Hyperphosphataemia in renal failure: causes, consequences and current management

Albumin-based nanoparticles as contrast medium for MRI: vascular imaging, tissue and cell interactions, and pharmacokinetics of second-generation nanoparticles

This multidisciplinary study examined the pharmacokinetics of nanoparticles based on albumin-DTPA-gadolinium chelates, testing the hypothesis that these nanoparticles create a stronger vessel signal than conventional gadolinium-based contrast agents and exploring if they are safe for clinical use. Nanoparticles based on human serum albumin, bearing gadolinium and designed for use in magnetic resonance imaging, were used to generate magnet resonance images (MRI) of the vascular system in rats ("blood pool imaging"). At the low nanoparticle doses used for radionuclide imaging, nanoparticle-associated metals were cleared from the blood into the liver during the first 4 h after nanoparticle application. At the higher doses required for MRI, the liver became saturated and kidney and spleen acted as additional sinks for the metals, and accounted for most processing of the nanoparticles. The multiple components of the nanoparticles were cleared independently of one another. Albumin was detected in liver, spleen, and kidneys for up to 2 days after intravenous injection. Gadolinium was retained in the liver, kidneys, and spleen in significant concentrations for much longer. Gadolinium was present as significant fractions of initial dose for longer than 2 weeks after application, and gadolinium clearance was only complete after 6 weeks. Our analysis could not account quantitatively for the full dose of gadolinium that was applied, but numerous organs were found to contain gadolinium in the collagen of their connective tissues. Multiple lines of evidence indicated intracellular processing opening the DTPA chelates and leading to gadolinium long-term storage, in particular inside lysosomes. Turnover of the stored gadolinium was found to occur in soluble form in the kidneys, the liver, and the colon for up to 3 weeks after application. Gadolinium overload poses a significant hazard due to the high toxicity of free gadolinium ions. We discuss the relevance of our findings to gadolinium-deposition diseases.

Elemental calcium intake associated with calcium acetate/calcium carbonate in the treatment of hyperphosphatemia

Background

Calcium-based and non-calcium-based phosphate binders have similar efficacy in the treatment of hyperphosphatemia; however, calcium-based binders may be associated with hypercalcemia, vascular calcification, and adynamic bone disease.

Scope

A post hoc analysis was carried out of data from a 16-week, Phase IV study of patients with end-stage renal disease (ESRD) who switched to lanthanum carbonate monotherapy from baseline calcium acetate/calcium carbonate monotherapy. Of the intent-to-treat population (N=2520), 752 patients with recorded dose data for calcium acetate (n=551)/calcium carbonate (n=201) at baseline and lanthanum carbonate at week 16 were studied. Elemental calcium intake, serum phosphate, corrected serum calcium, and serum intact parathyroid hormone levels were analyzed.

Findings

Of the 551 patients with calcium acetate dose data, 271 (49.2%) had an elemental calcium intake of at least 1.5 g/day at baseline, and 142 (25.8%) had an intake of at least 2.0 g/day. Mean (95% confidence interval [CI]) serum phosphate levels were 6.1 (5.89, 6.21) mg/dL at baseline and 6.2 (6.04, 6.38) mg/dL at 16 weeks; mean (95% CI) corrected serum calcium levels were 9.3 (9.16, 9.44) mg/dL and 9.2 (9.06, 9.34) mg/dL, respectively. Of the 201 patients with calcium carbonate dose data, 117 (58.2%) had an elemental calcium intake of at least 1.5 g/day, and 76 (37.8%) had an intake of at least 2.0 g/day. Mean (95% CI) serum phosphate levels were 5.8 (5.52, 6.06) mg/dL at baseline and 5.8 (5.53, 6.05) mg/dL at week 16; mean (95% CI) corrected serum calcium levels were 9.7 (9.15, 10.25) mg/dL and 9.2 (9.06, 9.34) mg/dL, respectively.

Conclusion

Calcium acetate/calcium carbonate phosphate binders, taken to control serum phosphate levels, may result in high levels of elemental calcium intake. This may lead to complications related to calcium balance.

Benzimidazole derivative fluorescent probe for cascade recognition of phosphate and iron ions in aqueous medium and its logic gate behavior

A fluorescent probe based on benzimidazole was synthesized, and its cascade recognition of PO₄³⁻ and Fe³⁺ ions was investigated using spectroscopic techniques.

Lanthanum carbonate oral powder: satisfaction, preference and adherence in French and Spanish patients with end-stage renal disease

BACKGROUND

Phosphate binders, such as lanthanum carbonate, control elevated serum-phosphate levels in patients with end-stage renal disease (ESRD). Lanthanum carbonate is available in oral powder and tablet form. The aim of this survey was to investigate satisfaction with, preference for, and adherence to lanthanum carbonate oral powder in patients with ESRD.

SCOPE

Patients from France and Spain who had been taking lanthanum carbonate powder for at least 4 weeks, and who had experience of other phosphate binders of any formulation, were asked to complete an online or telephone survey. Treatment satisfaction was measured using the Treatment Satisfaction Questionnaire for Medication-9; preference was measured using 5-point Likert scale agreement ratings; and adherence was measured using the Morisky Medication Adherence Scale-4. Data were evaluated using bivariate analyses.

FINDINGS

Overall, 160 patients participated (80 per country). Lanthanum carbonate powder was reported to have a higher effectiveness rating (p<0.05), be more convenient (p<0.05), and provide a higher level of satisfaction (p<0.01) than previous binders. There was an overall preference for lanthanum carbonate powder over previous binders of any formulation (p<0.001). Adherence to medication was similar for all binders analysed: 66.3% of French patients adhered to lanthanum carbonate powder, and 65.0% adhered to previous binder treatment (p=not significant); 52.5% of Spanish patients adhered to lanthanum carbonate powder, and 56.3% adhered to previous binder treatment (p=not significant).

LIMITATIONS

The survey enrolled patients who had already experienced phosphate binders before the study began. Information on patient preferences for and adherence to previous phosphate binders was therefore based on the patients' memories of these experiences, which may have been subject to change over time. Although most participants completed the online survey in this study, a telephone survey was used for individuals who could not access the online version; if only one method of data recording had been used, there may have been reduced variation in responses.

