Hydralazine (HYZ), a treatment for preeclampsia and hypertensive crisis, is listed by the World Health Organization as an essential medicine. Its mode of action has remained unknown through its seven decades of clinical use. Here, we identify 2-aminoethanethiol dioxygenase (ADO), a key mediator of targeted protein degradation, as a selective HYZ target.

Chemical platforms that facilitate both the identification and elucidation of new areas for therapeutic development are necessary but lacking. Activity-based protein profiling (ABPP) leverages active site-directed chemical probes as target discovery tools that resolve activity from expression and immediately marry the targets identified with lead compounds for drug design.

Electrophilic cofactors are widely distributed in nature and play important roles in many physiological and disease processes, yet they have remained blind spots in traditional activity-based protein profiling (ABPP) approaches that target nucleophiles. More recently, reverse-polarity (RP)-ABPP using hydrazine probes identified an electrophilic N-terminal glyoxylyl (Glox) group for the first time in secernin-3 (SCRN3).