Characterization of structure and function of ZS-9, a K+ selective ion trap

How to Improve Adherence to Life-saving Heart Failure Treatments with Potassium Binders

Medications that affect the renin-angiotensin-aldosterone system (RAAS) form the mainstay of current heart failure (HF) therapy in patients with reduced ejection fraction. Concerns about the risk of hyperkalaemia have created a significant barrier to optimal RAAS inhibitor therapy in patients with HF, however, and many patients are discontinuing or receiving suboptimal doses of these lifesaving therapies. This has serious health and economic implications due to adverse renal and cardiovascular events. There is therefore an important unmet need for novel therapeutic options for the long-term management of patients with, and at risk for, hyperkalaemia. Two new potassium-binding agents, patiromer and ZS-9, have been shown to be effective and safe for the treatment of hyperkalaemia, as well as the maintenance of normokalaemia, without dose reduction or discontinuation of RAAS inhibitors. In addition, the fast onset of ZS-9 action suggests that it may be useful in the treatment of acute hyperkalaemia. These agents may allow for dose optimisation of RAAS inhibitors for the long-term maintenance and protection of the renal and cardiovascular system.

Challenges in Treating Cardiovascular Disease: Restricting Sodium and Managing Hyperkalemia

High sodium intake, whether via diet or drugs, augments cardiorenal risk. Regardless of its source, high sodium intake can both lead to hypertension and reduce the efficacy of renin-angiotensin-aldosterone system inhibitors, which are currently guideline-recommended treatments for hypertension, chronic kidney disease, and heart failure. Reducing sodium intake is therefore recommended to reduce the risk of adverse cardiorenal outcomes. An inverse relationship exists between sodium and potassium, with foods high in sodium being lower in potassium. Diets high in potassium have been associated with reducing hypertension and heart failure; however, optimal renin-angiotensin-aldosterone system inhibitor dosing is often limited by hyperkalemia, which can lead to life-threatening cardiac arrhythmias and increased mortality. Potassium binders are effective at reducing potassium levels. Although some use sodium as the potassium exchange ion, thus increasing sodium intake, a new potassium binder uses another exchange ion and therefore does not increase sodium intake. When treatment options require agents that may precipitate hyperkalemia, particularly in patients at high cardiorenal risk, drugs that do not add to the sodium load may be preferred. A literature search was conducted using PubMed; search terms included potassium, sodium, hyperkalemia, potassium binders, and the literature search focused on manuscripts published more recently since 2000.

Potassium: friend or foe?

The kidney plays an essential role in maintaining homeostasis of ion concentrations in the blood. Because the concentration gradient of potassium across the cell membrane is a key determinant of the membrane potential of cells, even small deviations in serum potassium level from the normal setpoint can lead to severe muscle dysfunction, resulting in respiratory failure and cardiac arrest. Less severe hypo- and hyperkalemia are also associated with morbidity and mortality across various patient populations. In addition, deficiencies in potassium intake have been associated with hypertension and adverse cardiovascular and renal outcomes, likely due in part to the interrelated handling of sodium and potassium by the kidney. Here, data on the beneficial effects of potassium on blood pressure and cardiovascular and renal outcomes will be reviewed, along with the physiological basis for these effects. In some patient populations, however, potassium excess is deleterious. Risk factors for the development of hyperkalemia will be reviewed, as well as the risks and benefits of existing and emerging therapies for hyperkalemia.

Hyperkalemia in Heart Failure

Disorders of potassium homeostasis can potentiate the already elevated risk of arrhythmia in heart failure. Heart failure patients have a high prevalence of chronic kidney disease, which further heightens the risk of hyperkalemia, especially when renin-angiotensin-aldosterone system inhibitors are used. Acute treatment for hyperkalemia may not be tolerated in the long term. Recent data for patiromer and sodium zirconium cyclosilicate, used to treat and prevent high serum potassium levels on a more chronic basis, have sparked interest in the treatment of hyperkalemia, as well as the potential use of renin-angiotensin-aldosterone system inhibitors in patients who were previously unable to take these drugs or tolerated only low doses. This review discusses the epidemiology, pathophysiology, and outcomes of hyperkalemia in heart failure; provides an overview of traditional and novel ways to approach management of hyperkalemia; and discusses the need for further research to optimally treat heart failure.

