Phosphate in Cardiovascular Disease: From New Insights Into Molecular Mechanisms to Clinical Implications.

Hyperphosphatemia is a common feature in patients with impaired kidney function and is associated with increased risk of cardiovascular disease. This phenomenon extends to the general population, whereby elevations of serum phosphate within the normal range increase risk; however, the mechanism by which this occurs is multifaceted, and many aspects are poorly understood. Less than 1% of total body phosphate is found in the circulation and extracellular space, and its regulation involves multiple organ cross talk and hormones to coordinate absorption from the small intestine and excretion by the kidneys. For phosphate to be regulated, it must be sensed. While mostly enigmatic, various phosphate sensors have been elucidated in recent years. Phosphate in the circulation can be buffered, either through regulated exchange between extracellular and cellular spaces or through chelation by circulating proteins (ie, fetuin-A) to form calciprotein particles, which in themselves serve a function for bulk mineral transport and signaling. Either through direct signaling or through mediators like hormones, calciprotein particles, or calcifying extracellular vesicles, phosphate can induce various cardiovascular disease pathologies: most notably, ectopic cardiovascular calcification but also left ventricular hypertrophy, as well as bone and kidney diseases, which then propagate phosphate dysregulation further. Therapies targeting phosphate have mostly focused on intestinal binding, of which appreciation and understanding of paracellular transport has greatly advanced the field. However, pharmacotherapies that target cardiovascular consequences of phosphate directly, such as vascular calcification, are still an area of great unmet medical need.

Elevated luminal inorganic phosphate suppresses intestinal Zn absorption in 5/6 nephrectomized rats.

Zinc (Zn) is an essential trace element in various biological processes. Chronic kidney disease (CKD) often leads to hypozincemia, resulting in further progression of CKD. In CKD, intestinal Zn absorption, the main regulator of systemic Zn metabolism, is often impaired; however, the mechanism underlying Zn malabsorption remains unclear. Here, we evaluated intestinal Zn absorption capacity in a rat model of CKD induced by 5/6 nephrectomy (5/6 Nx). Rats were given Zn and the incremental area under the plasma Zn concentration-time curve (iAUC) was measured as well as the expression of ZIP4, an intestinal Zn transporter. We found that 5/6 Nx rats showed lower iAUC than sham-operated rats, but expression of ZIP4 protein was upregulated. We therefore focused on other Zn absorption regulators to explore the mechanism by which Zn absorption was substantially decreased. Because some phosphate compounds inhibit Zn absorption by coprecipitation and hyperphosphatemia is a common symptom in advanced CKD, we measured inorganic phosphate (Pi) levels. Pi was elevated in not only serum but also the intestinal lumen of 5/6 Nx rats. Furthermore, intestinal intraluminal Pi administration decreased the iAUC in a dose-dependent manner in normal rats. In vitro, increased Pi concentration decreased Zn solubility under physiological conditions. Furthermore, dietary Pi restriction ameliorated hypozincemia in 5/6 Nx rats. We conclude that hyperphosphatemia or excess Pi intake is a factor in Zn malabsorption and hypozincemia in CKD. Appropriate management of hyperphosphatemia will be useful for prevention and treatment of hypozincemia in patients with CKD.NEW & NOTEWORTHY We demonstrated that elevated intestinal luminal Pi concentration can suppress intestinal Zn absorption activity without decreasing the expression of the associated Zn transporter. Increased intestinal luminal Pi led to the formation of an insoluble complex with Zn while dietary Pi restriction or administration of a Pi binder ameliorated hypozincemia in chronic kidney disease model rats. Therefore, modulation of dietary Pi by Pi restriction or a Pi binder might be useful for the treatment of hypozincemia and hyperphosphatemia.

Tenapanor for peritoneal dialysis patients with hyperphosphatemia: a phase 3 trial.

