Patients with Leber’s congenital amaurosis (LCA) and retinitis pigmentosa (RP) have been able to gain significant mobility and light sensitivity after receiving gene therapy.
In a Phase 3 clinical trial by Spark Therapeutics, 29 patients received the gene therapy, which used a virus to transport a functioning copy of the RPE65 gene into their photoreceptor cells.
The RPE65 gene codes for a protein involved in the chemical cycle activated when light hits photosensitive pigments in the eye.
A malfunctioning copy of this gene causes approximately 16% of cases of LCA and 2% of cases of recessive RP.
One year after receiving the therapy, almost 90% of subjects improved their mobility to the maximum possible when navigating a course.
This group’s light sensitivity also improved to an average of nearly 200 times, and they were able to see an average of four and a half extra letters in a visual acuity test.
However, one subject did report a serious adverse reaction after receiving the treatment, but this was attributed to the surgical procedure rather than the gene therapy, Spark Therapeutics noted in the announcement.
The positive effects of the gene therapy appear to last for the three years that patients in a similar trial have been followed for, the company said.
Spark Therapeutics president, Dr Katherine High, explained that: “[We] have seen 27 of 29 – or 93% – of subjects respond, importantly demonstrating gains to visual function.”
She highlighted that her company: “will continue to analyse data from our clinical trials in order to further elucidate the potential for long-lasting benefit that [the gene therapy] may have on the lives of patients with RPE65-mediated inherited retinal disease.”
The gene therapy has received “orphan product” designation by the European Medicines Agency, which governs the regulatory approval of treatments for rare diseases.