This is a study designed to evaluate the effectiveness, safety and tolerability of QR-421a in different dose levels in participants with advanced vision loss due to mutations in exon 13 of USH2A gene. QR-421a is designed to specifically target mutations in exon 13 of USH2A gene which cause Retinitis Pigmentosa (RP) and overcome this genetic defect in the DNA to restore this important protein.

Approximately 81 participants are planned to be recruited for this study worldwide. Participants will be 12 years or older, study period is anticipated to be approximately 34 months and duration of the patient participation will be approximately 27 months (up to 12 weeks of screening and 24 months treatment).