Develop an engineered Cas effector for in vivo cell-targeted delivery in the eye to treat autosomal dominant BEST disease

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PROJECT SUMMARY/ABSTRACT – FOLLOWER PROJECT 2 Best Disease (BD) is a prevalent, primarily autosomal dominant, macular degenerative disorder that results in retinal pigment epithelium (RPE) dysfunction and progressive loss of central vision. BD results from >200 known missense mutations in the BEST1 gene. Whereas there are currently no viable treatment options for autosomal dominant BD, genome editing could offer a promising therapeutic strategy. The goal of this Follower Project 2 is to develop a safe and effective genome editing treatment for BD using Spotlight Therapeutics’ proprietary Targeted Active Gene Editors (TAGE) platform. TAGE is a novel, nonviral, non-nanoparticle delivery system wherein a functional CRISPR-Cas effector is fused to antibody (Ab) and cell-penetrating peptide (CPP) moieties, enabling in vivo cell-targeted delivery, intracellular trafficking to the nucleus and subsequent gene editing. A TAGE-101 lead will be developed through identification and optimization of these modular components and complexation with a human single guide RNA (sgRNA) that binds mutant Best1. A preclinical data package will be generated demonstrating >10% editing/knockout of the R218C mutant BEST1 allele, restored function, and acceptable off-target and genotoxicity profiles ex vivo, using patient iPSC-derived RPEs, and in non-GLP nonhuman primate (NHP) toxicity studies. INTERACT and pre-IND meetings with the FDA are planned to present a preclinical and upstream process development data package and a future development plan and to explore whether additional BD mutants can be addressed with patient-specific guides under a master IND for TAGE-101. At the end of the five-year grant horizon, the TAGE-101 development candidate will be poised to initiate IND-enabling studies and, ultimately, clinically tested in BEST1 patients. This Project and Project 3 aim to develop CRISPR-Cas-based gene editing therapies targeting a BEST1 mutant allele employing different delivery platforms. Synergy will exist in areas such as sgRNA development, ex vivo preclinical characterization studies in partnership with the Human Cell Assay Core, as well as a regulatory strategy for BD in partnership with the Regulatory Core. This project will also have synergy with Project 1 around pilot NHP studies, addressing RPE channelopathies via subretinal injection, in partnership with the Large Animal Core. Successful completion of this project will provide a rigorous, stepwise approach to nominate a development candidate poised to initiate IND-enabling studies for all individuals with BD resulting from a specific mutation. It will also advance the utility of iPSC models as custom preclinical tools to rapidly develop somatic cell genome editing strategies in conjunction with a novel cell-targeted CRISPR gene editing platform.