CONCLUSION

Patients with ESRD report increased satisfaction with and preference for lanthanum carbonate powder over other formulations, suggesting that lanthanum carbonate powder is more convenient and easier to use than other formulations.

Klotho: a humeral mediator in CSF and plasma that influences longevity and susceptibility to multiple complex disorders, including depression

Klotho is a hormone secreted into human cerebrospinal fluid (CSF), plasma and urine that promotes longevity and influences the onset of several premature senescent phenotypes in mice and humans, including atherosclerosis, cardiovascular disease, stroke and osteoporosis. Preliminary studies also suggest that Klotho possesses tumor suppressor properties. Klotho's roles in these phenomena were first suggested by studies demonstrating that a defect in the Klotho gene in mice results in a significant decrease in lifespan. The Klotho-deficient mouse dies prematurely at 8-9 weeks of age. At 4-5 weeks of age, a syndrome resembling human ageing emerges consisting of atherosclerosis, osteoporosis, cognitive disturbances and alterations of hippocampal architecture. Several deficits in Klotho-deficient mice are likely to contribute to these phenomena. These include an inability to defend against oxidative stress in the central nervous system and periphery, decreased capacity to generate nitric oxide to sustain normal endothelial reactivity, defective Klotho-related mediation of glycosylation and ion channel regulation, increased insulin/insulin-like growth factor signaling and a disturbed calcium and phosphate homeostasis accompanied by altered vitamin D levels and ectopic calcification. Identifying the mechanisms by which Klotho influences multiple important pathways is an emerging field in human biology that will contribute significantly to understanding basic physiologic processes and targets for the treatment of complex diseases. Because many of the phenomena seen in Klotho-deficient mice occur in depressive illness, major depression and bipolar disorder represent illnesses potentially associated with Klotho dysregulation. Klotho's presence in CSF, blood and urine should facilitate its study in clinical populations.

A terbium(III)-complex-based on-off fluorescent chemosensor for phosphate anions in aqueous solution and its application in molecular logic gates

A new Tb(III) complex based on a tripodal carboxylate ligand has been synthesized for the selective fluorescent recognition of phosphate anions, including inorganic phosphates and nucleoside phosphates (e.g., ATP), in Tris buffer solution. The resulting L · Tb complex shows the characteristic emission bands centered at about 495 and 550 nm from the Tb(III)-centered (5)D4 excited state to (7)FJ transitions with J = 6 and 5, where the chelating ligand acts only as an "antenna". Upon the addition of phosphate anions to the aqueous solution of Tb(III) complex, significant "on-off" fluorescence changes were observed, which were attributed to the inhibition of the "antenna" effect between the ligand and Tb(III) after the incorporation of phosphate anions. Furthermore, this unique Tb(III) complex has been successfully utilized to detect phosphate anions with filter papers and hydrogels. Notably, the Tb(III) complex also can be used for the construction of molecular logic gates with TRANSFER and INHIBIT logic functions by using the above fluorescence changes.

Calcimimetics for secondary hyperparathyroidism in chronic kidney disease patients

BACKGROUND

Calcimimetic agents lower abnormal serum parathyroid hormone (PTH) levels in people who have chronic kidney disease (CKD), but the benefits and harms on patient-level outcomes are uncertain. Since this review was first published in 2006 showing that evidence for calcimimetics was largely restricted to biochemical outcomes, additional studies have been conducted. This is an update of a review first published in 2006.

OBJECTIVES

To evaluate the benefits and harms of cinacalcet on patient-level outcomes in adults with CKD.

SEARCH METHODS

MEDLINE, EMBASE, CENTRAL and conference proceedings were searched for randomised controlled trials (RCTs) evaluating any calcimimetic against placebo or another agent in adults with CKD (persistent albuminuria > 30 mg/g with or without reduced glomerular filtration rate (GFR) (below 60 mL/min/1.73 m²)). We updated searches to 7 February 2013 including the Cochrane Renal Group's Specialised Register to complete this update.

SELECTION CRITERIA

We included all RCTs of a calcimimetic administered to patients with CKD for the treatment of elevated serum PTH levels.

DATA COLLECTION AND ANALYSIS

Data were extracted on all relevant patient-centred and surrogate outcomes. We summarised treatment estimates using random effects and expressed treatment effects as a risk ratio (RR) or mean difference (MD) with 95% confidence intervals (CI).

MAIN RESULTS

Eighteen studies (7446 participants) compared cinacalcet in addition to standard therapy with no treatment or placebo plus standard therapy. In adults with GFR category G5 (GFR below 15 mL/min/1.73 m²) treated with dialysis, routine cinacalcet treatment had little or no effect on all-cause mortality (RR 0.97, 95% CI 0.89 to 1.05), imprecise effects on cardiovascular mortality (RR 0.67, 95% CI 0.16 to 2.87), and prevented surgical parathyroidectomy (RR 0.49, 95% CI 0.40 to 0.59) and hypercalcaemia (RR 0.23, 95% CI 0.05 to 0.97), but increased hypocalcaemia (RR 6.98, 95% CI 5.10 to 9.53), nausea (RR 2.02, 95% CI 1.45 to 2.81) and vomiting (RR 1.97, 95% CI 95% CI 1.73 to 2.24). Cinacalcet decreased serum PTH (MD -281.39 pg/mL, 95% CI -325.84 to -234.94) and calcium (MD -0.87 mg/dL, 95% CI -0.96 to -0.77) levels, but had little or no effect on serum phosphorous levels (MD -0.23 mg/dL, 95% CI -0.58 to 0.12).Data were sparse for adults with GFR categories G3a to G4 (GFR 15 to 60 mL/min/1.73 m²) and kidney transplant recipients.Overall, based on GRADE criteria, evidence for cinacalcet in adults with GFR category G5 treated with dialysis (mortality, parathyroidectomy, hypocalcaemia, and nausea) is of high or moderate quality. High quality evidence suggests "further research is very unlikely to change our confidence in the estimate of treatment effect" and moderate quality evidence is "further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate". Information for adults with less severe CKD GFR category G3a to G4 is of low or very low quality. This means that further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate

AUTHORS' CONCLUSIONS

Routine cinacalcet therapy reduced the need for parathyroidectomy in adults treated with dialysis and elevated PTH levels but does not improve all-cause or cardiovascular mortality. Cinacalcet increases risks of nausea, vomiting and hypocalcaemia, suggesting harms may outweigh benefits in this population.

