Calcilytics: antagonists of the calcium-sensing receptor for the treatment of osteoporosis

The only bone anabolic agents currently available on the market are based on the parathyroid hormone (PTH). Secretion of endogenous PTH is controlled by a calcium-sensing receptor at the surface of the parathyroid glands. Antagonists of this receptor (calcilytics) induce the release of the hormone. Provided the effect of the calcilytic is of short duration, a bone anabolic effect. should also result. Although the first calcilytic series became known approximately 10 years ago, the number of different structural types is still small today. This article outlines the quest from hits to potent development candidates of all relevant calcilytic series currently known. Even after the front-runners unexpectedly failed in the clinic, the approach for an oral alternative to parenteral PTH remains highly attractive.