X‑ray Crystal Structure of ERK5 (MAPK7) in Complex with a Specific Inhibitor

The protein kinase ERK5 (MAPK7) is an emerging drug target for a variety of indications, in particular for cancer where it plays a key role mediating cell proliferation, survival, epithelial–mesenchymal transition, and angiogenesis. To date, no three-dimensional structure has been published that would allow rational design of inhibitors. To address this, we determined the X-ray crystal structure of the human ERK5 kinase domain in complex with a highly specific benzo­[<i>e</i>]­pyrimido­[5,4-<i>b</i>]­diazepine-6­(11<i>H</i>)-one inhibitor. The structure reveals that specific residue differences in the ATP-binding site, compared to the related ERKs p38s and JNKs, allow for the development of ERK5-specific inhibitors. The selectivity of previously observed ERK5 inhibitors can also be rationalized using this structure, which provides a template for future development of inhibitors with potential for treatment of disease.