The goal of this phase 1 clinical trial is to learn about the safety and efficacy of a gene therapy, VG901, in patients with a rare disorder of the eye called Retinitis Pigmentosa. The main questions the study aims to answer are: * What is the best tolerated dose and are there any side effects, in particular any inflammatory reactions post drug administration? * Are there any early signs of efficacy on visual function? Participants will be administered a single intravitreal dose of VG901 into the most affected eye through a syringe and followed up for a year to monitor safety and efficacy. There will be two cohorts of participants in this study. Study Cohort 1 will receive the low dose and Study Cohort 2 will receive the high dose as specified in the Protocol.