Mechanism of Action and Pharmacology of Patiromer, a Nonabsorbed Cross-Linked Polymer That Lowers Serum Potassium Concentration in Patients With Hyperkalemia

New treatments for hyperkalaemia: clinical use in cardiology

Hyperkalaemia causes significant burden, and even mild hyperkalaemia has been independently associated with increased morbidity and mortality. Patients with chronic disease states, such as heart failure, hypertension, chronic kidney disease and diabetes mellitus, are increasingly susceptible to the development of hyperkalaemia. Options for management of hyperkalaemia had mainly been limited to short-term, temporizing methods with focus on rapid achievement of normokalaemia. Until recently, there was a lack of safe, efficacious and well-tolerated therapies for long-term management. Two novel potassium binders, patiromer and sodium zirconium cyclosilicate, have recently been approved by the US Food and Drug Administration for the management of hyperkalaemia. This review discusses these potassium binders with focus largely on the clinical implications of these agents in patients with chronic cardiovascular conditions.

New frontiers for management of hyperkalaemia: the emergence of novel agents

Hyperkalaemia is a common electrolyte abnormality, associated with higher risk of morbid events, and increasing in prevalence—in part, due to increasing rates of comorbidities such as heart failure, chronic kidney disease, diabetes mellitus, and the use of renin-angiotensin-aldosterone system inhibitors (RAASi). In spite of this growing problem, the existing treatments for chronic hyperkalaemia have been limited, and are typically confined to dietary potassium restrictions and cessation or modification of RAASi, with latter option being potentially problematic given the known morbidity and mortality benefit of RAASi therapy in certain disease states, such as heart failure. The use of sodium polystyrene sulfonate (SPS/Kayexelate) for chronic hyperkalaemia has been low, due to poor tolerability, potential gastrointestinal safety concerns, and remaining uncertainty in regards to its efficacy. Given the shortcomings of existing therapies, novel treatments are clearly needed. There are now two novel treatment options, patiromer and sodium zirconium cyclosilicate (SZC), both approved by the FDA and EMA for treatment of chronic hyperkalaemia. These novel compounds have been demonstrated in multiple studies to be efficacious in achieving and maintaining normal serum potassium levels, over an extended time period, in patients with hyperkalaemia; and appear to be relatively safe and well-tolerated. Whether the correction of hyperkalaemia with these agents will allow optimization of RAASi, which could theoretically lead to improvement in clinical outcomes, especially in patients with heart failure, remains to be determined. Several clinical trials are ongoing to address these important knowledge gaps.

Pharmacology of new treatments for hyperkalaemia: patiromer and sodium zirconium cyclosilicate

Hyperkalaemia is a life-threatening condition, resulting from decreased renal function or dysfunctional homoeostatic mechanisms, often affecting patients with cardiovascular (CV) disease. Drugs such as renin-angiotensin-aldosterone system inhibitors (RAASi) are known to improve outcomes in CV patients but can also cause drug-induced hyperkalaemia. New therapeutic options exist to enhance potassium excretion in these patients. To this aim, we reviewed pharmacological properties and available data on patiromer and sodium zirconium cyclosilicate for the treatment of hyperkalaemia. These agents have been shown in randomized trials to significantly reduce serum potassium in patients with hyperkalaemia on renin-angiotensin-aldosterone system inhibitors. Additional research should focus on their long-term effects/safety profiles and drug-drug interactions.

Patiromer Acetate Induced Hypercalcemia: An Unreported Adverse Effect

Hyperkalemia, a potential life threating condition, is a commonly encountered problem in chronic kidney disease (CKD) patients. Patiromer acetate, a nonabsorbable cation exchange polymer, is a gastrointestinal agent for chronic therapy in patients with persistent hyperkalemia. Patiromer is generally well tolerated in patients; common side effects are gastrointestinal, such as diarrhea, constipation, flatulence, and vomiting. Hypercalcemia, although a theoretical possibility, has not been reported in any major clinical trials. We present a case of hypercalcemia associated with patiromer acetate used for treatment of hyperkalemia in a stage IV CKD patient. Clinicians should be aware of the possibility of hypercalcemia while taking patiromer.

