MND-ADA Transduction of CD34+ Cells From Children With ADA-SCID

The proposed study population is affected with adenosine deaminase-deficient severe combined
immune deficiency (ADA-SCID), an autosomal recessive congenital immune deficiency. The basis
of the proposed study (and product) is retroviral-mediated transduction of autologous, bone
marrow derived CD34+ hematopoietic progenitor cells with the MND-ADA retroviral vector in a 5
day cell processing period. Transduction is followed by infusion of the washed cells into
subjects not receiving enzyme replacement therapy with Polyethylene-conjugated ADA (PEG-ADA,
ADAGEN7) who have had their PEG-ADA injections discontinued, and have undergone bone marrow
cytoreductive therapy with a single non-ablative treatment course of Busulfan. The dose of
cells infused will be determined by the patient-to-patient variation of the number of
progenitors available from individual patients. Statistical analyses post-infusion will help
determine the dose-response of the number of cells infused to the level of engraftment and
resulting level of immune reconstitution. Following cellular infusion, a primary clinical
end-point will be the absolute numbers of T and B lymphocytes containing the transduced ADA
gene by quantitative, real-time PCR analyses. Measurement of blood mononuclear cell ADA
enzyme levels will be analyzed. Based on the degree of marking of lymphocytes and of
granulocytes, the selective advantage of lymphocytes may be gauged. Subjects will be
monitored for the development of clonal proliferation, under the 15 year plan required by the
FDA. One major aim of the study will be to see if subjects can remain off PEG-ADA and
maintain protective immunity from the population of transduced lymphocytes arising from
transduced progenitors. If sufficient gene-modified cells result, and PEG-ADA enzyme
replacement therapy can be permanently discontinued, the advantage of this therapeutic
approach may change the standard of care for these patients.

Inclusion Criteria:

1. Children > 1.0 months of age with a diagnosis of ADA-deficient SCID based on:

- Confirmed absence (<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

- 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 <200) or severely decreased T lymphocyte blastogenic
responses to phytohemagglutinin (deltaCPM<5,000), prior to institution of immune
restorative therapy.

OR

- Fulfillment of criterion:

- A in addition to evidence of genetic mutations affecting the ADA gene as
determined by a CLIA certified laboratory and clinical evidence of combined
immunodeficiency based on lymphopenia (absolute lymphocyte counts <2SD of
age-matched control values) and hypogammaglobulinemia (<2SD of age-matched
control values) or lack of specific antibody response to vaccination. In
addition, for patients to be eligible under this criterion, they must
present with a clinical history indicating life-threatening illness
characterized by increased frequency and/or severity of infections resulting
in hospitalization and/or the administration of intravenous antibiotics, for
bacterial or opportunistic infection.

2. Ineligible for allogeneic (matched sibling) bone marrow transplantation (BMT):

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

3. Written informed consent according to guidelines of the Institutional Review Board
(IRB) at the University of California Los Angeles (UCLA).

This study is also open to delayed/late onset ADA-deficient patients who fulfill the
criteria 1, 2.A, and 3 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:

1. Age less than 1 month

2. Hematologic

a. Anemia (hemoglobin <10.5 mg/dl at <2 years of age, or < 11.5 at >2 years of
age,with normal serum iron studies). b. Neutropenia i. absolute granulocyte count
<500/mm3 or ii. absolute granulocyte count 500-999/mm3 (1 month - 1 year of age) or
500-1499/mm3 (> 1 year of age)] and bone marrow aspirate and biopsy showing
myelodysplasia or other gross abnormality. c. Thrombocytopenia (platelet count
150,000/mm3, at any age). d. PT or PTT >2X normal. e. Cytogenetic abnormalities on
peripheral blood, or on cells collected by amniocentesis, if diagnosed in utero.

3. Infectious

a. Evidence of active opportunistic infection or infection with HIV-1, hepatitis B,
CMV or parvovirus B 19 by DNA PCR at time of assessment.

4. Pulmonary

1. Resting O2 saturation by pulse oximetry <95%.

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

5. 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, hypotension.

6. Neurologic

1. Significant neurologic abnormality by examination.

2. Uncontrolled seizure disorder.

7. Renal

1. Renal insufficiency: serum creatinine > or = 1.2 mg/dl, or > or = 3+ proteinuria.

2. Abnormal serum sodium, potassium, calcium, magnesium, phosphate at grade III or
IV by Division of AIDS Toxicity Scale.

8. Hepatic/GI:

1. Serum transaminases > 5X normal.

2. Serum bilirubin > 3.0 mg/dl.

3. Serum glucose > 250mg/dl.

4. Intractable severe diarrhea.

9. Oncologic (see below*)

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

2. Evidence of DFSP expected to require anti-neoplastic therapy within the 5 years
following the infusion of genetically corrected cells

3. Evidence of DFSP expected to be life limiting within the 5 years following the
infusion of genetically corrected cells

10. Known sensitivity to Busulfan

11. General

1. Expected survival <6 months.

2. Pregnant.

3. Major congenital anomaly.

4. Medically eligible HLA-matched sibling.

5. Other conditions which in the opinion of the P.I. or co-investigators,
contra-indicate infusion of transduced cells or indicate patient's inability to
follow protocol.