An Open-label, Phase 1/2 Trial of Gene Therapy 4D-125 in Males with X-linked Retinitis Pigmentosa (XLRP) Caused by Mutations in the RPGR Gene

Primary Objective

The study looks to evaluate the following objectives for the two parallel parts: Natural History • Characterize the population of patients with XLRP aged 6 years and older, and evaluate natural progression of disease. Phase 1/2 • Evaluate the safety and tolerability of 4D-125 following IVT administration. • Identify the appropriate dose level of 4D-125 for further evaluation. • Assess the relationship between the dose of 4D-125 and indicators of visual function. • Evaluate clinical activity and impact on health-related quality of life (HRQOL) of 4D-125 in males with XLRP.

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This is a multicenter study with two parallel parts: an observational Natural History Cohort and an open-label, prospective interventional trial in males with non-syndromic XLRP due to mutations in RPGR. The target population is restricted to avoid confounding atypical presentation in female patients. The Natural History Cohort seeks to examine the course of disease and aid in the development of clinical endpoints for male adult and pediatric patients with XLRP who do not seek experimental therapy in this study. The Phase 1/2 trial is designed to assess the safety and tolerability of 4D-125 following IVT administration; preliminary clinical efficacy will also be examined.

Main Procedures Involved: As the procedures involved in each part of the study vary, please inquire further for a more detailed explananation.

Duration of Participation: Prospective subjects will be screened for eligibility (up to 90 days). Maximum duration of participation in the Natural History Cohort is 12 months (15 months if genetic testing is required). Eligible subjects who enroll in the interventional cohorts will be monitored for 24 months following the subject’s last IVT administration. The end of the trial is defined as the date when the last subject completes the last protocol-specified assessment or otherwise discontinues participation.


6 to 100 years

Type of Study


Principal Investigator
Photograph of Marc Mathias,  MD

Marc Mathias, MD

Study ID

Protocol Number: 20-0130

More information available at NCT04517149


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