Disclosed herein are 4-phenyl-6-substituted-pyrimidine-2-carbonitrile derivatives having Formula I, ##STR00001## wherein each of the substituents is given the definition as set forth in the specification and claims; or a pharmaceutically acceptable salt thereof. Also disclosed are pharmaceutical compositions comprising these 4-phenyl-6-substituted-pyrimidine-2-carbonitrile derivatives and use of these 4-phenyl-6-substituted-pyrimidine-2-carbonitrile derivatives for the treatment of cathepsin K and cathepsin S related disorders, e.g. osteoporosis, atherosclerosis, inflammation and immune disorders such as rheumatoid arthritis and chronic pain.