Synthesis and structure-activity relationships of small-molecule 2-pyridone based CBX7 inhibitors

CBX7 plays an important role in the epigenetic regulation of aggressive malignancies. The discovery of small-molecule and drug-like inhibitors is key to studying this protein's biological function and in the development of therapeutics. Herein we report the campaign that led to the cell-active and potent CBX7 small-molecule inhibitor EC134. From an initial high throughput screen, a 2-pyridone compound class was identified and 30 structural analogs were made through a convergent synthetic route that allowed for easy diversification. Multiple regions of the scaffold were modified including the 2-pyridone, a piperazine core and a terminal aromatic group. An SAR was established identifying key substituents necessary for binding, and most intriguing was the positioning of methyl groups around a pyridine-aryl bond, showing a sharp line between potency and inactivity that we explored using molecular docking studies. This work resulted in four hit compounds with potent IC₅₀ values (<60 μM) and provides important insight in the development of small-molecule inhibitors for CBX7.