Systematic Review and Meta-Analysis of Patiromer and Sodium Zirconium Cyclosilicate: A New Armamentarium for the Treatment of Hyperkalemia

OBJECTIVE

To compare and contrast the efficacy and safety of patiromer and sodium zirconium cyclosilicate (ZS-9) in the treatment of hyperkalemia.

DESIGN

A systematic review and meta-analysis of phase II and III clinical trial data was completed.

PATIENTS OR PARTICIPANTS

Eight studies (two phase II and four phase III trials with two subgroup analyses) were included in the qualitative analysis, and six studies (two phase II and four phase III trials) were included in the meta-analysis.

MEASUREMENTS AND RESULTS

Significant heterogeneity was found in the meta-analysis with an I2 value ranging from 80.6-99.6%. A random-effects meta-analysis was applied for all end points. Each clinical trial stratified results by hyperkalemia severity and dosing; therefore, these were considered separate treatment groups in the meta-analysis. For patiromer, a significant -0.70 mEq/L (95% confidence interval [CI] -0.48 to -0.91 mEq/L) change was noted in potassium at 4 weeks. At day 3 of patiromer treatment, potassium change was -0.36 mEq/L (range of standard deviation 0.07-0.30). The primary end point for ZS-9-change in potassium at 48 hours-was -0.67 mEq/L (95% CI -0.45 to -0.89 mEq/L). By 1 hour after ZS-9 administration, change in potassium was -0.17 mEq/L (95% CI -0.05 to -0.30). Analysis of pooled adverse effects from these trials indicates that patiromer was associated with more gastrointestinal upset (7.6% constipation, 4.5% diarrhea) and electrolyte depletion (7.1% hypomagnesemia), whereas ZS-9 was associated with the adverse effects of urinary tract infections (1.1%) and edema (0.9%).

CONCLUSION

Patiromer and ZS-9 represent significant pharmacologic advancements in the treatment of hyperkalemia. Both agents exhibited statistically and clinically significant reductions in potassium for the primary end point of this meta-analysis. Given the adverse effect profile and the observed time-dependent effects, ZS-9 may play more of a role in treating acute hyperkalemia.

Clinical utility of patiromer, sodium zirconium cyclosilicate, and sodium polystyrene sulfonate for the treatment of hyperkalemia: an evidence-based review

INTRODUCTION

Hyperkalemia is a serious medical condition that often manifests in patients with chronic kidney disease and heart failure. Renin-angiotensin-aldosterone system inhibitors are known to improve outcomes in these disease states but can also cause drug-induced hyperkalemia. New therapeutic options exist for managing hyperkalemia in these patients which warrant evidence-based evaluation.

AIM

The objective of this article was to review the efficacy and safety evidence for patiromer, sodium zirconium cyclosilicate (ZS9), and sodium polystyrene sulfonate (SPS) for the treatment of hyperkalemia.

EVIDENCE REVIEW

Current treatment options to enhance potassium excretion are SPS and loop diuretics, which are complicated by ambiguous efficacy and known toxicities. Patiromer and ZS9 are new agents designed to address this treatment gap. Both unabsorbable compounds bind potassium in the gastrointestinal (GI) tract to facilitate fecal excretion. The capacity to bind other medications in the GI tract infers high drug-drug interaction potential, which has been demonstrated with patiromer but not yet investigated with ZS9 or SPS. Phase II and III clinical trials of patiromer and ZS9 demonstrated clear evidence of a dose-dependent potassium-lowering effect and the ability to initiate, maintain, or titrate renin-angiotensin-aldosterone system inhibitors. There is limited evidence base for SPS: two small clinical trials indicated potassium reduction in chronic hyperkalemia. All agents may cause adverse GI effects, although they are less frequent with ZS9. Concerns remain for SPS to cause rare GI damage. Electrolyte abnormalities occurred with patiromer and SPS, whereas urinary tract infections, edema, and corrected QT-interval prolongations were reported with ZS9.