Cost-minimization analysis of lanthanum carbonate versus sevelamer hydrochloride in US patients with end-stage renal disease

PURPOSE

Sevelamer hydrochloride (SH) and lanthanum carbonate (LC) are calcium-free phosphate binders used in the clinical management of hyperphosphatemia in patients with end-stage renal disease (ESRD). The objective of this analysis was to assess the cost-effectiveness of LC monotherapy compared with SH monotherapy in US patients with ESRD in a clinical practice setting.

METHODS

This was a post hoc assessment of phosphate binder costs among US patients with ESRD who converted from SH to LC monotherapy in a previously published, 16-week, Phase IV, real-world study. Calculations of drug costs used both average wholesale price (AWP) and wholesale acquisition cost (WAC).

FINDINGS

There were 953 patients with available baseline SH dose data; 950 also had a recorded LC dose >0 mg at baseline, and 691 had dose data available for both SH at baseline and LC at week 16 (post hoc analysis population). Baseline demographic characteristics were similar in excluded patients and the post hoc analysis population. Mean (SD) serum phosphate levels were 5.91 (1.66) mg/dL at baseline and 5.93 (1.85) mg/dL after conversion to LC monotherapy for 16 weeks. Mean AWP costs were US$35.72 (16.89) per day at baseline and US$24.69 (8.28) per day at week 16, yielding an overall mean cost change (defined as LC cost - SH cost) of -US$11.03 (16.37) per day in favor of LC. The overall mean WAC cost change was -US$9.17 (13.64) per day. Within baseline SH dose subgroups 2400 to 4800, >4800 to 7200, >7200 to 9600, and >9600 mg/d, the mean AWP cost change ranged from US$2.78 (9.26) per day in favor of SH for the 2400- to 4800-mg/d subgroup to -US$33.15 (12.58) per day in favor of LC for the >9600-mg/d subgroup. Mean WAC cost changes showed a similar trend, ranging from US$2.33 (7.72) per day to -US$27.59 (10.48) per day. Linear regression analyses revealed that the inflection SH doses corresponding to a mean cost change of zero were 4905 mg/d (AWP) and 4908 mg/d (WAC). For the 455 (66%) patients in the post hoc analysis population who had baseline SH doses at least as high (≥ 5600 mg/d) as these point estimates, the mean SH:LC tablet ratio was ≥ 3.7, indicating a mean reduction in the tablet burden after conversion to LC of ≥ 73%.

IMPLICATIONS

This real-world assessment of comparative phosphate binder drug costs between SH and LC among US patients with ESRD indicates that average cost savings with LC use increased with increasing SH doses. Conversion to LC from SH ≥ 5600 mg/d reduced drug costs and tablet burden while maintaining serum phosphate levels.

The real-world dose-relativity of sevelamer hydrochloride and lanthanum carbonate monotherapy in patients with end-stage renal disease

INTRODUCTION

Sevelamer hydrochloride (SH) and lanthanum carbonate (LC) are calcium-free phosphate binders used for the management of hyperphosphatemia in patients with end-stage renal disease (ESRD). The objective of this analysis was to evaluate the real-world dose-relativity between SH and LC monotherapy in US patients with ESRD.

METHODS

This was a post hoc analysis of a 16-week, real-world study (Vemuri et al. in BMC Nephrol 12:49, 2011) of the efficacy of conversion to LC monotherapy from other phosphate binders. The SH:LC dose-relativity ratio, based on the mean daily dose, was calculated in the subset of patients from the Vemuri study who converted from SH to LC monotherapy and had available SH and LC dose data.

RESULTS

A total of 950 patients converted from SH to LC monotherapy and had recorded dose data. The post hoc analysis population comprised 691 patients with available dose data for both SH at baseline and LC at week 16. The mean (SD) serum phosphate level at baseline was 5.91 (1.66) mg/dL. After conversion to LC monotherapy for 16 weeks, the mean (SD) serum phosphate level was 5.93 (1.85) mg/dL. The mean (SD) daily baseline SH dose was 7,703 (3,642) mg and the mean (SD) daily LC dose at week 16 was 2,800 (939) mg (9.6 versus 2.8 tablets, respectively; P < 0.0001), resulting in a SH:LC dose-relativity ratio of 2.8. The median individual patient SH:LC dose-relativity ratio was 2.6 (95% CI 2.6-2.8). Across baseline SH dose subgroups (2,400-4,800, >4,800-7,200, >7,200-9,600, and >9,600 mg/day), the mean daily SH dose was 4,051, 7,047, 9,253, and 13,150 mg, respectively. In comparison, the mean daily LC dose was 2,445-3,156 mg. Thus, patients requiring baseline SH doses >7,200 mg/day (41% of the analysis population) had higher SH:LC dose-relativity ratios of 3.1-4.2 (median individual patient ratios 3.1-4.0).

CONCLUSION

In this post hoc analysis of real-world dose-relativity, the overall SH:LC dose-relativity ratio was 2.8 (median individual patient ratio 2.6 (95% CI 2.6-2.8). These findings are consistent with the World Health Organization-defined daily dose and previous studies of the relative phosphate binding capacity of the two drugs. Patients requiring SH doses >7,200 mg/day had higher SH:LC dose-relativities of 3.1-4.2 (median individual patient ratios 3.1-4.0). These findings have implications for the tablet burden and cost-effectiveness of SH and LC in the treatment of hyperphosphatemia.

