Michel Michaelides, MD, of UCL Institute of Ophthalmology; Moorfields Eye Hospital provides an overview of X-linked retinitis pigmentosa (XLRP), including its symptoms, common treatments, as well as a summary of the latest interim data from the MGT009 trial.
XLRP is an inherited rare condition caused by mutations in the RPGR gene on the X chromosome which causes progressive vision loss in males. As Dr. Michaelides explains, the most common first symptom is loss of night vision or clumsiness due to loss of peripheral vision. Improvements in genetic testing have allowed individuals suspected of having this condition to be diagnosed more quickly.
Individuals with XLRP also tend to develop cataracts early in life. Macular edema is another common complication with XLRP. While there is currently no approved cure for XLRP, there are three ongoing phase I and phase II gene therapy trials underway, including the phase I/II MGT009 trial.
The MGT009 trial is a multi-center, open-label study investigating AAV-RPGR gene therapy for the treatment of patients with XLRP. Each patient is being treated with subretinal delivery of AAV-RPGR in the eye that was more affected at time of baseline. The patient’s other eye is serving as the control. In this trial, adults are administered a low, intermediate, or high dose of AAV-RPGR, and the primary endpoint is safety. As Dr. Michaelides says, the interim analysis is showing the gene therapy to be safe with the adverse events being manageable and mostly related to the surgical procedure. Based on the interim analysis, future studies will be using low and intermediate doses that were shown to be safer and led to improvements in retinal sensitivity.
For more information about XLRP and other rare eye diseases, visit checkrare.com/diseases/ophthalmology