BACKGROUND: Tenapanor is a novel selective inhibitor of intestinal sodium/hydrogen exchanger 3 transporter. This is the first trial to assess the efficacy and safety of tenapanor in Japanese patients with hyperphosphatemia who are undergoing peritoneal dialysis. METHODS: This phase 3, open-label, multicenter, single-arm clinical trial targeted patients whose serum phosphorus was within 3.5-7.0 mg/dL with phosphate binders at screening. After phosphate binder washout, tenapanor was orally administered twice-daily, stepwise from 5 to 30 mg/dose for 16 weeks. The primary endpoint, mean change in serum phosphorus level, was evaluated at week 8. The 16-week treatment period was completed with tenapanor alone, and only one phosphate binder type was allowed for combined use after the primary endpoint. RESULTS: Of the 54 patients enrolled, 34 completed the study. At week 8, the primary endpoint, mean change in serum phosphorus level (last observation carried forward), was - 1.18 mg/dL (95% confidence interval: - 1.54, - 0.81 mg/dL) with tenapanor. From a baseline value of 7.65 mg/dL, serum phosphorus decreased to 6.14 and 5.44 mg/dL at weeks 8 and 16, respectively, and 46.3% and 76.5% of patients achieved serum phosphorus within 3.5-6.0 mg/dL at week 8 and week 16, respectively. The most common adverse event, diarrhea, occurred in 74.1% of patients; the severity of diarrhea was mild or moderate. Thus, the discontinuation percentage due to diarrhea was low at 5.6%. CONCLUSIONS: Administration of tenapanor resulted in a sufficient reduction in serum phosphorus level at week 8 and was considered safe and tolerable. TRIAL REGISTRATION: NCT04766385.

Effect of renin-angiotensin system inhibitors on cardiovascular events in hemodialysis patients with hyperphosphatemia: A post hoc analysis of the LANDMARK trial.

INTRODUCTION: The clinical benefits of renin-angiotensin system inhibitors (RASi) in patients undergoing hemodialysis remain obscure. METHODS: This is a post hoc cohort analysis of the LANDMARK trial investigate whether RASi use was associated with cardiovascular events (CVEs) and all-cause mortality. A total of 2135 patients at risk for vascular calcification were analyzed using a Cox proportional hazards model with propensity-score matching. RESULTS: The risk of CVEs was similar between participants with RASi use at baseline and those without RASi use at baseline and between participants with RASi use during the study period and those without RASi use during the study period. No clinical benefits of RASi use on all-cause mortality were observed. Serum phosphate levels were significantly associated with the effect of RASi on CVEs. CONCLUSIONS: RASi use was not significantly associated with a lower risk of CVEs or all-cause mortality in hemodialysis patients at risk of vascular calcification.

Biochemical markers of iron status and iron accumulation in peritoneal dialysis patients treated with ferric citrate.

BACKGROUND: Hyperphosphataemia is a common complication of kidney disease. Current dialysis techniques do not provide enough phosphorus clearance, hence the need to use phosphorus binders. Treatment options include calcium carbonate, calcium acetate, lanthanum carbonate, sevelamer hydrochloride and iron-based binders. Patients receiving peritoneal dialysis (PD) with sustained elevated ferritin levels exceeding 800 ng/mL are at a higher risk of death. We identify PD patients treated with iron-based binders and compare ferritin and risk of iron accumulation to patients treated with non-iron-based binders. METHODS: All records of patients receiving PD at Emory dialysis centres until 30 October 2021 were reviewed for phosphorus binders. Basic demographics and laboratory data were time-referenced to the days on treatment with a particular binder. Patients were followed until discontinuation of the phosphorus binder, death, transplant, transfer to another dialysis provider or censoring at 36 months after medication was started. RESULTS: Compared to calcium acetate and sevelamer, ferric citrate utilisation in PD patients resulted in a sustained increase in ferritin. The proportion of patients with a ferritin equal to or greater than 800 ng/dL and transferrin saturation greater than 40% increased over time in patients treated with ferric citrate and was higher during the second and third year of follow-up compared to baseline values and to patients treated with calcium acetate or sevelamer. Two patients (7%) treated with ferric citrate developed clinically significant haemosiderosis. CONCLUSIONS: Use of ferric citrated in PD resulted in significant iron accumulation as judged by ferritin levels.

Efficacy and Safety of Sucroferric Oxyhydroxide Compared with Sevelamer Carbonate in Chinese Dialysis Patients with Hyperphosphataemia: A Randomised, Open-Label, Multicentre, 12-Week Phase III Study.