Additional reduction in serum phosphorus levels by pulverized lanthanum carbonate chewable in hemodialysis patients

Lanthanum carbonate (LC) is one of the relatively new phosphate binders. The general LC dosage form is a chewable pharmaceutical preparation. This investigation was targeted to subjects who do not chew LC chewable preparations adequately, for the purpose of studying the clinical efficacy of changing to pulverized prescriptions, such as changes in serum phosphorus levels (P levels). The study took place at Minamisenju Hospital in October 2011, with 41 subjects on maintenance hemodialysis. We pulverized all of the LC chewable medicines of the LC insufficient mastication group (non-chewing: NC group, n = 18) using a crusher, and changed them to pulverized prescriptions. The testing period was set at 10 weeks. In the NC group, there was a significant lowering of P levels from 5.86 ± 1.31 mg/dL before pulverization of the LC chewable preparation (week 0) to 5.38 ± 1.26 mg/dL after 2 weeks of administration of the pulverized medication (P = 0.0310), 5.20 ± 1.25 mg/dL after 4 weeks (P = 0.0077), and 5.12 ± 1.34 mg/dL after 6 weeks (P = 0.0167). P levels in other patients than NC group showed no significant change. In this study, the P levels in the NC group was lowered significantly by changing the LC chewable to the pulverized prescription, and the residual LC images on the abdominal X-rays disappeared to the point where they could barely be confirmed.

Effects of gum arabic (Acacia senegal) on renal function in diabetic mice

BACKGROUND/AIMS

Gum arabic (GA) is a Ca(2+)-, Mg(2+)- and K(+)-rich dietary fiber used for the treatment of patients with chronic kidney disease in Middle Eastern countries. In healthy mice, GA treatment increases creatinine clearance, renal ADH excretion, as well as intestinal and renal excretion of Mg(2+) and Ca(2+). GA decreases plasma Pi concentration, urinary Pi and Na(+) excretion. The present study explored the effects of GA on renal function in diabetic mice.

METHODS

Metabolic cage experiments were performed on Akita mice (akita(+/-)), which spontaneously develop insulin deficiency and thus hyperglycemia. Plasma and urinary concentrations of Na(+), K(+) and Ca(2+) were measured by flame photometry (AFM 5051, Eppendorf, Germany), creatinine by the Jaffé method, phosphate photometrically, urea by an enzymatic method, glucose utilizing a glucometer and an enzymatic kit, aldosterone using an RIA, urinary albumin fluorometrically, and blood pressure by the tail-cuff method.

RESULTS

GA (10% in drinking water) significantly increased urinary excretion of Ca(2+) and significantly decreased plasma phosphate and urea concentrations, urinary flow rate, urinary Na(+), phosphate and glucose excretion, blood pressure and proteinuria.

CONCLUSIONS

GA treatment decreases blood pressure and proteinuria in diabetic mice and may thus prove beneficial in diabetic nephropathy.

Cost-effectiveness of lanthanum carbonate in the treatment of hyperphosphatemia in chronic kidney disease before and during dialysis

OBJECTIVES

Hyperphosphatemia is a common and harmful condition in patients with chronic kidney disease (CKD). We determined the cost-effectiveness of the noncalcium-based phosphate binder lanthanum carbonate (LC) as second-line treatment of hyperphosphatemia after therapy failure with calcium-based binders (CB).

METHODS

Two CKD populations were modeled: 1) predialysis CKD patients and 2) incident dialysis patients. Patients not responding to CB with a serum phosphate (SP) level >5.5 mg/dl received a trial with LC. Patients not responding to LC (SP >4.6 mg/dl) returned to CB treatment. Patient-level data were obtained from clinical trials in predialysis and dialysis. Time-dependent, life-long Markov models (discounting at 3.5% annually) were developed, using a UK National Health Service perspective.

RESULTS

The health gains with second-line LC treatment compared to CB treatment were 44 and 56 quality-adjusted life-years (QALYs) for the predialysis and incident dialysis populations, respectively. Second-line LC was a cost-saving strategy in the predialysis population because of the cost-savings of delayed CKD progression. Second-line LC was cost-effective at £6900 (90% probability interval: £5800-£8300) per QALY gained in the dialysis population. Results were robust to plausible variations in other model parameters; inclusion of future unrelated dialysis costs had a large influence on cost-effectiveness estimates.

CONCLUSIONS

Second-line treatment with LC is associated with considerable clinical benefits and good value for money in CKD, irrespective of dialysis status. These results support Kidney Disease Outcomes Quality Initiative guidelines to treat CKD patients with hyperphosphatemia irrespective of dialysis status.

Daily magnesium intake and hypermagnesemia in hemodialysis patients with chronic kidney disease

OBJECTIVE

The aim of this study was to evaluate daily magnesium intake and the relation to its serum concentration in hemodialysis (HD) patients with chronic kidney disease (CKD).

DESIGN

This is a prospective, open-label, cross-sectional clinical study analyzing daily magnesium intake based on nutritional questionnaire.

PARTICIPANTS

A total of 101 HD patients with CKD were screened for hypermagnesemia. All patients with serum magnesium >1.5 mmol/L were asked to fill in the standard 3-day nutritional questionnaire. The control group consisted of twice as many randomly selected HD patients with serum magnesium concentration <1.5 mmol/L and 20 subjects with normal kidney function on usual diet.

RESULTS

Mean (±standard deviation) serum magnesium concentration in HD patients was 1.32 ± 0.18 mmol/L. Hypermagnesemia >1.5 mmol/L was found in 17 (16.8%) patients. There was no one case of severe hypermagnesemia (>2.0 mmol/L). The daily intake of magnesium was higher by 31.7% in the group with serum magnesium >1.5 mmol/L. Hypermagnesemia was observed in patients ingesting >281 mg of magnesium daily. In univariate analysis, there was a strong positive correlation between magnesium intake and serum concentration in the whole group (r = 0.870, P < .001). No correlation between Kt/V or residual diuresis and serum magnesium concentration was found.

CONCLUSIONS

Magnesium consumption is the most important determinant of serum magnesium concentration in HD patients with CKD. Magnesium-containing phosphate binders can be considered in the therapy of hyperphosphatemia in HD patients without hypermagnesemia.

