AZD5904 is a pselective and irreversible inhibitor of human Myeloperoxidase (MPO) with an IC50 of 140 nM and has similar potency in mouse and rat. It is 10 to 19-fold selective compare to the closely related lactoperoxidase and thyroid peroxidase; >70-fold to a broad panel of other enzymes, ion channels, and receptors. In isolated human neutrophils, 1 µM AZD5904 inhibits PMA stimulated HOCl by >90%.