Gene Therapy for Leber Hereditary Optic Neuropathy

Abstract

OBJECTIVE To determine the effects of escalating doses of AAV2(Y444,500,703F)-P1ND4v2 in patients with LHON caused by the G11778A mutation in mitochondrial DNA. DESIGN Prospective open-label, unilateral single-dose, intravitreal injection of AAV2(Y444,500,703F)-P1ND4v2 per subject in a phase I clinical trial study initiated in 2014. PARTICIPANTS Fourteen patients with visual loss and mutated G11778A mitochondrial DNA. INTERVENTION Intravitreal injection with the gene therapy vector AAV2(Y444,500,703F)-P1ND4v2 into one eye. Six participants with chronic bilateral visual loss greater than 12 months (Group I), 6 participants with bilateral visual loss less than 12 months (Group II) and 2 participants with unilateral visual loss (Group III) were treated. Nine patients had at least 12 months of follow-up. Clinical testing included ETDRS visual acuity, visual fields, OCT, PERG and neuro-ophthalmic examinations. GEE methods were used for longitudinal analyses. PRIMARY OUTCOME MEASURE Loss of visual acuity. RESULTS For Groups I and II, month 12 average acuity improvements with treatment relative to baseline were 0.24 logMAR. Fellow eyes had a 0.09 logMAR improvement. A post-hoc comparison found that at month 12, the difference between study eye minus fellow eye improvement in Group II patients of 0.53 logMAR was greater than that observed in our prior acute natural history patients of 0.21 logMAR (p=0.053). At month 18, the difference between study eye minus fellow eye improvement in our acute Group II gene therapy patients of 0.96 was greater than that observed in our prior acute natural history patients (0.17 logMAR) p<0.001. Two patients developed asymptomatic uveitis that resolved without treatment. OCT of treated eyes had an average temporal RNFL thickness of 54 μm prior to injection and 55 μm at month 12. For fellow eyes prior to injection it was 56 μm dropping to 50 μm at month 12, p = 0.013. GEE suggested that PERG amplitudes worsened more in treated eyes than in fellow eyes by about 0.05 uV (p exchangeable = 0.009). No difference between eyes in outcomes of other visual function measures was evident. CONCLUSIONS Allotopic gene therapy for LHON at low and medium doses appears safe and does not damage the temporal RNFL opening the door for testing of the high dose next.

Enhancement of Adeno-Associated Virus-Mediated Gene Therapy Using Hydroxychloroquine in Murine and Human Tissues

“…[25][26][27] This occurrence would ultimately cause localized tissue inflammation and reduced therapeutic efficacy, and it may underlie the cases of intraocular inflammation encountered in retinal gene therapy trials. [14][15][16] The upregulation of innate immune mediators detected on day 7 post-subretinal gene therapy in vivo does not rule out the presence of background levels of pre-existing surveillance innate sensors. Active AAV particles may be present within the subretinal space for a prolonged period (e.g., days) during which repeated waves of viral entry into the host cells may occur.…”

“…[10][11][12][13] Consequently, despite promising results seen with retinal gene therapy, cases of intraocular inflammation have been encountered. [14][15][16] Therefore, one of the major challenges of gene therapy for retinal diseases is how to achieve sufficient levels of gene replacement at a safe vector dose.…”

Therapies for mitochondrial diseases and current clinical trials

“…Additional results for this study have been recently published and showed an improvement in average acuity for 12 subjects with LHON and bilateral visual loss who received unilateral treatment. This study also demonstrated the safety of allotropic gene therapy for LHON [92]. …”

Strategies for fighting mitochondrial diseases

“…There are several AAV‐based clinical trials registered for LHON disease and one has been completed using allotopic expression of ND4, that is expression of mtDNA‐encoded protein from the nucleus. Although there is weak evidence that allotopically expressed mtDNA‐encoded subunits can enter into mitochondria and can be inserted into respiratory complexes, Guy et al reported amelioration of visual acuity in the injected eyes [119]. An alternative explanation to this clinical effect could be the presence of a secondary mutation in mtDNA and a spontaneous recovery that is often observed especially in the m.11778G> A mutation [120].…”