Michael Amdahl

Paricalcitol versus cinacalcet plus low-dose vitamin D therapy for the treatment of secondary hyperparathyroidism in patients receiving haemodialysis: results of the IMPACT SHPT study

Background Optimal treatment for secondary hyperparathyroidism (SHPT) has not been defined. The IMPACT SHPT (ClinicalTrials.gov identifier: NCT00977080) study assessed whether dose-titrated paricalcitol plus supplemental cinacalcet only for hypercalcaemia is superior to cinacalcet plus low-dose vitamin D in controlling intact parathyroid hormone (iPTH) levels in patients with SHPT on haemodialysis. Methods In this 28-week, multicentre, open-label Phase 4 study, participants were randomly selected to receive paricalcitol or cinacalcet plus low-dose vitamin D. Randomization and analyses were stratified by mode of paricalcitol administration [intravenous (IV) or oral]. The primary efficacy end point was the proportion of subjects who achieved a mean iPTH value of 150–300 pg/mL during Weeks 21–28. Results Of 272 subjects randomized, 268 received one or more dose of study drug; 101 in the IV and 110 in the oral stratum with two or more values during Weeks 21–28 were included in the primary analysis. In the IV stratum, 57.7% of subjects in the paricalcitol versus 32.7% in the cinacalcet group (P = 0.016) achieved the primary end point. In the oral stratum, the corresponding proportions of subjects were 54.4% for paricalcitol and 43.4% for cinacalcet (P = 0.260). Cochran–Mantel–Haenszel analysis, controlling for stratum, revealed overall superiority of paricalcitol (56.0%) over cinacalcet (38.2%; P = 0.010) in achieving iPTH 150–300 pg/mL during Weeks 21–28. Hypercalcaemia occurred in 4 (7.7%) and 0 (0%) of paricalcitol-treated subjects in the IV and oral strata, respectively. Hypocalcaemia occurred in 46.9% and 54.7% of cinacalcet-treated subjects in the IV and oral strata, respectively. Conclusion Paricalcitol versus cinacalcet plus low-dose vitamin D provided superior control of iPTH, with low incidence of hypercalcaemia.

Differential Effects of Paricalcitol and Calcitriol on Intestinal Calcium Absorption in Hemodialysis Patients

Background/Aims: Increased parathyroid activity associated with chronic kidney disease is often managed with calcitriol, which can elevate serum calcium (Ca) by increasing bone resorption and intestinal absorption, whereas paricalcitol promotes less bone resorption. This study compared intestinal Ca absorption in hemodialysis patients treated with calcitriol versus paricalcitol (dose ratio 1:3). Methods: Patients (n = 22) aged ≧20 years, on maintenance hemodialysis for ≧2 months with intact parathyroid hormone (iPTH) levels of >200 pg/ml were enrolled in a single-center, double-blind, active-controlled, randomized, crossover trial. Mean fractional intestinal Ca absorption (±SE) was measured by the single-tracer method (42Ca) and evaluated with an analysis of variance crossover model. Results: Mean fractional intestinal Ca absorption was significantly lower after paricalcitol (0.135 ± 0.006) versus calcitriol treatment (0.158 ± 0.006, p = 0.022), a 0.023 difference in absolute Ca absorption fraction. Overall Ca absorption was low in the study population, indicating that regulation of Ca absorption may be dysfunctional. There were no significant differences in serum PTH, Ca, phosphorus (P), or Ca × P. Conclusion: Overall, paricalcitol-treated patients absorbed ∼14% less Ca compared with calcitriol-treated patients with similar effects on PTH. In hemodialysis patients, paricalcitol may provide a benefit by lowering the Ca available for removal by dialysis and/or for deposit in bone or soft tissues.

The Selective Vitamin D Receptor Activator for Albuminuria Lowering (VITAL) Study: Study Design and Baseline Characteristics

Background: Patients with diabetic nephropathy are at high risk for further progressive renal function loss. Treatments that decrease albuminuria have been linked with renal and cardiovascular protection. However, even when taking optimal treatment, residual renal and cardiovascular risk remains high which correlates with the magnitude of residual albuminuria. Use of vitamin D receptor activators, such as calcitriol and paricalcitol, is associated with improved sur- vival. A small study with paricalcitol showed reductions in albuminuria. The VITAL study tests the hypothesis whether paricalcitol persistently reduces albuminuria in diabetic subjects already receiving angiotensin-converting enzyme inhibitor (ACEI) and/or angiotensin receptor blocker (ARB) therapy. Methods: Randomization in this double-blind trial is equal allocation to paricalcitol 1 μ/day, 2 μg/day, or placebo. Inclusion criteria include: a diagnosis of type 2 diabetes, urinary albumin/creatinine ratio (UACR) between 100–3,000 mg/g, estimated glomerular filtration rate (eGFR) between 15–90 ml/min/1.73 m2, serum calcium <9.8 mg/dl, and parathyroid hormone (PTH) between 35–500 pg/ml. Results: Baseline characteristics of the 281 subjects are: 69% men, mean age 64.9 ± 10.4 years, eGFR 40.7 ± 16.7 ml/min, median UACR (interquartile range) 612.3 mg/g (281–1,181 mg/g) and PTH 98.4 ± 63.8 pg/ml. Conclusion: This trial will be the first clinical test of the hypothesis that paricalcitol possesses pleiotropic effects and can modulate albuminuria in the setting of ACEI and/or ARB therapy. Results will have important clinical implications and are expected in November 2009.

