MeiraGTx and Janssen Pharmaceuticals have announced nine-month data from the ongoing phase I/II trial of their investigational gene therapy for X-linked retinitis pigmentosa (XLRP).

XLRP is a progressive condition that causes deterioration of the visual field and is the most severe form of retinitis pigmentosa – a group of inherited retinal diseases. The most frequent cause of XLRP is disease-causing variants in the RPGR gene, accounting for more than 70% of XLRP cases.

In nine-month data from the phase I/II trial, MeiraGTx and Janssen’s investigational gene therapy AAV-RPGR continued to demonstrate significant improvement in retinal sensitivity in treated eyes, across both the low and intermediate dose cohorts.

In addition, data from the assessment of vision-guided mobility carried out at the nine-month timepoint demonstrated a significant improvement in walk time, compared to baseline in treated eyes compared to untreated eyes in the low and intermediate dose cohorts.

“There are currently no treatment options for XLRP, and vision in patients suffering from this disease inevitably declines over time,” said Michel Michaelides, trial investigator, consultant pphthalmologist, Moorfields Eye Hospital and professor of Ophthalmology, University College London.

“Data from this clinical trial demonstrate that patients treated with AAV-RPGR had significant and sustained improvement in retinal sensitivity, as well as improved ability to navigate in low light conditions. These exciting results continue to suggest that AAV-RPGR has the potential to be a much-needed and important treatment option for those living with XLRP,” he added.

MeiraGTx and Janssen are jointly developing AAV-RPGR as part of a wider collaboration to develop and commercialise gene therapies for the treatment of inherited retinal diseases.