Towards the development of a chemical probe targeting the disruption of SYK tandem SH2 domain and FCεR1γ interactions for Alzheimer’s disease

Background Spleen tyrosine kinase (SYK) and FCεR1γ were identified as targets for Alzheimer’s disease (AD) via multi‐omics human data by AMP‐AD teams. These proteins were selected for further target validation and medicinal chemistry efforts by members of the Target Enablement to Accelerate Therapy Development for Alzheimer’s Disease (TREAT‐AD) program. SYK has a reported role in AD (PMID: 31324720), and SYK activation can occur upon binding to the phospho‐ITAM region of the FCεR1γ receptor via the tandem SH2 domains (tSH2) of SYK (PMID: 29440271). Therefore, disruption of this interaction is proposed to slow AD related pathology. Through the generation of target enabling packages (TEPs) we aim to provide experimental validation of these targets for AD and develop a high‐quality chemical probe that targets this interaction. Method Firstly, tSH2 domains of SYK were purified, followed by crystallography of these tSH2 in the presence of phospho‐ITAM‐containing peptides. A TR‐FRET‐based assay was developed using the SYK tSH2 domain and phospho‐ITAM peptide of FCεR1γ. This assay was miniaturized for ultra‐high‐throughput screening (uHTS) of a screening library of compounds. In parallel, a DNA encoded library (DEL) screen was executed to identify compounds that bind the SYK tSH2 domain. The hits generated using these hit finding campaigns were validated in dose‐response and via orthogonal biophysical methods. Medicinal chemistry campaigns to expand upon these hits are underway. Result We have crystallography data of the SYK tSH2 domains bound to phospho‐ITAM peptides and have established a TR‐FRET based assay to identify inhibitors of the interaction between FCεR1γ and SYK. Hit compounds have been identified through uHTS and DEL screening methods. Further validation of these hits in orthogonal assays are underway, alongside medicinal chemistry efforts to identify more potent analogues. Conclusion Through the generation of a SYK/FCεR1γ TEP, we have provided the tools to allow for experimental validation of these target for AD and have begun to generate inhibitors of this interaction.