Nonmyeloablative Haploidentical Peripheral Blood Mobilized Hematopoietic Precursor Cell Transplantation for Sickle Cell Disease

Nonmyeloablative allogeneic peripheral blood stem cell (PBSC) transplants are currently being
investigated in phase I/II trials assessing engraftment, efficacy, and toxicity at a number
of transplant centers. Our ongoing protocol for patients with severe congenital anemias,
particularly sickle cell disease (SCD), and an HLA-matched sibling donor has had excellent
preliminary results. None of the patients who engrafted had sickle-related events or any
evidence of graft versus host disease (GVHD). There was no significant toxicity associated
with the conditioning regimen. An additional protocol is ongoing for patients with high risk
of graft rejection which employs pentostatin and oral cyclophosphamide (PC) pre-transplant to
further deplete recipient lymphocytes in an attempt to decrease the rate of graft rejection.
Four of 4 patients transplanted remain free of SCD.

Our main limitation has been a lack of HLA-matched sibling donors in the majority of
patients. We performed a study in which patients with severe SCD who lacked a suitable donor
underwent a search for a matched unrelated donor or umbilical cord donor. The vast majority
of patients were not found to have an appropriate alternative donor. We therefore seek to
develop a safe nonmyeloablative regimen to be applied to the haploidentical setting so that
family members can serve as donors and greatly expand the donor pool.

We developed a nonmyeloablative haploidentical PBSC transplant protocol which included 3
cohorts, with stopping rules built in for regimen failure, defined as graft rejection or
severe GVHD. All included 400 cGy total body irradiation (TBI), alemtuzumab, and sirolimus.
The first cohort included no cyclophosphamide. The 2nd included one dose of cyclophosphamide
given at 50mg/kg on day 3 post-transplant, and the 3rd included 100mg/kg cyclophosphamide
given in divided doses on days 3 and 4 post-transplant. The engraftment rate and percentage
of patients who remained free of SCD improved with each successive cohort. However, the graft
rejection rate in the 3rd cohort remained high at 50%. To attempt to reduce the rate of graft
rejection in the haploidentical setting, this protocol will add PC to the conditioning
regimen.

In this protocol, we propose PBSC transplantation in patients with SCD considered at high
risk for complications from or ineligible for standard bone marrow transplantation, with
allogeneic peripheral blood stem cells from a haploidentical donor using a novel
immunosuppressive regimen without myeloablation in an attempt to further decrease the
transplant-related morbidity/mortality. The low intensity nonmyeloablative conditioning
regimen will consist of a relatively low radiation dose for therapeutic radiation,
Alemtuzumab (Campath ), Sirolimus (Rapamune ), Cyclophosphamide (Cytoxan ), and pentostatin
(Nipent ) as a strategy to provide adequate immunosuppression to allow sufficient engraftment
for clinical remission with a lower risk of GVHD development. T-cell replete, donor-derived,
granulocyte colony-stimulating factor (G-CSF)-mobilized PBSC will be used to establish
hematopoietic and lymphoid reconstitution.

The primary endpoint of this study is the percentage of patients at 100 days post-transplant
who have not rejected their grafts, and who are without severe GVHD (defined as grade 3 and
higher acute GVHD and moderate to severe chronic GVHD). Other endpoints include degree of
donor-host chimerism necessary for long-term graft survival and disease amelioration,
incidence of acute and chronic GVHD, incidence of graft rejection, transplant-related
morbidity, as well as disease-free and overall survival.

- INCLUSION CRITERIA-RECIPIENTS:

Patients with any type of sickle cell disease who are at high risk for disease-related
morbidity or mortality, defined by having severe end-organ damage (A, B, or C) or
potentially modifiable complication(s) not ameliorated by hydroxyurea (D):

A. Stroke defined as a clinically significant neurologic event that is accompanied by an
infarct or hemorrhage on cerebral MRI or cerebral arteriopathy requiring chronic
transfusion therapy; OR

B. Tricuspid regurgitant jet velocity (TRV) of greater than or equal to 2.5 m/s at baseline
(without vaso-occlusive crisis) and/or pulmonary hypertension; OR Sickle hepatopathy
defined as either ferritin >1000 mcg/L and platelet count < 250,000/uL (without
vaso-occlusive crisis) OR direct bilirubin > 0.4 mg/dL and platelet count <250,000/uL
(without vaso-occlusive crisis)

C. Sickle hepatopathy defined as EITHER ferritin >1000mcg/L OR direct bilirubin >0.4 mg/dL
AND platelet count <250,000/uL at baseline (without vaso-occlusive crisis)

D. Any one of the below complications:

- Complication-Vaso-occlusive crises; Eligible for hydroxyurea*-At least 3 hospital
admissions in the last year; Eligible for HSCT-More than 1 hospital admission per year
while on maximal tolerated dose of hydroxyurea*

- Complication-Acute chest syndrome; Eligible for hydroxyurea*-2 prior ACS; Eligible for
HSCT-any ACS while on hydroxyurea*.

- hydroxyurea at maximum tolerated dose for at least 6 months

Non-disease specific:

A. Age greater than or equal to 18 years

B. Haploidentical relative donor available

C. Ability to comprehend and willing to sign an informed consent

D. Negative serum beta-HCG

E. Ejection fraction greater than or equal to 35%

F. Glomerular filtration rate >60 mL/min/1.73m^2 by cystatin C-based or othalamate-based or
other equivalent GFR testing

G. Adjusted DLCO greater than or equal to 35%

EXCLUSION CRITERIA-RECIPIENT:

Any of the following would exclude the subject from participating

1. Available 6/6 HLA-matched sibling donor

2. ECOG performance status of 3 or more

3. Evidence of uncontrolled bacterial, viral, or fungal infections (currently taking
medication and progression of clinical symptoms) within one month prior to starting
the conditioning regimen.

4. Patients with fever or suspected minor infection should await resolution of symptoms
before starting the conditioning regimen.

5. Major anticipated illness or organ failure incompatible with survival from PBSC
transplant

6. Pregnant or lactating

7. Anti-donor HLA antibodies

8. Patients seronegative for EBV who have EBV seropositive donors

INCLUSION CRITERIA-DONOR:

1. Haploidentical relative donor

2. Weight > 20 kg (insofar that the weight difference between recipient and donor does
not exceed a reasonable likelihood of being able to obtain an adequate cell dose from
the donor within two aphereses)

3. Fit to receive filgrastim (G-CSF) and to give peripheral blood stem cells (blood
counts and blood pressure within DTM standards)

4. No history of congestive heart failure or unstable angina, and no history of stroke

5. Ability to comprehend and willing to sign an informed consent; assent obtained from
minors

EXCLUSION CRITERIA-DONOR:

Any of the following would exclude the donor from participating

1. Pregnant or breastfeedingl

2. HIV positive

3. Hemoglobin S > 50%