In addition to diphtheria antitoxin, which must be applied rapidly to bind the extracellular DT prior to internalization into cells, the novel chaperone/PPIase inhibitors, which prevent the transport of DTA from already internalized DT into the host cell cytosol, could be a valuable addition to the therapeutic strategies to prevent and treat diphtheria. This evidence concerns the gene FKBP4 and diphtheria.