CONCLUSION

Patiromer and ZS9 have improved upon the age-old standard SPS for the treatment of hyperkalemia. Additional research should focus on drug-drug interactions in patients on multiple medications, incidence of rare adverse events, and use in high-risk populations.

Role of Hyperkalemia in Heart Failure and the Therapeutic Use of Potassium Binders

Hyperkalemia can be a life-threatening disorder, especially for at-risk patients with heart failure, chronic kidney disease, with diabetes, and patients on certain drugs like renin-angiotensin-aldosterone system antagonists and mineralocorticoid receptor antagonists. There are limited therapeutic options available for hyperkalemia, and they have narrow effectiveness because of their unfavorable side effects profile in long-term and high cost utilization requiring inpatient care. Patiromersorbitex calcium and sodium zirconium cyclosilicate are novel potassium-lowering compounds for the treatment and prevention of hyperkalemia in at-risk population. These therapeutic agents have shown encouraging results in early phase II and phase III clinical trials. However, there is need to further study their efficacy and safety in heart failure population in order to establish their clinical use. The focus of this chapter will be to promote better understanding of potassium homeostasis in heart failure patients and the mechanistic overview of novel drugs, with emphasis on heart failure population.

Emergency management of severe hyperkalemia: Guideline for best practice and opportunities for the future

Hyperkalemia is a common electrolyte disorder, especially in chronic kidney disease, diabetes mellitus, or heart failure. Hyperkalemia can lead to potentially fatal cardiac dysrhythmias, and it is associated with increased mortality. Determining whether emergency therapy is warranted is largely based on subjective clinical judgment. The Investigator Network Initiative Cardiovascular and Renal Clinical Trialists (INI-CRCT) aimed to evaluate the current knowledge pertaining to the emergency treatment of hyperkalemia. The INI-CRCT developed a treatment algorithm reflecting expert opinion of best practices in the context of current evidence, identified gaps in knowledge, and set priorities for future research. We searched PubMed (to August 4, 2015) for consensus guidelines, reviews, randomized clinical trials, and observational studies, limited to English language but not by publication date. Treatment approaches are based on small studies, anecdotal experience, and traditional practice patterns. The safety and real-world effectiveness of standard therapies remain unproven. Prospective research is needed and should include studies to better characterize the population, define the serum potassium thresholds where life-threatening arrhythmias are imminent, assess the potassium and electrocardiogram response to standard interventions. Randomized, controlled trials are needed to test the safety and efficacy of new potassium binders for the emergency treatment of severe hyperkalemia in hemodynamically stable patients. Existing emergency treatments for severe hyperkalemia are not supported by a compelling body of evidence, and they are used inconsistently across institutions, with potentially significant associated side effects. Further research is needed to fill knowledge gaps, and definitive clinical trials are needed to better define optimal management strategies, and ultimately to improve outcomes in these patients.

Challenges and Considerations in the Management of Hyperkalaemia in Patients With Chronic Kidney Disease

rof David Goldsmith opened the symposium by highlighting the objectives of the meeting. The education objectives of the symposium were to summarise the mechanisms that regulate potassium balance, specifically highlighting how these mechanisms are affected by inhibition of the renin-angiotensinaldosterone system (RAAS); to examine the pathophysiology of hyperkalaemia and illustrate the impact on clinical outcomes; to evaluate current clinical evidence and outline key considerations that help determine the urgency; and to describe recent clinical trial data on investigational oral ion exchangers and the potential future role of these emerging therapies in clinical practice. In the first presentation, Prof Johannes F. E. Mann discussed the predisposing factors of hyperkalaemia by presenting a case of a heart failure (HF) patient with Stage 3 chronic kidney disease (CKD), and also discussed the epidemiology and pathophysiology of hyperkalaemia. Dr Martin H. de Borst then discussed the current therapeutic options available for the outpatient treatment of hyperkalaemia, along with recent clinical data on novel treatments, in particular patiromer and zirconium cyclosilicate (known as ZS-9).

