Koichiro Takahashi (#), Atsushi Shirahata, Shinji Fukushima, Satoshi
Kokubo, Kyoko Teramura and Shinji Usuda
Applied Pharmacology Research, Pharmacology Laboratories, Institute for Drug Discovery Research, Yamanouchi Pharmaceutical Co., Ltd., 1-8, Azusawa 1-chome, Itabashi-ku, Tokyo 174, Japan
(#) Present address for correspondence: Applied Pharmacology Laboratories, Institute for Drug Discovery Research, Yamanouchi Pharmaceutical Co., Ltd., 21, Miyukigaoka, Tsukuba, Ibaraki 305-8585, Japan
Abstract: YM175 (disodium cycloheptylaminomethylenediphosphonate monohydrate) is a new-generation bisphosphonate with stronger inhibitory activity on bone resorption than first-generation bisphosphonates. In the present study, the effect of YM175 on hypercalcemia induced in rats by single administration of either parathyroid hormone-related protein (PTHrP) or concomitant administration of PTHrP and interleukin 1beta (IL-1beta) was investigated. YM175 (0.01 - 1 mg/kg, i.v.) inhibited the increase in serum free calcium concentration induced by continuous administration of PTHrP alone (3 microg/rat/day, s.c., 7 days) dose-dependently. The inhibitory effect of YM175 appeared the day after administration and remained 3 days after administration. The effect of YM175 reached a maximum 2 days after administration, at which time the ED50 value of YM175 was calculated to be 0.041 mg/kg, i.v., revealing a potency approximately 50- and 10-fold stronger than those of either pamidronate or alendronate, respectively. In contrast, elcatonin (1 - 10 units/kg, s.c.) only transiently inhibited PTHrP-induced free calcium increase. YM175 (0.1 - 3 mg/kg, i.v.) also inhibited the increase in the serum free calcium concentration induced by continuous concomitant administration of both PTHrP and IL-1beta in a dose-dependent manner. These results indicated that YM175 is expected to be a useful drug for hypercalcemia associated with malignant tumors due to its efficacy and range of effect.
Keywords: Bisphosphonate, Hypercalcemia, Parathyroid hormone-related protein, Interleukin 1beta, Bone resorbing factor