Key Inclusion Criteria: * Are willing and able to give informed consent for participation in the study. * Have a documented genetically-confirmed diagnosis of CHM. * Have active disease clinically visible within the macular region in the study eye. * Have a BCVA of 34-73 ETDRS letters (equivalent to worse than or equal to 6/12 or 20/40 Snellen acuity, but better than or equal to 6/60 or 20/200 Snellen acuity) in the study eye. Key Exclusion Criteria: * Have a history of amblyopia in the eligible eye. * Have had previous intraocular surgery performed in the study eye within 3 months of Visit 1. * Have any other significant ocular or non-ocular disease/disorder which, in the opinion of the investigator, may either put the participants at risk because of participation in the study, or may influence the results of the study, or the participant's ability to participate in the study. * Have participated in another research study involving an investigational product in the past 12 weeks or received a gene/cell-based therapy at any time previously. * Are unwilling to use barrier contraception methods, or abstain from sexual intercourse, for a period of 3 months, if treated with AAV2-REP1. NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.