NPS 2143 (hydrochloride)

Calcium-sensing receptor (CaSR) is a G protein-coupled receptor that is involved in calcium homeostasis.{29237,26276} Activation of CaSR on parathyroid cells decreases the secretion of parathyroid hormone (PTH), which in turn reduces blood calcium concentration.{29237,26276} NPS 2143 is a potent and selective antagonist of CaSR (IC50 = 43 nM) that stimulates PTH secretion from parathyroid cells in vitro (EC50 = 39 nM).{29235,29236} It is effective in vivo, causing a sustained increase in plasma PTH in rats when given intravenously.{29235,29236} Daily oral administration of NPS 2143 to osteopenic ovariectomized rats results in a dramatic increase in bone turnover, as well as increased circulating PTH levels.{29235}