Long-term treatment of secondary hyperparathyroidism with the calcimimetic cinacalcet HCl

Background. Patients with secondary hyperparathyroidism often require therapy that provides longterm control of parathyroid hormone concentrations without increasing calcium and phosphorus concentrations. Cinacalcet modulates the calcium-sensing receptor on the parathyroid gland to reduce secretion of parathyroid hormone and lower serum calcium, phosphorus and calcium - phosphorus product in haemodialysis patients. Methods. Dialysis patients with secondary hyperparathyroidism [ parathyroid hormone ( PTH) level >= 300 pg/ml] who were enrolled in one of four phase 2 placebo-controlled studies were eligible to enrol in an open-label extension study in which all patients received cinacalcet. For this extension study, cinacalcet was initiated at 30 mg in all patients and the dose was escalated to a maximum of 180 mg once daily if PTH concentrations were > 250 pg/ml. Use of concomitant vitamin D sterols and phosphate binders was not restricted. Results. The analysis of all patients ( n = 59) completing 100 weeks of cinacalcet treatment showed long- term control of PTH and calcium - phosphorus product. Approximately 55% achieved a PTH concentration >= 300 pg/ml at the week-100 study visit, and similar to 60% had at least a 30% reduction in PTH from baseline. Serum calcium, phosphorus and the calcium - phosphorus product did not increase during the study. Concomitant vitamin D sterol and phosphate binder therapy remained stable. Cinacalcet was safe and generally well tolerated at doses up to 180 mg/day. Conclusions. In this long-term study, cinacalcet effectively sustained reductions in PTH for up to 3 years without increasing concentrations of serum calcium, phosphorus or calcium - phosphorus product.