Safety and Efficacy Study in Subjects With Leber Congenital Amaurosis

Leber congenital amaurosis (LCA) is a disease where part of the eye (the retina) is severely
diseased. Usually it is detected in affected people within the first few months of life, as
there is significantly poor vision at birth. Cells in the retina are lost over time in people
with LCA, which typically leads to total blindness. There are no pharmacological treatments
available. This study will focus on the form of LCA caused by changes (mutations) in DNA that
makes a certain protein (called the 65 kDa retinal pigment epithelium (RPE)-specific protein,
or RPE65). This can be confirmed by a special method of testing (molecular testing) to verify
the presence of RPE65 gene mutations.

This study uses a gene therapy vector made from an adeno-associated virus (AAV) called
AAV2-hRPE65v2 (voretigene neparovec-rzyl). Gene therapy refers to the incorporation of new
DNA into cells with the goal of supplying a therapeutic gene or a gene that is missing or not
functioning in the cell. The AAV parts of the gene therapy vector work as a delivery vehicle
for providing the normal human RPE65 gene to the cells of the retina. An earlier Phase 1
clinical study of AAV2-hRPE65v2 was conducted based on the demonstration of safety and
effectiveness of the vector in animals with a similar eye disease. The earlier Phase 1
clinical study was a dose-escalation study primarily designed to evaluate safety in humans,
and tested three doses of the vector in twelve children and adults. The safety of injecting
into the second eye was also evaluated. The results from these earlier Phase 1 studies showed
an acceptable safety profile.

This study will deliver AAV2-hRPE65v2 vector (voretigene neparvovec-rzyl) to at least sixteen
intervention group subjects, age three or older; subjects will receive the vector in both
eyes via subretinal injections during surgeries (on separate days). The purpose of this
research study is to assess the efficacy and safety of the AAV2-hRPE65v2 gene therapy vector
(voretigene neparvovec-rzyl) as a possible treatment for LCA due to RPE65 gene mutations. The
control group of at least eight subjects will be able to cross-over to the intervention group
after one year, provided they still meet all eligibility criteria.

Inclusion Criteria:

- Willingness to adhere to protocol and long-term follow-up as evidenced by written
informed consent or parental permission and subject assent (where applicable).

- Diagnosis of LCA due to RPE65 mutations; molecular diagnosis is to be performed, or
confirmed, by a CLIA-approved laboratory.

- Age three years old or older.

- Visual acuity worse than 20/60 (both eyes) and/or visual field less than 20 degrees in
any meridian as measured by a III4e isopter or equivalent (both eyes).

- Sufficient viable retinal cells as determined by non-invasive means, such as optical
coherence tomography (OCT) and/or ophthalmoscopy. Must have either: 1) an area of
retina within the posterior pole of >100 µm thickness shown on OCT; 2) ≥ 3 disc areas
of retina without atrophy or pigmentary degeneration within the posterior pole; or 3)
remaining visual field within 30 degrees of fixation as measured by a III4e isopter or
equivalent.

- Subjects must be evaluable on mobility testing (the primary efficacy endpoint) to be
eligible for the study. Evaluable is defined as: 1) The ability to perform mobility
testing within the luminance range evaluated in the study. Individuals must receive an
accuracy score of ≤ 1 during screening mobility testing at 400 lux or less to be
eligible; individuals with an accuracy score of > 1 on all screening mobility test
runs at 400 lux, or those who refuse to perform mobility testing at screening, will be
excluded. 2) The inability to pass mobility testing at 1 lux. Individuals must fail
screening mobility testing at 1 lux to be eligible; individuals that pass one or more
screening mobility test runs at 1 lux will be excluded.

Exclusion Criteria:

- Unable or unwilling to meet requirements of the study, including receiving bilateral
subretinal vector administrations.

- Any prior participation in a study in which a gene therapy vector was administered.

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

- Use of retinoid compounds or precursors that could potentially interact with the
biochemical activity of the RPE65 enzyme; individuals who discontinue use of these
compounds for 18 months may become eligible.

- Prior intraocular surgery within six months.

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

- Pre-existing eye conditions or complicating systemic diseases that would preclude the
planned surgery or interfere with the interpretation of study. 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). 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). Also excluded would be subjects with
immunodeficiency (acquired or congenital) as there could be susceptibility to
opportunistic infection (such as CMV retinitis).

- Individuals of childbearing potential who are pregnant or unwilling to use effective
contraception for four months following vector administration.

- Individuals incapable of performing mobility testing (the primary efficacy endpoint)
for reason other than poor vision, including physical or attentional limitations.

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

- Subjects will not be excluded based on their gender, race, or ethnicity.