Gene therapy for wet AMD shows promising long-term results

Take-home message: Three-year follow-up from the phase I/IIa trial of rAAV.sFlt-1 subretinal injection is encouraging for gene therapy for exudative age-related macular degeneration.

Perth, Australia-A single injection of a gene therapy construct rAAV.sFLlt-1 for advanced age-related macular degeneration (AMD) has shown safety and efficacy through 3 years in a small cohort, said Ian J. Constable, MBBS.

The investigator-initiated study (supported by Avalanche Biotechnologies) has 3-year data from a phase I/IIa study on AVA-101 (also known as sFlt-1). Prof. Constable noted the idea was that this single injection might be able to continuously secrete a therapeutic protein over an extended period to avoid the need for frequent injections in the neovascular AMD patient.

“All patients were recruited with wet macula and had [undergone] anti-vascular endothelial growth factor therapy beforehand,” said Prof. Constable, professor of ophthalmology, Centre for Ophthalmology and Visual Science (incorporating Lions Eye Institute), The University of Western Australia, Perth. “When they were recruited, they all had ranibizumab at day 0 and day 28.”

The gene construct injection was done at day 7 coupled with vitrectomy. Patients were randomly assigned (3:1) to receive either 1 × 10¹⁰ vector genomes (vg; low-dose rAAV.sFLT-1 group) or 1 × 10¹¹ vg (high-dose rAAV.sFLT-1 group), or no gene-therapy treatment (control group). All subjects had monthly assessments and received ranibizumab rescue injections as mandated by optical coherence swirling, loss of corrected vision, or fluorescein angiography.

Results published in 2015 on the first eight treated subjects “showed that at 1 year in the pilot study there was no loss of vision and there were minimal or no rescues required. Likewise, the center point thickness which was reduced with the booster doses at the beginning was largely maintained, although the retinal thickness was still above normal in some of the cases,” Prof. Constable said.