Methods and compositions are provided comprising a therapeutically effective amount of a compound of formula I wherein R.sup.1-4, W, X, Y and Z are as defined in the specification, for inhibiting and treating diseases and disorders associated with pathogenic proteins causing neurodegenerative diseases and amyloid diseases, such as protease resistant prion proteins (PrP.sup.Sc) and those associated with transmissible spongiform encephalopathies (TSEs), Alzheimer's Disease, amyloidosis, and the like.