BUSINESS OVERVIEW 6 The following close-up image depicts a cross-section of the human retina: The layers of the retina are visible in the right panel, and the LHON patients indicate that the ND4 mutation accounts for up left panel is a cross-section of the eye including unlabeled viral to 70% of LHON cases. In Asian countries, the proportion of ND4 particles. mutation is higher, ranging from 80% to 85%. No Effective Existing Therapies for the Treatment of LHON Our Solution: GS010 for the Treatment of LHON No treatments for LHON have been approved in the United GS010 is developed through our MTS technology platform and States. In the European Union, the European Medicines Agency, is designed to restore the function of NADH dehydrogenase or EMA, granted Marketing Authorization, or MAA, for Raxone/ and therefore improves vision. Our GS010 product candidate is Idebenone under “exceptional circumstances” as a treatment for a recombinant AAV vector, serotype 2, or AAV2, containing the LHON in September 2015, though no clinically significant effect human wild-type mitochondrial ND4 gene combined with our of this agent has been demonstrated or studied in randomized proprietary MTS technology. We are developing GS010 for the clinical trials. A MAA under exceptional circumstances is when treatment of LHON due to the ND4 gene mutation with visual comprehensive data cannot be provided, and therefore the MAA loss of less than one year. is reviewed annually to re-assess the risk-benefit balance, in an Our novel, proprietary MTS platform technology has enabled us annual re-assessment procedure. to develop GS010 with potential advantages, including: Market Opportunity for LHON • IVT administration, a straightforward and common approach LHON is the most common il lness caused by mitochondrial well-accepted by ophthalmologists, in contrast to subretinal DNA mutations. We estimate the incidence of LHON to be injections; approximately 1,400 to 1,500 new patients who lose their sight • use of the AAV2 vector, which is the most studied of all AAVs, every year in the United States and Europe. LHON is estimated to with a demonstrated safety profile and validated manufacturing have a prevalence of between one in 31,000 and one in 40,000 process; in addition, there are currently no IP rights attached to in Northern Europe. European and North American studies of AAV2 and thus no royalty payments associated with its use; GENSIGHT BIOLOGICS – 2017 Registration Document– 71