Pharmacology of the phosphate binder, lanthanum carbonate

Safety and efficacy of a feed additive consisting of lanthanum carbonate octahydrate for dogs (Porus GmbH)

Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of lanthanum carbonate octahydrate as a zootechnical feed additive for dogs. The additive is already authorised for use in feed for cats. The FEEDAP Panel concluded that the additive lanthanum carbonate octahydrate is safe for adult dogs at the maximum recommended level of 7500 mg/kg complete feed. The additive is not irritant to skin or eyes, is not a skin sensitiser and exposure by inhalation is considered to be unlikely. The Panel also concluded that lanthanum carbonate octahydrate is efficacious in the reduction of phosphorus bioavailability in adult dogs at the minimum inclusion level of 1500 mg/kg complete feed.

Mineral Bone Disorders in Kidney Disease Patients: The Ever-Current Topic

Chronic kidney disease (CKD) is a complex and multifactorial disease, and one of the most prevalent worldwide. Chronic kidney disease-mineral bone disorders (CKD-MBD) with biochemical and hormonal alterations are part of the complications associated with the progression of CKD. Pathophysiology of CKD-MBD focused on abnormalities in serum levels of several biomarkers (such as FGF-23, klotho, phosphate, calcium, vitamin D, and PTH) which are discussed in this review. We therefore examine the prognostic association between CKD-MBD and the increased risk for cardiovascular events, mortality, and CKD progression to end-stage kidney disease (ESKD). Lastly, we present specific treatments acting on CKD to prevent and treat the complications associated with secondary hyperparathyroidism (SHPT): control of hyperphosphatemia (with dietary restriction, intestinal phosphate binders, and adequate dialysis), the use of calcimimetic agents, vitamin D, and analogues, and the use of bisphosphonates or denosumab in patients with osteoporosis.

Combination treatment with tenapanor and sevelamer synergistically reduces urinary phosphorus excretion in rats

The majority of patients with chronic kidney disease (CKD) receiving dialysis do not achieve target serum phosphorus concentrations, despite treatment with phosphate binders. Tenapanor is a nonbinder, sodium/hydrogen exchanger isoform 3 (NHE3) inhibitor that reduces paracellular intestinal phosphate absorption. This preclinical study evaluated the effect of tenapanor and varying doses of sevelamer carbonate on urinary phosphorus excretion, a direct reflection of intestinal phosphate absorption. We measured 24-h urinary phosphorus excretion in male rats assigned to groups dosed orally with vehicle or tenapanor (0.3 mg/kg/day) and provided a diet containing varying amounts of sevelamer [0-3% (wt/wt)]. We also evaluated the effect of the addition of tenapanor or vehicle on 24-h urinary phosphorus excretion to rats on a stable dose of sevelamer [1.5% (wt/wt)]. When administered together, tenapanor and sevelamer decreased urinary phosphorus excretion significantly more than either tenapanor or sevelamer alone across all sevelamer dose levels. The Bliss statistical model of independence indicated that the combination was synergistic. A stable sevelamer dose [1.5% (wt/wt)] reduced mean ± SE urinary phosphorus excretion by 42 ± 3% compared with vehicle; together, tenapanor and sevelamer reduced residual urinary phosphorus excretion by an additional 37 ± 6% (P < 0.05). Although both tenapanor and sevelamer reduce intestinal phosphate absorption individually, administration of tenapanor and sevelamer together results in more pronounced reductions in intestinal phosphate absorption than if either agent is administered alone. Further evaluation of combination tenapanor plus phosphate binder treatment in patients receiving dialysis with hyperphosphatemia is warranted.

Digital radiography as an alternative method in the evaluation of bone density in uremic rats

INTRODUCTION

Digital radiography (DRx) may provide a suitable alternative to investigate mineral and bone disorder (MBD) and loss of bone density (BD) in rodent models of chronic kidney disease (CKD). The objective of this study was to use DRx to evaluate BD in CKD rats, and to evaluate the correlation between DRx findings and serum MBD markers and bone histomorphometry.

METHODS

Uremia was induced by feeding Wistar rats an adenine-enriched diet (0.75% for 4 weeks/0.10% for 3 weeks); outcomes were compared to a control group at experimental weeks 3, 4, and 7. The following biochemical markers were measured: creatinine clearance (CrC), phosphate (P), calcium (Ca), fractional excretion of P (FeP), alkaline phosphatase (ALP), fibroblast growth factor-23 (FGF-23), and parathyroid hormone (PTH). DRx imaging was performed and histomorphometry analysis was conducted using the left femur.

