Targeted insertion of an optimized donor DNA is effective in a humanized mouse model of dominant retinitis pigmentosa

Retinitis pigmentosa (RP) affects 1 in 3,000 individuals worldwide, with 30%-40% of cases inherited as autosomal dominant (AD). Mutations in RHO (RP4) are the most common cause of ADRP. Because most RHO mutations exert gain-of-function or dominant-negative effects, conventional gene supplementation is insufficient, requiring mutant allele inactivation. Allele-specific editing is impractical, as each mutation requires a unique therapeutic strategy. We present a mutation-agnostic, RHO-specific approach using adeno-associated viral vector-mediated homology-independent targeted integration (AAV-HITI). Optimized donor DNA design enables targeted integration and efficient transgene expression from the endogenous RHO locus. In a humanized RP4 mouse model harboring the RHO P23H mutant allele alongside an endogenous wild-type mouse Rho allele, AAV-HITI significantly improves retinal structure, function, and visual acuity up to 1 year post-treatment. Comprehensive molecular analyses characterize on-target editing in mouse retina and off-target editing in a human cell line. These findings establish an effective, human-centric AAV-HITI platform for RP4 and support its evaluation in this and other dominant genetic conditions.