Covalent inhibitor discovery by electrophile fragment screening

Covalent chemical probes and covalent acting drugs can display unmatched potency, selectivity and duration of action; however, their discovery is challenging. We develop technologies for covalent ligand discovery. Here, I will present our approach for empirical covalent fragment screening. We constructed a library of 993 mildly electrophilic fragments, characterized it by a new high-throughput thiol-reactivity assay and screened them against ten cysteine-containing proteins. Highly reactive and promiscuous fragments were rare and could be easily eliminated. By contrast, we found selective hits for most targets. Combination with high-throughput crystallography allowed rapid progression to potent and selective probes for two enzymes, the deubiquitinase OTUB2, and the pyrophosphatase NUDT7. No inhibitors were previously known for either. This approach will enable the discovery of a new generation of covalent probes for many various protein targets.