INTRODUCTION: This study aimed to investigate the efficacy and safety of sucroferric oxyhydroxide (SFOH) versus sevelamer carbonate in controlling serum phosphorus (sP) in adult Chinese dialysis patients with hyperphosphataemia (sP >1.78 mmol/L). METHODS: Open-label, randomised (1:1), active-controlled, parallel group, multicentre, phase III study of SFOH and sevelamer at starting doses corresponding to 1,500 mg iron/day and 2.4 g/day, respectively, with 8-week dose titration and 4-week maintenance (NCT03644264). Primary endpoint was non-inferiority analysis of change in sP from baseline to week 12. Secondary endpoints included sP over time and safety. RESULTS: 415 patients were screened; 286 were enrolled and randomised (142 and 144 to SFOH and sevelamer, respectively). Mean (SD) baseline sP: 2.38 (0.57) and 2.38 (0.52) mmol/L, respectively. Mean (SD) change in sP from baseline to week 12: - 0.71 (0.60) versus -0.63 (0.52) mmol/L, respectively; difference (sevelamer minus SFOH) in least squares means (95% CI): 0.08 mmol/L (-0.02, 0.18) with the lower limit of 95% CI above the non-inferiority margin of -0.34 mmol/L. The SFOH group achieved target sP (1.13-1.78 mmol/L) earlier than the sevelamer group (56.5% vs. 32.8% at week 4) and with a lower pill burden (mean 3.7 vs. 9.1 tablets/day over 4 weeks of maintenance, respectively). Safety and tolerability of SFOH was consistent with previous studies, and no new safety signals were observed. CONCLUSION: SFOH effectively reduced sP from baseline and was non-inferior to sevelamer after 12 weeks of treatment but had a lower pill burden in Chinese dialysis patients with hyperphosphataemia; SFOH benefit-risk profile is favourable in Chinese patients.

Health Economic Benefits of Introducing Sucroferric Oxyhydroxide in the Treatment of Patients with Chronic Kidney Disease under Dialysis in the Kingdom of Saudi Arabia.

Hyperphosphatemia is an electrolyte disorder highly prevalent in patients with chronic kidney disease undergoing hemodialysis (HD) that usually requires treatment with oral phosphate binders (PBs). Sucroferric oxyhydroxide (SO) is a calcium-free, iron-based PB indicated for the control of serum phosphorus. In the real-world setting, SO has shown clinical effectiveness with a lower pill burden and has also been associated with reduced hospital admission rates. This study aims to assess the potential economic benefits resulting from the introduction of SO to the health-care setting of the Kingdom of Saudi Arabia (KSA). An economic analysis using data from a retrospective real-world study that compared HD patients with uninterrupted SO prescriptions with patients who discontinued SO and switched to other PBs (oPBs). Annual drug costs for the estimated PB-eligible population in KSA were quantified. Costs per responder were estimated for all treatments. Hospital admissions' incidence rates were converted into annual inpatient cost savings and were deducted from drug costs to estimate the annual economic effect of SO versus oPBs. Sensitivity and breakeven analyses were also conducted. The eligible population for PB therapy in KSA was estimated at n = 14,748. Treating therapy-eligible populations exclusively with SO was estimated to generate annual inpatient cost-savings of SAR 107.4-119.4 million compared to treating the population with oPBs. The estimated economic effect signified overall annual savings ranging from SAR 82.8 to SAR 94.8 million when the population is treated with SO. Sensitivity analyses showed persistent cost savings. The estimated benefit-cost ratios showed that for every SAR 1 spent on SO, the expected return on investment was SAR 4.4-4.9. SO is an effective therapy that may result in substantial cost savings from reducing hospital admission costs that are attributable to hyperphosphatemia among HD patients.

A 47-Year-Old Man with Hyperphosphatemia Due to Chronic Renal Failure Treated with Lanthanum Carbonate Tablets Presenting Acutely with Partial Large Bowel Obstruction.

