French gene therapy company GenSight has announced its GS010 drug indicated for eye condition Leber Hereditary Optic Neuropathy (LHON) failed to meet the primary endpoint at week 48 of a Phase III trial.

The 39 participants of the RESCUE study received a GS010 injection in one eye and a sham injection in the other randomised for best and worst-affected eyes. The mean-best corrected visual activity (BCVA) was similar for the placebo and drug groups; both worsened to a low point and then began to improve by week 48.

At 48 weeks, the mean improvement from the low point during the period was +13 ETDRS letter equivalent for GS010-treated eyes and +11 for sham-treated eyes, whereas the primary endpoint was +15 ETDRS letters higher for the drug group, compared to the placebo.

GenSight co-founder and CEO Bernard Gilly said: "As expected, the RESCUE results at Week 48 present a more complex picture because of the intense, brutal and extremely rapid onset of the retinal ganglion cells’ degeneration."

Other measures of visual functions and anatomies showed results along a similar trajectory as BCVA results. The numerically superior changes from baseline for GS010 were not statistically significant for ganglion cell volume or papillo-macular bundle thickness.

Similar 48-week data was recorded from the Phase III REVERSE trial where both eyes saw a +11 ETDRS letter improvement. GenSight reported sustained quality of life improvements at 72 weeks from the REVERSE trial; RESCUE study subjects will also be re-evaluated at 72 weeks and 96 weeks.

GenSight chief medical officer Dr Barrett Katz said: "In our REVERSE trial, which included patients with vision loss between six and 12 months prior to treatment, we saw more improvement in both anatomic measures and visual functions as the disease entered its chronic phase. The planned readouts of RESCUE data at Weeks 72 and 96 should confirm GS010’s efficacy."

Gilly continued: "But as with REVERSE, later readouts are likely to confirm our confidence in the efficacy of GS010. We eagerly await these upcoming readouts, even as we prepare to discuss the results with the relevant authorities.

"We remain committed to bringing GS010 as early as possible to the market so that LHON patients can have an effective treatment for their relentlessly blinding disease."

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