MeiraGTx Reports Experimental Gene Therapy Improves Vision in X-Linked Retinitis Pigmentosa Patients

Rare Daily Staff

MeiraGTx reported six-month data from the ongoing phase 1/2 clinical trial their experimental gene therapy in development for the treatment of patients with X-linked retinitis pigmentosa with genetically confirmed variants in the RPGR gene.

X-linked retinitis pigmentosa (XLRP) is the most severe form of retinitis pigmentosa, a group of inherited retinal diseases characterized by progressive retinal degeneration and vision loss. XLRP is caused by mutations in the RPGR gene that affects boys and young men. The condition begins with night blindness and is followed by progressive constriction of the field of vision. There are currently no approved treatments for XLRP.

In the ten-person dose escalation phase of the trial, seven patients in the low and medium dose cohorts saw significant improvement in vision, and the gene therapy, AAV-RPGR, was generally well tolerated. These initial results from the trial are being presented as a late-breaker oral presentation at the American Society of Retina Specialists 2020 Virtual Annual Meeting.

The ongoing phase 1/2 clinical trial consists of three phases: dose-escalation, dose-confirmation, and dose-expansion. In the dose-escalation phase, 10 adults were administered low, intermediate, or high dose AAV-RPGR. Each patient was treated with subretinal delivery of AAV-RPGR in the eye that was more affected at baseline. The patient’s other eye served as an untreated control. The primary endpoint of the trial is safety, with secondary endpoints assessing changes in visual function at pre-specified time points post-treatment. Baseline values were determined in triplicate.

At six months, significant improvement in retinal sensitivity was demonstrated in patients treated with low and intermediate dose AAV-RPGR. Improvement was evident at first post-treatment perimetry assessments at three months, with improvements generally sustained or increased at six months. Significant differences were observed in retinal sensitivity between treated and untreated eyes over time. Based on the robust safety and efficacy signals observed in the dose escalation portion of the study, the low and intermediate doses were selected for use in the ongoing randomized, controlled dose-expansion phase of the trial.

“These early data suggest AAV-RPGR has the potential to address some of the key functional manifestations of this severe disease for which there is no currently available therapy,” said Alexandria Forbes, president and CEO of MeiraGTx.

MeiraGTx and Janssen Pharmaceuticals are jointly developing AAV-RPGR as part of a broader collaboration to develop and commercialize gene therapies for the treatment of inherited retinal diseases that was struck in February 2019.

Based on the encouraging safety and efficacy data demonstrated in the phase 1/2 trial to date, MeiraGTx and Janssen expect to advance AAV-RPGR into a phase 3 clinical trial for the treatment of patients with XLRP caused by mutations in RPGR gene.

AAV-RPGR has been granted Fast Track and Orphan Drug designations by the U.S. Food and Drug Administration and PRIME, ATMP and Orphan designations by the European Medicines Agency.

Photo: Alexandria Forbes, president and CEO of MeiraGTx