Dutacatib is cathepsin K inhibitor developed by Novartis which reached a Phase I osteoporosis trial. Dutacatib reversibly binds to the catalytic site of cathepsin K, blocking substrate binding and subsequent cleavage. In preclinical models of breast cancer bone metastasis, treatment and preventive protocols with the cathepsin K inhibitor dutacatib (AFG495) alone or in combination with ZOL decreased tumour-induced osteolysis and skeletal tumour burden and did not affect primary breast tumour growth.