Treatment of Persistent Hyperparathyroidism in Renal Transplant Patients With Cinacalcet Improves Control of Blood Pressure

Parathyroidectomy or cinacalcet: Do we still not know the best option for graft function in kidney-transplanted patients? A meta-analysis

BACKGROUND

Tertiary hyperparathyroidism occurs in 25% to 50% of kidney-transplanted patients. Indication of parathyroidectomy is now discussed, since the calcimimetic agent, cinacalcet, is an alternate option. The effects of either of these treatments on graft function remain controversial, studied only in small cohorts showing either decrease or absence of modification. We performed a meta-analysis to evaluate the evolution of graft function after surgical or medical treatment.

METHODS

Studies assessing graft function in tertiary hyperparathyroidism after parathyroidectomy or cinacalcet introduction were enrolled into quantitative analysis using Pubmed, Embase, and Cochrane databases following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis reporting guidelines. Among 68 screened studies, 18 had no missing data and were included for statistical analyses. We performed random effect meta-analysis to determine changes in serum creatinine and estimated glomerular filtration rate.

RESULTS

Seven studies assessing the evolution of graft function 6 and/or 12 months after parathyroidectomy and 13 after administration of cinacalcet were included. Meta-analysis found no significant variations after parathyroidectomy in serum creatinine (6 studies, 314 patients) and estimated glomerular filtration rate (2 studies, 105 patients). No significant variation was found after administration of cinacalcet in serum creatinine (10 studies, 404 patients) and estimated glomerular filtration rate (6 studies, 149 patients). A significant heterogeneity between the studies (P < .01, Cochran's Q) was found.

CONCLUSION

Meta-analysis shows that parathyroidectomy and cinacalcet do not significantly impair graft function in patients with tertiary hyperparathyroidism. However, the significant heterogeneity between selected studies, partially explained by the lack of consensual definition of tertiary hyperparathyroidism, limits the conclusions of all previously published series.

The use of cinacalcet after pediatric renal transplantation: an international CERTAIN Registry analysis

BACKGROUND

Secondary hyperparathyroidism (SHPT) may persist after renal transplantation (RTx), inducing hypophosphatemia and hypercalcemia that precludes the use of vitamin D analogs. The calcimimetic cinacalcet improved plasma calcium and parathyroid hormone (PTH) levels in randomized controlled trials in adults after RTx, but pediatric data are scarce.

METHODS

In this retrospective study, we analyzed 20 pediatric patients from the Cooperative European Paediatric Renal TransplAnt Initiative (CERTAIN) Registry who received cinacalcet after RTx. The results are presented as median and interquartile range (25th-75th percentile).

RESULTS

At 13.7 (11.0-16.5) years of age, 20 pediatric patients received a renal allograft. Cinacalcet was introduced at 0.4 (0.3-2.7) years post-transplant at an estimated glomerular filtration rate (eGFR) of 50 (34-66) mL/min/1.73 m², plasma calcium of 2.58 (2.39-2.71) mmol/L, age-standardized (z score) phosphate of - 1.7 (- 2.7-- 0.4), and PTH of 136 (95-236) ng/L. The starting dose of cinacalcet was 0.5 (0.3-0.8) mg/kg per day, with a maximum dose of 1.1 (0.5-1.3) mg/kg per day. With a follow-up of 3.0 (1.5-3.6) years on cinacalcet therapy, eGFR remained stable; PTH levels decreased to 66 (56-124) ng/L at the last follow-up (p = 0.015). One patient displayed hypocalcemia (1.8 mmol/L). Cinacalcet was withdrawn in three patients (hypocalcemia, parathyroidectomy, incompliance). Nephrocalcinosis of the graft was not reported.

CONCLUSIONS

This pilot study suggests that cinacalcet as off-label therapy for SHPT after pediatric RTx is efficacious in controlling post-transplant SHPT with acceptable tolerability. Continuing cinacalcet even with normal PTH can lead to dangerous life-threatening hypocalcemia. Therefore, at each subsequent visit, the need to continue cinacalcet must be assessed.