Klotho deficiency causes vascular calcification in chronic kidney disease

Soft-tissue calcification is a prominent feature in both chronic kidney disease (CKD) and experimental Klotho deficiency, but whether Klotho deficiency is responsible for the calcification in CKD is unknown. Here, wild-type mice with CKD had very low renal, plasma, and urinary levels of Klotho. In humans, we observed a graded reduction in urinary Klotho starting at an early stage of CKD and progressing with loss of renal function. Despite induction of CKD, transgenic mice that overexpressed Klotho had preserved levels of Klotho, enhanced phosphaturia, better renal function, and much less calcification compared with wild-type mice with CKD. Conversely, Klotho-haploinsufficient mice with CKD had undetectable levels of Klotho, worse renal function, and severe calcification. The beneficial effect of Klotho on vascular calcification was a result of more than its effect on renal function and phosphatemia, suggesting a direct effect of Klotho on the vasculature. In vitro, Klotho suppressed Na(+)-dependent uptake of phosphate and mineralization induced by high phosphate and preserved differentiation in vascular smooth muscle cells. In summary, Klotho is an early biomarker for CKD, and Klotho deficiency contributes to soft-tissue calcification in CKD. Klotho ameliorates vascular calcification by enhancing phosphaturia, preserving glomerular filtration, and directly inhibiting phosphate uptake by vascular smooth muscle. Replacement of Klotho may have therapeutic potential for CKD.

In vitro and in vivo anticancer activity of a novel nano-sized formulation based on self-assembling polymers against pancreatic cancer

PURPOSE

To evaluate the in vitro and in vivo pancreatic anticancer activity of a nano-sized formulation based on novel polyallylamine grafted with 5% mole cholesteryl pendant groups (CH(5)-PAA).

METHODS

Insoluble novel anticancer drug, Bisnaphthalimidopropyldiaaminooctane (BNIPDaoct), was loaded into CH(5)-PAA polymeric self-assemblies by probe sonication. Hydrodynamic diameters and polydispersity index measurements were determined by photon correlation spectroscopy. The in vitro cytotoxicity evaluation of the formulation was carried out by the sulforhodamine B dye assay with human pancreatic adenocarcinoma BxPC-3 cells, while for the in vivo study, Xenograff mice were used. In vitro apoptotic cell death from the drug formulation was confirmed by flow cytometric analysis.

RESULTS

The aqueous polymer-drug formulation had a mean hydrodynamic size of 183 nm. The drug aqueous solubility was increased from negligible concentration to 0.3 mg mL(-1). CH(5)-PAA polymer alone did not exhibit cytotoxicity, but the new polymer-drug formulation showed potent in vitro and in vivo anticancer activity. The mode of cell death in the in vitro study was confirmed to be apoptotic. The in vivo results revealed that the CH(5)-PAA alone did not have any anti-proliferative effect, but the CH(5)-PAA-drug formulation exhibited similar tumour reduction efficacy as the commercial drug, gemcitabine.

CONCLUSIONS

The proposed formulation shows potential as pancreatic cancer therapeutics.

Effect of different classes of gadolinium-based contrast agents on control and nephrogenic systemic fibrosis-derived fibroblast proliferation

PURPOSE

To determine the ability of different types of gadolinium-based contrast agents (GBCAs) to stimulate fibroblast proliferation in monolayer cell culture.

MATERIALS AND METHODS

The National Health Service West Glasgow Ethics Committee granted approval for this study. Fibroblasts established from healthy volunteers (control subjects) and from lesional skin of patients with nephrogenic systemic fibrosis were exposed to a range of concentrations of ionic and nonionic linear and macrocyclic contrast agents over 4 days, and the effect on growth was determined. The lowest concentration of contrast agent that stimulated the maximum effect on fibroblast growth was selected for determination of its effect on fibroblast growth over 8 days. The effect of contrast agents on hyaluronan and collagen synthesis was determined with an enzyme-linked immunosorbent assay. Responses were assessed with analysis of variance (general linear model).

RESULTS

The linear gadolinium contrast agents (gadodiamide, gadoversetamide, gadopentetate dimeglumine, and gadobenate dimeglumine) produced a maximum stimulation of fibroblast proliferation at a concentration of 0.1 mmol/L, with cell numbers increasing up to 2.3-fold. The macrocyclic contrast agents (gadoteric acid and gadoteridol) produced a maximum stimulation of fibroblast proliferation at a concentration of 5 mmol/L. The reference gadolinium agents (N-methylglucamine gadolinium ethylenediaminetetraacetic acid and gadolinium trichloride) stimulated fibroblast proliferation at a concentration of 0.01 mmol/L and were toxic at a concentration greater than 1 mmol/L. Growth curves supported the dose-response observations. Hyaluronan synthesis was stimulated by gadoversetamide, gadobenate dimeglumine, gadodiamide, and gadopentetate dimeglumine at a concentration of 0.1 mmol/L and by gadolinium trichloride at a concentration of 0.01 mmol/L, whereas collagen synthesis was unaffected.

CONCLUSION

This study provides evidence that different classes of gadolinium chelates stimulate human fibroblast proliferation.

Phosphate homeostasis and the renal-gastrointestinal axis

Transport of phosphate across intestinal and renal epithelia is essential for normal phosphate balance, yet we know less about the mechanisms and regulation of intestinal phosphate absorption than we do about phosphate handling by the kidney. Recent studies have provided strong evidence that the sodium-phosphate cotransporter NaPi-IIb is responsible for sodium-dependent phosphate absorption by the small intestine, and it might be that this protein can link changes in dietary phosphate to altered renal phosphate excretion to maintain phosphate balance. Evidence is also emerging that specific regions of the small intestine adapt differently to acute or chronic changes in dietary phosphate load and that phosphatonins inhibit both renal and intestinal phosphate transport. This review summarizes our current understanding of the mechanisms and control of intestinal phosphate absorption and how it may be related to renal phosphate reabsorption; it also considers the ways in which the gut could be targeted to prevent, or limit, hyperphosphatemia in chronic and end-stage renal failure.

