GS010 is a gene therapy being developed by GenSight for the treatment of Leber hereditary optic neuropathy (LHON), a rare genetic mitochondrial disease that causes severe loss of sight, blindness, and disability in teens and young adults. It affects males much more often than females.

How GS010 works

LHON develops due to the presence of mutations in mitochondrial genes ND1, ND4, and ND6, which encode for the proteins that are responsible for the production of energy in the mitochondria. The mutations in these genes cause dysfunctions in the retinal ganglion cells that are present in the retina of the eye, leading to the loss of sight.

GS010 consists of a small, harmless virus containing the healthy version of the ND4 gene. Upon administration of GS010, the gene it carries is delivered to the target cells, providing the information necessary for the cells to start making healthy ND4 protein. It is hoped this will restore the normal function of the cells affected by the mutations.

GS010 in clinical trials

The safety and tolerability of GS010 are being evaluated in different clinical trials. A Phase 1/2 clinical trial (NCT02064569) is evaluating the safety of the approach in 21 patients with LHON. The preliminary data from the trial, released by the company in a press release, revealed that patients treated with a single injection of GS010 showed a long-term sustained improvement in visual acuity when examined 2.5 years later.

The effectiveness of GS010 also is being evaluated in two Phase 3 clinical trials. RESCUE (NCT02652767) and REVERSE (NCT02652780) are evaluating the effectiveness of GS010 in treating patients who have developed LHON as a result of the mutation in the mitochondrial ND4 gene.

The main goal of the RESCUE study is to assess the effectiveness of GS010 in improving visual outcomes in patients who experience vision loss up to six months from the onset of LHON. The main goal of the REVERSE study is to evaluate the effectiveness of GS010 in improving the visual outcomes for patients who have experienced vision loss from seven months to up to one year from the onset of LHON. Patient recruitment for both studies already has been completed and top-line data are expected to be released by the second and third quarters of 2018.

Two new clinical trials, REFLECT (NCT03293524) and REALITY (NCT03295071), also are underway. The main objective of the REFLECT study is to evaluate the safety and effectiveness of GS010 in treating vision loss up to one year from the onset of LHON. REALITY is a registry study that is being conducted to understand the evolution of visual, functional, and structural changes and other associated symptoms in patients with LHON. Neither trial is open for recruitment yet.

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