Enantioselective synthesis of (R)-Cinacalcet via cobalt-catalysed asymmetric Negishi cross-coupling

A novel enantioselective synthesis of (R)-cinacalcet with 99% enantiomeric excesses (ee) has been achieved. The main strategies of the approach include a gram-scale cobalt-catalysed asymmetric cross-coupling of racemic ester with arylzinc reagent, Hoffman-type rearrangement of acidamide, the amidation of chiral amine, and improving the ee of chiral amide from 87% to 99% via recrystallization.

Mineral and Bone Disorders After Kidney Transplantation

The risk of mineral and bone disorders among patients with chronic kidney disease is substantially elevated, owing largely to alterations in calcium, phosphorus, vitamin D, parathyroid hormone, and fibroblast growth factor 23. The interwoven relationship among these minerals and hormones results in maladaptive responses that are differentially affected by the process of kidney transplantation. Interpretation of conventional labs, imaging, and other fracture risk assessment tools are not standardized in the post-transplant setting. Post-transplant bone disease is not uniformly improved and considerable variation exists in monitoring and treatment practices. A spectrum of abnormalities such as hypophosphatemia, hypercalcemia, hyperparathyroidism, osteomalacia, osteopenia, and osteoporosis are commonly encountered in the post-transplant period. Thus, reducing fracture risk and other bone-related complications requires recognition of these abnormalities along with the risk incurred by concomitant immunosuppression use. As kidney transplant recipients continue to age, the drivers of bone disease vary throughout the post-transplant period among persistent hyperparathyroidism, de novo hyperparathyroidism, and osteoporosis. The use of anti-resorptive therapies require understanding of different options and the clinical scenarios that warrant their use. With limited studies underscoring clinical events such as fractures, expert understanding of MBD physiology, and surrogate marker interpretation is needed to determine ideal and individualized therapy.

Long-Term Use of Cinacalcet in Kidney Transplant Recipients With Hypercalcemic Secondary Hyperparathyroidism: A Single-Center Prospective Study

OBJECTIVES

Persistent secondary hyperparathyroidism is common after successful kidney transplant, with concomitant hypercalcemia and hypophosphatemia potentially leading to reduced graft survival and increased cardiovascular risk. Cinacalcet, a calcimimetic agent that activates the calcium-sensing receptors in parathyroid glands, is a therapeutic option. In this study, we assessed the long-term treatment effects of cinacalcet for a period of up to 5 years in a cohort of kidney transplant recipients.

MATERIALS AND METHODS

Forty-seven patients with secondary hyperparathyroidism (intact parathyroid hormone level > 70 pg/mL or 7.43 pmol/L) and hypercalcemia (corrected calcium > 10.4 mg/dL or 2.6 mmol/L) were considered eligible for treatment with cinacalcet and were included in the analysis. Data were recorded at initiation of treatment and every 6 months up to a maximum follow-up of 60 months. A control group of patients treated with placebo, conventional treatment, or surgical treatment was not available for this study.

RESULTS

Mean follow-up time was 45 ± 16 months. Treatment with cinacalcet was initiated at a median of 25 months after renal transplant. Serum calcium decreased by 0.21 mmol/L (2.69 vs 2.48 mmol/L; 95% confidence interval, 0.08-0.345; P < .001) during the first 6 months, and this reduction was sustained during follow-up. Intact parathyroid hormone level decreased by 7.68 pmol/L (32.96 ± 36.4 vs 25.28 ± 19.5 pmol/L; 95% confidence interval, -6.42 to 21.75; P = not significant) at 6 months, whereas at the end of follow-up intact parathyroid hormone level decreased further by 20.07 pmol/L (32.96 ± 36.4 vs 12.89 ± 5.73 pmol/L; 95% confidence interval, 2.02-38.1; P < .01). Mean starting dose of cinacalcet was 33.5 ± 10 mg/day. According to the therapeutic response, cinacalcet dose increased steadily and reached 51.1 ± 33 mg/day at the end of the observation period. Mean serum phosphorus increased significantly, whereas estimated glomerular filtration rate remained virtually stable throughout follow-up. Adverse reactions were observed in 4 patients, comprising mild gastro-intestinal complaints.

