Phosphate binders for the treatment of hyperphosphatemia in chronic kidney disease patients on dialysis: a comparison of safety profiles

Introduction: Hyperphosphatemia is common in the late stages of chronic kidney disease (CKD) and is associated with elevated parathormone levels, abnormal bone mineralization, extraosseous calcification and increased risk of cardiovascular events and death. Several classes of oral phosphate binders are available to help control phosphorus levels. Although effective at lowering serum phosphorus, they all have safety issues that need to be considered when selecting which one to use.

Areas covered: This paper reviews the use of phosphate binders in patients with CKD on dialysis, with a focus on safety and tolerability. In addition to the more established agents, a new resin-based phosphate binder, colestilan, is discussed.

Expert opinion: Optimal phosphate control is still an unmet need in CKD. Nonetheless, we now have an extending range of phosphate binders available. Aluminium has potentially serious toxic risks. Calcium-based binders are still very useful but can lead to hypercalcemia and/or positive calcium balance and cardiovascular calcification. No long-term data are available for the new calcium acetate/magnesium combination product. Lanthanum is an effective phosphate binder, but there is insufficient evidence about possible long-term effects of tissue deposition. The resin-based binders, colestilan and sevelamer, appear to have profiles that would lead to less vascular calcification, and the main adverse events seen with these agents are gastrointestinal effects.     

Effect of phosphate binders on supplemental iron absorption in healthy subjects

A single-dose, prospective, randomized, four-treatment, four-period crossover study was conducted to determine the acute effect of therapeutically equivalent doses of three commonly used phosphate binders on oral iron absorption. Twenty-three healthy subjects received 65 mg of elemental iron alone and with each phosphate binder (calcium carbonate 3000 mg, calcium acetate 2668 mg, or sevelamer HCl 2821 mg). Area under the change in plasma iron concentration-time curve over 6 hours postdosing was measured. ANOVA was used to assess the statistical significance of differences in iron absorption among the treatments. The relative bioavailability of iron administered with each phosphate binder compared to iron administered alone was estimated. The relative iron bioavailabilities (95% confidence intervals) for the calcium carbonate, calcium acetate, and sevelamer HCI treatments were 0.81 (0.70, 0.94), 0.73 (0.63, 0.85), and 0.90 (0.78, 1.05), respectively. Thus, single doses of both calcium-based phosphate binders significantly reduced single-dose iron absorption, while sevelamer HCl did not.     

Lanthanum carbonate

Controlling hyperphosphatemia in patients with chronic renal failure on renal dialysis is a major problem. None of the available calcium- or aluminum-based phosphate binders match the requirements for an ideal agent, each having its own limitations. The introduction of sevelamer hydrochloride represented a step change in management. Lanthanum carbonate is an alternative nonaluminium, noncalcium phosphate binder. Taken with food, it is well tolerated. It is poorly absorbed and does not require functioning kidneys to be removed from the body. There is no evidence from current studies that it accumulates to biologically significant levels in tissues, but despite the large numbers of patients included in clinical trials, experience with long-term dosing is limited and, as with every new drug used in this type of clinical setting, patients should be carefully monitored as experience with the drug increases. Lanthanum carbonate binds phosphate effectively across the physiological pH range of the upper gastrointestinal tract, and has no detrimental effect on calcium, vitamin D or parathyroid hormone metabolism. From the extensive trial data it seems that lanthanum carbonate is an effective and practical phosphate binder. Lanthanum carbonate and sevelamer are two new oral phosphate binding agents that with others currently in preclinical trials, such as stabilized polynuclear iron idroxide, could well represent a significant breakthrough in the management of hyperphosphatemia in patients with chronic renal failure in whom dietary phosphate restriction and cheaper oral phosphate binding agents prove unsatisfactory. Comparative trials and enhanced clinical experience are needed before the exact place of these competing and complementary therapies can be properly identified in patient management.     

Iron-based phosphate binders – a new element in management of hyperphosphatemia

Introduction: Management of serum phosphorus in patients with chronic kidney disease remains a significant clinical challenge. A pivotal component of the clinical approach to maintaining serum phosphorus concentrations towards the normal range is the use of phosphate binding agents in addition to comprehensive dietary counseling. The available agents work similarly by capitalizing on a cation within the agent to bind negatively charged phosphorus, forming an insoluble complex and reducing ingested phosphorus absorption. Despite several effective options for phosphate binder therapies, patient adherence remains an issue, mainly due to adverse effect profiles and large daily pill burdens.

