Synthesis, identification, and biological characterisation of sterol transport protein inhibitors

Sterols transport proteins (STPs) are an important class of proteins responsible for cellular cholesterol trafficking, regulating a number of different processes including viral entry and maintaining cholesterol homeostasis. STPs have therefore been implicated as targets for treatment of neurodegenerative diseases, viral infections, and multiple cancers. Despite this, few selective inhibitors of STPs are known and available for use in studying STP-related biology, in part due to the difficulty in targeting their conserved sterol-binding domains.

To address this unmet need, a concept to synthesise and identify novel STP inhibitors was developed. A collection of 65 sterol-inspired compounds was synthesized by fusion of a sterol-inspired scaffold to different heterocyclic scaffolds, anticipating that such compounds should retain the ability to bind STPs whilst offering selectivity for one STP over another. Using three complementary biological techniques the collection was screened for their ability to bind and modulate STP-mediated cholesterol transfer, ultimately resulting in the identification new inhibitors of the Aster family of STPs. Astercin-2 was identified as the most potent and selective inhibitor of Aster-C alongside Asterpyrin-1, a new class of Aster-A inhibitor. Both compounds were subsequently tested in cells, revealing their capabilities to modulate levels and localisation of cellular cholesterol and demonstrating their utility as tool compounds to study Aster-related biology.

The presented concept for synthesising and identifying new inhibitors of STPs therefore holds great value in identifying new inhibitors of other STP families, and as such could assist in determining the therapeutic relevance of additional STPs.