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) in divided doses 1 and 2 days prior to transplant, 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 cerebrovascular morbidity or early mortality, defined by having severe end-organ damage (A, B, C, D, or E):

A. A neurologic event resulting in focal neurologic deficits that lasted >= 24 hours (classical clinical definition of stroke, not requiring imaging studies of the brain) OR a focal neurological event resulting in abnormalities on T2- weighted or FLAIR images using an MRI scan, indicative of an acute infarct, with no other reasonable medical explanation (definition of a stroke supported with MRI imaging scans of the brain), OR both; OR

B. Tricuspid regurgitant jet velocity (TRV) of >= 2.7 m/s at baseline (without vaso- occlusive crisis) and/or pulmonary hypertension; OR

C. 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)

D. Any acute chest syndrome episode resulting in intensive care admission requiring non- mechanical ventilatory support: simple nasal cannula, face mask that requires oxygen content (venti mask, non-rebreather), continuous positive airway pressure (CPAP), Bilevel positive airway pressure (BiPAP), high flow nasal cannula (HFNC) or invasive mechanical ventilatory support (delivered by endotracheal tube or tracheostomy).

E. Silent cerebral infarct defined as an infarct-like lesion based on an MRI signal abnormality at least 3 mm in one dimension and visible in two planes on FLAIR or T2- weighted images (or similar image with 3D imaging) and documented neurological examination performed by a neurologist demonstrating the participant has a normal neurologic or an abnormality on examination that could not be explained by the location of the brain lesion(s).

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 iothalamate-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)

• Available 6/6 HLA-matched sibling donor
• ECOG performance status of 3 or more (See Appendix A)
• 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.
• Patients with fever or suspected minor infection should await resolution of symptoms before starting the conditioning regimen.
• Major anticipated illness or organ failure incompatible with survival from PBSC transplant
• Pregnant or breast-feeding
• Donor specific anti-HLA antibodies (DSAs) greater than or equal to 2000 Mean Fluorescence Intensity (MFI)
• Patients seronegative for EBV who have EBV seropositive donors

Inclusion criteria

-DONOR:

Haploidentical relative donor deemed suitable and eligible, and willing to donate, per clinical evaluations who are additionally willing to donate blood for research. Related donors will be evaluated in accordance with existing Standard NIH Policies and Procedures for determination of eligibility and suitability for clinical donation. Note that participation in this study is offered to all related donors, but is not required for a do le that not all related donors will enroll onto this study.

Exclusion criteria

-DONOR:

None