Riding toward Selectivity: Optimization of Covalent 7-Azaindole-Based BMX Kinase Inhibitors

High Resolution Image Download MS PowerPoint Slide The tyrosine kinase expressed in hepatocellular carcinoma (TEC) family comprises five nonreceptor tyrosine kinases─BTK, ITK, BMX, TXK, and TEC─with key roles in immune signaling. Although BTK and ITK have been extensively studied, selective inhibitors for TEC, TXK, and BMX remain scarce. Recently, we identified 7-azaindole-based covalent BMX inhibitors with potent inhibitory activity and robust cellular target engagement but limited selectivity across TEC family members, especially BTK. Here, we describe a new generation of BMX inhibitors designed to exploit subtle structural differences between BMX and BTK by incorporating diverse N -acylamino substituents at the azaindole 5-position or variations at the linker and warhead. Our compounds display subnanomolar BMX potency and improved selectivity over BTK and other TEC kinases. Key compound 11i showed strong cellular target engagement, good in vitro metabolic stability, a favorable kinome profile, and rapid covalent inactivation kinetics, positioning it among the best BMX chemical probes currently available.