Absorption and excretion of colestilan in healthy subjects

Colestilan, an anion-exchange resin binding both phosphate and bile-acid anions, is under development for the treatment of hyperphosphataemia and dyslipidaemia, which occur in the majority of end-stage renal disease patients. This study using 14C-colestilan was conducted to investigate the absorption and excretion of colestilan in humans. Following a 28-day run-in period with administration of colestilan 3 g three times daily, 12 subjects received a single oral dose of 14C-colestilan 100 mg (approximately 4.0 MBq) and colestilan 3 g under fasted conditions on the morning of day 1. A total of 9 g of colestilan was administered three times daily on days 1-4. Total radioactivity levels in whole blood (at 4, 8, 12 and 24 hours and then at 24-hour intervals) and in the urine and faeces (from 0 to 24 hours and then at 24-hour intervals) were monitored up to 216 hours postdose (day 10). Total radioactivity measured in all whole-blood samples was below the lower limit of quantification (0.025 microg equivalent of 14C-labelled colestilan/mL of whole blood). Total radioactivity assessed in all urine samples was also below the lower limit of quantification (0.003 microg equivalent/mL for urine), except at 0-24 hours postdose, when 0.01% of the radioactive dose was excreted by all subjects. This level was below the predetermined water soluble impurity level of 0.04%. The mean cumulative excretion of total radioactivity in the faeces was 99.66% by 216 hours postdose, excluding one subject with incomplete collection of faecal samples. These results demonstrate that colestilan is not absorbed from the gastrointestinal tract and is completely excreted in the faeces.

Functional polymers as therapeutic agents: concept to market place

Biologically active synthetic polymers have received considerable scientific interest and attention in recent years for their potential as promising novel therapeutic agents to treat human diseases. Although a significant amount of research has been carried out involving polymer-linked drugs as targeted and sustained release drug delivery systems and prodrugs, examples on bioactive polymers that exhibit intrinsic therapeutic properties are relatively less. Several appealing characteristics of synthetic polymers including high molecular weight, molecular architecture, and controlled polydispersity can all be utilized to discover a new generation of therapies. For example, high molecular weight bioactive polymers can be restricted to gastrointestinal tract, where they can selectively recognize, bind, and remove target disease causing substances from the body. The appealing features of GI tract restriction and stability in biological environment render these polymeric drugs to be devoid of systemic toxicity that are generally associated with small molecule systemic drugs. The present article highlights recent developments in the rational design and synthesis of appropriate functional polymers that have resulted in a number of promising polymer based therapies and biomaterials, including some marketed products.

Treatment Options for Hyperphosphatemia in Feline CKD: What's Out there?

Practical relevance Phosphorus is retained in chronic kidney disease (CKD), promoting renal secondary hyperparathyroidism and eventually resulting in hyperphosphatemia. Most agree that phosphate retention is a major contributor to the progression of CKD in many species and it is well known that hyperphosphatemia is associated with a significant mortality risk in humans with end-stage renal disease.

Patient group Chronic kidney disease is a common ailment of geriatric cats.

Evidence base There is evidence in cats suggesting that the use of a phosphate-restricted diet in IRIS stage 2–3 disease has a beneficial effect on clinical outcome. However, despite the fact that intestinal phosphate binders are commonly used in veterinary practice for patients with CKD, there have been few published reports focusing on the safety and efficacy of these products in veterinary medicine. No phosphorus binders are licensed as medications for dogs or cats. This article draws on data from clinical trials in humans and studies in cats to discuss treatment goals and options for phosphate retention and hyperphosphatemia in feline CKD.

Clinical significance With careful monitoring of serum phosphate and parathyroid hormone, and implementation of phosphate-restricted dietary management and intestinal phosphate binders, progression of CKD and the degree of hyperparathyroidism in cats may be reduced.

Audience Companion animal and feline practitioners are at the forefront in the management of CKD in cats.

Stability of gadolinium-based magnetic resonance imaging contrast agents in human serum at 37 degrees C

OBJECTIVES

Assessment of the complex stability and Gd3+ dissociation rate of all marketed gadolinium-based MRI contrast agents (GBCA) in human serum at pH 7.4 and 37 degrees C.

METHODS AND RESULTS

The kinetic profiles of Gd3+ dissociation of GBCAs were determined by incubation for 15 days in human serum from healthy volunteers at a concentration of 1 mmol/L, pH 7.4, and 37 degrees C. The initial rates of Gd3+ release and the amounts of Gd3+ released after 15 days were established by HPLC-ICP-MS analysis. In an attempt to simulate the situation in patients with end-stage renal disease who often have elevated serum phosphate levels, the influence of 10 mmol/L phosphate on Gd3+ dissociation was also investigated.The GBCAs were grouped and ranked in the following order according to their stabilities in native human serum at pH 7.4 and 37 degrees C [% Gd release after 15 days and initial rate (%/d) (95% confidence interval) in brackets]. NONIONIC LINEAR GBCAS: Optimark [21 (19-22) %, 0.44 (0.40-0.51) %/d) and Omniscan [20 (17-20) %, 0.16 (0.15-0.17) %/d]. IONIC LINEAR GBCAS: Magnevist [1.9 (1.2-2.0) %, 0.16 (0.12-0.36) %/d], Multihance [1.9 (1.3-2.1) %, 0.18 (0.13-0.38) %/d], Vasovist [1.8 (1.4-1.9) %, 0.12 (0.11-0.18) %/d], and Primovist [1.1 (0.76-1.2) %, 0.07 (0.05-0.08) %/d]. MACROCYCLIC GBCAS: Gadovist, Prohance, and Dotarem (all < limit of quantification of 0.1%, <0.007%/d).In the presence of additional 10 mmol/L phosphate in serum, the initial Gd release rates of the nonionic linear GBCAs, Omniscan, and Optimark increased about 100-fold, and, after 15 days, the amount of Gd3+ released from these agents was more than 75% higher than in native serum. The initial rates found for the ionic linear GBCAs increased about 12- to 30-fold, but, despite this, increase in the initial rate, the amount of Gd3+ released after 15 days was comparable to that in native serum. The elevated phosphate level did not lead to any measurable release of Gd3+ from the 3 macrocyclic GBCAs.

CONCLUSIONS

The release of Gd from all linear Gd3+ complexes in human serum was several orders of magnitude greater than predicted by the conditional stability constants. After 15 days, release of Gd3+ from the nonionic linear GBCAs was about 10 times higher than from the ionic linear GBCAs. Elevated serum phosphate levels accelerated the release of Gd3+ from nonionic linear GBCAs and, to a lesser degree, from the ionic linear GBCAs. All 3 macrocyclic GBCAs remained stable in human serum at both normal and elevated phosphate levels.

