Cinacalcet (KRN1493) effectively decreases the serum intact PTH level with favorable control of the serum phosphorus and calcium levels in Japanese dialysis patients

Background. Cinacalcet hydrochloride (KRN1493) acts on the parathyroid calcium receptors to suppress parathyroid hormone (PTH) secretion, and is already in wide use in the United States and the European countries. In this study, we examined the efficacy and safety of cinacalcet in Japanese patients on maintenance haemodialysis. Methods. One hundred forty-four patients with serum intact PTH (iPTH) levels >= 300 pg/ml were enrolled and randomly allocated to two groups assigned to receive either cinacalcet or placebo for 14 weeks. Cinacalcet was started at the dose of 25 mg/day and titrated up to 100 mg/day to achieve the target iPTH level of <250 pg/ml. Results. Cinacalcet significantly decreased the median iPTH level from 606.5 pg/ml to 241.0 pg/ml, despite the mean dialysis vintage being 2.4 times longer (14.3 +/- 7.1 years) and the proportion of patients receiving vitamin D sterols being higher, than in the phase 3 studies conducted in the US/EU. The target iPTH level was achieved in 51.4% of the patients in the cinacalcet group, in sharp contrast to only 2.8% in the placebo group. Furthermore, the percentage of patients with both the serum calcium and phosphorus levels within the target range in the K/DOQI guidelines increased from 4.2% to 26.4% by cinacalcet. Conclusions. These results suggest that lower dose levels of cinacalcet, as compared to those in US/EU studies, may be sufficient effectively suppress the serum iPTH levels and allow favourable management of the serum calcium and phosphorus levels in Japanese patients, having a longer average dialysis vintage.