Reasons for phosphate binder discontinuation vary by binder type

Tenapanor in Chinese ESRD patients with hyperphosphatemia on haemodialysis: a randomised, phase 3 trial

Background

The efficacy and safety of tenapanor has not been confirmed in Chinese end-stage renal disease (ESRD) patients with hyperphosphatemia on haemodialysis (HD).

Methods

This was a randomised, double blind, phase 3 trial conducted at 26 dialysis facilities in China (https://www.chictr.org.cn/index.aspx; CTR20202588). After a 3-week washout, adults with ESRD on HD with hyperphosphatemia were randomised (1:1) using an interactive web response system to oral tenapanor 30 mg twice a day or placebo for 4 weeks. The primary endpoint was the change in mean serum phosphorous level from baseline to the endpoint visit (day 29 or last serum phosphorus measurement). Efficacy was analysed in the intention-to-treat population. Safety was assessed in all patients who received at least one dose of the study drug.

Results

Between 5 March 2021 and 8 June 2022, 77 patients received tenapanor and 73 received placebo. Tenapanor treatment (n = 75) resulted in a significantly greater least squares (LS) mean reduction in serum phosphate at the endpoint visit versus placebo (n = 72): LS mean difference -1.17 mg/dl (95% CI -1.694 to -0.654, P < .001). More patients receiving tenapanor achieved a serum phosphorous level <5.5 mg/dl at the endpoint visit (44.6% versus 10.1%). The most common treatment-related adverse event was diarrhoea [tenapanor 28.6% (22/77), placebo 2.7% (2/73)], which was mostly mild and led to treatment discontinuation in two patients receiving tenapanor.

Conclusions

Tenapanor significantly reduced the serum phosphorous level versus placebo in Chinese ESRD patients on HD and was generally well tolerated.

Managing Phosphate Burden in Patients Receiving Dialysis: Beyond Phosphate Binders and Diet

Most patients receiving dialysis rely on dietary restriction and phosphate binders to minimize the risk of hyperphosphatemia, which is associated with increased mortality. However, dietary restriction is difficult because of hidden phosphate additives in processed foods and medications. Restriction of dietary phosphate sources such as protein may increase the risk of malnutrition. Phosphate binders, the only pharmacologic option for phosphate management since aluminum salts were introduced several decades ago, are often insufficient for binding the 1400-2500 mg of phosphate potentially consumed daily. Over the last decade, serum phosphate levels in the United States have risen, and >69% of patients receiving dialysis exhibited a most recent phosphate level >4.5 mg/dl (above the normal range), indicating an urgent need for new, more effective therapies to manage phosphate burden. Novel, nonbinder therapies such as transcellular and paracellular phosphate absorption inhibitors may be used for phosphate management, and future studies should examine whether they allow fewer dietary restrictions for patients receiving dialysis, potentially improving patient quality of life and nutritional status. It is imperative that we collaborate to move beyond the restrictive approaches available today and provide patients and clinicians with an array of strategies so that they may choose the most appropriate patient-centered therapy.

Past, Present, and Future of Phosphate Management

Cardiovascular (CV) disease (CVD) accounts for >50% of deaths with known causes in patients on dialysis. Elevated serum phosphorus levels are an important nontraditional risk factor for bone mineral disease and CVD in patients with chronic kidney disease (CKD). Given that phosphorus concentrations drive other disorders associated with increased CV risk (e.g., endothelial dysfunction, vascular calcification, fibroblast growth factor-23, parathyroid hormone), phosphate is a logical target to improve CV health. Phosphate binders are the only pharmacologic treatment approved for hyperphosphatemia. Although their safety has improved since inception, the mechanism of action leads to characteristics that make ingestion difficult and unpleasant; large pill size, objectionable taste, and multiple pills required for each meal and snack make phosphate binders a burden. Side effects, especially those affecting the gastrointestinal (GI) system, are common with binders, often leading to treatment discontinuation. The presence of “hidden” phosphates in processed foods and certain medications makes phosphate management even more challenging. Owing to these significant issues, most patients on dialysis are not consistently achieving and maintaining target phosphorus concentrations of <5.5 mg/dl, let alone more normal levels of <4.5 mg/dl, indicating novel approaches to improve phosphate management and CV health are needed. Several new nonbinder therapies that target intestinal phosphate absorption pathways have been developed. These include EOS789, which acts on the transcellular pathway, and tenapanor, which targets the dominant paracellular pathway. As observational evidence has established a strong association between phosphorus concentration and clinical outcomes, such as mortality, phosphate is an important target for improving the health of patients with CKD and end-stage kidney disease (ESKD).

