GenSight Biologics announced it has finished a pre-submission meeting with the European Medicines Agency (EMA), a key step in filing a request for the approval of Lumevoq, its gene therapy for Leber hereditary optic neuropathy (LHON).

The company expects to file the request, called a marketing authorization application (MAA), in September.

“We are excited about our progress towards our regulatory filing of Lumevoq in Europe, as this brings us closer to making a novel, effective and safe treatment available to a large proportion of LHON patients,” Bernard Gilly, co-founder and CEO of GenSight Biologics, said in a press release.

“We have been and continue to be extremely grateful for the support and guidance we have received from the European authorities,” Gilly added.

Lumevoq (lenadogene nolparvovec, previously GS010) is a gene therapy designed to improve visual acuity among those with LHON, a rare genetic mitochondrial disease that causes vision loss.

The therapy works by using a harmless virus vector called adeno-associated virus 2 (AAV2) to deliver a functional copy of ND4 — the mitochondrial gene that is faulty in patients with LHON — to patients’ cells. It is administered by an intravitreal injection, one into the eye.

Reported findings from two completed Phase 3 trials — RESCUE (NCT02652767) and REVERSE (NCT02652780) — showed that a single intravitreal injection of Lumevoq led to sustained improvements in visual acuity and quality of life in patients with LHON up to 96 weeks post-injection.

People who completed both trials have been invited to participate in a three-year follow-up study.

GenSight also launched a natural history study called REALITY (NCT03295071) to document changes in visual acuity and other clinical parameters in up to 50 untreated LHON patients. The study may still be recruiting participants at several sites across the U.S. and Europe.

GenSight will use data from REALITY as a basis for comparison with patients treated with Lumevoq in REVERSE and RESCUE. Interim data from REALITY highlighted marked improvements with the gene therapy’s use; 15 patients in REALITY in the December update had an initial decline in visual acuity with no evidence of change for the better.

The company is also conducting animal studies to complement the findings from its two trials.

At the pre-submission meeting, EMA provided the company with the information needed for its planned MAA submission. The agency also provided additional guidance on several administrative aspects, and suggestions on topics that should be discussed when GenSight and regulators who will be considering its application are set to meet in June.