RESULTS

As expected, at week 7, uremic rats presented with reduced CrC and higher levels of P, FeP, and ALP compared to controls. DRx confirmed the lower BD in uremic animals (0.57±0.07 vs. 0.68 ± 0.06 a.u.; p = 0.016) compared to controls at the end of week 7, when MBD was more prominent. A severe form of high-turnover bone disease accompanied these biochemical changes. BD measured on DRx correlated to P (r=-0.81; p = 0.002), ALP (r = -0.69, p = 0.01), PTH (r = -0.83, p = 0.01), OS/BS (r = -0.70; p = 0.02), and ObS/BS (r = -0.70; p = 0.02).

CONCLUSION

BD quantified by DRx was associated with the typical complications of MBD in CKD and showed to be viable in the evaluation of bone alterations in CKD.

[Studies of the Various Chronic Kidney Failure Rat Models and Hemodialysis Mini-pig Model for the Evaluation of Anti-hyperphosphatemia Drugs]

Animal models of chronic kidney failure (CKF) have been developed for the pharmacodynamic evaluation of various phosphate binders that are used clinically to treat hyperphosphatemia in patients with chronic kidney disease. However, these models represent different disease states and severities, depending on the experimental conditions and are not clearly defined for pharmacological evaluation. In addition, experimental models have not yet been established for artificial dialysis. The purpose of this study was to confirm the utility of the various rat models of CKF and the mini-pig model of hemodialysis as models of hyperphosphatemia for pharmacodynamic evaluation. Various rat models of pre-dialysis CKF (oral adenine dosing, 5/6 resection, and ligation nephrectomy model) were evaluated through determinations of serum and urinary parameters (osmolality, creatinine, and phosphorus), pathological observations of kidney, and the phosphorus-absorbing properties of lanthanum carbonate (La) formulations. The rat and mini-pig models were compared based on each evaluation index. In the oral adenine dosing model, serum phosphorus increased markedly and the area under the serum phosphorus concentration-time curve (phosphorus AUC) decreased in a dose-dependent manner with the administration of La formulations. In contrast, a significant decrease in serum phosphorus AUC, a prolongation of the dialysis interval, and an improvement in dialysis efficiency were observed after administration of La formulations to the mini-pig hemodialysis model. Furthermore, the results of bioequivalence studies between two La formulations (Fosrenol and SW670, a generic formulation) suggested that the rat and mini-pig models are useful and precise as pre-dialysis and dialysis models, respectively.

Human health risk associated with the management of phosphorus in freshwaters using lanthanum and aluminium

The use of geo-engineering materials to manage phosphorus in lakes has increased in recent years with aluminium and lanthanum based materials being most commonly applied. Hence the potential impact of the use of these compounds on human health is receiving growing interest. This review seeks to understand, evaluate and compare potential unintended consequences on human health and ecotoxicological risks associated with the use of lanthanum- and aluminium-based materials to modify chemical and ecological conditions in water bodies. In addition to their therapeutic use for the reduction of intestinal phosphate absorption in patients with impaired renal function, the phosphate binding capacity of aluminium and lanthanum also led to the development of materials used for water treatment. Although lanthanum and aluminium share physicochemical similarities and have many common applications, their uptake and kinetics within the human body and living organisms importantly differ from each other which is reflected in a different toxicity profile. Whilst a causal role in the development of neurological pathologies, skeletal lesions, hematopoietic disorders and respiratory effects has unequivocally been demonstrated with increased exposure to aluminium, studies until now have failed to find such a clear association after exposure to lanthanum although caution is warranted. Our review indicates that lanthanum and aluminium have a distinctly different profile with respect to their potential effects on human health. Regular monitoring of both aluminium and lanthanum concentrations in lanthanum-/aluminium-treated water by the responsible authorities is recommended to avoid acute accidental or chronic low level accumulation.

