The purpose of this open-label, multicenter study is to determine the long-term safety, pharmacokinetics and effects of ALK-001 (C20-D3-retinyl acetate) on the progression of Stargardt disease. This study is an extension of NCT02402660 and enrolls participants who are at least 8 years old. Enrollment is by invitation only.

Funding Source - FDA OOPD

Simplified Inclusion Criteria:

• Clinical diagnosis of Stargardt disease (STGD1)
• Has at least two ABCA4 disease-causing mutations, unless authorized by sponsor
• Has a best-corrected visual acuity (BCVA) greater than approximately 20/160 in at least one eye
• Healthy as judged by investigator
• Able and willing to comply with study requirements, restrictions and instructions and is likely to complete the 24-month study
• Has been invited to participate in this extension, and has signed and dated the informed consent forms (or assent where appropriate) to participate
• Female of childbearing potential has signed the attestation on contraception requirements

Simplified Exclusion Criteria:

• Is lactating or pregnant
• Has a medical condition likely to prevent compliance with the protocol and/or interfere with absorption of ALK-001 or performance of study procedures
• Has abnormal laboratory result(s) at screening
• Has an ocular disorder that may confound ocular assessments
• Has a history of ocular intervention within 90 days of screening