Mito Research Around The World

GS010 Gene Therapy

What is GS010 Gene Therapy?

A French biotechnology company Gensight Biologics is working on a gene therapy-based approach to treating a particular form of Mitochondrial Disease known as Leber’s hereditary optic neuropathy (LHON). LHON is caused by genetic mistakes (mutations) in mitochondrial DNA and symptoms are mostly limited to the cells at the back of the eye. LHON is characterised by a rapid loss of sight in both eyes.

How does gene therapy work?

Gene therapy is the introduction of normal genes into cells, to replace missing or defective ones in order to correct the genetic disorder. To do this, the normal gene is packaged into a viral vector and injected into the part of the body where it is needed. The use of viral vectors has been shown to be a safe way of transferring genes into cells.

What is GS010 supposed to do?

The most common genetic mutation that causes LHON is in a gene called ND4 found within the mitochondrial DNA. The ND4 gene usually produces a building block that forms part of the energy chain and is therefore important for energy production by the mitochondria. A mutation in ND4 associated with LHON can lead to decreased energy production and higher levels of harmful chemicals called ‘free radicals’ within certain cells of the eye. This, in turn, can lead to cell damage and loss of vision.

GS010 is a viral vector that contains the normal ND4 gene. By injecting GS010 into the cells at the back of the eye, the faulty building block within the energy chain can be replaced with a normal version. This may restore the ability of the cells to produce energy and could lead to improved vision.

Is it a cure?

GS010 aims to correct the underlying genetic mutation that causes LHON within certain cells of the eye. It may be possible to administer the treatment once, or a limited number of times, to achieve a long-term benefit and potentially a cure for vision loss. The genetic mutation will still be present throughout other cells of the body but the symptoms of LHON are often restricted to the eyes only.

What types of Mitochondrial Disease could it treat?

Gensight plan to investigate gene therapy to treat other LHON mutations. They have already initiated a research program for their next potential product candidate, GS011, which targets the ND1 gene mutation causing LHON.

In theory, gene therapy could be used to treat other Mitochondrial Diseases caused by different genetic mutations. The difficulty is making sure enough of the normal gene is delivered to the part of the body where it is needed. This is especially challenging for Mitochondrial Diseases that often affect multiple tissues and organs.

Have there been any trials?

Gensight published results from a phase 1/2 study in June 2016. This confirmed good safety and tolerability of GS010 and improved vision in patients with a disease onset of less than 2 years. Further results were published in June 2017 confirming the long-term safety of GS010 after nearly 2 years of follow-up. Improved vision in LHON patients with less than 2 years visual loss before treatment also continued over this time.

Two parallel Phase III clinical trials, known as the RESCUE and REVERSE studies, are currently ongoing in several medical centres within the US and Europe, including a centre in the UK. Both studies aim to assess the benefits of GS010 for treatment of vision loss in LHON patients with the ND4 mutation, either with a disease onset of up to 6 months (RESCUE) or up to 1 year (REVERSE). Both studies have recently completed enrolment and results are expected in the first half of 2018. 

Is there more information?

More information can be found using the following links:,cntnt01,detail,0&cntnt01item_id=86&cntnt01returnid=37



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