CONCLUSIONS

Long-term treatment with cinacalcet in kidney transplant recipients with secondary hyperparathyroidism is effective in controlling hypercalcemia and correcting hypophosphatemia, without affecting graft function while being well-tolerated.

Systematic review of surgical and medical treatment for tertiary hyperparathyroidism

BACKGROUND

A significant proportion of patients with chronic kidney disease and secondary hyperparathyroidism (HPT) remain hyperparathyroid after kidney transplantation, a state known as tertiary HPT. Without treatment, tertiary HPT can lead to diminished kidney allograft and patient survival. Parathyroidectomy was commonly performed to treat tertiary HPT until the introduction of the calcimimetic drug, cinacalcet. It is not known whether surgery or medical treatment is superior for tertiary HPT.

METHODS

A systematic review was performed and medical literature databases were searched for studies on the treatment of tertiary HPT that were published after the approval of cinacalcet.

RESULTS

A total of 1669 articles were identified, of which 47 were included in the review. Following subtotal and total parathyroidectomy, initial cure rates were 98·7 and 100 per cent respectively, but in 7·6 and 4 per cent of patients tertiary HPT recurred. After treatment with cinacalcet, 80·8 per cent of the patients achieved normocalcaemia. Owing to side-effects, 6·4 per cent of patients discontinued cinacalcet treatment. The literature regarding graft function and survival is limited; however, renal graft survival after surgical treatment appears comparable to that obtained with cinacalcet therapy.

CONCLUSION

Side-effects and complications of both treatment modalities were mild and occurred in a minority of patients. Surgical treatment for tertiary HPT has higher cure rates than medical therapy.

The calcilytics Calhex-231 and NPS 2143 and the calcimimetic Calindol reduce vascular reactivity via inhibition of voltage-gated Ca2+ channels

The present study investigates the effect of commonly used negative and positive allosteric modulators of the calcium-sensing receptor (CaSR) on vascular reactivity. In wire myography studies, increasing [Ca2+]o from 1mM to 6mM induced concentration-dependent relaxations of methoxamine-induced pre-contracted rabbit mesenteric arteries, with 6mM [Ca2+]o producing almost complete relaxation. [Ca2+]o-induced relaxations were attenuated in the presence of the calcilytics Calhex-231 and NPS 2143, and abolished by the removal of the endothelium. In addition to their calcilytic effects, Calhex-231 and NPS 2143 also produced concentration-dependent inhibitions of methoxamine- or KCl-induced precontracted tone, which were unaffected by removal of the endothelium and unopposed in the presence of the calcimimetic Calindol. In vessels with depleted Ca2+ stores, contractions mediated by Ca2+ influx via voltage-gated Ca2+ channels (VGCCs) were inhibited by Calhex231. In freshly isolated single rabbit mesenteric artery smooth muscle cells, Calhex-231 and NPS 2143 inhibited whole-cell VGCC currents. Application of Calindol also inhibited methoxamine- and KCl-induced pre-contracted tone, and inhibited whole-cell VGCC currents. In conclusion, in addition to their CaSR-mediated actions in the vasculature, Calhex-231, NPS 2143 and Calindol reduce vascular contractility via direct inhibition of VGCCs.

Cinacalcet for hypercalcaemic secondary hyperparathyroidism after renal transplantation: a multicentre, retrospective, 3-year study

AIMS

Our aim was to evaluate the long-term effect of cinacalcet in patients with hypercalcaemic secondary hyperparathyroidism (SHPT) after renal transplantation (RT) in order to expand real-world data in this population.

METHODS

We performed a multicentre, observational, retrospective study in 17 renal transplant units from Spain. We collected data from renal recipients with hypercalcaemic (calcium >10.2 mg/dL) SHPT (intact parathyroid hormone (iPTH) > 120 pg/mL) who initiated cinacalcet in the clinical practice.