Areas covered: Two new iron-based phosphate binder therapies have recently become available in the United States, sucroferric oxyhydroxide and ferric citrate. These agents have both been shown to effectively reduce serum phosphorus comparably to widely used calcium-based binders and sevelamer salts.

Expert opinion: The two new iron-based binders differ substantially with regard to phosphate binding chemistry and iron absorption profiles. Their place in therapy is still evolving and the impact of pill burden, gastrointestinal adverse effect profiles, potential cost reduction of anemia therapies and physiologic effects of long-term iron exposure need to be further evaluated.     

Lanthanum carbonate

Lanthanum carbonate is a novel, non-aluminium, non-calcium phosphate binding agent that forms a water-insoluble compound, lanthanum phosphate, in the gut. Lanthanum carbonate (elemental lanthanum 375-3000 mg/day) reduced serum phosphorus levels compared with placebo in two randomised, double-blind, multicentre 4-week trials in patients with chronic renal failure receiving regular haemodialysis. In two large, randomised trials in patients with chronic renal failure requiring haemodialysis, lanthanum carbonate (elemental lanthanum 375-3000 mg/day) was as effective as calcium carbonate and/or other conventional phosphate binders in reducing and maintaining serum phosphorus levels (< or =5.6 mg/dL over 6 months and < or =5.9 mg/dL over 2 years). Lanthanum carbonate was generally well tolerated. Most adverse events were mild-to-moderate in severity, with gastrointestinal events being the most common. The tolerability profile of lanthanum carbonate was similar to those of conventional phosphate binders; however, hypercalcaemic episodes occurred significantly less frequently over 6 months with lanthanum carbonate than with calcium carbonate. In a randomised 1-year trial, numerically fewer lanthanum carbonate (elemental lanthanum < or =3750 mg/day) recipients had renal bone disease at study end than at baseline; however, in the calcium carbonate < or =9000 mg/day group, numerically more patients had renal bone disease at study end compared with baseline.     

A long-term,open-label extension study on the safety of treatment with lanthanum carbonate,a new phosphate binder,in patients receiving hemodialysis

ABSTRACT

Background: Lanthanum carbonate, a new phosphate binder, is effective in reducing serum phosphorus levels in patients with end-stage renal disease. A 1-year extension study to two randomized controlled studies was conducted to evaluate the long-term safety of lanthanum carbonate in patients who received hemodialysis.

Research design and methods: Patients from two previous lanthanum carbonate studies were eligible to continue treatment in a 1-year open-label extension. A total of 77 patients (N = 77; 11 from Study 1, 66 from Study 2) were enrolled in this extension. The mean age of patients was 60.9 years (SD ± 12.5 years); 65% were male and 35% were female. All patients received lanthanum carbonate at the optimal dose for phosphorus control, determined in their previous study. Safety and tolerability were assessed by monitoring adverse events, laboratory parameters, and vital signs. The number of patients who maintained serum phosphorus levels at ≤ 5.9?mg/dL (1.9?mmol/L) was recorded, along with serum calcium, calcium × phosphorus product, and parathyroid hormone levels.

Results: Lanthanum carbonate was well tolerated and was associated with few treatment-related adverse events. The most commonly reported adverse events were nausea (26.0%), peripheral edema (23.4%), and myalgia (20.8%). No treatment-related serious adverse events occurred. By Week 4, the mean serum phosphorus level had decreased by approximately 1?mg/dL to 5.7 ± 2.0?mg/dL (1.84 ± 0.7?mmol/L). At the end of the study, the mean pre-dialysis serum phosphorus level was 5.7 ± 1.4?mg/dL (1.84 ± 0.5?mmol/L); 53% of patients had controlled phosphorus levels. Calcium × phosphorus product decreased during Week 1 and remained within a clinically acceptable range thereafter. There were no clinically significant changes in serum calcium, or parathyroid hormone levels.

Conclusion: Lanthanum carbonate is well tolerated and is effective for the long-term maintenance of serum phosphorus control in patients with end-stage renal disease.     

An economic evaluation of sevelamer in patients new to dialysis

ABSTRACT

Objective: The overall objective of this study was to estimate the costs and outcomes associated with treatment with sevelamer for hyperphosphataemia compared with calcium-based binders.

