A Follow-on Study for Second-Eye Treatment for Participants Previously Treated With Gene Therapy for X-Linked Retinitis Pigmentosa (XLRP)

Primary outcomes

1. Number of Participants With Adverse Events (AE)

   Time frame: From baseline up to 5.5 years

   An AE is any untoward medical occurrence in a clinical study participant administered a pharmaceutical (investigational or non investigational) product. An AE does not necessarily have a causal relationship with the intervention. An AE can be any unfavorable and unintended sign (including an abnormal finding), symptom, or disease temporally associated with the use of a medicinal (investigational or non investigational) product, whether or not related to that medicinal (investigational or non investigational) product.

2. Change from Baseline in Best Corrected Visual Acuity (BCVA) by Early Treatment Diabetic Retinopathy Study (ETDRS) Chart Letter Scores

   Time frame: Baseline, Months 12, 24, 36, 48 and 60

   Change from baseline in BCVA by ETDRS chart letter scores in monocular assessment of the second treated eye will be assessed. BCVA was measured using the ETDRS Scale (ranging from 0 to 100 letters) in the study eye. An increase in the number of letters read correctly means that vision has improved and vice-versa.

3. Change from Baseline in Low Luminance Visual Acuity (LLVA) by ETDRS Chart Letter Score

   Time frame: Baseline, Months 12, 24, 36, 48 and 60

   Change in LLVA by ETDRS chart letter scores from baseline in monocular assessment of second treated eye will be assessed. Visual function assessments included LLVA assessment in each eye by ETDRS letters. The letter score ranges from 0 (worse score) to 100 (best score), and a gain in LLVA from baseline indicates an improvement in visual acuity.