Mobilization and Collection of Peripheral Blood Stem Cells in Patients With Fanconi Anemia Using G-CSF and AMD3100
Condition: Fanconi Anemia
MeSH terms: Fanconi Syndrome; Anemia; Fanconi Anemia
Study type: Interventional
Phase: Phase 1/Phase 2

Summary: 
      The purpose of this research study is to determine whether an experimental drug called
      AMD3100 used in combination with another medication called G-CSF is safe and can help to
      increase the amount of blood stem cells (called CD34+ stem cells) found in the peripheral
      blood of patients with Fanconi anemia. While AMD3100 has been used successfully in adult
      volunteers and cancer patients, it has not been used in children or patients with Fanconi
      anemia and in only a few children with cancer.

      Fanconi anemia is a rare genetic disease. Most Fanconi anemia patients eventually develop
      bone marrow failure, a condition in which the bone marrow no longer produces red blood cells
      (to carry oxygen), white blood cells (to fight infection), and platelets (to help blood
      clot). The only successful treatment for patients with Fanconi anemia with bone marrow
      failure is bone marrow transplantation. However, this treatment has many risks and is not
      available to all patients with Fanconi anemia.

      CD34+ cells include stem cells found in the bone marrow or peripheral blood which are capable
      of making the red blood cells, white blood cells, and platelets. CD34+ stem cells can be
      collected from bone marrow or peripheral blood and purified using an experimental device
      called the CliniMACS. However, most Fanconi anemia patients do not have enough CD34+ stem
      cells in their bone marrow or peripheral blood to be collected using standard methods that
      work well in children and adults who don't have Fanconi anemia.
    

Detailed description: 
      Fanconi anemia is a rare autosomal recessive syndrome comprised of progressive bone marrow
      failure, congenital anomalies and a predisposition to malignancy. The heterozygote rate in
      the United States may be as high as 1 in 300. The mean age for the onset of aplastic anemia
      is approximately eight years. Although improved supportive care has prolonged the survival of
      these patients from only a few years from the diagnosis of bone marrow failure, the mean age
      of death is still approximately 24 years of age. Most patients die from complications of bone
      marrow failure including bleeding, or infection, or from malignancy or complications of stem
      cell transplantation. In a recent 20 year review of patients in the Fanconi anemia registry,
      the actual risk of developing leukemia or other cancers was approximately 30%.

      The diagnosis of Fanconi anemia initially rested upon finding the combination of bone marrow
      failure with congenital anomalies. These anomalies include cafe au lait spots and/or hypo
      pigmentation of the skin, short stature, upper limb malformations (often involving the thumb
      or radius), renal and gastrointestinal abnormalities, microcephaly, and characteristic facies
      with a broad nasal base, epicanthal folds, narrow set and small eyes and micrognathia. The
      bone marrow failure is characterized by slow progression to severe bone marrow aplasia and
      pancytopenia, stress erythropoiesis with fetal features including macrocytosis, elevated
      hemoglobin F, and i antigen expression. Attempts to culture bone marrow progenitors in vitro
      from patients with Fanconi anemia demonstrates decreased numbers of myeloid and erythroid
      colonies (CFU) consistent with clinical bone marrow failure.

      Fanconi anemia cells appear to have a defect in DNA repair that leads to increased
      spontaneous chromosomal breakage. This feature increases the susceptibility of Fanconi anemia
      cells to DNA bifunctional cross-linking agents such as mitomycin C and diepoxybutane (DEB).
      The diagnosis of Fanconi anemia now relies upon detecting increased chromosomal breakage
      after in vitro treatment with DEB. 11 Similarly, cells cultured from patients with Fanconi
      anemia display increased susceptibility to the cytotoxicity of mitomycin C. More recently,
      cells from patients with Fanconi anemia have been demonstrated to display G2 phase
      prolongation/arrest, increased sensitivity to toxicity by oxygen, defective p53 induction and
      increased apoptosis.

      Fanconi anemia can be classified into at least thirteen complementation groups by somatic
      cell hybrids. The complementation is based upon correction of the chromosomal sensitivity to
      cross-linking agents in hybrid cells. Twelve independent genes have been cloned and
      characterized within these 13 complementation groups. A loss of function in any of these
      genes including FANC A, B, C, D2, E, F, G, J, L, M, N, and FANC D1 (which is BRCA2) can cause
      Fanconi anemia. However, complementation groups A, C, and G account for approximately 80-85%
      of patients with Fanconi anemia in the United States. Discrete mutations in these genes have
      been identified in families with the disorder. Expression of the complementary cDNA gene in
      the respective Fanconi anemia cells in vitro corrects the increased chromosomal breakage from
      DEB and the increased sensitivity to mitomycin C. Expression of gene products in bone marrow
      progenitors from patients with Fanconi anemia increases survival in in vitro assays.

      The current treatment for Fanconi anemia relies upon hematological support in the form of red
      blood cell and platelet transfusions. Aplastic anemia will transiently respond to androgen
      therapy in 50% of children. G-CSF has also been utilized in published studies from our own
      group to improve the number of myeloid cells in the peripheral circulation. Bone marrow
      transplantation has cured some patients of their bone marrow failure; however, there appears
      to be more toxicity to the conditioning regimens and there may be increased numbers of solid
      tumors post transplant compared to patients without the disorder. Survival five years after a
      matched sibling transplant now exceeds 65% and after an unrelated donor transplant 30%. More
      recent studies in unrelated donor transplant for Fanconi anemia at Cincinnati Children's
      Hospital and the University of Minnesota have reported survival rates approaching those
      observed in matched sibling donor transplants. However, graft failure resulting in death
      remains a major obstacle. The availability of sufficient numbers of (previously purified and
      cryopreserved) autologous HSC for re-infusion after graft failure may prevent this
      complication.

      Finally, gene therapy approaches are being pursued, but to date, there is no evidence for
      cure with this approach in humans, although correction has been reported in murine models.
      These studies are hampered by the fact that mouse knockouts of FA genes do not develop
      spontaneous aplastic anemia and thus are not phenocopies of the human disease. Thus in
      previously reported mouse-studies, gene therapy approaches required ablative total body
      irradiation of the recipient mice to ensure engraftment of the gene corrected stem cells.

      An obvious limitation of Fanconi anemia hematopoietic stem cell gene transfer is that the
      necessary target for genetic manipulation, the hematopoietic stem cell (or its surrogate,
      CD34+ cell) is progressively lost during the development of aplastic anemia. Thus at the time
      of severe aplasia and the greatest need for treatment, target stem cells for genetic
      modification are deficient. Collection of a meaningful number of HSC prior to the onset of
      aplastic anemia for eventual use in a therapeutic gene therapy trial will be explored in the
      study outlined here. Key questions remaining are whether corrected HSC from Fanconi anemia
      patients will engraft after autologous re-infusion without any cyto-reductive treatment of
      the recipient and, if engrafted, whether the corrected cells will demonstrate a proliferative
      advantage over uncorrected stem cells.
    

Intervention name(s): AMD3100; AmCell CliniMACs
Intervention type(s): Drug; Device
Intervention description(s): 240 mcg/kg subcutaneously, minimum of two days; maximum of eight days; CD34+ cell selection from peripheral collection
Intervention MeSH terms: Plerixafor
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Supportive Care