II. SCIENTIFIC SUMMARY 
Scientific Abstracl 
Gaucher disease is the most common lysosomal storage disorder. It is due to an 
inborn error of glycosphingol ipid metabolism resulting from mutations in the gene coding 
for gl ucocerebrosidase (GC) (E.C. 3.2.1.45). The GC gene has been mapped to chromosome 
lq21. More than 20 different mutations have been described in the human GC gene. Two , 
common mutations account for 80% of the mutant alleles. A correlation between the 
genotype and clinical phenotype permits separation of the rare neurodegenerative cases j 
from the more common non-neuronopathic disease. The latter, Type 1 disease, occurs 
commonly among Ashkenazi Jews where it is the most prevalent inherited disorder. Type 
I disease accounts for 90% of the clinical cases of Gaucher disease. All patients with 
Gaucher disease have clinical complications frequently leading to discomfort and 
disability. Complications include hepatospl enomegaly, hyperspl eni sm, anemia, 
thrombocytopenia and degenerative changes in the skeleton. Many patients have aggressive 
disease with clinical presentation early in life marked by profound organomegaly, 
bleeding diatheses, liver failure, esophageal varices, pulmonary compromise, pathologic 
fractures, bone deformity, and an early death. 
There is a need for new forms of therapy to correct this genetic defect. Current 
treatments are either unavailable or prohibitively expensive. The objective of this 
proposal is to evaluate gene therapy for Type 1 Gaucher disease. We propose to perform 
autologous bone marrow transplantation with CD34 + cells transduced by the normal human 
GC gene. Preclinical data in the mouse model of bone marrow transplantation provides 
evidence of efficient transduction of bone marrow stem cells and long term expression of | 
the human gene in their progeny. Expression of the transferred human GC gene in 
macrophages derived from the bone marrow of these animals endures for the life of the 
mice and is about 4 times the endogenous activity. In Gaucher disease, storage of the 
undegraded lipid occurs only in this cell type and the pathology of the disorder is 
mediated by macrophages. Preclinical studies with macrophages from Gaucher patients 
indicate that transduction of human Gaucher macrophages in culture is sufficient to 
correct their activity to within the normal range. These results suggest that gene 
transfer and expression of the GC enzyme in human macrophages is feasible. We have i 
provided evidence that enzymatically competent macrophages are sufficient to treat the ! 
disease by either allogeneic transplantation of normal bone marrow or direct correction 
of macrophage enzymatic activity. We propose to genetically correct CD34 + cells capable 
of reconstituting the whole BM including M0. Transfer of the GC gene to CD34 + cells 
obtained from blood of a Gaucher patient demonstrates a transduction efficiency of 
approximately 20% and expression of enzyme activity to 20-40 times the amount of activity 
in enzyme deficient cells. 
We will transduce CD34 + cells obtained from the blood of Gaucher patients using a 
replication defective retroviral vector called R-GC. The vector carries the human GC 
cDNA. Five (5) patients will be studied over the first year of the study. Patients will 
be transplanted with autologous CD34 + cells that have been genetically corrected. The 
transplanted patient will be assessed for the carriage and expression of the transduced 
gene in peripheral blood leukocytes. GC activity will be used to quantify the extent of 
restoration of enzyme in these cells. The criteria of clinical responsiveness will be 
the ability to withdraw enzyme following the transplantation of patients previously 
treated with enzyme or clinical reversal of symptoms in the patient not receiving enzyme. 
Clinical parameters to be followed include organ size, hemoglobin/hematocrit, platelet 
count, plasma angio-tensin converting enzyme concentration, serum non-tartrate 
inhibitable acid phosphatase, bone marrow morphology and bone structure by x-rays and 
scans. 
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Recombinant DNA Research, Volume 17 
