To treat inflammation and other disorders, 2-cyano-4-amino - cysteine protease inhibitors with pyrimidine structure and cathepsin k inhibitory activity

The invention provides compounds of formula I or a pharmaceutically acceptable salt or ester thereof (I), wherein the symbols have meaning as defined, which are inhibitors of cathepsin K and find use pharmaceutically for treatment of diseases and medical conditions in which cathepsin K is implicated, e.g., various disorders including inflammation, rheumatoid arthritis, osteoarthritis, osteoporosis and tumors.