Effect of cross-linked chitosan iron (III) on vascular calcification in uremic rats

Cross-linked chitosan iron (III) is a chitin-derived polymer with a chelating effect on phosphorus, but it is untested in vascular calcification. We evaluated this compound's ability to reduce hyperphosphatemia and its effect on vascular calcification in uremic rats using an adenine-based, phosphorus-rich diet for seven weeks. We used a control group to characterize the uremia. Uremic rats were divided according the treatment into chronic kidney disease, CKD-Ch-Fe(III)CL (CKD-Ch), CKD-calcium carbonate, or CKD-sevelamer groups. We measured creatinine, phosphorus, calcium, alkaline phosphatase, phosphorus excretion fraction, parathyroid hormone, and fibroblast growth factor 23. Vascular calcification was assessed using the aortic calcium content, and a semi-quantitative analysis was performed using Von Kossa and hematoxylin-eosin staining. At week seven, rats in the chronic kidney disease group had higher creatinine, phosphorus, phosphorus excretion fraction, calcium, alkaline phosphatase, fibroblast growth factor 23, and aortic calcium content than those in the Control group. Treatments with cross-linked chitosan iron (III) and calcium carbonate prevented phosphorus increase (20%-30% reduction). The aortic calcium content was lowered by 88% and 85% in the CKD-Ch and CKD-sevelamer groups, respectively. The prevalence of vascular changes was higher in the chronic kidney disease and CKD-calcium carbonate (62.5%) groups than in the CKD-Ch group (37.5%). In conclusion, cross-linked chitosan iron (III) had a phosphorus chelating effect similar to calcium carbonate already available for clinical use, and prevented calcium accumulation in the aorta. Impact statement Vascular calcification (VC) is a common complication due to CKD-related bone and mineral disorder (BMD) and is characterized by deposition of calcium in vessels. Effective therapies are not yet available but new phosphorus chelators can prevent complications from CV. We tested the effect of chitosan, a new phosphorus chelator, on the VC of uremic animals. It has recently been proposed that chitosan treatment may be effective in the treatment of hyperphosphataemia. However, its action on vascular calcification has not been investigated yet. In this study, we demonstrated that chitosan reduced the calcium content in the aorta, suggesting that this may be a therapeutic approach in the treatment of hyperphosphatemia by preventing CV.

Effects of phosphate binders on the gastrointestinal absorption of arsenate and of an SGLT2 inhibitor drug on the urinary excretion of arsenite in mice

Arsenate (As^V) and arsenite (As^III) are typical sources of acute and chronic arsenic poisoning. Therefore, reducing inner exposure to these arsenicals is a rational objective. Because As^V mimics phosphate, phosphate binder drugs may decrease the intestinal As^V absorption. Indeed, lanthanum and aluminium salts and sevelamer removed As^V from solution in vitro, especially at acidic pH. In mice gavaged with As^V, lanthanum chloride, lanthanum carbonate and aluminium hydroxide given orally also lowered the urinary excretion and tissue levels of As^V and its metabolites, indicating that they decreased the gastrointestinal As^V absorption. As some glucose transporters may carry As^III, the effect of the SGLT2 inhibitor dapagliflozin was investigated in As^III-injected mice. While producing extreme glucosuria, dapagliflozin barely affected the urinary excretion and tissue concentrations of As^III and its metabolites. Thus, phosphate binders (especially lanthanum compounds) can reduce the gastrointestinal absorption of As^V; however, SGLT2 inhibition cannot diminish the renal reabsorption of As^III.

Gastric mucosal status susceptible to lanthanum deposition in patients treated with dialysis and lanthanum carbonate

Lanthanum carbonate is a popular chemical which is administered for patients with end-stage kidney disease to reduce the absorption of phosphate, and lanthanum deposition in the gastroduodenal mucosa has recently been reported. The aim of this study was to assess whether any histologic changes of the gastric mucosa are related to the deposition of lanthanum. Twenty-four patients who revealed the histology of lanthanum deposition on gastroduodenal biopsy between 2011 and 2014 were included in the study, and their clinical records and gastroduodenal biopsies obtained from 2011 to 2015 were reviewed, adding the review of gastroduodenal biopsies before 2011 if possible. Analysis of the deposited materials by scanning electron microscopy-energy dispersive x-ray spectroscopy was performed for a representative gastric biopsy. All patients were diagnosed as having renal insufficiency due to chronic kidney disease and treated with dialysis for more than 5 years, with confirmation of lanthanum carbonate use for 22 patients. Of 121 gastric biopsies and 10 duodenal ones between 2011 and 2015, 86 gastric biopsies (71.1%) and 3 duodenal biopsies (30%), respectively, revealed histology consistent with lanthanum deposition, which was confirmed by scanning electron microscopy-energy dispersive x-ray spectroscopy analysis for a representative case. The deposition tended to occur in the gastric mucosa with regenerative change, intestinal metaplasia, or foveolar hyperplasia (P<.05). Such mucosal changes were observed in about half of the gastric biopsy samples obtained prior to 2010, in which no lanthanum deposition was identified irrespective of the gastric mucosal status. Although direct association between lanthanum deposition and clinical symptoms is not clear, the evaluation of the gastric mucosal status (prior to administration) seems to be important to predict lanthanum deposition when lanthanum carbonate is administered for patients with chronic kidney disease treated with dialysis.