Current treatment and unmet needs of hyperkalaemia in the emergency department

Hyperkalaemia is a common electrolyte abnormality and can cause life-threatening cardiac arrhythmia. Even though it is common in patients with diabetes, heart failure, and kidney disease, there is poor consensus over its definition and wide variability in its treatment. Medications used to treat hyperkalaemia in the emergent setting do not have robust efficacy and safety data to guide treatment leading to mismanagement due to poor choice of some agents or inappropriate dosing of others. Moreover, the medications used in the emergent setting are at best temporizing measures, with dialysis being the definitive treatment. New and old k binder therapies provide means to excrete potassium, but their roles are unclear in the emergent setting. Electrocardiograms are the corner stones of hyperkalaemia management; however, recent studies show that they might manifest abnormalities infrequently, even in severe hyperkalaemia, thus questioning their role. With an aging population and a rise in rates of heart and kidney failure, hyperkalaemia is on the rise, and there is a need, now more than ever, to understand the efficacy and safety of the current medications and to develop newer ones.

Real-World Evaluation of Patiromer for the Treatment of Hyperkalemia in Hemodialysis Patients

Introduction

Patiromer is a potassium (K⁺) binding polymer indicated for treating hyperkalemia. Among patients receiving chronic hemodialysis (HD), this study aimed to identify patient characteristics associated with patiromer initiation, describe patiromer utilization, and analyze serum K⁺ pre- and post-patiromer initiation.

Methods

In a retrospective cohort study, using electronic health record data from a large dialysis provider in the United States (study period: December 21, 2015, to December 20, 2016), HD patients were included who had a medication order for patiromer, sodium polystyrene sulfonate (SPS), or laboratory evidence of hyperkalemia (no K⁺ binder [NoKb] cohort). The index date was the first order for patiromer/SPS, or the first K⁺ ≥5.0 mEq/l (NoKb cohort), respectively. Using multivariable logistic regression, we identified patient characteristics associated with patiromer initiation. We evaluated patiromer utilization using Kaplan-Meier methodology and proportion of days covered. Serum K⁺ concentrations were assessed pre- versus post-patiromer initiation.

Results

Study cohorts included 527 (patiromer), 852 (SPS), and 8747 (NoKb) HD patients. Median follow-up was 141 days. Patiromer initiators were 2.6 times more likely to have had multiple prior episodes of hyperkalemia (odds ratio [OR]: 2.6; 95% confidence interval [CI]: 1.8-3.7). Most (61%) commenced patiromer on 8.4 g once daily; 60% of patients' first patiromer order remained open after 180 days. Statistically significant reductions in K⁺, averaging approximately -0.5 mEq/l, were observed post-patiromer initiation (48% pre-patiromer vs. 22% post-patiromer had K⁺ ≥6.0 mEq/l [P < 0.001]).

Conclusion

Patiromer initiators receiving chronic hemodialysis had comparatively more severe, uncontrolled baseline hyperkalemia. Medication order data show long-term patiromer use was associated with significantly reduced K⁺.

Patiromer: A Review in Hyperkalaemia

Patiromer (Veltassa^®) for oral suspension is a non-absorbed, sodium-free potassium binding polymer that exchanges calcium for potassium in the gastrointestinal (GI) tract, thereby increasing faecal potassium excretion and reducing serum potassium levels. Patiromer was approved in the USA in 2015 and is now approved in several other countries, including those of the EU, for the treatment of hyperkalaemia in adults. In clinical trials, patiromer reduced serum potassium levels and the risk of recurrent hyperkalaemia in patients with chronic kidney disease (CKD) and/or diabetic nephropathy with or without heart failure (HF), allowing the majority of patients to continue receiving renin-angiotensin-aldosterone system (RAAS) inhibitors (drugs that inhibit the renal excretion of potassium) for up to 52 weeks. Patiromer also maintained normokalaemia in patients with HF and a propensity for hyperkalaemia, enabling concomitant administration and up-titration of spironolactone. Patiromer was generally well tolerated, with a low risk of hypokalaemia. GI disorders and hypomagnesaemia were the most common adverse events; these were generally of mild or moderate severity. Therefore, oral patiromer is a valuable treatment option for the long-term management of hyperkalaemia.