Methods: Using published data on mortality and hospitalisation rates, a Markov model was developed to predict health outcomes and associated costs for the treatment of hyperphosphataemia using either sevelamer or calcium binders in chronic kidney disease patients who had recently started haemodialysis. Patient outcomes were modelled for 5 years, and incremental cost-effective ratios (ICERs) were calculated for sevelamer relative to calcium carbonate and calcium acetate binders. The perspective adopted was that of the UK National Health Service.

Results: The total 5-year discounted treatment cost for patients treated with sevelamer is £24?216, while for the calcium carbonate group total cost was £17?695. This is an incremental cost of £6521 per sevelamer-treated patient over 5 years. Patients receiving sevelamer can be expected to experience 2.70 quality-adjusted life years (QALYs) compared to 2.46 for those treated with calcium carbonate (i.e. an incremental gain of 0.24 QALYs). This results in an incremental cost per QALY of £27?120 and an incremental cost per life year gained of £15?508. Results were similar with calcium acetate.

Conclusion: Together with the unique morbidity and mortality benefits, this study suggests that treatment with sevelamer confers clinical benefits with a modest investment of additional economic resources.     

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.     

Emerging drugs for hyperphosphatemia

Cardiovascular mortality is the leading cause of death in the uremic patient. Hyperphosphatemia is considered an independent risk factor associated with cardiovascular morbidity and mortality in dialysis patients. As phosphate control is not efficient with diet or dialysis, phosphate binders are commonly prescribed in patients with chronic renal failure. Aluminum salts, the first phosphate binders, even if effective, have several side effects due to their deposition in CNS, bone and hematopoietic cells. Calcium-containing phosphate binders, used in the last 15 years, increase total body calcium load and may exacerbate metastatic calcification, thus, increasing the risk of cardiovascular mortality. Recently two new compounds non-aluminum and non-calcium phosphate binders, sevelamer hydrochloride and lanthanum carbonate, have been introduced. Sevelamer, besides the effect on phosphate, has been associated with reduction of coronary and aortic calcification and with other pleiotropic effects especially on lipid metabolism. Lanthanum carbonate has similar phosphate control to calcium-based binders with less incidence of hypercalcemia but long-term clinical studies are needed for testing long-term exposure. Recently the authors found in dialysis patients, that salivary phosphorus correlated with serum phosphorus. Therefore, they supposed that the use of salivary phosphate binders could reduce its absorption and represent a chance for reducing the serum phosphate concentration in uremic patients.     

Emerging drugs for hyperphosphatemia

Cardiovascular mortality is the leading cause of death in the uremic patient. Hyperphosphatemia is considered an independent risk factor associated with cardiovascular morbidity and mortality in dialysis patients. As phosphate control is not efficient with diet or dialysis, phosphate binders are commonly prescribed in patients with chronic renal failure. Aluminum salts, the first phosphate binders, even if effective, have several side effects due to their deposition in CNS, bone and hematopoietic cells. Calcium-containing phosphate binders, used in the last 15 years, increase total body calcium load and may exacerbate metastatic calcification, thus, increasing the risk of cardiovascular mortality. Recently two new compounds non-aluminum and non-calcium phosphate binders, sevelamer hydrochloride and lanthanum carbonate, have been introduced. Sevelamer, besides the effect on phosphate, has been associated with reduction of coronary and aortic calcification and with other pleiotropic effects especially on lipid metabolism. Lanthanum carbonate has similar phosphate control to calcium-based binders with less incidence of hypercalcemia but long-term clinical studies are needed for testing long-term exposure. Recently the authors found in dialysis patients, that salivary phosphorus correlated with serum phosphorus. Therefore, they supposed that the use of salivary phosphate binders could reduce its absorption and represent a chance for reducing the serum phosphate concentration in uremic patients.     

Phosphate handling in CKD-MBD from stage 3 to dialysis and the three strengths of lanthanum carbonate

Introduction: High phosphate levels are associated with unfavorable outcomes in ESRD. Recent data suggested that phosphate levels within the normal range are equally associated with poor outcomes in the community and CKD stage 3 – 4. Several concept papers support the potential role of phosphate load as a first-line toxin in the beginning of CKD-MBD processes via the activation of FGF23 cascade. Phosphate load is thereafter involved in the progression of vascular calcification (VC) and bone disorder typical of CKD-MBD.

Areas covered: Herein the authors cover the recent evidence on the pathophysiology of phosphate handling through the natural history of CKD, with particular emphasis on FGF23 cascade, its potential surrogate markers, VC and bone disorder. The major characteristics of lanthanum carbonate are therefore discussed, focusing on its potential advantages for the treatment of difficult cases in CKD-MBD.

