Use of Calcimimetics in Uremic Patients with Secondary Hyperparathyroidism: Review

Abstract

Recognition of the role of the extracellular calcium sensing receptor (CaR) in mineral metabolism has greatly improved our understanding of calcium homeostasis. The activation of this receptor by small changes in extracellular ionized calcium (ec(Ca2+)) regulates PTH, calcitonin secretion, urinary calcium excretion, and ultimately, bone turnover. The cloning of this CaR and the discovery of mutations making the receptor less or more sensitive to calcium allowed a better understanding of several hereditary disorders characterized either by hyperparathyroidism or hypoparathyroidism. This CaR became an ideal target for the development of compounds, the calcimimetics, able to amplify the sensitivity of the CaR to ec(Ca2+) suppressing PTH levels with a resultant fall in blood Ca2+. The first clinical studies with first-generation calcimimetic agents have demonstrated their efficacy lowering plasma intact PTH concentration in uremic patients with secondary hyperparathyroidism. However, the low bioavailability of these first calcimimetics predicts a difficult clinical utilization. The second-generation calcimimetic AMG-073, with a better pharmacokinetic profile, appears to be effective and safe for the treatment of secondary hyperparathyroidism, producing suppression of PTH levels with a simultaneous reduction in serum phosphorus levels and the calcium X phosphorus product. The advantage of controlling PTH secretion without the complications related to hypercalcemia, hyperphosphatemia, and increased calcium X phosphorus product is very promising.

Novel Role of the Calcium-Sensing Receptor in Blood Pressure Modulation

“…3 These drugs have been introduced recently in the treatment of uremic secondary hyperparathyroidism. 4 The binding of Ca 2ϩ o or other CaR agonists to the CaR elicits complex intracellular signals through modulation by the CaR of a wide array of intracellular signaling proteins, including G proteins and phospholipase C, which stimulates inositol triphosphate production. Downstream of or in parallel with phospholipase C, the CaR also activates mitogen-activated protein kinases (MAPKs).…”

Artificial Organs 2003: A Year in Review

“…Pablo Urena of the Clinique de l’Orangerie (Aubervilliers, France) reviewed the use of calcimimetics in uremic patients with secondary hyperparathyroidism (105). The development of positive allosteric modulators of the extracellular calcium sensing receptor has been very encouraging.…”

Differential effects of intermittent PTH(1–34) and PTH(7–34) on bone microarchitecture and aortic calcification in experimental renal failure

“…Although the mechanism of resistance is incompletely understood, uremic patients require PTH levels 2-3 times normal to maintain bone turnover [56]. Excessive suppression of PTH secretion, however, may lead to low bone turnover, so-called adynamic bone disease [12, 13]. …”