How to improve adherence the captors of phosphorus on hemodialysis: Experience in real life with sucroferric oxyhydroxide

INTRODUCTION

The lack of adherence to phosphate -binders (PB) is the most important factor in not achieving the objectives of serum phosphorus (sP). Studies in the real-world population are needed to understand the influence of PBs on adherence and how to modify it.

METHODS

Prospective study conducted during 3 months in usual clinical practice. Out of 105 hemodialysis patients, 57 were switched to SFOH and 48 maintained their baseline treatment (control group). sP levels and the percentage of patients with sP levels <5mg/dl were compared. Adherence before and after introduction of SFOH, number of pills of PB, preferences in the administration mode and side effects were analyzed.

RESULTS

The percentage of patients with controlled sP (<5mg/dl) increased significantly in the SFOH users' group (62.1-92.9%, p<0.001), but not in the control group (83-83.3%, p=NS). The average of daily tablets decreased significantly in the SFOH group (7.2-2.3 comp, p<0.001), but not in the control group (5.6-5.6, p=NS) and 100% of the patients used only one PB in SFOH group. The use of SFOH increased the adherence according to the SMAQ questionnaire (57.8-84.3%; OR 13.1, p<0.001). The possibility to choose the preferred mode of administration (split-swallowing 89% compared to chewing 11%), improved the acceptance (44.7-78%). 14% of the patients experienced side effects and in 5.2% SFOH was discontinued for this reason.

CONCLUSIONS

SFOH controlled serum sP in 93% of patients, 100% in monotherapy, and with fewer tablets. The exploration and adaptation of preferences in the mode of administration influenced the acceptance of the drug by the patient and, probably, the future adherence.

Phosphate Binders and Nonphosphate Effects in the Gastrointestinal Tract

Phosphate binders are commonly prescribed in patients with end-stage kidney disease to prevent and treat hyperphosphatemia. These binders are usually associated with gastrointestinal distress, may bind molecules other than phosphate, and may alter the gut microbiota, altogether having systemic effects unrelated to phosphate control. Sevelamer is the most studied of the available binders for nonphosphate-related effects including binding to bile acids, endotoxins, gut microbiota-derived metabolites, and advanced glycation end products. Other binders (calcium- and noncalcium-based binders) may bind vitamins, such as vitamin K and folic acid. Moreover, the relatively new iron-based phosphate binders may alter the gut microbiota, as some of the iron or organic ligands may be used by the gastrointestinal bacteria. The objective of this narrative review is to provide the current evidence for the nonphosphate effects of phosphate binders on gastrointestinal function, nutrient and molecule binding, and the gut microbiome.

A randomized controlled trial of different serum phosphate ranges in subjects on hemodialysis

Background

Hyperphosphataemia in dialysis subjects is associated with increased mortality. However cause and effect has not been proven, and the ideal phosphate target range is unknown despite KDOQI’s call for studies over 12 years ago. The design and conduct of a randomized controlled trial is challenging because maintaining two groups within differing target ranges of serum phosphate has not been achieved over a long follow-up of 1 year, in a trial setting, before. The SPIRiT study examines the subject acceptance, recruitment and retention rates for such a study in which subjects were randomised to two distinct serum phosphate concentrations, then titrated and maintained over 12 months.

Methods

A two center trial of 104 hemodialysis subjects randomized to lower range LRG 0.8–1.4 mmol/L or 2.5–4.3 mg/dL) and higher range (HRG 1.8–2.4 mmol/L or 5.6–7.4 mg/dL) serum phosphate groups. Two months’ titration and ten months’ maintenance phase. Interventions were non-calcium phosphate binders, self-help questionnaires, with blood tests at specified time intervals.

Results

Thirteen percent of the eligible dialysis population were successfully recruited. A mean separation by serum phosphate of 1.1 mg/dL was achieved and maintained between the groups over 10 months. Drop-out rate was 27% with mortality 10%. Nine subjects in the HRG (17.6%) and two subjects in the LRG (3.8%) died during the study, however the study was not powered to detect significant differences in outcomes.

Conclusion

Randomizing dialysis subjects to separate treatment targets for serum phosphate can achieve a clinically significant sustained separation over 12 months. A large scale longer term study is required to examine outcomes including mortality.

Trial registration

The trial registration number is ISRCTN24741445 – Date of registration 16th January, retrospectively registered.

Phosphate-control adherence in hemodialysis patients: current perspectives

OBJECTIVES

This review summarizes factors relevant for adherence to phosphate-control strategies in dialysis patients, and discusses interventions to overcome related challenges.

METHODS

A literature search including the terms "phosphorus", "phosphorus control", "hemo-dialysis", "phosphate binder medications", "phosphorus diet", "adherence", and "nonadherence" was undertaken using PubMed, PsycInfo, CINAHL, and Embase.

