The invention is directed to modified Coversin polypeptides which exhibit leukotriene or hydroxyeicosanoid binding activity and reduced or absent C5 binding relative to the unmodified Coversin polypeptide; to nucleic acid molecules encoding said modified Coversin polypeptides; vectors and host cells comprising said nucleic acid molecules; and methods of treating or preventing diseases or conditions mediated by a leukotriene or hydroxyeicosanoid in a subject comprising administering said modified polypeptides or nucleic acids to a subject.