BACKGROUND Hyperphosphatemia is a complication of chronic renal failure (CRF) due to reduction in the glomerular filtration rate. Lanthanum carbonate is a commonly used phosphate binder for patients with CRF and hyperphosphatemia, but has adverse effects if patients are not monitored. This report is of a 47-year-old man with hyperphosphatemia due to CRF treated with lanthanum carbonate tablets who presented acutely with partial large bowel obstruction. The incidence of lanthanum carbonate causing intestinal obstruction is rare, and few cases in the literature have described the course of the disease in detail. CASE REPORT A 47-year-old man diagnosed with diabetic nephropathy underwent hemodialysis treatment and was prescribed 0.5 g/day of chewable lanthanum carbonate tablets. After taking lanthanum carbonate for 5 months, the patient experienced symptoms of decreased bowel movements and exhaustion, which progressively worsened. Abdominal computed tomography (CT) revealed multiple hyperdensities in the large bowel, indicating the presence of lanthanum deposition. Lanthanum carbonate was promptly discontinued. After undergoing enema and catharsis treatment, the large bowel obstruction was relieved, and the hyperdensities in the abdominal CT disappeared. The colonoscopy and histologic examination revealed ulcerations and inflammatory changes in the large bowel mucosa. CONCLUSIONS This report highlights the rare association between the use of lanthanum carbonate tablets and intestinal obstruction. Healthcare providers should enhance their vigilance regarding lanthanum carbonate-induced serious gastrointestinal adverse reactions and actively seek to detect lanthanum deposition by abdominal CT or radiography (X-ray). After the occurrence of lanthanum deposition, drug withdrawal and promotion of defecation are primary treatment methods.

Long-term safety and decrease of pill burden by tenapanor therapy: a phase 3 open-label study in hemodialysis patients with hyperphosphatemia.

Phosphate binders (PBs) generally have a high pill burden. Tenapanor selectively inhibits sodium/hydrogen exchanger isoform 3, reducing intestinal phosphate absorption. Tenapanor is a novel drug administered as a small tablet, twice daily. This multicenter, open-label, single-arm, phase 3 study aimed to evaluate the long-term safety of tenapanor and its efficacy in decreasing PB pill burden. Tenapanor 5 mg twice daily was administered to hemodialysis patients with serum phosphorus level 3.5-7.0 mg/dl at baseline; the dose could be increased up to 30 mg twice daily. Patients could also switch from PBs. The primary endpoint was safety during 52-week administration. The key secondary endpoint was a ≥ 30% reduction in the total pill number of daily PBs and tenapanor from baseline. Of 212 patients starting treatment, 154 completed the study. Diarrhea was the most frequent adverse event, occurring in 135 patients (63.7%); most events were classified as mild (74.8%). No clinically significant changes occurred other than serum phosphorus level. At Week 52/discontinuation, 158/204 patients (77.5%) achieved the key secondary endpoint. Complete switching from PBs to tenapanor was achieved in 50-76 patients (26.7%-41.5%), and 80 patients (51.9%) at Week 8-12 and Week 50, respectively. Serum phosphorus remained generally stable within the target range (3.5-6.0 mg/dl). These findings suggest the long-term safety and tolerability of tenapanor. Tenapanor could reduce or eliminate PB pill burden while controlling serum phosphorus levels.Trial registration: NCT04771780.

Reducing the risk of denosumab-induced hypocalcemia in patients with advanced chronic kidney disease: a quality improvement initiative.

