Developing new active compounds to correct mutant BEST1 chloride conductance – Establishing a targeted therapy for Best vitelliform macular dystrophy

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Bestrophin 1 (BEST1) forms a calcium-activated chloride channel composed of five homomeric BEST1 subunits. Mutations in the BEST1 gene are associated with a clinical spectrum of retinal dystrophies among others the Best vitelliform macular dystrophy (BVMD). To date, there is no treatment option for BVMD or any of the BEST1-linked conditions leaving a high medical need for an effective therapy. In our recent work, we have identified two substances belonging to the sub-class of isoflavonoids, namely Biochanin A and Mundulone, which have the ability to restore mutation-impaired BEST1-mediated anion conductance in vitro. To further develop these active substances in a preclinical setting, the next step is to initially expand the repertoire of active substances by generating derivatives of Biochanin A and Mundulone, followed by testing these compounds for safety and efficacy in cell cultures (in vitro) and animal models (in vivo). To this end, we have commissioned the manufacturing of a total of 41 Biochanin A and Mundulone derivatives, which are characterized, for example, by replacing individual acetate ester groups with (carboxy) ester and other functional groups with phosphate, carbamate, or carbonate residues. The current application now aims at achieving three specific objectives which include (1) analyzing the newly synthesized compounds using a functional test known as YFP halide transport assay in MDCKII cells. Promising candidates will be verified for restoring chloride conductivity via patch clamping of patient-derived retinal pigment epithelium (RPE) cells; (2) analysis of absorption, distribution, metabolism, elimination, and toxicity properties of the verified candidates in vitro and finally (3) testing of the most promising compounds in homozygous Best1(Y227N) knock-in mice to demonstrate feasibility of restoring Best1 function in vivo. The overall goal of the project is focused on identifying active lead compounds from the sub-class of isoflavonoids which will then undergo extensive and cost-intensive optimization.