RESULTS

Hyperphosphatemia is associated with cardiovascular and all-cause mortality in dialysis patients. Management of hyperphosphatemia depends on phosphate binder medication therapy, a low-phosphorus diet, and dialysis. Phosphate binder therapy is associated with a survival benefit. Dietary restriction is complex because of the need to maintain adequate protein intake and, alone, is insufficient for phosphorus control. Similarly, conventional hemodialysis alone is insufficient for phosphorus control due to the kinetics of dialytic phosphorus removal. Thus, all three treatment approaches are important contributors, with dietary restriction and dialysis as adjuncts to the requisite phosphate binder therapy. Phosphate-control adherence rates are suboptimal and are influenced directly by patient, provider, and phosphorus-control strategy-related factors. Psychosocial factors have been implicated as influential "drivers" of adherence behaviors in dialysis patients, and factors based on self-motivation associate directly with adherence behavior. Higher-risk subgroups of nonadherent patients include younger dialysis patients and non-whites. Provider attitudes may be important - yet unaddressed - determinants of adherence behaviors of dialysis patients.

CONCLUSION

Adherence to phosphate binders, low-phosphorus diet, and dialysis prescription is suboptimal. Multicomponent strategies that concurrently address therapy-related factors such as side effects, patient factors targeting self-motivation, and provider factors to improve attitudes and delivery of culturally sensitive care show the most promise for long-term control of phosphorus levels. Moreover, it will be important to identify patients at highest risk for lack of control, and for programs to be ready to deliver flexible person-centered strategies through training and dedicated resources to align with the needs of all patients.

An integrative review of the methodology and findings regarding dietary adherence in end stage kidney disease

BACKGROUND

Dietary modification is an important component of the management of end stage kidney disease (ESKD). The diet for ESKD involves modifying energy and protein intake, and altering sodium, phosphate, potassium and fluid intake. There have been no comprehensive reviews to date on this topic. The aims of this integrative review were to (i) describe the methods used to measure dietary adherence (ii) determine the rate of dietary adherence and (iii) describe factors associated with dietary adherence in ESKD.

METHODS

The Web of Science and Scopus databases were searched using the search terms 'adherence' and 'end stage kidney disease'. Of the 787 potentially eligible papers retrieved, 60 papers of 24,743 patients were included in this review. Of these papers, 44 reported the rate of dietary adherence and 44 papers described factors associated with adherence.

RESULTS

Most of the evidence regarding dietary adherence is derived from studies of hemodialysis patients (72% of patients). The most common method of measuring dietary adherence in ESKD was subjective techniques (e.g. food diaries or adherence questionnaires). This was followed by indirect methods (e.g. serum potassium, phosphate or interdialytic weight gain). The weighted mean adherence rate to ESKD dietary recommendations was 31.5% and 68.5% for fluid recommendations. Adherence to protein, sodium, phosphate, and potassium recommendations were highly variable due to differences in measurement methods used, and were often derived from a limited evidence base. Socioeconomic status, age, social support and self-efficacy were associated with dietary adherence. However, factors such as taste, the impact of the diet on social eating occasions; and dietetic staffing also appear to play a role in dietary adherence.

CONCLUSION

Dietary adherence rates in people with ESKD are suboptimal. Further research is required on dietary adherence in patients with ESKD from different social, educational, economic and ethnic groups. This research may identify other factors which may impact upon adherence, and could be used to inform the design of future strategies to improve dietary adherence. Future research that reports not just the rate of adherence to individual components of the nutrient prescription but also the overall quality of the diet would be useful.

Adherence rates to ferric citrate as compared to active control in patients with end stage kidney disease on dialysis

INTRODUCTION

Oral phosphate binders are the main stay of treatment of hyperphosphatemia. Adherence rates to ferric citrate, a recently approved phosphate binder, are unknown.

METHODS

We conducted a post-hoc analysis to evaluate whether adherence rates were different for ferric citrate vs. active control in 412 subjects with end stage kidney disease (ESKD) who were randomized to ferric citrate vs. active control (sevelamer carbonate and/or calcium acetate). Adherence was defined as percent of actual number of pills taken to total number of pills prescribed.

FINDINGS

There were no significant differences in baseline characteristics including gender, race/ethnicity, and age between the ferric citrate and active control groups. Baseline phosphorus, calcium, and parathyroid hormone levels were similar. Mean (SD) adherence was 81.4% (17.4) and 81.7% (15.9) in the ferric citrate and active control groups, respectively (P = 0.88). Adherence remained similar between both groups after adjusting for gender, race/ethnicity, age, cardiovascular disease (CVD), and diabetic nephropathy (mean [95% CI]: 81.4% [78.2, 84.6] and 81.5% [77.7, 85.2] for ferric citrate and active control, respectively). Gender, race/ethnicity, age, and diagnosis of diabetic nephropathy did not influence adherence to the prescribed phosphate binder. Subjects with CVD had lower adherence rates to phosphate binder; this was significant only in the active control group.

