Gene Transfer Therapy for Severe Combined Immunodeficieny Disease (SCID) Due to Adenosine Deaminase (ADA) Deficiency

This is a clinical gene transfer study that aims to verify the safety and efficacy of the use
of retroviral vectors to introduce the human adenosine deaminase (ADA) gene into the
hematopoietic progenitors of patients affected with severe combined immunodeficiency due to
ADA deficiency. In addition, this protocol will examine the effects of the ADA gene transfer
on the immune system of treated patients. Patients with ADA deficiency and ineligible for
matched sibling allogeneic bone marrow transplantation are eligible to participate to the
study. To increase engraftment and selective advantage of gene-corrected cells, busulfan will
be used as cytoreduction agent and enzyme replacement (PEG-ADA) therapy will be discontinued.
CD34+ hematopoietic progenitors will be isolated from the patient bone marrow or cord blood,
exposed to retroviral vector-mediated gene transfer and reinfused into the patient through a
peripheral vein. Clinical, immunological and molecular follow-up studies will assess safety,
toxicity, and efficacy of the procedure.

- INCLUSION CRITERIA:

Patients will be enrolled into this study if they fulfill the following three criteria:

A. Patients of age greater than or equal to 1 month with a diagnosis of ADA-deficiency
based on:

1. Confirmed absence (less than 3% of normal levels) of ADA enzymatic activity in
peripheral blood or (for neonates) umbilical cord erythrocytes and/or leukocytes, or
in cultured fetal cells derived from either chorionic villus biopsy or amniocentesis,
prior to institution of enzyme replacement therapy.

AND

2. Evidence of severe combined immunodeficiency based on either:

Family history of first order relative with ADA deficiency and clinical and laboratory
evidence of severe immunologic deficiency

OR

Evidence of severe immunologic deficiency in subject based on lymphopenia (absolute
lymphocyte count less than 200) or severely decreased T lymphocyte blastogenic
responses to phytohemagglutinin (cpm less than 5,000) prior to institution of immune
restorative therapy

OR

3. Evidence of genetic mutations affecting the ADA gene as determined by the CLIA
certified laboratory and clinical evidence of combined immunodeficiency based on
lymphopenia (absolute lymphocyte counts less than 2SD of age-matched control values)
and hypogammaglobulinemia (less than 2SD of age-matched control values) or lack of
specific antibody response to vaccination. Evidence of life-threatening illness
(increased frequency and/or severity of infections resulting in hospitalization and/or
the administration of intravenous antibiotics) is necessary for patients to be
eligible under this criterion.

B. Patients ineligible for allogeneic (matched sibling) bone marrow transplantation (BMT)
based on:

1. Absence of a medically eligible HLA-identical sibling with normal immune function who
may serve as an allogenic bone marrow donor

OR

2. Election by the parents or the adult patients to forgo allogeneic BMT in favor of
PEG-ADA enzyme therapy after being invited to discuss alternative treatment options
with a physician not connected with the protocol.

C. Written informed consent according to guidelines of the NHGRI IRB, NIH or the
Committee on Clinical Investigations (CCI) at Children's Hospital Los Angeles (CHLA).

This study is also open to delayed/late onset ADA-deficient patients who fulfill the
criteria A, B.1, and C and who are not receiving PEG-ADA treatment after being invited
to discuss all alternative treatment options with a physician not connected with the
protocol.

EXCLUSION CRITERIA:

Age:

a. Age less than 1 month

Hematologic:

1. Anemia (hemoglobin less than 10.5 mg/dl, for subjects 2 years of age or less or
hemoglobin less than 11.5 mg/dl for subjects older than 2 years of age in the
presence of normal iron studies).

2. Neutropenia

i. absolute granulocyte count <500/mm (3) or

ii. absolute granulocyte count 500-999/mm (3) (ages 1-12 months) or 500-1,499/mm (3)
for ages >1 year) and bone marrow studies showing myelodysplasia or other gross
abnormalities.

c. Thrombocytopenia (platelet count less than 150,000 mm(3) at any age)

d. PT or PTT greater than 2 times normal.

e. Cytogenic abnormalities on peripheral blood.

Infectious:

a. Evidence of active opportunistic infection or infection with HIV-1, hepatitis B,
CMV or parvovirus B19 by DNA PCR at time of assessment.

Pulmonary:

1. Resting O2 saturation by pulse oximetry less than 95%.

2. Chest X-ray indicating active or progressive pulmonary disease.

Cardiac:

1. Abnormal electrocardiogram (EKG) indicating cardiac pathology.

2. Uncorrected congenital cardiac malformation.

3. Active cardiac disease, including clinical evidence of congestive heart failure,
cyanosis, or hypotension.

Neurologic:

1. Significant neurologic abnormality by examination.

2. Uncontrolled seizure disorder.

Renal:

1. Renal insufficiency: for pediatric patients serum creatinine greater than or
equal to 1.2 mg/dl, or greater than or equal to 3+ proteinuria, for adults values
at grades greater than or equal to of the NCI Common Toxicity Criteria (CTC).

2. Abnormal serum sodium, potassium, calcium, magnesium, phosphate at grade III or
IV by DAIDS Toxicity Scale or NCI CTC.

Hepatic/Gl:

1. Serum transaminases greater than 5 times normal.

2. Serum bilirubin greater than 3.0 mg/dl.

3. Serum glucose greater than 250 mg/dl.

4. Intractable severe diarrhea.

Oncologic:

a. Evidence of active malignant disease other than dermatofibrosarcoma protuberans
(DFSP)

General:

1. Expected survival less than 6 months.

2. Major congenital anomaly.

3. Subject pregnant.

4. Medically eligible HLA-identical sibling available.

5. Known hypersensitivity to busulfan.

6. Other conditions which in the opinion of the P.I. or co-investigators,
contra-indicate infusion of transduced cells or ability to follow protocol.