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RNA therapeutics in the treatment of retinal disease - delivering the potential

Fletcher, S., Hall, C., Anastasas, M., Martin, A., Chai, T., Priebatsch, K., Stirnweiss, A., Francis, R.W., Juraja, S.M., Mills, A.D., Ong, F., Florez, L., Kerfoot, M., Nicholls, J., Champain, D. and Cunningham, P. (2021) RNA therapeutics in the treatment of retinal disease - delivering the potential. Investigative Ophthalmology and Visual Science, 62 (8). Art. 1196.


Purpose : Treatment options for inherited retinal diseases (IRD), the leading cause of vision loss in persons aged 15 - 45 years have been limited, however, novel gene and molecular therapeutics are now demonstrating significant potential in the treatment of IRDs. RNA therapeutics hold unique promise in these diseases; although achieving safe and efficient delivery of molecular drugs to the retina and the retinal pigmented epithelium in particular, remains a significant obstacle to clinical application. Antisense oligomers (AO) are a well-established class of RNA therapeutic whose potential is yet to be fully realised due to this delivery challenge. We report an AO conjugate that traffics through the vitreous after intravitreal administration, reaching the deepest layers of the retina and localising to the nuclei to modulate gene expression. This class of therapeutic holds substantial promise in the treatment of IRDs.

Methods : We exploit peptide libraries derived from 82 microorganism genomes and 118 synthetic viral genes to identify cell penetrating peptides (CPP) to deliver AO cargos to cells in vitro and to tissues and organs in vivo. The CPPs were screened initially against mammalian cells using a cytosolic extraction method, followed by next generation sequencing and selection using a combination of algorithms known to produce a favourable toxicology and efficacy profile in the eye.

Results : The CPPs were conjugated to an antisense morpholino oligomer designed to mediate exon selection in a reporter mRNA. Standout performance in the latter assay, when administered via intravitreal injection, and a clean toxicology profile identified a lead peptide for our retinal disease program. CPP conjugation to our candidate AO therapeutic and evaluation in IRD patient-derived retinal pigmented epithelium rescued target gene expression and improved cell function.

Conclusions : Notable CPPs in pre-clinical and clinical development include chemical stabilisation or poly-arginine that can limit efficacy or increase toxicity. Our discovery peptides are derived from nature, lack chemical modifications, and yield optimal amino acid sequences with enhanced efficacy and toxicity performance. The lead CPP, HPG_0031, traffics the AO through the vitreous, into the retinal pigment epithelium with no evidence of retinal damage, resulting in enhanced exon skipping and 6-fold lower cytotoxicity than the competitor CPP.

Item Type: Journal Article
Murdoch Affiliation(s): Centre for Molecular Medicine and Innovative Therapeutics (CMMIT)
Publisher: Association for Research in Vision and Ophthalmology
Copyright: © 2021 Association for Research in Vision and Ophthalmology.
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