Paricalcitol versus cinacalcet plus low-dose vitamin D for the treatment of secondary hyperparathyroidism in patients receiving haemodialysis: study design and baseline characteristics of the IMPACT SHPT study

Background. Paricalcitol and cinacalcet are common therapies for patients on haemodialysis with secondary hyperparathyroidism (SHPT). We conducted a multi-centre study in 12 countries to compare the safety and efficacy of paricalcitol and cinacalcet for the treatment of SHPT. Methods. Patients aged ≥18 years with Stage 5 chronic kidney disease receiving maintenance haemodialysis and with intact parathyroid hormone (iPTH) 300–800 pg/mL, calcium 8.4–10.0 mg/dL (2.09–2.49 mmol/L) and phosphorus ≤6.5 mg/dL (2.09 mmol/L) were randomized within two strata defined by the mode of paricalcitol administration to treatment with paricalcitol- (intra-venous, US and Russian sites, IV stratum; oral, non-US and non-Russian sites, oral stratum) or cinacalcet-centred therapy. The primary endpoint is the proportion of patients in each treatment group who achieve a mean iPTH value of 150–300 pg/mL during Weeks 21–28 of treatment. Assuming efficacy response rates of 36 and 66% for cinacalcet and paricalcitol, respectively, and a 20% discontinuation rate, 124 subjects in each stratum were estimated to provide 81% power to detect a 30% absolute difference in the primary endpoint. Results. Of 746 patients screened, 272 (mean age, 63 years; mean iPTH, 509 pg/mL) were randomized. Mean duration of haemodialysis at baseline was 3.7 years. Comorbidities included hypertension (90.4%), Type 2 diabetes (40.4%), congestive heart failure (17.3%), coronary artery disease (34.6%) and gastrointestinal disorders (75%). Conclusions. The study participants are representative of a multinational cohort of patients on haemodialysis with elevated iPTH. The study results will provide valuable information on the best available treatment of SHPT in patients on haemodialysis.

Effects of paricalcitol on calcium and phosphate metabolism and markers of bone health in patients with diabetic nephropathy: results of the VITAL study

Background Chronic kidney disease (CKD) is associated with elevations in serum phosphate, calcium–phosphorus product and bone-specific alkaline phosphatase (BAP), with attendant risks of cardiovascular and bone disorders. Active vitamin D can suppress parathyroid hormone (PTH), but may raise serum calcium and phosphate concentrations. Paricalcitol, a selective vitamin D activator, suppressed PTH in CKD patients (stages 3 and 4) with secondary hyperparathyroidism (SHPT) with minimal changes in calcium and phosphate metabolism. Methods The VITAL study enrolled patients with CKD stages 2–4. We examined the effect and relationship of paricalcitol to calcium and phosphate metabolism and bone markers in a post hoc analysis of VITAL. The study comprised patients with diabetic nephropathy enrolled in a double-blind, placebo-controlled, randomized trial of paricalcitol (1 or 2 μg/day). Urinary and serum calcium and phosphate, serum BAP, and intact PTH (iPTH) concentrations were measured throughout the study. Results Baseline demographics and calcium, phosphate, PTH (49% with iPTH <70 pg/mL), and BAP concentrations were similar between groups. A transient, modest yet significant increase in phosphate was observed for paricalcitol 2 μg/day (+0.29 mg/dL; P < 0.001). Dose-dependent increases in serum and urinary calcium were observed; however, there were few cases of hypercalcemia: one in the 1-μg/day group (1.1%) and three in the 2-μg/day group (3.2%). Significant reductions in BAP were observed that persisted for 60 days after paricalcitol discontinuation (P < 0.001 for combined paricalcitol groups versus placebo). Paricalcitol dose-dependent reductions in iPTH were observed. Paricalcitol in CKD patients (±SHPT) was associated with modest increases in calcium and phosphate. Conclusion Paricalcitol reduces BAP levels, which may be beneficial for reducing vascular calcification. Trial registration Trial is registered with ClinicalTrials.gov, number NCT00421733.

Efficacy and initial dose determination of paricalcitol for treatment of secondary hyperparathyroidism in Chinese subjects.

AIM Prevalence of secondary hyperparathyroidism (SHPT), a renal disease complication, is increasing in China. Available therapies may not optimally control SHPT, particularly in patients with hypercalcemia, hyperphosphatemia, and parathyroid hyperplasia. This study examined efficacy and safety of two dosing regimens of selective vitamin D receptor activator paricalcitol. MATERIALS AND METHODS Subjects with SHPT (n = 216) undergoing hemodialysis were treated with paricalcitol i.v. for 12 weeks. One group was treated according to the EU paricalcitol package insert (PI) (initial μg dose based on iPTH/80), and the other was treated according to the US PI (initial dose of 0.04 μg/kg). Dose titration was based on iPTH and serum calcium (Ca) and phosphorus (P) levels. RESULTS The primary endpoint of two consecutive ≥ 30% iPTH decreases was achieved by 88.6% and 55.9% of subjects in the EU and US PI groups, respectively. Noninferiority of the EU PI group vs. the US PI group was demonstrated (lower bound of the 1-sided 97.5% CI = 21.3%). Superiority of the EU PI group was shown (lower limit > 0%) and confirmed by Fishers exact test (p < 0.001); both groups showed similar achievement of recommended KDIGO iPTH levels. Ca and P levels were relatively constant. CONCLUSION Both EU and US PI paricalcitol dosing strategies effectively reduced iPTH levels in Chinese subjects with SHPT, with minimal impact on Ca and P levels.