Denosumab can improve bone health in advanced kidney disease (CKD) but is associated with hypocalcemia. We created a clinical care pathway focused on the safe provision of denosumab in advanced CKD that reduced the risk of hypocalcemia by 37% at our hospital. Similar pathways could be adopted and tested in other centers. PURPOSE: There is an increased risk of hypocalcemia with denosumab in advanced chronic kidney disease (CKD). We aimed to reduce the proportion of patients with advanced CKD who experienced denosumab-induced hypocalcemia at our center. METHODS: We conducted a quality improvement (QI) project of patients with CKD stage 3b or less (i.e., estimated glomerular filtration rate <45 mL/min/1.73m2 including dialysis) who were part of the Osteoporosis and Bone Disease Program at St. Joseph's Health Care London (Canada) between December 2020 and January 2023. Our intervention was a clinical care pathway which optimized CKD mineral and bone disorder (CKD-MBD) and 25-hydroxyvitamin levels; provided calcium and vitamin D prophylaxis; promoted multidisciplinary communication between bone and kidney specialists; and carefully monitored calcium post-denosumab injection. Our primary outcome measure was the proportion of patients with hypocalcemia (defined by albumin-corrected serum calcium <1.9mmol/L) at 60 days. Process measures included the appropriate provision of calcium and vitamin D prophylaxis. Balance measures included the development of hypercalcemia and hyperphosphatemia following prophylaxis. We used plan-do-see-act cycles to study four tests of change and presented results using descriptive statistics and run charts. RESULTS: There were 6 patients with advanced CKD treated with denosumab prior to the implementation of our care pathway (March 2015-October 2020; 83% receiving dialysis). At the time of their denosumab injection, 83% were using 500-1000 mg of calcium, and 83% used 1000-2000 IU of vitamin D3. Fifty percent developed denosumab-induced hypocalcemia. Following the implementation of our care pathway, 15 patients (40% receiving dialysis) were treated with denosumab. Ninety-three percent received calcium at a daily dose of 350 to 2250 mg and 87% received 1000-2000 IU of vitamin D3. Thirteen percent developed denosumab-induced hypocalcemia. There was no hypercalcemia or hyperphosphatemia. CONCLUSIONS: A clinical care pathway focused on the safe provision of denosumab in advanced CKD reduced the risk of hypocalcemia in patients treated in our hospital. Similar pathways could be adopted and tested in other centers.

Efficacy and Safety of Ferric Citrate on Hyperphosphatemia among Chinese Patients with Chronic Kidney Disease Undergoing Hemodialysis: A Phase III Multicenter Randomized Open-Label Active-Drug-Controlled Study.

INTRODUCTION: Hyperphosphatemia in chronic kidney disease (CKD) patients is positively associated with mortality. Ferric citrate is a potent phosphorus binder that lowers serum phosphorus level and improves iron metabolism. We compared its efficacy and safety with active drugs in Chinese CKD patients with hemodialysis. METHODS: Chinese patients undergoing hemodialysis were randomized into two treatment groups in a 1:1 ratio, receiving either ferric citrate or sevelamer carbonate, respectively, for 12 weeks. Serum phosphorus levels, calcium concentration, and iron metabolism parameters were evaluated every 2 weeks. Frequency and severity of adverse events were recorded. RESULTS: 217 (90.4%) patients completed the study with balanced demographic and baseline characteristics between two groups. Ferric citrate decreased the serum phosphorus level to 0.59 ± 0.54 mmol/L, comparable to 0.56 ± 0.62 mmol/L by sevelamer carbonate. There was no significant difference between two groups (p > 0.05) in the proportion of patients with serum phosphorus levels reaching the target range, the response rate to the study drug, and the changes of corrected serum calcium concentrations, and intact-PTH levels at the end of treatment. The change of iron metabolism indicators in the ferric citrate group was significantly higher than those in the sevelamer carbonate group. There are 47 (40.5%) patients in the ferric citrate group, and 26 (21.3%) patients in the sevelamer carbonate group experienced drug-related treatment emergent adverse events (TEAEs); most were mild and tolerable. Common drug-related TEAEs were gastrointestinal disorders, including diarrhea (12.9 vs. 2.5%), fecal discoloration (14.7 vs. 0%), and constipation (1.7 vs. 7.4%) in ferric citrate and sevelamer carbonate group. CONCLUSION: Ferric citrate capsules have good efficacy and safety in the control of hyperphosphatemia in adult patients with CKD undergoing hemodialysis. Efficacy is not inferior to sevelamer carbonate. The TEAEs were mostly mild and tolerated by the patients.

Family-centered empowerment approach to optimize phosphate management among hemodialysis patients: an experimental study.