Sodium Zirconium Cyclosilicate (ZS-9): A Novel Agent for the Treatment of Hyperkalemia

Hyperkalemia is a potentially life-threatening electrolyte abnormality that may be caused by select medications, underlying organ dysfunction, or alterations in potassium homeostasis. Treatment for this condition has remained largely unchanged since the release of sodium polystyrene sulfonate (SPS) in 1958. Despite its widespread use, the safety and efficacy of SPS remains controversial. Two novel potassium-binding resins have emerged in recent years. Patiromer was the first of these to receive U.S. Food and Drug Administration approval for the treatment of hyperkalemia in October 2015. A second potassium-binding resin, a zirconium cyclosilicate currently known as ZS-9, may provide yet another alternative to the archetypal treatment with SPS. ZS-9 is an orally administered nonabsorbed inorganic compound that selectively binds potassium ions in vivo. Two phase III multicenter, randomized, placebo-controlled, double-blind trials have evaluated ZS-9 for the treatment of acute hyperkalemia. In this review, we discuss the pharmacology, clinical efficacy, safety, and potential place in therapy of ZS-9 for the enhanced elimination of potassium in the setting of hyperkalemia.

The Unappreciated Role of Extrarenal and Gut Sensors in Modulating Renal Potassium Handling: Implications for Diagnosis of Dyskalemias and Interpreting Clinical Trials

In addition to the classic and well-established "feedback control" of potassium balance, increasing investigative attention has focused on a novel and not widely recognized complementary regulatory paradigm for maintaining potassium homeostasis-the "feed-forward control" of potassium balance. This regulatory mechanism, initially defined in rumen, has recently been validated in normal human subjects. Studies are being conducted to determine the location for this putative potassium sensor and to evaluate potential signals, which might increase renal potassium excretion. Awareness of this more updated integrative control mechanism for potassium homeostasis is ever more relevant today, when the medical community is increasingly focused on the challenges of managing the hyperkalemia provoked by renin-angiotensin-aldosterone system inhibitors (RAASis). Recent studies have demonstrated a wide gap between RAASi prescribing guidelines and real-world experience and have highlighted that this gap is thought to be attributable in great part to hyperkalemia. Consequently we require a greater knowledge of the complexities of the regulatory mechanisms subserving potassium homeostasis. Sodium polystyrene sulfonate has long been the mainstay for treating hyperkalemia, but its administration is fraught with challenges related to patient discomfort and colonic necrosis. The current and imminent availability of newer potassium binders with better tolerability and more predictive dose-response potassium removal should enhance the management of hyperkalemia. Consequently it is essential to better understand the intricacies of mammalian colonic K+ handling. We discuss colonic transport of K+ and review evidence for potassium (BK) channels being responsible for increased stool K+ in patients with diseases such as ulcerative colitis.

The safety of mineralocorticoid receptor antagonists (MRAs) in patients with heart failure

INTRODUCTION

Mineralocorticoid receptor antagonists (MRAs) have been accorded a class 1 indication for patients with chronic heart failure and a reduced left ventricular ejection fraction (HFREF) in both European and American guidelines. Uptake, however, has been less than optimal largely due to concerns about their safety, in particular the risk of hyperkalemia and renal dysfunction.

AREAS COVERED

This review presents the current state of affairs regarding the safety of MRAs in heart failure with reduced ejection fraction.

EXPERT OPINION

Careful patient selection and adherence to guideline-recommended inclusion and exclusion criteria, dosing, and serial monitoring of serum potassium and renal function, along with patient education regarding the potassium content of common foods, should minimize these risks and allow increased use of MRAs. Additionally, this may also result in a further reduction in cardiovascular mortality and hospitalizations for heart failure. The development of new non-steroidal MRAs, and especially new potassium binding molecules that are well tolerated and effective, hold the promise for increased safety and, therefore, increased and more prolonged use of MRAs in patients with heart failure, especially those with chronic kidney disease, diabetes mellitus, and the elderly.

