The invention provides compounds of general formula (I)
or a pharmaceutically acceptable salt, polymorph or solvate thereof, including all tautomers and stereoisomers thereof, wherein K, W, X; Y and Z are described throughout the description and claims.
The compounds of the present invention are useful as inhibitors of prolyl endopeptidase (PEP, EC 3.4.21.26) and/or IL-6.