Trial design
The STAR study was prospectively registered in EudraCT as Participant randomization into a treatment or control group occurred at visit 1, during which time a surgical date was scheduled (visit 2) for participants in the treatment group. The requirement of a vitrectomy for administration of the vector meant that a sham treatment was not ethically feasible, and all members of the control group were instead given dates for ‘projected’ surgical visits. This ethical consideration meant that the sponsor, investigator and participants were all unblinded to the surgical procedure for the treatment group; however, for the two doses of timrepigene emparvovec (1.0 × 10Visit 2, the projected or actual surgical visit, corresponded to day 0 of the study timeline and took place no later than 8 weeks after visit 1. Visits 3 and 4 were postoperative follow-up visits on day 1 and day 7 that were conducted in-person for participants in a treatment group and by telephone contact for participants in the control group. All participants, regardless of treatment randomization, were planned to attend visits 5–8 on-site, which were scheduled for 1 month, 4 months, 8 months and 12 months after visit 2, respectively. Participants were considered to have completed the study after their eighth study visit.The investigators (listed in Supplementary Table 