Hyperphosphatemia Management in Patients with Chronic Kidney Disease

Hyperphosphatemia in chronic kidney disease (CKD) patients is a potentially life altering condition that can lead to cardiovascular calcification, metabolic bone disease (renal osteodystrophy) and the development of secondary hyperparathyroidism (SHPT). It is also associated with increased prevalence of cardiovascular diseases and mortality rates. To effectively manage hyperphosphatemia in CKD patients it is important to not only consider pharmacological and nonpharmacological treatment options but also to understand the underlying physiologic pathways involved in phosphorus homoeostasis. This review will therefore provide both a background into phosphorus homoeostasis and the management of hyperphosphatemia in CKD patients. In addition, it will cover some of the most important reasons for failure to control hyperphosphatemia with emphasis on the effect of the gastric pH on phosphate binders efficiency.

A comparison of the long-term effects of lanthanum carbonate and calcium carbonate on the course of chronic renal failure in rats with adriamycin-induced nephropathy

Lanthanum carbonate (LA) is an effective phosphate binder. Previous study showed the phosphate-binding potency of LA was twice that of calcium carbonate (CA). No study in which LA and CA were given at an equivalent phosphate-binding potency to rats or humans with chronic renal failure for a long period has been reported to date. The objective of this study was to compare the phosphate level in serum and urine and suppression of renal deterioration during long-term LA and CA treatment when they were given at an equivalent phosphate-binding potency in rats with adriamycin (ADR)-induced nephropathy. Rats were divided into three groups: an untreated group (ADR group), a CA-treated (ADR-CA) group and a LA-treated (ADR-LA) group. The daily oral dose of LA was 1.0 g/kg/day and CA was 2.0 g/kg/day for 24 weeks. The serum phosphate was lower in the ADR-CA or ADR-LA group than in the ADR group and significantly lower in the ADR-CA group than in the ADR group at each point, but there were no significant differences between the ADR and ADR-LA groups. The serum phosphate was also lower in the ADR-CA group than in the ADR-LA group, and there was significant difference at week 8. The urinary phosphate was significantly lower in the ADR-CA group than in the ADR or ADR-LA group at each point. The urinary phosphate was also lower in the ADR-LA group than in the ADR group at each point, and significant difference at week 8. There were no significant differences in the serum creatinine or blood urea nitrogen among the three groups. In conclusion, this study indicated the phosphate-binding potency of LA isn’t twice as strong as CA, and neither LA nor CA suppressed the progression of chronic renal failure in the serum creatinine and blood urea nitrogen, compared to the untreated group.

Phosphate: an old bone molecule but new cardiovascular risk factor

Phosphate handling in the body is complex and involves hormones produced by the bone, the parathyroid gland and the kidneys. Phosphate is mostly found in hydroxyapatite. however recent evidence suggests that phosphate is also a signalling molecule associated with bone formation. Phosphate balance requires careful regulation of gut and kidney phosphate transporters, SLC34 transporter family, but phosphate signalling in osteoblasts and vascular smooth muscle cells is likely mediated by the SLC20 transporter family (PiT1 and PiT2). If not properly regulated, phosphate imblanace could lead to mineral disorders as well as vascular calcification. In chronic kidney disease-mineral bone disorder, hyperphosphataemia has been consistently associated with extra-osseous calcification and cardiovascular disease. This review focuses on the physiological mechanisms involved in phosphate balance and cell signalling (i.e. osteoblasts and vascular smooth muscle cells) as well as pathological consequences of hyperphosphataemia. Finally, conventional as well as new and experimental therapeutics in the treatment of hyperphosphataemia are explored.