DISCUSSION

Adherence rates to the phosphate binder, ferric citrate, were similar to adherence rates to active control. Similar adherence rates to ferric citrate are notable since tolerance to active control was an entry criteria and the study was open label. Gender, race/ethnicity, nor age influenced adherence.

Patient-Reported Factors Associated With Poor Phosphorus Control in a Maintenance Hemodialysis Population

OBJECTIVE

The purpose of this study was to determine the influence of patient-reported medication adherence and phosphorus-related knowledge on phosphorus control and pharmacy-reported adherence to phosphorus binding medication among patients on maintenance hemodialysis.

DESIGN

Retrospective, cross-sectional cohort study.

SUBJECTS

Seventy-nine hemodialysis patients (mean age 64.2 years, SD = 14 years; 46.8% female) in a stand-alone hemodialysis unit within an integrated learning healthcare system. Ten percent (10%) of subjects were Caucasian, 42% Latino, 19% African American, and 29% Asian. Forty-eight percent had diabetes; 72% had BMI ≥ 30. Inclusion criteria included the provision of survey data and having medication refill data available in the pharmacy system. 77.2% had mean phosphorus levels ≤ 5.5 mg/dL; 22.8% had mean phosphorus levels > 5.5 mg/dL.

INTERVENTION

Subjects were administered the 8-item Morisky Medication Adherence Scale (MMAS-8) and also reported on their phosphorus-related knowledge.

MAIN OUTCOME MEASURE

Phosphorus levels within an adequate range.

RESULTS

The mean serum phosphorus level was 4.96 mg/dL (SD = 1.21). In the well-controlled group, mean phosphorus was 4.44 mg/dL (SD = 0.76). In the poorly controlled group, mean phosphorus was 6.69 mg/dL (SD = 0.74). A total of 61% of patients reported at least some unintentional medication nonadherence, and 48% reported intentional medication nonadherence. Phosphorus-specific knowledge was low, with just under half of patients reporting that they could not name two high-phosphorus foods or identify a phosphorus-related health risk. Phosphorus binder-related nonadherence was substantially higher in the uncontrolled than the controlled group. Adjusting for age, individuals with poorer self-reported binder adherence were less likely to have controlled phosphorus levels (odds ratio = 0.71, P = .06).

CONCLUSION

Phosphorus-related non-adherence, but not low phosphorus-specific knowledge, was associated with poorer phosphorus control. Such findings provide important information for the development of evidence-based strategies for improving phosphorus control among patients on dialysis.

A phase III study of the efficacy and safety of a novel iron-based phosphate binder in dialysis patients

Efficacy of PA21 (sucroferric oxyhydroxide), a novel calcium-free polynuclear iron(III)-oxyhydroxide phosphate binder, was compared with that of sevelamer carbonate in an open-label, randomized, active-controlled phase III study. Seven hundred and seven hemo- and peritoneal dialysis patients with hyperphosphatemia received PA21 1.0–3.0 g per day and 348 received sevelamer 4.8–14.4 g per day for an 8-week dose titration, followed by 4 weeks without dose change, and then 12 weeks maintenance. Serum phosphorus reductions at week 12 were −0.71 mmol/l (PA21) and −0.79 mmol/l (sevelamer), demonstrating non-inferiority of, on average, three tablets of PA21 vs. eight of sevelamer. Efficacy was maintained to week 24. Non-adherence was 15.1% (PA21) vs. 21.3% (sevelamer). The percentage of patients that reported at least one treatment-emergent adverse event was 83.2% with PA21 and 76.1% with sevelamer. A higher proportion of patients withdrew owing to treatment-emergent adverse events with PA21 (15.7%) vs. sevelamer (6.6%). Mild, transient diarrhea, discolored feces, and hyperphosphatemia were more frequent with PA21; nausea and constipation were more frequent with sevelamer. After 24 weeks, 99 hemodialysis patients on PA21 were re-randomized into a 3-week superiority analysis of PA21 maintenance dose in 50 patients vs. low dose (250 mg per day (ineffective control)) in 49 patients. The PA21 maintenance dose was superior to the low dose in maintaining serum phosphorus control. Thus, PA21 was effective in lowering serum phosphorus in dialysis patients, with similar efficacy to sevelamer carbonate, a lower pill burden, and better adherence.