RESULTS

We included 193 patients with a mean (standard deviation (SD)) age of 52 (12) years, 58% men. Cinacalcet treatment was initiated at a median of 20 months after RT (median dose 30 mg/day). Mean calcium levels decreased from a mean (SD) of 11.1 (0.6) at baseline to 10.1 (0.8) at 6 months (9.0% reduction, P < 0.0001). Median iPTH was reduced by 23.0% at 6 months (P = 0.0005) and mean phosphorus levels increased by 11.1% (P < 0.0001). The effects were maintained up to 3-years. No changes were observed in renal function or anticalcineurin drug levels. Only 4.1% of patients discontinued cinacalcet due to intolerance and 1.0% due to lack of efficacy.

CONCLUSIONS

In renal transplant patients with hypercalcaemic SHPT, cinacalcet controlled serum calcium, iPTH and phosphorus levels up to 3 years. Tolerability was good.

Cinacalcet for the treatment of hyperparathyroidism in kidney transplant recipients: a systematic review and meta-analysis

BACKGROUND

Hyperparathyroidism is present in up to 50% of transplant recipients 1 year after transplant, often despite good graft function. Posttransplant patients frequently have hypercalcemia-associated hyperparathyroidism, limiting the role of vitamin D analogues and sometimes requiring parathyroidectomy. Multiple observational studies have investigated treatment of posttransplant hyperparathyroidism with the calcimimetic agent cinacalcet.

METHODS

We performed a systematic review and meta-analysis of prospective and retrospective studies from 2004 through January 26, 2012, using MEDLINE. We identified studies evaluating treatment with cinacalcet in renal transplant recipients with hyperparathyroidism. We performed random effects meta-analysis to determine changes in calcium, phosphorus, parathyroid hormone, and serum creatinine.

RESULTS

Twenty-one studies with 411 kidney transplant recipients treated with cinacalcet for hyperparathyroidism met inclusion criteria. Patients were treated for 3 to 24 months. By meta-analysis, calcium decreased by 1.14 mg/dL (95% confidence interval, -1.00 to -1.28), phosphorus increased by 0.46 mg/dL (95% confidence interval, 0.28-0.64), parathyroid hormone decreased by 102 pg/mL (95% confidence interval, -69 to -134), and there was no significant change in creatinine (0.02 mg/dL decrease; 95% confidence interval, -0.09 to 0.06). Cinacalcet resulted in hypocalcemia in seven patients. The most common side effect was gastrointestinal intolerance.

CONCLUSIONS

From nonrandomized studies, cinacalcet appears to be safe and effective for the treatment of posttransplant hyperparathyroidism. Larger observational studies and randomized controlled trials, performed over longer follow-up times and looking at clinical outcomes, are needed to corroborate these findings.

Calcimimetic R-568 and its enantiomer S-568 increase nitric oxide release in human endothelial cells

Background

Calcimimetics, such as R-568, are thought to activate G protein-linked Ca²⁺-sensing receptor (CaSR) by allosterically increasing the affinity of the receptor for Ca²⁺ allowing for efficient control of uremic hyperparathyroidism. Several recent studies suggest they possess additional vascular actions. Although it has been postulated that calcimimetics may have a direct effect on CaSR in the blood vessels, further studies are needed to elucidate their vascular CaSR-dependent versus CaSR-independent effects.

Methodology/Principal Findings

Focusing on human umbilical vein endothelial cells (HUVECs), we studied the CaSR expression and distribution by Immunofluorescence and Western Blot analysis. CaSR function was evaluated by measuring the potential effect of calcimimetic R-568 and its enantiomer S-568 upon the modulation of intracellular Ca²⁺ levels (using a single cell approach and FURA-2AM), in the presence or absence of Calhex-231, a negative modulator of CaSR. To address their potential vascular functions, we also evaluated R- and S-568-stimulated enzymatic release of Nitric Oxide (NO) by DAF-2DA, by Nitric Oxide Synthase (NOS) radiometric assay (both in HUVECs and in Human Aortic Endothelial Cells) and by measuring eNOS-ser1177 phosphorylation levels (Immunoblotting). We show that, although the CaSR protein was expressed in HUVECs, it was mainly distributed in cytoplasm while the functional CaSR dimers, usually localized on the plasma membrane, were absent. In addition, regardless of the presence or absence of Calhex-231, both R- and S-568 significantly increased intracellular Ca²⁺ levels by mobilization of Ca²⁺ from intracellular stores, which in turn augmented NO release by a time- and Ca²⁺-dependent increase in eNOS-ser1177 phosphorylation levels.