BACKGROUND: This study aimed to investigate the effect of a family-centered empowerment program on hyperphosphatemia management. METHOD: This experimental study was performed on 80 randomly selected eligible patients with hyperphosphatemia undergoing hemodialysis. Patients were assigned randomly to two groups of family-centered empowerment program (FCEPG) and control group (CG) by coin toss (40 people per group). Data collection tools were the researcher-made Phosphate Control Knowledge Scale, the researcher-made Adherence to Dietary Restriction of Phosphorus Intake Scale, the eight-item Morisky Medication Adherence Scale, and serum phosphorus measurements. Data were collected before the intervention, one month, and three months after the intervention. Patients in FCEPG participated in a family-centered empowerment program. The statistical significance level was considered to be 0.05. RESULTS: Inter-group comparisons showed no significant difference between FCEPG and CG in terms of the mean score of knowledge of phosphate control, adherence to dietary restriction of phosphorus intake, adherence to medication, and the mean serum phosphorus level before the empowerment program, but showed significant differences between them in these respects at one month after the program and three months after the program (p < 0.05). Intra-group comparisons showed a significant difference in FCEPG between the mean and standard deviation of all four variables before the empowerment program and the corresponding values one month and three months after the program (P < 0.05). CONCLUSION: The findings of this study can be used in various fields of healthcare in the hospital and community.

Effects of iron-based phosphate binders on mortality and cardiovascular events in patients receiving maintenance dialysis.

Phosphate binders are the main treatment for hyperphosphatemia in patients with chronic kidney disease, and iron-based phosphate binders have been used with increasing frequency in recent years. This study examined the association of the use of iron-based, rather than non-iron-based, phosphate binders with the incidence of cardiovascular events, in a real-world setting. We used data from a cohort comprising representative adult patients on maintenance hemodialysis in Japan. The exposure of interest was the time-varying use of phosphate binders, classified into "iron-based", "only non-iron-based", and "no use". The primary outcome was a composite of cardiovascular events and all-cause deaths. A marginal structural Cox regression model was used to deal with possible time-dependent confounding. Of the 2247 patients from 58 hemodialysis facilities, iron-based and only non-iron-based phosphate binders were used in 328 (15%) and 1360 (61%), respectively, at baseline. Hazard ratios (95% confidence intervals) for iron-based and non-iron-based phosphate binders versus no use of phosphate binders were 0.35 (0.24, 0.52) and 0.44 (0.33, 0.58), respectively. The hazard ratio for iron-based relative to non-iron-based phosphate binders was 0.81 (0.58, 1.13), which was not statistically significant. Further studies are warranted to elucidate whether the use of iron-based phosphate binders reduces the event rate.

Comparative Efficacy and Acceptability of 12 Phosphorus-Lowering Drugs in Adults with Hyperphosphatemia and Chronic Kidney Disease: A Systematic Review and Network Meta-Analysis.

BACKGROUND: Hyperphosphatemia is associated with cardiovascular morbidity and mortality in adults with chronic kidney disease (CKD). Drug therapy has an irreplaceable role in the management of hyperphosphatemia. OBJECTIVES: We aimed to compare and rank phosphorus-lowering drugs, including phosphate binder and nonphosphate binder, in hyperphosphatemia adults with CKD. METHODS: We did a systematic review and frequentist random-effect network meta-analysis. We searched in PubMed, Cochrane Library, Web of Science, and Embase from inception to February 1, 2023, for randomized controlled trials of 12 phosphorus-lowering drugs in adults with hyperphosphatemia and CKD. Primary outcomes were efficacy (changes in serum phosphorus) and acceptability (treatment withdrawals due to any cause). We ranked each drug according to the value of surface under the cumulative ranking curve. We applied the Confidence in Network Meta-Analysis frameworks to rate the certainty of evidence. This study was registered with PROSPERO, number CRD42022322270. RESULTS: We identified 2,174 citations, and of these, we included 94 trials comprising 14,459 participants and comparing 13 drugs or placebo. In terms of efficacy, except for niacinamide, all drugs lowered the level of serum phosphorus compared with placebo, with mean difference ranging between -1.61 (95% credible interval [CrI], -2.60 to -0.62) mg/dL for magnesium carbonate and -0.85 (-1.66 to -0.05) mg/dL for bixalomer. Only ferric citrate with odds ratios 0.56 (95% CrI: 0.36-0.89) was significantly associated with fewer dropouts for acceptability. Of the 94 trials, 43 (46%), 7 (7%), and 44 (47%) trials were rated as high, moderate, and low risk of bias, respectively, the certainty of the evidence was moderate to very low. CONCLUSIONS: Magnesium carbonate has the best phosphorus-lowering effect in hyperphosphatemia adults with CKD; considering efficacy and acceptability, ferric citrate shows evidence to be the most appropriate drug with or without dialysis.

