The spindle-assembly checkpoint (SAC) is a safety mechanism which secures accurate chromosome segregation during mitosis. BUB1, a serine/threonine kinase, is one of the proteins involved in this... Show moreThe spindle-assembly checkpoint (SAC) is a safety mechanism which secures accurate chromosome segregation during mitosis. BUB1, a serine/threonine kinase, is one of the proteins involved in this checkpoint and its inhibition is thought to have therapeutic potential for the treatment of cancer. Although the exact role of BUB1 in the SAC remains controversial, inhibition of its kinase function has previously been shown to reduce tumor size in mouse xenograft models when combined with paclitaxel. The research described in this thesis aimed to develop novel BUB1 kinase inhibitors for which high-throughput screening was used as starting point for drug discovery. Medicinal chemistry efforts were performed to improve potency after which the obtained inhibitors were further evaluated in cellular assays. In addition, the development of a cellular BUB1 target engagement assay is described. Hit optimization led to the discovery of two lead compounds with good physicochemical properties, subnanomolar affinity for BUB1, good cellular BUB1 target engagement, acceptable selectivity over other kinases and a favorable in vitro ADME profile. Show less
Drug development is a time- and resource-consuming process that starts with the discovery and validation of a (protein) target that contributes to pathogenesis or disease progression. One of the... Show moreDrug development is a time- and resource-consuming process that starts with the discovery and validation of a (protein) target that contributes to pathogenesis or disease progression. One of the essential steps in this process is to validate that pharmacological modulation (e.g. inhibition) of the target leads to the desired phenotype, a process which is collectively referred to as target validation. Target validation heavily relies on the availability of suitable chemical tools to study engagement of the compound to the intended biological target. The development of selective chemical tools can be challenging to achieve due to the off-target activity towards structurally and/or functionally related homologs, e.g. other members within the same protein class. The field of chemical genetics combines the specificity of genetics with benefits of acute, pharmacological modulation by small molecules. This thesis describes chemical genetic approaches that can be used for target engagement and target validation studies of two different enzyme classes: kinases and serine hydrolases. Show less