Pharmacodynamics and pharmacokinetics of sodium zirconium cyclosilicate [ZS-9] in the treatment of hyperkalemia

INTRODUCTION

Hyperkalemia is a common electrolyte disorder that arises from dysfunctional homeostatic mechanisms or as a consequence of decreased renal function. Sodium zirconium cyclosilicate (ZS-9) is a potential new therapy for hyperkalemia in both acute and chronic settings.

AREAS COVERED

Here we discuss mechanisms of potassium homeostasis and preclinical and clinical studies that present pharmacokinetics/pharmacodynamics, efficacy and safety profiles of ZS-9.

EXPERT OPINION

ZS-9 has a unique mechanism of action consisting of thermodynamically favorable sequestration of potassium ions, enabling rapid trapping and removal of excess potassium. The potassium lowering action of ZS-9 is predictable and rapid, leading to significant reduction of serum potassium within 1 hour of administration by irreversibly eliminating excess potassium rather than acting via intracellular translocation. Its safety profile, including gastrointestinal events, has been generally similar to that of placebo, with the exception of infrequent but manageable events of peripheral edema and transient hypokalemia. ZS-9 has demonstrated potential for enabling renin-angiotensin-aldosterone system inhibitors in mid-term studies, with long-term studies ongoing.

Potassium-Binding Agents to Facilitate Renin-Angiotensin-Aldosterone System Inhibitor Therapy

OBJECTIVE

To evaluate safety and efficacy data for potassium-binding resins in renin-angiotensin-aldosterone system (RAAS)-associated hyperkalemia.

DATA SOURCES

A search of MEDLINE (EBSCOhost; 1946 to February 2016) was conducted using the terms hyperkalemia, rennin-angiotensin-aldosterone system, angiotensin-converting enzyme inhibitor, angiotensin receptor blocker, aldosterone antagonists, resin, and binder Results were limited to human trials in English language journals. References of identified articles were reviewed to identify other relevant articles.

STUDY SELECTION AND DATA EXTRACTION

Concurrent potassium-binding agents and RAAS inhibitor use literature were reviewed. Inclusion criteria a 2-week minimum therapy duration with hyperkalemia or high-risk patients receiving concurrent RAAS-inhibiting agents. Seven articles met inclusion criteria: 1 retrospective case series for sodium polystyrene sulfonate (SPS), 1 noncontrolled study using patiromer, and 5 randomized, placebo-controlled trials using 3 different agents-2 patiromer, 2 sodium zirconium cyclosilicate (SZC), and 1 cross-linked polyelectrolyte (CLP).

DATA SYNTHESIS

SPS efficacy data are limited to a mean potassium reduction of 1.8 mEq/L in a 14-patient uncontrolled case series. CLP did not reduce hyperkalemia incidence compared with placebo. Patiromer effectively maintained potassium at 0.45 to 0.72 mmol/L lower than placebo while allowing spironolactone dose titration in more patients (91% vs 74%, P = 0.019). SZC also safely and effectively normalized and maintained potassium levels in patients receiving RAAS inhibitors (71%-85% vs 48% for placebo, P < 0.01).

CONCLUSIONS

Currently, the literature does not support SPS and CLP for preventing RAAS inhibitor-associated hyperkalemia. Patiromer and SZC safely and effectively lower serum potassium and prevent hyperkalemia redevelopment in patients receiving RAAS inhibitors for up to 4 and 8 weeks,0 respectively.

Current and future treatment options for managing hyperkalemia

Hyperkalemia is associated with life-threatening cardiac arrhythmias and increased mortality. Hyperkalemia is most often observed in patients with chronic kidney disease and/or in those with congestive heart failure being treated with drugs that limit renal potassium excretion, especially drugs that inhibit the renin-angiotensin-aldosterone system. Treatment of hyperkalemia may be either acute, as needed during rapid changes in serum potassium, which are associated with cardiac arrhythmia, or chronic, which stabilizes serum potassium levels and limits the development of life-threatening arrhythmias. There are a number of both acute and chronic treatments available for the treatment of hyperkalemia, but some are limited by complex administration requirements and/or serious side effects. Hyperkalemia remains a vexing problem for clinicians, particularly in the care of patients with chronic kidney disease and cardiovascular disease.