Lanthanum carbonate delays progression of coronary artery calcification compared with calcium-based phosphate binders in patients on hemodialysis: a pilot study

BACKGROUND AND OBJECTIVES

Coronary artery calcification (CAC) is associated with future cardiovascular events and/or death of patients on hemodialysis (HD). We investigated whether progression of CAC in patients on HD could be delayed by switching from a calcium (Ca)-based phosphate (Pi) binder to lanthanum carbonate.

DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS

The CAC scores were evaluated at study enrollment and after 6 months in 52 patients on HD using calcium carbonate (CC) as a Pi binder. Patients were randomly divided into 2 groups assigned to receive either CC or lanthanum carbonate (LC), and the CAC scores were evaluated after a 6-month treatment period. Progression of CAC was assessed, as were serum levels of Ca, Pi, and intact parathyroid hormone (iPTH).

RESULTS

Forty-two patients completed the study (23 receiving CC and 19 receiving LC). In the 6 months prior to randomization, all patients were treated with CC. During this 6-month period, the CAC scores increased significantly in all 42 patients. Once randomized, there was significantly less progression in the group treated with LC than with CC. Changes in CAC scores from 6 to 12 months were significantly smaller in the LC group than the CC group (-288.9 ± 1176.4 vs 107.1 ± 559.6, P = .036), and percentage changes were also significantly different (-6.4% vs 41.2%, P = .024). Serum Ca, Pi, and iPTH levels were similar in both groups during the study period.

CONCLUSIONS

This pilot study suggested that LC delayed progression of CAC in patients on HD compared with CC.

Ferric citrate hydrate, a new phosphate binder, prevents the complications of secondary hyperparathyroidism and vascular calcification

BACKGROUND/AIMS

Ferric citrate hydrate (JTT-751) is being developed as a treatment for hyperphosphatemia in chronic kidney disease patients, and shows serum phosphorus-reducing effects on hyperphosphatemia in hemodialysis patients. We examined whether JTT-751 could reduce phosphorus absorption in normal rats and prevent the progression of ectopic calcification, secondary hyperparathyroidism and bone abnormalities in chronic renal failure (CRF) rats.

METHODS

Normal rats were fed a diet containing 0.3, 1 or 3% JTT-751 for 7 days. The effects of JTT-751 on phosphorus absorption were evaluated with fecal and urinary phosphorus excretion. Next, a CRF model simulating hyperphosphatemia was induced by feeding rats a 0.75% adenine diet. After 21 days of starting the adenine diet feeding, 1 or 3% JTT-751 was administered for 35 days by dietary admixture. The serum phosphorus levels and mineral parameters were measured. Calcification in the aorta was examined biochemically and histopathologically. Hyperparathyroidism and bone abnormalities were evaluated by histopathological analysis of the parathyroid and femur, respectively.

RESULTS

In normal rats, JTT-751 increased fecal phosphorus excretion and reduced phosphorus absorption and urinary phosphorus excretion. In CRF rats, JTT-751 reduced serum phosphorus levels, the calcium-phosphorus product and calcium content in the aorta. Serum intact parathyroid hormone levels and the incidence and severity of parathyroid hyperplasia were also decreased. JTT-751 reduced femoral bone fibrosis, porosity and osteoid formation.

CONCLUSIONS

JTT-751 could bind with phosphate in the gastrointestinal tract, increase fecal phosphorus excretion and reduce phosphorus absorption. JTT-751 could prevent the progression of ectopic calcification, secondary hyperparathyroidism and bone abnormalities in rats.

Lanthanum, constipation, bafflying X-rays and a perforated colonic diverticulum

Lanthanum carbonate (LC) is used as a phosphate binder in dialysed patients. Abdominal pain and constipation are known side effects of its use. Furthermore, in radiological studies, LC tablets are seen as intense radio-opaque deposits within the entire gastrointestinal tract—findings which can lead to diagnostic misinterpretations. An elderly patient on peritoneal dialysis and taking LC presented with peritonitis, secondary to a perforated colonic diverticulum. The possible association between the use of LC, worsening constipation and complications arising from colonic diverticular disease, are discussed.