Progress in pharmacotherapy for the treatment of hyperphosphatemia in renal failure.

INTRODUCTION: Among the clinical and metabolic complications of progressive chronic kidney disease (CKD), CKD-mineral bone disorder (CKD-MBD) significantly contributes to morbidity and mortality. While overt and persistent hyperphosphatemia is typical of advanced CKD and requires treatment, other abnormalities of calcium/phosphate metabolism begin to occur since the early stages of the disease. AREAS COVERED: We searched on the PubMed database, without restrictions for language or time range, for randomized clinical trials and meta-analyses investigating phosphate-lowering therapies. The various phosphate binders show different safety profiles and diverse effects on calcium/phosphate metabolism and vascular calcification. The in-depth knowledge of the characteristics of these drugs is crucial to ensure adequate treatment to CKD patients. EXPERT OPINION: A proper control of serum phosphate can be achieved using phosphate binders. These medications may induce side effects. Moreover, data on their impact on clinical outcomes are partly controversial or scarce, especially for the new generation drugs. Hyperphosphatemia favors cardiovascular disease and increases the risk for CKD progression. These effects are partially mediated by fibroblast growth factor 23 (FGF23), a phosphaturic hormone that raises to maintain normal serum phosphate. Since there are no data supporting the use of phosphate-lowering agents when phosphataemia is normal, a key role is played by reducing dietary phosphate intake with the aim to control serum phosphate and the compensatory FGF23 and parathyroid hormone (PTH) increase.

PLAIN LANGUAGE SUMMARY: The progressive reduction in renal function, a condition known as chronic kidney disease (CKD), is characterized by several clinical and metabolic complications. Among them are the alterations of calcium and phosphorous metabolism that are part of the so-called CKD-MBD (chronic kidney disease-mineral bone disorder) and contribute to increase morbidity and mortality, especially due to vascular calcification. Persistent hyperphosphatemia is typical of advanced CKD but other abnormalities occur earlier to maintain normal serum calcium and phosphorus levels. These compensatory mechanisms are also involved in the pathophysiology of CKD-MBD and should be counteracted to improve clinical outcomes of CKD patients. Given the crucial role of hyperphosphatemia, numerous therapeutic strategies have been developed over time to help maintain phosphate serum levels within the normal range and prevent or treat CKD-MBD and its consequences. Phosphate binders act by binding dietary phosphate in the gastrointestinal lumen to prevent its absorption. According to their molecular structure, these drugs can be classified into calcium-based (calcium carbonate, calcium acetate), non-calcium-containing (sevelamer carbonate, sevelamer hydrochloride, lanthanum carbonate), aluminum-containing (aluminum hydroxide), and iron-based (sucroferric oxyhydroxide, ferric citrate) compounds. The various phosphate binders show different safety profiles and diverse effects on calcium/phosphate metabolism and vascular calcification. Despite the ability of hyperphosphatemia to favor CKD-MBD development and cardiovascular risk, there are no data supporting the use of phosphate-lowering agents when serum phosphate is normal also due to the potential adverse effects of long-term therapies. Accordingly, a key role is played by reducing dietary phosphate overload since the first stages of CKD.

Meta-analysis of the efficacy and safety of sevelamer as hyperphosphatemia therapy for hemodialysis patients.