Potential New Agents for the Management of Hyperkalemia

Hyperkalemia is a common electrolyte disturbance with multiple potential etiologies. It is usually observed in the setting of reduced renal function. Mild to moderate hyperkalemia is usually asymptomatic, but is associated with poor prognosis. When severe, hyperkalemia may cause serious acute cardiac arrhythmias and conduction abnormalities, and may result in sudden death. The rising prevalence of conditions associated with hyperkalemia (heart failure, chronic kidney disease, and diabetes) and broad use of renin-angiotensin-aldosterone system (RAAS) inhibitors and mineralocorticoid receptor antagonists (MRAs), which improve patient outcomes but increase the risk of hyperkalemia, have led to a significant rise in hyperkalemia-related hospitalizations and deaths. Current non-invasive therapies for hyperkalemia either do not remove excess potassium or have poor efficacy and tolerability. There is a clear need for safer, more effective potassium-lowering therapies suitable for both acute and chronic settings. Patiromer sorbitex calcium and sodium zirconium cyclosilicate (ZS-9) are two new potassium-lowering compounds currently in development. Although they have not yet been approved by the US FDA, both have demonstrated efficacy and safety in recent trials. Patiromer sorbitex calcium is a polymer resin and sorbitol complex that binds potassium in exchange for calcium; ZS-9, a non-absorbed, highly selective inorganic cation exchanger, traps potassium in exchange for sodium and hydrogen. This review discusses the merits of both novel drugs and how they may help optimize the future management of patients with hyperkalemia.

Potassium-Binding Agents for the Clinical Management of Hyperkalemia

Use of sodium polystyrene sulfonate (SPS) dominates the long-term treatment of hyperkalemia, but two new agents, sodium zirconium cyclosilicate and the recently FDA-approved patiromer, may offer potential advantages compared with SPS.

Recent advances in treatment of heart failure

With the total cases and economic burden of heart failure continuing to rise, there is an overwhelming need for novel therapies. Several drugs for heart failure have succeeded in preclinical and early-phase clinical trials, but most of them failed to show the real benefit in pivotal clinical trials. Meanwhile, the US Food and Drug Administration recently approved two promising new drugs to treat heart failure: ivabradine and sacubitril/valsartan. Furthermore, some of the newer agents in testing offer the potential for significant progress in addition to these drugs. Patiromer and zirconium cyclosilicate are attractive agents that are expected to prevent hyperkalemia during renin-angiotensin-aldosterone system inhibition, and serelaxin and urodilatin are promising drugs in the treatment of acute heart failure. Future clinical trials with more appropriate study designs, optimal clinical endpoints, and proper patient selection are mandatory to assess the true efficacy of these attractive compounds in clinical practice.

Sodium zirconium cyclosilicate (ZS-9) for the treatment of hyperkalemia

INTRODUCTION

Hyperkalemia is a common, sometimes fatal electrolyte abnormality seen in patients with heart failure (HF) or kidney disease. Acute treatments that cause the intracellular translocation of potassium can be effective in the short-term but they simply buy time until definitive removal by dialysis or binding agents (e.g., sodium polystyrene sulfonate) can occur. In contrast, treatment for chronic hyperkalemia, which often occurs in the setting of HF treated with renin-angiotensin-aldosterone inhibitors (RAASi) or mineralocorticoid receptor antagonists (MRA), is limited and has questionable efficacy.

AREAS COVERED

Sodium zirconium cyclosilicate (ZS-9), a novel, non-absorbed, potassium-selective cation exchanger, has demonstrated activity in acutely lowering and maintaining normal potassium levels. When used chronically, maintenance of normal serum potassium has been demonstrated for up to 1 month. Although higher doses of ZS-9 have been associated with modest increases in the rates of edema and hypokalemia, the overall adverse event rate is similar to placebo.

