Identification and optimisation of small molecule modulators of Orai3 and TRPC4 as potential therapeutics

Ca2+ signalling pathways require different types of ion channels to help control the concentration of Ca2+ in the cell in order to carry out diverse physiological activities. Excessive Ca2+ leads to therapeutic diseases such as necrosis,[1] cancer,[2] and heart failure.[3] Unfortunately, many of the available calcium inhibitors suffer from weak potency and selectivity profiles (i.e TRP, sodium, potassium channels). Two Ca2+ ion proteins (Orai3 and TRPC4) were selected to target with novel chemical probes to better understand their biological function and potential utility as therapeutic targets.
The investigation of Orai3 has been focused on computational studies for the identification of possible binding sites for small molecules as well as identification of virtual hits. We evaluated different docking techniques to predict the binding of small molecules and investigated the potential to incorporate ligand-based design to enhance the results of docking alone.
In the TRPC4 studies, three general approaches were used to identify novel chemical probes as the starting points for optimisation, including (i) synthetic directed SAR study based on use of a published (weak potency) inhibitor, (ii) the use of computational-ligand based techniques (ROCS and Phase), and (iii) a HTS campaign. Compounds of interest were either synthesised or sourced/purchased and further evaluated in vitro assays targeting TRPC4 (and TRPC5 for selectivity). Optimisation of the known inhibitor (Clemizole) led to the identification of a compound with improved potency and selectivity in comparison to Clemizole. Furthermore, several hits were identified from the HTS study conducted, including several novel analogues of Clemizole as well as a novel dianiline scaffold exhibiting low micromolar potencies.
The discovery of novel potent and selective inhibitors targeting either Orai3 or TRPC4 could assist in the development of possible future therapeutics as well as validate their potential as therapeutic targets for drug discovery.