Optimal dose obtained for engraftment and minimizing toxicity

Many genetic diseases of lymphohematopoietic cells (such as sickle cell anemia, thalassemia, Diamond-Blackfan anemia, Combined Immune Deficiency (CID), Wiskott-Aldrich syndrome, chronic granulomatous disease, X-linked lymphoproliferative disease, and metabolic diseases affecting hematopoiesis) are sublethal diseases caused by mutations that adversely affect the development or function of different types of blood cells. Although pathophysiologically diverse, these genetic diseases share a similar clinical course of significant progressive morbidity, overall poor quality of life, and ultimate death from complications of the disease or its palliative treatment. Supportive care for these diseases includes chronic transfusion, iron chelation, and surgery (splenectomy or cholecystectomy) for the hemoglobinopathies; prophylactic antibiotics, intravenous immunoglobulin, and immunomodulator therapies for the immune deficiencies; and enzyme replacement injections and dietary restriction for some of the metabolic diseases. The suboptimal results of such supportive care measures have led to efforts to implement more aggressive therapeutic interventions to cure these lymphohematopoietic diseases. The most logical strategies for cure of these diseases have been either replacement of the patient's own hematopoietic stem cells (HSC) with those derived from a normal donor allogeneic bone marrow transplant (BMT) or hematopoietic stem cell transplant (HSCT), or to genetically modify the patient's own stem cells to replace the defective gene (gene therapy).

The present study is to evaluate de-escalation of the cyclophosphamide (CY) dose in an innovative conditioning regimen with fludarabine and alemtuzumab as additional agents to achieve immunoablation, in combination with Busulfan (BU) to achieve myeloablation. Replacement of at least part of the cyclophosphamide dose by fludarabine in the conditioning regimen would be expected to maintain immunosuppression (and, therefore, engraftment) while reducing transplant-related complications (mucositis, hepatotoxicity, cardiotoxicity, pulmonary toxicity, hemorrhagic cystitis, mucositis, and possibly GVHD), thereby improving disease-free survival rates. Similarly, the potential benefits of alemtuzumab in the proposed conditioning regimen are increased rates of hematopoietic engraftment with less toxicity than that observed with cyclophosphamide, ultimately resulting in improved immune function and enhanced quality of life (12,13). A fludarabine/alemtuzumab-based, less intensive conditioning regimen with adequate immunosuppressive activity could conceivably allow more successful engraftment of stem cells from related donors in patients with genetic lymphohematological diseases, as well as lower rates of transplant-related mortality.

Regimen-related toxicity is also believed to be a major contributing factor to GVHD (14). Therefore, conditioning regimens that cause less tissue injury may also lead to reduced GVHD. In the present study, the use of alemtuzumab in the conditioning regimen may be an added benefit, as this antibody causes T-cell depletion, thus, the risk of GVHD may also be reduced (15). The overall goal of the study is to improve the therapeutic index of HSCT by decreasing and, if possible, eliminating cyclophosphamide as a component of the pre-transplant conditioning for patients with genetic diseases of lymphohematopoiesis. The investigation will explore the risks and benefits of the proposed novel-conditioning regimen using a decreased dose of cyclophosphamide and additional immunosuppression with fludarabine and alemtuzumab to prevent graft rejection and recurrence of disease. The investigators will evaluate this regimen's impact on conditioning-related morbidity and mortality, and measure the success of the transplant procedure by engraftment and disease-free survival. If this regimen is able to successfully permit engraftment and reduce regimen-related toxicity, the next phase of treatment will test a further dose de-escalation for cyclophosphamide. It is anticipated that there will be four dose levels of cyclophosphamide in the overall study: 1) 105 mg/kg; 2) 70 mg/kg; 3) 35 mg/kg; and then finally, 4) 0 mg/kg. This study design was chosen to minimize study risks possibly associated with substitution of fludarabine and alemtuzumab for CY as immunoablation. The present protocol represents Level 1 in the study design; an amended protocol will be prepared prior to further de-escalation of the cyclophosphamide dose.

Inclusion Criteria:

• All patients with lethal or sublethal genetic lymphohematological disease (such as Hemaphagocytic lymphohistiocytosis (HLH) / Familial Erythrophagocytic Lymphohistiocytosis (FEL), Hurler's Syndrome, Hunter's Syndrome, Kostmann's Syndrome, Blackfan-Diamond Anemia, Chronic granulomatous Disease (CGD), Red Cell Aplasia, CID, Sickle Cell Anemia, Thalassemia, Adreno-leukodystrophy, metachromatic leukodystrophy, Wiskott-Aldrich Syndrome, X-Linked Lymphoproliferative Disease (XLD), Metabolic diseases affecting hematopoiesis, but not limited to), who are candidates for allogeneic transplantation for their disease and have a histocompatible sibling or related donor, ages 0 to 21 years, will be candidates for this study protocol. The suitable related donor is a 10/10 or 9/10 allele Human Leukocyte Antigen (HLA) match with the patient. All patients who have previously had serious life- threatening events due to disease process may be included in the study. Patients must have adequate physical function and vital organ function to tolerate transplant procedure, as measured by:
• Cardiac: Shortening fraction >26% or left ventricular ejection fraction at rest must be > 40%.
• Hepatic: Bilirubin, Alanine Aminotransferase (ALT) and Aspartate Aminotransferase (AST) < 3x upper limit of normal (as per local laboratory) for age (with the exception of isolated hyperbilirubinemia due to Gilbert's syndrome).
• Renal: Serum creatinine < 2x upper limit of normal for age or if serum creatinine elevated beyond normal range patient must have creatinine Clearance or Glomerular filtration rate (GFR) >50% lower limit of normal for age.
• Pulmonary: Forced expiratory volume (FEV)1, Forced Vital Capacity (FVC), and Diffusing Lung Capacity for Carbon Monoxide (DLCO) (corrected for Hgb) > 50% predicted. For patients where pulse oximetry is performed, O2 saturation > 92%
• Evaluation of iron status in patients who have received more than 12 red cell transfusions. Measurements of serum ferritin levels and MRI of the liver and heart tissue will evaluate the iron stores. If high iron load is identified in these organs further evaluation will be done to determine the suitability as transplant recipient. Should these studies indicate that chelation is necessary the following should apply: That the treating hematologist will provide the specific chelation type and timing. Evaluation of organ iron load will be part of the HSCT work-up and if high iron load is identified then the BMT team will work with the hematologist attending in developing a plan for the patient.

Exclusion Criteria:

• Karnofsky performance status < 70%, or Lansky < 40% for patients < 16 years old.
• Uncontrolled bacterial, viral, or fungal infections (currently taking medication yet clinical symptoms progress).
• Seropositivity for the human immunodeficiency virus (HIV).
• Acute active hepatitis.
• Diagnosis of end-organ dysfunction that precludes the ability to tolerate the transplant procedure.
• Patients with a diagnosis of Fanconi Anemia are excluded.

Tranplant data is reported to CIBMTR and is available to the other investigators