Sevelamer hydrochloride: a review of its use for hyperphosphataemia in patients with end-stage renal disease on haemodialysis

Sevelamer (Renagel), an orally administered metal-free cationic hydrogel polymer/resin that binds dietary phosphate in the gastrointestinal (GI) tract, is approved for use in the US, Europe and several other countries for the treatment of hyperphosphataemia in adult patients with end-stage renal disease (ESRD) on haemodialysis or peritoneal dialysis.Clinical evidence shows that sevelamer was at least as effective as calcium acetate and calcium carbonate at controlling serum phosphorus, calcium-phosphorus product (Ca x P) and intact parathyroid hormone (iPTH) levels, but generally reduced serum calcium levels to a greater extent and was associated with a lower risk of hypercalcaemic episodes than calcium-based phosphate binders. Sevelamer appeared to slow the progression of cardiovascular calcification in patients with ESRD and also had a beneficial effect on serum low-density lipoprotein-cholesterol (LDL-C) levels. In patients receiving chronic haemodialysis, there was no between-group difference in all-cause mortality between sevelamer and calcium-based phosphate binder therapy in the primary efficacy analysis in the large (n >2100), 3-year DCOR trial; in the smaller (n = 109) nonblind RIND trial in patients new to dialysis, data suggest there is an overall survival benefit with sevelamer versus calcium-based phosphate binder treatment. The relative survival benefits and cost effectiveness of these phosphate binder therapies remains to be fully determined. Sevelamer treatment was generally as well tolerated as calcium acetate or calcium carbonate treatment. Overall, sevelamer is a valuable option for the management of hyperphosphataemia in patients with ESRD on haemodialysis.

Metal based drugs: from serendipity to design

The platinum anticancer drug cisplatin has made a major contribution to the treatment of testicular and ovarian cancer. This chance discovery has been the stimulus for research into other metal-based drugs. Inorganic chemistry offers many opportunities for medicinal chemistry, and the discovery of metal-based drugs has moved on from chance discovery to rational drug design. There are however, many challenges associated with the drug discovery and development process. The aim of this review is to provide case histories exemplifying the role of rational drug design in modern inorganic medicinal chemistry in the context of these challenges. The evolution of platinum drugs from cisplatin to third generation drugs is described. The molecular target for the platinum agents is DNA. Alternative molecular targets such as thiol-containing proteins and redox processes are proposed. The example of a simple, safe, efficacious metal-based drug, Fosrenol, is reviewed.

Intestinal phosphate absorption in a model of chronic renal failure

Hyperphosphatemia is an important consequence of chronic renal failure (CRF). Lowering of the plasma phosphate concentration is believed to be critical in the management of patients with CRF, especially those on dialysis. Reports of the effect of CRF on the intestinal handling of phosphate in vitro have been conflicting; but what happens in vivo has not been studied. What effect a reduction in the dietary phosphate intake has on intestinal phosphate absorption in CRF in vivo is unclear. In this study, we have used the in situ intestine loop technique to determine intestinal phosphate absorption in the 5/6-nephrectomy rat model of CRF under conditions of normal and restricted dietary phosphate intake. In this model of renal disease, we found that there is no significant change in the phosphate absorption in either the duodenum or jejunum regardless of the dietary phosphate intake. There was also no change in the expression of the messenger RNA of the major intestinal phosphate carrier the sodium-dependent-IIb transporter. Furthermore, we found no change in the intestinal villus length or in the location of phosphate uptake along the villus. Our results indicate that in CRF, unlike the kidney, there is no reduction in phosphate transport across the small intestine. This makes intestinal phosphate absorption a potential target in the prevention and treatment of hyperphosphatemia.

Calcimimetics for secondary hyperparathyroidism in chronic kidney disease patients

BACKGROUND

Calcimimetic agents have recently been evaluated in the treatment of secondary hyperparathyroidism (SHPT) as add-on therapy to calcitriol and vitamin D analogues and dietary phosphate binders.

OBJECTIVES

To evaluate the benefits and harms of calcimimetics for the prevention of secondary hyperparathyroid bone disease (including osteitis fibrosa cystica and adynamic bone disease) in dialysis patients with chronic kidney disease (CKD).

SEARCH STRATEGY

MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials and conference proceedings were searched for randomised controlled trials (RCTs) evaluating any calcimimetic against placebo or another agent in pre-dialysis or dialysis patients with CKD.

SELECTION CRITERIA

We included all RCTs of any calcimimetic agent, cinacalcet HCl (AMG-073, Sensipar), NPS R-467 or NPS R-568 administered to patients with CKD for the treatment of SHPT.

DATA COLLECTION AND ANALYSIS

Data were extracted on all relevant patient-centred and surrogate outcomes. Analysis was by a random effects model and results expressed as relative risk (RR) or weighted mean difference (MD) with 95% confidence intervals.

MAIN RESULTS

Eight studies (1429 patients) were identified, which compared a calcimimetic agent plus standard therapy to placebo plus standard therapy. The end of treatment values of parathyroid hormone (pg/mL) (MD -290.79, 95% CI -360.23 to -221.34), serum calcium (mg/dL) (MD -0.85, 95% CI -1.14 to -0.56), serum phosphorus (mg/dL) (MD -0.29, 95% CI -0.50 to -0.08) and the calcium by phosphorus product (mg(2)/dL(2))(MD -7.90, 95% CI -10.25 to -5.54) were significantly lower with calcimimetics compared to placebo. No significant effects on patient-based endpoints were demonstrated except for the risk of hypotension which was significantly reduced with calcimimetics compared to placebo (RR 0.53, 95%CI 0.36 to 0.79).

AUTHORS' CONCLUSIONS

Calcimimetic treatment of SHPT leads to significant improvements in biochemical parameters that observational studies have shown to be associated with increased mortality, cardiovascular risk and osteitis fibrosa, but patient-based benefits have not yet been demonstrated in trials. For patients with SHPT, the benefits of calcimimetics over standard therapy remain uncertain until further RCTs become available.

Meta-Analysis of Biochemical and Patient-Level Effects of Calcimimetic Therapy

BACKGROUND

Many randomized trials have now evaluated the effects of calcimimetics in patients with chronic kidney disease and secondary hyperparathyroidism (SHPT) on standard therapy with vitamin D and/or phosphate binders. We conducted a meta-analysis to evaluate outcomes of therapy with these novel agents.

