I or II sickle lung disease,

- Sickle nephropathy (moderate or severe proteinuria or a glomerular filtration
rate [GFR] 30-50% of the predicted normal value),

- Bilateral proliferative retinopathy and major visual impairment in at least one
eye,

- Osteonecrosis of multiple joints with documented destructive changes,

- Requirement for chronic transfusions but with RBC alloimmunization >2 antibodies
during long term transfusion therapy.

- Patients with transfusion dependent Thalassemia 0-35 years of age with an
HLA-identical or 1 HLA antigen mismatched bone marrow or up to 2 HLA antigen
mismatched UCB donor.

- Second Transplants

- Patients with sickle cell disease or Thalassemia who have failed to engraft or
have autologous recovery are eligible for this protocol.

- Patients must meet above criteria.

- If first transplant was a non-myeloablative regimen, the second transplant can
occur at any time.

- If the first transplant was a myeloablative regimen, then the second transplant
must be > 6 months from the first transplant.

Exclusion Criteria:

- Patients with one or more of the following:

- Karnofsky or Lansky performance score <70,

- Acute hepatitis or evidence of moderate or severe portal fibrosis or cirrhosis
on biopsy,

- Stage III-IV lung disease,

- GFR<30% predicted normal values.

- Pregnant or lactating females.

- Active serious infection whereby patient has been on intravenous antibiotics for one
week prior to study entry. Any patient with AIDS or ARC or HIV seropositivity. Any
patient with invasive aspergillums infection within one year of study entry.

- Psychologically incapable of undergoing BMT with associated strict isolation or
documented history of medical non-compliance.

- Patients not able to receive TLI due to prior radiation therapy.

Donor Inclusion Criteria

- Donor must be in good health based on review of systems and results of physical
examination.

- Donor must have a normal hemoglobin, white count, platelet count and PTT.

- Female donors of childbearing potential must have a negative pregnancy test.

Donor Exclusion Criteria

- Donor has active infection (including HIV, hepatitis).

- Donor is a lactating female.

Donor Selection

In the case where more than one donor meets the eligibility criteria, donor selection will
be guided by the following considerations:

- HLA A, B, DRB1 identical sibling donor is preferable to an unrelated donor

- Homozygous normal donor is preferable to heterozygote (carrier)

- ABO-compatible donor is preferable to ABO-incompatible donor

- Younger donor is preferable to older

- Cytomegalovirus seronegative donor is preferable to CMV seropositive donor, if the
patient is CMV negative