Study to Evaluate Sepofarsen in Subjects With Leber Congenital Amaurosis (LCA) Type 10 (HYPERION)

Inclusion Criteria:

1. Confirmed clinical diagnosis of LCA10 and a molecular diagnosis of homozygosity orcompound heterozygosity for the c.2991+1655A>G mutation in CEP290.

2. Adults: >=18 years / Minors: 6 to <18 years.

3. BCVA (FrACT) equal to or worse than logMAR +0.4 (approximate Snellen equivalent 20/50) to +2.9 logMAR based on quantifiable, reliable FrACT. LP subjects withdocumented evidence of prior better vision eligible.

4. Symmetrical disease between the two eyes as defined by a BCVA (FrACT) within 0.2logMAR at baseline.

5. Detectable ONL in the macular area as determined by the CRC at Screening.

Exclusion Criteria:

1. Mutations in genes other than the CEP290 gene associated with other IRD diseases orsyndromes.

2. Presence of any ocular pathology in either eye that may make comparison of the eyesnot feasible.

3. Presence of unstable concurrent CME, or subject started on (or changed dose of)topical or systemic carbonic anhydrase inhibitor treatment in the 3 months prior toenrollment. CME is allowed if stable for 3 months (with or without treatment).

4. Presence of any clinically significant lens opacities/cataracts based on the AREDSlens grading scale.

5. Any prior receipt of genetic or stem-cell therapy for ocular or non-ocular disease.