Ocular Post-Mortem Analyses with Histopathological and Molecular Assessments in LHON Following AAV2 Gene Therapy

Abstract

Purpose : To perform post-mortem ocular analyses in two patients with Leber hereditary optic neuropathy (LHON) caused by the m.11778G>A MT-ND4 mutation who received lenadogene nolparvovec (AAV2-ND4) gene therapy.

Methods : Two patients with MT-ND4 LHON, participating in the RESCUE clinical study, received an intravitreal injection of AAV2-ND4 in one eye and a sham injection in the other within 6 months after bilateral vision loss. Eye post-mortem histopathological and molecular (ddPCR) analyses on laser captured retinal and optic nerve specimens were conducted.

Results : During the study, both patients developed intraocular inflammation in the treated eye within 2 months of gene therapy: one patient had moderate inflammation in the anterior chamber and vitreous, while the other had mild vitritis; both events resolved within months. Patient 1 died of acute alcohol toxicity and patient 2 of cardiac arrest. Patient 1 had a severe optic atrophy and loss of retinal ganglion cells (RGCs). Patient 2 was much milder case of LHON, with a consistent preservation of RGCs and optic nerve axons, being only the temporal fibers lost. For patient 1, there was noted an angiocentric lymphocytic chronic inflammation at the optic nerve head and in the temporal retina. No histopathological evidence of persistent inflammation was seen in patient 2. In both patients, AAV2-ND4 distribution was asymmetric in the treated eye, most prevalent in temporal RGCs. A much lower level of AAV2-ND4 was detected in the retina of the untreated eye in both cases, being however more consistent and in higher amount in patient 2, for whom AAV2-ND4 was found also in blood vessels and optic nerve. Finally, mtDNA copy number was upregulated in both eyes of patient 2, possibly reflecting the better RGC and axonal preservation. Increased mtDNA copy number remarkably characterized all LHON vessels as compared with controls, pointing to mitochondrial microangiopathy.

Conclusions : This is the first postmortem study of human eyes unilaterally injected with AAV2-based gene therapy. Successful gene transfection of RGCs was found in both eyes despite unilateral administration. The analysis of eyes, nerves, optic chiasm and optic tracts, available from patient 2, may confirm and better characterize the AAV2-ND4 transfer, which according to the current results seems facilitated by axonal preservation.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.