A potent, irreversible, and specific inhibitor of the peroxidation activity of myeloperoxidase (MPO; IC₅₀ = 300 nM). Does not affect catalase or glutathione peroxidase activities. Also displays no effect on the production of superoxide by neutrophils. Shown to inhibit H₂O₂-induced apoptosis in HL-60, human leukemia cells.