Conclusions/Significance

Taken together, these data indicate that in human endothelium there is no stereoselectivity in the responses to calcimimetics and that CaSR is probably not involved in the action of R- and S-568. This suggests an additional mechanism in support of the CaSR-independent role of calcimimetics as vasculotrope agents.

Effect of cinacalcet on renal electrolyte handling and systemic arterial blood pressure in kidney transplant patients with persistent hyperparathyroidism

BACKGROUND

The calcimimetic cinacalcet has recently been increasingly used for persistent hyperparathyroidism after renal transplantation. The present study investigated the short-term effects of cinacalcet on urinary electrolyte concentration and arterial blood pressure in kidney transplant patients with persistent hyperparathyroidism.

METHODS

In a prospective controlled single-center cross-over study, we examined 10 stable kidney transplant patients (mean estimated glomerular filtration rate 51±10 mL/min/1.73 m(2)) who received cinacalcet daily for persistent hyperparathyroidism. Urine specimens were collected at baseline and every 2 hr for a total study period of 6 hr after ingestion of 30 mg cinacalcet and without cinacalcet. Intact parathyroid hormone was determined at baseline and 2 hr later. Using ambulatory blood pressure measurement, arterial blood pressure was determined every 15 min.

RESULTS

Intact parathyroid hormone was significantly reduced with cinacalcet as compared with controls (-37±27.7% vs. -9.6±10.3%, P=0.009). With cinacalcet, urinary calcium and magnesium concentration were increased (P=0.042 and P=0.007, respectively) and differed significantly as compared with the control phase without cinacalcet. After 4 hr, an increased urinary sodium concentration was also found compared with the control phase (P=0.039). Systolic blood pressure was reduced with cinacalcet (P<0.001) and differed significantly from control phase (-13.7±9.9 mm Hg vs. -3.2±5.2 mm Hg after 2 hr, P=0.009; -18.1±10.8 mm Hg vs. -1.9±5.2 mm Hg after 4 hr, P=0.001).

CONCLUSIONS

In the short term, cinacalcet increases the urinary concentration of calcium, magnesium, and sodium. The observed antihypertensive effect might be beneficial in patients with a high cardiovascular risk after kidney transplantation.

Pharmacotherapy of chronic kidney disease and mineral bone disorder

INTRODUCTION

Disturbances of the bone and mineral metabolism are a common complication of chronic kidney disease (CKD); these disturbances are known as CKD-mineral bone disorder (CKD-MBD). A better understanding of the pathophysiological mechanisms of CKD-MBD, along with its negative impact on other organs and systems, as well as on survival, has led to a shift in the treatment paradigm of this disorder. The use of phosphate binders changed dramatically over the last decade when noncalcium-containing phosphate binders, such as sevelamer and lanthanum carbonate, became possible alternative treatments to avoid calcium overload. Vitamin D receptor activators, such as paricalcitol and doxercalciferol, with fewer calcemic and phosphatemic effects, have also been introduced to control parathormone production and the interest in native vitamin D supplementation has grown. Furthermore, a new drug class, the calcimimetics, has recently been introduced into the therapeutic arsenal for treating secondary hyperparathyroidism.

AREAS COVERED

This review discusses the advantages and disadvantages of the above pharmacological options to treat CKD-MBD.

EXPERT OPINION

The individual-based use of phosphate binders, vitamin D and calcimimetics, separately or in combination, constitute a reasonable approach to treat CKD-MBD. These treatments aim to achieve a rigorous control of phosphorus and parathormone levels, while avoiding calcium overload.