Expert opinion: Lanthanum carbonate, being the most potent calcium-free phosphate binder available in clinical practice, could be decisive for those cases where controlling phosphate load is complicated by poor compliance to medications, stubborn high phosphorus intake, extended VC and bone disorders.     

Current and potential treatment options for hyperphosphatemia

Introduction: Hyperphosphatemia is common in late stages of chronic kidney disease and is often associated with elevated parathormone levels, abnormal bone mineralization, extra-osseous calcification, and increased risk of cardiovascular events and death. Several classes of oral phosphate binders are available to help control plasma phosphorus levels. Although effective at lowering serum phosphorus, they all have safety, tolerability, and compliance issues that need to be considered when selecting which one to use.

Areas covered: This paper reviews the most established treatment options for hyperphosphatemia, in patients with chronic kidney disease, focusing on the new inhibitors of active phosphate absorption.

Expert opinion: The prevention and the treatment of hyperphosphatemia is today far to be satisfactory. Nonetheless, an extending range of phosphate binders are now available. Aluminum has potentially serious toxic risks. Calcium-based binders are very effective but can lead to hypercalcemia and/or positive calcium balance and progression of cardiovascular calcification. No long-term data are available for the new calcium acetate/magnesium combination product. Lanthanum is an effective phosphate binder, and long-term effects of tissue deposition seem clinically irrelevant. Sevelamer, appear to have profiles that would lead to pleiotropic effects and reduced progression of vascular calcification, and the main adverse events seen with these agents are gastrointestinal. Iron has a powerful capability of binding phosphate, thus numerous preparations are available, both with and without significant systemic absorption of the iron component. The inhibitors of active intestinal phosphate transport, with their very selective mechanism of action and low pill burden seem the most interesting approach; however, do not seem at present to be effective alone, in reducing serum phosphorus levels.     

Hyperphosphatemia and phosphate binders.

PURPOSE: The pathophysiology of hyperphosphatemia associated with end-stage renal disease and treatment with phosphate binders are discussed. SUMMARY: Phosphorus is an essential element necessary for the normal function of the human body, required for skeletal construction and synthesis of DNA, proteins, and adenosine triphosphate. In healthy individuals, serum phosphorus concentrations are maintained between 2.5 and 4.5 mg/dL through diet and renal excretion. In renal insufficiency, phosphorus excretion declines and hyperphosphatemia develops. The body's compensation mechanisms cause secondary hyperparathyroidism and renal osteodystrophy. Phosphate binders provide an effective means for managing serum phosphate. Commercially available phosphate binders include calcium carbonate, calcium acetate, sevelamer, lanthanum, and, rarely, aluminum hydroxide. Because of aluminum's known toxicities, aluminum-based phosphate binders have a limited place in therapy. Calcium carbonate's benefits are seen over a narrow gastric pH range, thereby limiting the drug's utility. Calcium acetate is effective over a wide pH range. Other phosphate binders, including sevelamer hydrochloride and lanthanum carbonate, have recently entered the market, but their use remains controversial. CONCLUSION: If left untreated, hyperphosphatemia can result in secondary hyperparathyroidism, renal osteodystrophy, and metastatic calcification of blood vessels and soft tissue. The treatment of hyperphosphatemia in patients with chronic renal failure includes dialysis, dietary phosphorus restrictions, phosphate-binding medications, and vitamin D analogs. Selection of phosphate binders should be based on patient characteristics, including serum phosphate, serum calcium, and intact parathyroid hormone concentrations, and patient tolerability.     

Relative in vitro efficacy of the phosphate binders lanthanum carbonate and sevelamer hydrochloride

The high tablet burden and poor compliance associated with phosphate-binding drugs has led to a search for more potent agents. In vitro-binding studies were performed on the recently introduced binder, lanthanum carbonate (LC; Fosrenol), to compare its phosphate-binding affinity with sevelamer hydrochloride (SH; Renagel). Langmuir equilibrium binding affinities (K(1)) for LC and SH were established using different phosphorus (5-100 mM) and binder (134-670 mg per 50 mL) concentrations at pH 3-7, with or without salts of bile acids present (30 mM). At all pH levels, LC had a higher binding affinity for phosphate than SH. For LC, K(1) was 6.1 +/- 1.0 mM(-1) and was independent of pH. For SH, K(1) was pH dependent, being 1.5 +/- 0.8 mM(-1) at pH 5-7 and 0.025 +/- 0.002 mM(-1) at pH 3, that is, >200 times lower than for LC. In the presence of 30 mM bile salts, SH lost 50% of its phosphate, whereas no displacement of phosphate occurred for LC. These findings indicate that LC binds phosphate more effectively than SH across the pH range encountered in the gastrointestinal tract, and has a lower propensity for bound phosphate to be displaced by competing anions in the intestine.     

