Cinacalcet reduces plasma intact parathyroid hormone, serum phosphate and calcium levels in patients with secondary hyperparathyroidism irrespective of its severity.

Aims: To evaluate the relationship between the severity of secondary hyperparathyroidism (SHPT) - defined in terms of baseline plasma intact parathyroid hormone (iPTH) level - and the magnitude of response to cinacalcet.

Materials And Methods: In this post hoc analysis, data were pooled from three randomized, placebo-controlled trials in which dialysis patients with iPTH ≥ 300 pg/ml were dose-titrated with cinacalcet or placebo in addition to conventional treatment to achieve iPTH ≤ 250 pg/ml. In 953 patients analyzed (cinacalcet, 545; placebo, 408), baseline iPTH levels were categorized in 100 pg/ml intervals (300 - ≥ 1,000 pg/ml), and the impact of baseline iPTH on changes in iPTH, phosphate (P), calcium (Ca) and calcium- phosphate product (Ca × P) was evaluated.

Results: Cinacalcet reduced iPTH (47% reduction), P (9%), Ca (7%), and Ca × P (15%) across all subgroups. For patients receiving cinacalcet, the mean percentage reduction from baseline in iPTH varied from 35 to 55%, being consistently decreased across the severity subgroups. The mean absolute change in iPTH was more pronounced in patients with higher baseline iPTH levels, particularly in the ≥ 1,000 pg/ml subgroup vs. the other subgroups. However, as baseline iPTH levels increased, iPTH ≤ 250 pg/ml was achieved in fewer patients. A trend towards greater absolute change from baseline was observed for P in patients with more severe disease (iPTH ≥ 800 pg/ml) treated with cinacalcet compared with patients with less severe disease (iPTH 300 - < 800 pg/ml).

Conclusions: Cinacalcet lowers plasma iPTH and serum P, Ca and Ca × P levels in dialysis patients with SHPT, regardless of disease severity. Patients with more severe disease experienced greater reductions in PTH and P, but fewer achieved iPTH ≤ 250 pg/ml by the efficacy assessment phase. Use of cinacalcet when baseline PTH is lower may result in more stable control of SHPT and help to control bone and mineral alterations.