Safety Study in Subjects With Leber Congenital Amaurosis

Leber Congenital Amaurosis (LCA)is a severe early onset retinal degeneration. Diagnosis is
usually made during the first few months of life in infants who present with severely
impaired vision, abnormal eye movements (nystagmus) and abnormal electroretinograms (ERG)
indicating decreased retinal function. There is an inevitable progression to total blindness
in these individuals due to death of photoreceptor cells. There is presently no treatment for
this disease. The primary objective of this study is to determine the safety and tolerability
of subretinal administration of AAV2-hRPE65v2 to subjects with LCA due to confirmed biallelic
RPE65 mutations. The secondary objective is to assess the objective clinical measures of
efficacy in human subjects.

Inclusion Criteria:

- Male and female subjects of any ethnic group are eligible for participation in this
study, providing they meet the following criteria:

1. Must be willing to adhere to protocol and companion protocol for long-term
follow-up as evidenced by written informed consent or parental permission and
subject assent.

2. Adults and children diagnosed with LCA.

3. Molecular diagnosis of LCA due to RPE65 mutations (homozygotes or compound
heterozygotes) by a CLIA-approved laboratory.

4. Age eight years old or older at the time of administration.

5. Visual acuity ≤ 20/160 or visual field less than 20 degrees in the eye to be
injected.

Exclusion Criteria:

SUBJECTS WILL NOT BE EXCLUDED BASED ON THEIR GENDER, RACE OR ETHNICITY.

Subjects who meet any of the following conditions are excluded from the clinical study:

1. Unable or unwilling to meet requirements of the study.

2. Participation in a clinical study with an investigational drug in the past six months.

3. Pre-existing eye conditions that would preclude the planned surgery or interfere with
the interpretation of study endpoints (for example, glaucoma, corneal or lenticular
opacities).

4. Lack of sufficient viable retinal cells as determined by non-invasive means, such as
optical coherence tomography (OCT) and/or ophthalmoscopy. Specifically, if indirect
ophthalmoscopy reveals less than 1 disc area of retina which is not involved by
complete retinal degeneration (indicated by geographic atrophy, thinning with tapetal
sheen, or confluent intraretinal pigment migration), these eyes will be excluded. In
addition, in eyes where optical coherence tomography (OCT) scans of sufficient quality
can be obtained, areas of retina with thickness measurements less than 100 um, or
absence of neural retina, will not be targeted for delivery of AAV2-hRPE65v2.

5. Complicating systemic diseases or clinically significant abnormal baseline laboratory
values. Complicating systemic diseases would include those in which the disease
itself, or the treatment for the disease, can alter ocular function. Examples are
malignancies whose treatment could affect central nervous system function (for
example, radiation treatment of the orbit; leukemia with CNS/optic nerve involvement).
Also excluded would be subjects with immuno-compromising diseases, as there could be
susceptibility to opportunistic infection (such as CMV retinitis). Subjects with
diabetes or sickle cell disease would be excluded if they had any manifestation of
advanced retinopathy (e.g. macular edema or proliferative changes). Subjects with
juvenile rheumatoid arthritis could be excluded due to increased infection risk after
surgery due to poor wound healing. Subjects who are positive for hepatitis B, C, and
HIV will be excluded.

6. Prior ocular surgery within six months.

7. Known sensitivity to medications planned for use in the peri-operative period.

8. Individuals of childbearing potential who are pregnant or unwilling to use effective
contraception for the duration of the study.

9. Any other condition that would not allow the potential subject to complete follow-up
examinations during the course of the study and, in the opinion of the investigator,
makes the potential subject unsuitable for the study.

10. Subjects will be excluded if immunological studies show presence of neutralizing
antibodies to AAV2 above 1:1000.