Sevelamer carbonate for the treatment of hyperphosphatemia in patients with kidney failure (CKD III – V)

Importance of the field: Altered mineral metabolism in chronic kidney disease (CKD) is associated with increased morbidity, mortality, hospitalization, cost of care and reduced quality of life. Phosphorus control, one component of CKD metabolic derangements, is potentially related to impaired outcomes and has significant room for improvement.

Areas covered in this review: Historical, present and future aspects of treatment of hyperphosphatemia focusing on sevelamer hydrochloride and sevelamer carbonate.

What the reader will gain: Comprehensive insight into the background and controversies regarding phosphate binders.

Take home message: While calcium-free phosphate binders with a sevelamer backbone may offer therapeutic advantages for CKD patients at risk, more studies comprising significant patient numbers are warranted to answer compelling clinical questions.     

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.     

新型磷结合剂的研究进展

慢性肾脏病(CKD)患者肾功能减退,引发钙磷的代谢紊乱,进一步导致各种疾病的发生。高磷血症可能会升高CKD患者的发病率和死亡率。因而,有效控制血清磷的水平将是CKD患者预后的关键。传统磷结合剂常含钙、铝成分,虽能有效降低血清磷,但不良反应较多。综述上市的和临床研究中的新型磷结合剂如司维拉姆、碳酸镧、考来替兰和柠檬酸铁等,其不含钙、铝,能有效控制血清磷水平,却不升高血钙,为控制高磷血症和减少血管钙化风险提供了治疗前景。     

新型磷结合剂的研究进展

慢性肾脏病（CKD）患者肾功能减退,引发钙磷的代谢紊乱,进一步导致各种疾病的发生。高磷血症可能会升高CKD患者的发病率和死亡率。因而,有效控制血清磷的水平将是CKD患者预后的关键。传统磷结合剂常含钙、铝成分,虽能有效降低血清磷,但不良反应较多。综述上市的和临床研究中的新型磷结合剂如司维拉姆、碳酸镧、考来替兰和柠檬酸铁等,其不含钙、铝,能有效控制血清磷水平,却不升高血钙,为控制高磷血症和减少血管钙化风险提供了治疗前景。     

醋酸钙联合碳酸镧治疗尿毒症血液透析高磷血症的疗效观察

目的探讨醋酸钙片联合碳酸镧咀嚼片治疗尿毒症血液透析患者高磷血症的临床疗效。方法选取2014年8月—2016年9月在青岛市市立医院进行尿毒症血液透析高磷血症患者134例,根据血磷水平随机分为醋酸钙组(43例)、碳酸镧组(45例)、醋酸钙和碳酸镧联合组(46例)。醋酸钙组口服醋酸钙片,2片/次,3次/d;碳酸镧组口服碳酸镧咀嚼片,2片/次,3次/d;联合组口服碳酸镧咀嚼片、醋酸钙片,2片/次,3次/d。3组患者均持续治疗12周。观察各组的临床疗效,比较各组的观察指标。结果碳酸镧组总有效率(75.5%)高于醋酸钙组(69.7%),但差异无统计学意义。联合组总有效率(94.5%)高于醋酸钙组、碳酸镧组,差异均具有统计学意义(P0.05)。治疗后,各组血磷、血甲状旁腺素(PTH)均显著降低,碳酸镧组血钙、冠状动脉钙化积分(CACs)降低,醋酸钙组、联合组血钙、CACs升高,与同组治疗前比较差异具有统计学意义(P0.05)。治疗后,与醋酸钙组比较,碳酸镧组、联合组的血磷、血钙、血PTH、CACs均降低,差异具有统计学意义(P0.05);与碳酸镧组比较,联合组的血磷、血PTH降低,血钙、CACs升高,差异具有统计学意义(P0.05)。结论碳酸镧和醋酸钙均能有效降低血磷,但碳酸镧对血钙的影响较小,并能明显延缓CACs的进展。碳酸镧联合醋酸钙控制血磷效果最好,但有增加CAC的进展的风险,有待于进一步研究。