This invention relates to 
pyrimidine compounds of formula (I), formula (I′), and formula (I″):and pharmaceutically acceptable salts, solvates, clathrates, and prodrugs thereof, wherein R1, R2, R3, R4, R5, U, V, W, X, Y, Z, and n are defined herein. This invention also relates to compositions comprising these compounds and methods for using them. The compounds and compositions of this invention are useful to treat or prevent disorders associated with excessive bone loss, including, without limitation 
periodontal disease, non-malignant bone disorders (such as 
osteoporosis, Pagers-
disease of bone, osteogenesis imperfecta, fibrous 
dysplasia, and primary 
hyperparathyroidism) 
estrogen deficiency, inflammatory bone loss, bone 
malignancy, 
arthritis, 
osteopetrosis, and certain 
cancer-related disorders (such as hypercalcemia of 
malignancy (HCM), osteolytic bone lesions of 
multiple myeloma and osteolytic bone metastases of 
breast cancer and other metastatic cancers).