Inhibition by a new bisphosphonate (YM175) of bone resorption induced by the MBT-2 tumour of mice.

A new bisphosphonate, disodium dihydrogen (cycloheptylamino) methylene bisphosphonate monohydrate (YM175), was compared with 3-amino-1-hydroxypropylidene-1, 1-bisphosphonate (AHPrBP) and 1-hydroxyethylidene-1,1-bisphosphonate (HEBP) in terms of its effect on tumour induced osteolysis using a bladder tumour in mice (MBT-2). The method consisted of inoculating tumour cells subcutaneously (SC) over the calvaria in mice, resulting in a local tumour causing fragmentation of the bone. The compounds were active not only when administered preventively before establishment of bone resorption, but also in an inhibitory fashion once the variables were already under the influence of the tumour. This osteolysis was evaluated by measuring the increased area of bone resorption in reduced opacity to radiograph and histology. The results showed the following sequence of potency: YM175 > AHPrBP = HEBP. This inhibition was obtained with no apparent effect on the growth of the MBT-2 tumour. YM175 appears to be an interesting new bisphosphonate with possible clinical application.