GSK-484 is a potent and reversible inhibitor of PAD4 (Protein Arginine Deiminase 4) (IC₅₀ = 50 nM) that binds to the low-calcium form of the enzyme. It is selective for PAD4 over PAD1-3. GSK-484 blocks the citrullination of PAD4 target proteins in human neutrophils and inhibits the formation of neutrophil extracellular traps in both mouse and human neutrophils.