This study was designed to examine the relative safety and efficacy of sevelamer in the treatment of chronic kidney disease (CKD) patients in comparison to placebo, calcium carbonate (CC), or lanthanum carbonate (LC). The PubMed, Embase, Cochrane Library, and China National Knowledge Infrastructure (CNKI) databases were searched for articles published through 18 June 2022. The quality of relevant studies was independently analyzed by two investigators who also extracted data from these manuscripts as per Cochrane Collaboration Handbook 5.3. The safety and efficacy of sevelamer as a treatment for hyperphosphatemia in CKD patients were then examined through a meta-analysis, with the primary patient-level outcomes of interest in this analysis being all-cause mortality and the incidence of gastrointestinal adverse effects. Vascular calcification score was also examined as an intermediate outcome, while serum biochemical parameters including levels of phosphate (P), calcium (Ca), intact parathyroid hormone (iPTH), lipids, C-reactive protein (CRP), or fibroblast growth factor-23 (FGF-23) were additionally assessed. In total, this meta-analysis incorporated data from 34 randomized controlled trials (RCTs) enrolling 2802 patients. Sevelamer was associated with reduced all-cause mortality (RR 0.28, CI 0.19 - 0.41, very low certainty) and Vessel calcification score (RR -0.58, CI -1.11 to -0.04, low certainty) and induced less hypercalcemia (MD -0.28, CI 0.40 to -0.16, low certainty) and hyperphosphatemia (MD -0.22, CI -0.32 to -0.13, low certainty) when compared with Ca-based binders in CKD5D individuals. No significant differences in gastrointestinal adverse events (GAEs) incidence were observed. These data suggest that sevelamer may represent a beneficial means of protecting CKD patients against death and vessel calcification when used to treat hyperphosphatemia, while we found no clinically important benefits in decreasing gastrointestinal adverse effects.

Efficacy and safety of tenapanor in hemodialysis patients with hyperphosphatemia: A systematic review and meta-analysis of randomized placebo-controlled trials.

BACKGROUND: The effects of tenapanor in reducing serum phosphorus in hemodialysis patients with hyperphosphatemia are uncertain and no relevant meta-analysis has been conducted. We performed a meta-analysis of randomized placebo-controlled trials to evaluate the efficacy and safety of tenapanor. METHODS: All randomized controlled trials of tenapanor were searched up to 1 August 2022. The primary endpoint was the change in serum phosphorus level from baseline with tenapanor and placebo. Data on drug-related adverse events (AEs), gastrointestinal AEs and diarrhea were collected to determine the safety of tenapanor. RESULTS: There were 533 patients throughout five trials that were eligible. Tenapanor significantly lowered blood phosphorus level by 1.79 mg/dl in the mean difference than the placebo. Diarrhea, gastrointestinal AEs, and drug-related AEs were more severe than placebo. CONCLUSIONS: This meta-analysis showed that although drug side effects were common, tenapanor significantly reduced serum phosphorus level in hemodialysis patients.

Effects of EOS789, a novel pan-phosphate transporter inhibitor, on phosphate metabolism : Comparison with a conventional phosphate binder.

BACKGROUND: Inorganic phosphate (Pi) binders are the only pharmacologic treatment approved for hyperphosphatemia. However, Pi binders induce the expression of intestinal Pi transporters and have limited effects on the inhibition of Pi transport. EOS789, a novel pan-Pi transporter inhibitor, reportedly has potent efficacy in treating hyperphosphatemia. We investigated the properties of EOS789 with comparison to a conventional Pi binder. METHODS: Protein and mRNA expression levels of Pi transporters were measured in intestinal and kidney tissues from male Wistar rats fed diets supplemented with EOS789 or lanthanum carbonate (LC). 32Pi permeability was measured in intestinal tissues from normal rats using a chamber. RESULTS: Increased protein levels of NaPi-2b, an intestinal Pi transporter, and luminal Pi removal were observed in rats treated with LC but not in rats treated with EOS789. EOS789 but not LC suppressed intestinal protein levels of the Pi transporter Pit-1 and sodium/hydrogen exchanger isoform 3. 32Pi flux experiments using small intestine tissues from rats demonstrated that EOS789 may affect transcellular Pi transport in addition to paracellular Pi transport. CONCLUSION: EOS789 has differing regulatory effects on Pi metabolism compared to LC. The properties of EOS789 may compensate for the limitations of LC therapy. The combined or selective use of EOS789 and conventional Pi binders may allow tighter control of hyperphosphatemia. J. Med. Invest. 70 : 260-270, February, 2023.