Rare Daily Staff

GenSight Biologics said topline results from a late-stage clinical trial evaluating the safety and efficacy of a single intravitreal injection of its experimental gene therapy for Leber Hereditary Optic Neuropathy, a rare degenerative eye disease, showed benefit in treated eyes, but failed to meet the study’s endpoint because researchers found untreated eyes essentially experienced the same improvement.

In the study, patients with the disease were given a single treatment of its gene therapy GenSight’s GS010, a gene therapy, and a sham treatment in their other eye.

Eyes treated with GS010 had a clinically meaningful improvement of +11 ETDRS letters in treated eyes at 48 weeks as compared to baseline in all 37 patients in the study. The ETDRS is a standardized measure of visual acuity that measures the ability of a patient to read letters on an eye chart.

But the trial did not meet its primary endpoint, defined as a difference of improvement in visual acuity in GS010-treated eyes compared to sham-treated eyes at 48 weeks, because the untreated eyes experienced similar improvements. The study is ongoing for another year.

“We will have to investigate this unexpected and atypical finding of improved acuity in the untreated eye,” said Barrett Katz, chief medical officer for Gensight, during a conference call discussing the results with investors. “This is counter to what we expected. It is counter to what clinicians thought they knew about the natural history of the disease, and we have to look at this and try to explain a possible treatment effect in the untreated eye.”

Katz said the company will be analyzing other metrics that are clinically meaningful to try to understand the results.

“We will continue to analyze the data to better understand our results,” said Bernard Gilly, CEO of GenSight, “but they suggest that GS010 benefits both eyes in a way that is still to be understood.”

April 4, 2018
Photo: Graph of trial results of GenSight gene therapy compared to sham treatment