In vivo expression and efficacy following subretinal delivery of GT005, an investigational gene therapy for the treatment of geographic atrophy (GA)

Abstract

Purpose : Report non-clinical in vivo expression data and efficacy in the mouse laser-induced choroidal neovascularization (CNV) model after subretinal delivery of GT005, an investigational AAV2 gene therapy expressing recombinant human complement factor I (hCFI).

Methods : HEK-293 cells were transduced with GT005 to confirm expression of hCFI at both the mRNA and protein levels. Expressed CFI protein function was evaluated with a C3b cleavage assay. In rodent expression studies, GT005 was unilaterally, subretinally injected in mice at 2x10⁷-2x10⁸ GC/eye. 28 days later ocular fluids and tissues were collected for expression analyses including qRT-PCR, ELISA, in situ hybridization and immunohistochemistry. In laser CNV model studies, GT005 or mGT005, which encodes for murine CFI, was subretinally injected in mice at 2x10⁷-2x10⁸ GC/eye 28 days prior to lasering. Negative control animals received empty vector at 2x10⁸ GC/eye. Positive control mice received 80 ug aflibercept intravitreally after lasering. CNV leakage was assessed 4 and 7 days post-lasering by optical coherence tomography (OCT) and fluorescence angiography (FA). Lesion area was evaluated by staining RPE/choroid flatmounts with FITC-conjugated isolectin-B4 7 days after lasering.

Results : Expression and secretion of functional, processed hCFI was demonstrated in vitro after transduction of HEK-293 cells with GT005, and in vivo after subretinal injection of GT005 to mice. hCFI mRNA and protein were mainly localized in the outer retina and was enriched in the bleb area. In the CNV model, no significant difference was detected in CNV leakage at days 4 and 7 in mice treated with GT005 or a murine version (mGT005) compared to the negative control. However, both showed a dose-dependent effect in reducing CNV lesion size which was statistically significant at the 5x10⁷ and 2x10⁸ GC/eye doses (mGT005: P=0.040 and P=0.011 respectively).

Conclusions : GT005 leads to expression of functional CFI protein in vitro and in vivo in mice, localizing to the target tissues that are affected in dry age-related macular degeneration (AMD). GT005 shows therapeutic efficacy in the mouse CNV model, a model of wet AMD in which complement activation plays a key pathophysiological role. These data support the therapeutic potential of GT005 for the treatment of GA by complement system modulation.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.