Pharmacodynamic Study of Emixustat Hydrochloride in Subjects With Macular Atrophy Secondary to Stargardt Disease

Inclusion Criteria, including, but not limited to: * Clinical diagnosis of macular atrophy (MA) secondary to Stargardt disease (STGD) in one or both eyes * At least 2 pathogenic mutations of the ABCA4 gene * Early Treatment Diabetic Retinopathy Study BCVA of ≥ 20 letters (approximately ≥ 20/400 Snellen) in the study eye * Adequate clarity of ocular media and adequate pupillary dilation to permit good quality imaging of MA in the study eye * Able and willing to provide written informed consent before undergoing any study-related procedures * Able to reliably administer oral medication by self or with available assistance Exclusion Criteria, including, but not limited to: * Macular atrophy associated with a condition other than STGD in either eye. * Presence in either eye of an active ocular disease that in the opinion of the Investigator compromises or confounds visual function. * History of any intraocular or ocular surface surgery in either eye within 3 months of screening. * Current or previous participation in an interventional study to treat STGD using gene therapy or stem cell therapy at any time, or participation in an interventional study of a vitamin A derivative ≤3 months prior to screening. * Pre-specified laboratory abnormalities at screening * Presence of other medical or ophthalmic disease, physical examination finding, or clinical laboratory finding that in the opinion of the Investigator may contraindicate the use of an investigational drug and place the subject at risk * Current or history of cancer (except for adequately treated basal cell or squamous cell carcinoma of the skin) within 1 year of screening * History of myocardial infarction, stroke, unstable ischemic heart disease, uncontrolled cardiac arrhythmia, or hospitalization for congestive heart failure within 6 months of screening. * Anticipated hospitalization for a medical/surgical procedure(s) that could result in interruption/premature cessation of study treatment or participation. * Electrocardiogram with a clinically significant abnormal finding * Female subjects who are pregnant or lactating * Female subjects of childbearing potential or male subjects who are not surgically sterile who are not willing to practice a medically accepted method of birth control with their sexual partner from screening through 30 days after the final dose of study drug