A covalent inhibitor targeting Cys16 on RhoA in colorectal cancer.

RhoA is a key cancer driver and potential colorectal cancer (CRC) therapy target but remains undrugged clinically. Using activity-based protein profiling (ABPP) and mass spectrometry (MS), we identified CL16, a covalent inhibitor targeting the unique Cys16 on RhoA subfamily, which confers high specificity over other Rho family proteins. Cys16 is adjacent to the nucleotide-binding pocket and switch regions, which are critical for RhoA function. The binding by CL16 effectively disrupts GTP binding and inhibits RhoA activity in CRC cells, leading to cytotoxic killing of CRC cells through cell-cycle arrest and apoptosis. In mouse CRC models, CL16 exhibits strong antitumor and antimetastatic effects, promotes T cell infiltration into the tumor microenvironment, and shows no observable toxicity. Our findings suggest that covalent targeting of the druggable Cys16 on RhoA offers a promising strategy for CRC treatment, providing a foundation for developing specific RhoA inhibitors for clinical application.