EXPERT OPINION

The efficacy of ZS9 has been shown in patients with chronic hyperkalemia, offering promise for conditions such as HF, where optimized therapy with RAASi and MRA is often limited by a concomitant, drug-induced increase in potassium. Further, in acute hyperkalemia it has potential to become an important option by rapidly lowering potassium levels, thus delaying or potentially averting the need for emergent dialysis. While further randomized trials demonstrating improved clinical outcomes are required for both these indications, initial data suggests a promising role for this agent in the management of both acute and chronic hyperkalemia.

Potassium and Its Discontents: New Insight, New Treatments

Hyperkalemia is common in patients with impaired kidney function or who take drugs that inhibit the renin-angiotensin-aldosterone axis. During the past decade, substantial advances in understanding how the body controls potassium excretion have been made, which may lead to improved standard of care for these patients. Renal potassium disposition is primarily handled by a short segment of the nephron, comprising part of the distal convoluted tubule and the connecting tubule, and regulation results from the interplay between aldosterone and plasma potassium. When dietary potassium intake and plasma potassium are low, the electroneutral sodium chloride cotransporter is activated, leading to salt retention. This effect limits sodium delivery to potassium secretory segments, limiting potassium losses. In contrast, when dietary potassium intake is high, aldosterone is stimulated. Simultaneously, potassium inhibits the sodium chloride cotransporter. Because more sodium is then delivered to potassium secretory segments, primed by aldosterone, kaliuresis results. When these processes are disrupted, hyperkalemia results. Recently, new agents capable of removing potassium from the body and treating hyperkalemia have been tested in clinical trials. This development suggests that more effective and safer approaches to the prevention and treatment of hyperkalemia may be on the horizon.

Maintenance of serum potassium with sodium zirconium cyclosilicate (ZS-9) in heart failure patients: results from a phase 3 randomized, double-blind, placebo-controlled trial

Aims

Hyperkalaemia in heart failure patients limits use of cardioprotective renin–angiotensin–aldosterone system inhibitors (RAASi). Sodium zirconium cyclosilicate (ZS‐9) is a selective potassium ion trap, whose mechanism of action may allow for potassium binding in the upper gastrointestinal tract as early as the duodenum following oral administration. ZS‐9 previously demonstrated the ability to reduce elevated potassium levels into the normal range, with a median time of normalization of 2.2 h and sustain normal potassium levels for 28 days in HARMONIZE—a Phase 3, double‐blind, randomized, placebo‐controlled trial. In the present study we evaluated management of serum potassium with daily ZS‐9 over 28 days in heart failure patients from HARMONIZE, including those receiving RAASi therapies.

Methods and results

Heart failure patients with evidence of hyperkalaemia (serum potassium ≥5.1 mmol/L, n = 94) were treated with open‐label ZS‐9 for 48 h. Patients (n = 87; 60 receiving RAASi) who achieved normokalaemia (potassium 3.5–5.0 mmol/L) were randomized to daily ZS‐9 (5, 10, or 15 g) or placebo for 28 days. Mean potassium and proportion of patients maintaining normokalaemia during days 8–29 post‐randomization were evaluated. Despite RAASi doses being kept constant, patients on 5 g, 10 g, and 15 g ZS‐9 maintained a lower potassium level (4.7 mmol/L, 4.5 mmol/L, and 4.4 mmol/L, respectively) than the placebo group (5.2 mmol/L; P<0.01 vs. each ZS‐9 group); greater proportions of ZS‐9 patients (83%, 89%, and 92%, respectively) maintained normokalaemia than placebo (40%; P < 0.01 vs. each ZS‐9 group). The safety profile was consistent with previously reported overall study population.

Conclusion

Compared with placebo, all three ZS‐9 doses lowered potassium and effectively maintained normokalaemia for 28 days in heart failure patients without adjusting concomitant RAASi, while maintaining a safety profile consistent with the overall study population.