METHODS

MEDLINE, EMBASE, the Cochrane Controlled Trials Register, and conference proceedings were searched for randomized controlled trials evaluating any calcimimetic against placebo or another agent in predialysis or dialysis patients with chronic kidney disease. Data were extracted for all relevant patient-centered and surrogate outcomes. Analysis was by means of a random-effects model, and results are expressed as relative risk or weighted mean difference (WMD) with 95% confidence intervals (CIs).

RESULTS

Eight trials (1,429 patients) were identified that compared a calcimimetic agent plus standard therapy with placebo plus standard therapy. End-of-treatment values for parathyroid hormone (4 trials; 1,278 patients; WMD, -290.49 pg/mL; 95% CI, -359.91 to -221.07), serum calcium (3 trials; 1,201 patients; WMD, -0.85 mg/dL; 95% CI, -1.14 to -0.56), serum phosphorus (3 trials; 1,195 patients; WMD, -0.29 mg/dL; 95% CI, -0.50 to -0.08), and calcium x phosphorus product (3 trials; 1,194 patients; WMD, -7.90 mg2/dL2; 95% CI, -10.25 to -5.54) were significantly lower with calcimimetic therapy compared with placebo. No significant effects on patient-based end points were shown.

CONCLUSION

Calcimimetic treatment of patients with SHPT leads to significant improvements in biochemical parameters that observational studies have associated with increased mortality, cardiovascular risk, and osteitis fibrosa, but patient-based benefits have not yet been shown. For patients with SHPT, the benefits of calcimimetics over standard therapy remain uncertain until additional randomized trials become available.

The therapeutic application of lanthanides

The biological properties of the lanthanides, based on their similarity to calcium, have stimulated research into their therapeutic application. Historical medical uses of the lanthanides and recent advances and successes will be described in the context of the biological chemistry of lanthanides, including a new metal-based drug, lanthanum carbonate, which has recently been approved as a phosphate binder for the treatment of hyperphosphatemia. This tutorial review will be of interest to those working on metal-based drugs, including inorganic chemists, and biological scientists.

Lanthanum carbonate (Fosrenol): a novel agent for the treatment of hyperphosphataemia in renal failure and dialysis patients

Approximately 70% of patients with end-stage renal disease and dialysis have hyperphosphataemia, which is associated with renal osteodystrophy, metastatic calcification and increased mortality and morbidity. Despite dietary restriction and dialysis, most patients will require a phosphate-binding agent to treat this condition. However, phosphate control has not significantly improved over the last two decades, mainly because of the lack of an ideal phosphate-binding agent. Aluminium-based and calcium-based agents are associated with major side-effects despite their efficacy. Although sevelamer hydrochloride represents a step forward in the management of hyperphosphataemia, it has drawbacks and therefore is not the ideal phosphate binder. Lanthanum carbonate is a non-calcium, non-aluminium phosphate-binding agent. It has shown to be effective, well-tolerated and has a positive effect on bone histology.

Lanthanum carbonate for the treatment of hyperphosphataemia in renal failure and dialysis patients

Hyperphosphataemia is a usual accompaniment of end stage renal disease and dialysis, in the absence of dietary phosphate restriction or supplemental phosphate binders. It is associated with renal osteodystrophy, metastatic calcification and increased mortality and morbidity. Despite dietary restriction and dialysis, most patients will require a phosphate-binding agent to treat this condition. However, phosphate control has not significantly improved over the last two decades, mainly because of the lack of an ideal oral phosphate-binding agent. Aluminium- and calcium-based agents are associated with major side effects, despite their undoubted efficacy. Although sevel-amer hydrochloride represents a step forward in the management of hyperphosphataemia, it is not an ideal phosphate binder due to its cost and tablet burden. Lanthanum carbonate is the most recent non-calcium, non-aluminium, phosphate-binding agent. It is effective and well-tolerated, and no negative effects on bone histology have been observed.

Accumulation of Metals and Minerals from Phosphate Binders

Metals and minerals that depend on renal clearance may accumulate to toxic levels in patients with marginal kidney function. Toxicities of aluminum-based phosphate binders became apparent approximately 25 years ago. Nephrologists now recognize cardiovascular calcification may follow use of calcium-based phosphate binders. Five lessons can be learned: (1)safety must not be assumed in absence of data; (2) all evidence for causal linkage of toxicities from therapeutics must be considered, including animal data; (3) clinical trials are unlikely to reveal the spectrum of problems from long-term drug exposure; (4) complications can remain unrecognized until late in post-introduction surveillance; (5) minerals important for normal function can be toxic with excess accumulation. Introduction of new agents necessitates caution - it is difficult to change practice once a therapeutic is commonplace. Lessons learned about hazards of past phosphate binders must be applied judiciously when evaluating long-term risks/safety of novel metal-based binders such as lanthanum carbonate.

Risk factors for decreased total body and regional bone mineral density in hemodialysis patients with severe secondary hyperparathyroidism

Hyperparathyroidism contributes significantly to decreased bone mineral density (BMD) in end-stage renal disease patients, but this negative influence is not homogeneous throughout the skeleton. We studied the BMD by dual-energy X-ray absorptiometry on total body and on different regions of the skeleton in 42 patients with severe hyperparathyroidism on hemodialysis. We also evaluated the relationship between different risk factors and BMD found on the regions examined in these patients. The legs and other sites where cortical bone predominate were mostly affected, whereas trabecular bone was relatively preserved. This is probably the result of the different effects of hyperparathyroidism on cortical and trabecular bone, but we cannot rule out the interference of ectopic calcifications and sclerotic lesions of vertebral end-plates falsely increasing lumbar spine BMD. The main determinants of low total-body BMD were, in order of importance, immobility, high intact parathyroid hormone levels, low body mass index, and low albumin. Eleven patients presented with pathologic fractures, mainly in the legs, and BMD was lower in this group than in patients without fractures. In conclusion, our study makes clear that hyperparathyroidism is a great threat to bone density in hemodialysis patients, mainly in the legs, the site mostly affected by fragility fractures in our patients. Physicians must worry not only with high parathyroid hormone levels, but also with the nutritional state of these patients.