Tertiary hyperparathyroidism resistant to cinacalcet treatment

Cinacalcet hydrochloride (cinacalcet) has been reported to be efficacious for patients with tertiary hyperparathyroidism (THPT). We experienced five patients with THPT requiring parathyroidectomy (PTx) because of resistance to cinacalcet treatment and investigated their clinical characteristics and clinical course. The maximum diameter of the parathyroid gland estimated by ultrasonography before renal transplantation was evaluated. Serum total calcium, phosphorus, intact parathyroid hormone (iPTH), alkaline phosphatase (ALP), and creatinine (Cr) levels were investigated every three months after the administration of cinacalcet and at PTx. After surgery, the Cr levels were followed. In all five patients, at least one parathyroid gland had a largest diameter of more than 1 cm, and the mean diameter was 18.7 mm (range 14.9-24.1 mm). Intact PTH and ALP levels gradually increased after the initiation of cinacalcet and the Cr levels transiently increased after PTx. These findings suggest that the existence of a severely enlarged nodular hyperplastic gland is a main factor involved in resistance to cinacalcet.

The effect of cinacalcet on bone remodeling and renal function in transplant patients with persistent hyperparathyroidism

BACKGROUND

Parathyroidectomy is associated with renal functional losses in transplant patients; cinacalcet offers an attractive alternative.

METHODS

We performed a prospective observational study in 58 patients with persisting hyperparathyroidism after renal transplantation (Ca≥2.6 mmol/L) and impaired renal transplant function (estimated glomerular filtration rate [eGFR] <50 mL/min). The patients received 30 to 90 mg cinacalcet for 12 months with the target to normalize serum Ca. We measured parathyroid hormone (PTH), serum Ca, serum phosphorus, alkaline phosphatase, bone-specific alkaline phosphatase, osteocalcin, and telopeptide at 0, 1, 2, 3, 6, 9, and 12 months of cinacalcet treatment. Fractional excretion of calcium and phosphorus (n=24) were monitored at 0 and 1 month.

RESULTS

At inclusion, creatinine was 181±70 μmol/L, eGFR 43±19 mL/min, PTH 371±279 pg/mL, and Ca 2.73±0.22 mmol/L. We observed nephrocalcinosis in 58% of biopsied patients at enrollment. After cinacalcet, Ca decreased significantly and normalized at nearly any measurement. Phosphorus increased significantly at months 1, 9, and 12. PTH decreased significantly, but only at months 9 and 12 and did not normalize. Bone-specific alkaline phosphatase increased significantly (>normal) by month 12. eGFR decreased and serum creatinine increased at all time points. The Δ(creatinine) % increase correlated significantly with the Δ(PTH) % decrease at month 1 and 12. Telopeptide and alkaline phosphatase correlated with PTH and telopeptide also correlated with serum creatinine.

CONCLUSION

Calcium-phosphorus homeostasis in hypercalcemic renal transplant patients normalizes under cinacalcet and PTH decreases, albeit not to normal. The renal functional decline could be PTH mediated, analogous to the effects observed after parathyroidectomy.

Cinacalcet improves bone density in post-kidney transplant hyperparathyroidism

The recent availability of cinacalcet has provided a possible alternative to parathyroidectomy in kidney transplant patients with persistent hyperparathyroidism, but its effect on bone mass density (BMD) is unknown. From our database containing 163 kidney transplants performed at our center from 1999 to 2007, we compared recipients who received cinacalcet for persistent hypercalcemia and hyperparathyroidism following renal transplantation (n = 8) with up to two other posttransplant patients matched for age, sex, race, and graft function (n = 15). The outcome of the study was BMD changes from baseline to 12, 24, and 36 months post-renal transplantation. Repeated-measures mixed model was used to assess the difference of BMD change between two groups. Cinacalcet therapy was started at a median of 9 (range = 1 to 24) months posttransplant with a mean dose 56 ± 29 mg/d (mean duration = 1.6; range = 1 to 2.1 years). Cinacalcet therapy was associated with significant reduction of serum calcium compared to control. Cinacalcet therapy was associated with greater BMD increase at the hip over the 36-month posttransplant period. Cinacalcet was well tolerated. Our results suggest that cinacalcet may have a small but favorable effect on bone density following kidney transplantation.