Gene replacement therapy in Bietti crystalline corneoretinal dystrophy:an open-label,single-arm,exploratory trial

Bietti crystalline corneoretinal dystrophy is an inherited retinal disease caused by mutations in CYP4V2,which results in blindness in the working-age population,and there is currently no available treatment.Here,we report the results of the first-in-human clinical trial(NCT04722107)of gene therapy for Bietti crystalline corneoretinal dystrophy,including 12 participants who were followed up for 180-365 days.This open-label,single-arm exploratory trial aimed to assess the safety and efficacy of a recombinant adeno-associated-virus-serotype-2/8 vector encoding the human CYP4V2 protein(rAAV2/8-hCYP4V2).Participants received a single unilateral subretinal injection of 7.5×10^(10)vector genomes of rAAV2/8-hCYP4V2.Overall,73 treatment-emergent adverse events were reported,with the majority(98.6%)being of mild or moderate intensity and considered to be procedure-or corticosteroid-related;no treatment-related serious adverse events or local/systemic immune toxicities were observed.Compared with that measured at baseline,77.8%of the treated eyes showed improvement in best-corrected visual acuity(BCVA)on day 180,with a mean±standard deviation increase of 9.0±10.8 letters in the 9 eyes analyzed(p=0.021).By day 365,80%of the treated eyes showed an increase in BCVA,with a mean increase of 11.0±10.6 letters in the 5 eyes assessed(p=0.125).Importantly,the patients’improvement observed using multifocal electroretinogram,microperimetry,and Visual Function Questionnaire-25 further supported the beneficial effects of the treatment.We conclude that the favorable safety profile and visual improvements identified in this trial encourage the continued development of rAAV2/8-hCYP4V2(named ZVS101e).