Effect of Patiromer in Hyperkalemic Patients Taking and Not Taking RAAS Inhibitors

Introduction:

Hyperkalemia (potassium >5.0 mEq/L) affects heart failure patients with renal disease regardless of the use of renin–angiotensin–aldosterone system inhibitors (RAASi). The open-label TOURMALINE study showed that patiromer, a sodium-free, nonabsorbed potassium binder, lowers serum potassium of hyperkalemic patients similarly when given with or without food; unlike prior studies, patients were not required to be taking RAASi. We conducted post hoc analyses to provide the first report of patiromer in patients not taking RAASi.

Methods:

Hyperkalemic patients received patiromer, 8.4 g/d to start, adjusted to achieve and maintain serum potassium of 3.8 to 5.0 mEq/L. If taking RAASi, stable doses were required. The primary end point was the proportion of patients with serum potassium 3.8 to 5.0 mEq/L at week 3 or 4. This analysis presents data by patients taking or not taking RAASi.

Results:

Demographics and baseline characteristics were similar in patients taking (n = 67) and not taking RAASi (n = 45). Baseline mean (SD) serum potassium was 5.37 (0.37) mEq/L and 5.42 (0.43) mEq/L in patients taking and not taking RAASi, respectively. Mean (SD) daily patiromer doses were similar (10.7 [3.2] and 11.5 [4.0] g, respectively). The primary end point was achieved in 85% (95% confidence interval [CI]: 74-93) of patients taking RAASi and in 84% (95% CI: 71-94) of patients not taking RAASi. From baseline to week 4, the mean (SE) change in serum potassium was −0.67 (0.08) mEq/L in patients taking RAASi and −0.56 (0.10) mEq/L in patients not taking RAASi (both P < .0001 vs baseline, P = nonsignificant between groups). Adverse events were reported in 26 (39%) patients taking RAASi and 25 (54%) not taking RAASi; the most common adverse event was diarrhea (2% and 11%, respectively; no cases were severe). Five patients (2 taking RAASi) reported 6 serious adverse events; none considered related to patiromer.

Conclusions:

Patiromer was effective and generally well-tolerated for hyperkalemia treatment, whether or not patients were taking RAAS inhibitors.

Long-term effects of patiromer for hyperkalaemia treatment in patients with mild heart failure and diabetic nephropathy on angiotensin-converting enzymes/angiotensin receptor blockers: results from AMETHYST-DN

AIMS

Chronic kidney disease (CKD) in heart failure (HF) increases the risk of hyperkalaemia (HK), limiting angiotensin-converting enzyme inhibitor (ACE-I) or angiotensin receptor blocker (ARB) use. Patiromer is a sodium-free, non-absorbed potassium binder approved for HK treatment. We retrospectively evaluated patiromer's long-term safety and efficacy in HF patients from AMETHYST-DN.

METHODS AND RESULTS

Patients with Type 2 diabetes, CKD, and HK [baseline serum potassium >5.0-5.5 mmol/L (mild) or >5.5-<6.0 mmol/L (moderate)], with or without HF (New York Heart Association Class I and II, by investigator judgement), on ACE-I/ARB, were randomized to patiromer 8.4-33.6 g to start, divided twice daily. Overall, 105/304 (35%) patients had HF (75%, Class II). Mean (standard deviation) ejection fraction (EF) was 44.9% (8.2) (n = 81) in patients with HF; 26 had EF ≤40%. In HF patients, mean serum potassium decreased by Day 3 through Week 52. At Week 4, estimated mean (95% confidence interval) change in serum potassium was -0.64 mmol/L (-0.72, -0.55) in mild and -0.97 mmol/L (-1.14, -0.80) in moderate HK (both P < 0.0001). Most HF patients with mild (>88%) and moderate (≥73%) HK had normokalaemia at each visit from Weeks 12 to 52. Three HF patients were withdrawn because of high (n = 1) or low (n = 2) serum potassium. The most common patiromer-related adverse event was hypomagnesaemia (8.6%).

CONCLUSIONS

In patients with a clinical diagnosis of HF, diabetes, CKD, and HK on ACE-I/ARB, patiromer was well tolerated and effective for HK treatment over 52 weeks.

Evaluation of an individualized dose titration regimen of patiromer to prevent hyperkalaemia in patients with heart failure and chronic kidney disease

AIMS

Hyperkalaemia risk precludes optimal renin-angiotensin-aldosterone system inhibitor use in patients with heart failure (HF), particularly those with chronic kidney disease (CKD). Patiromer is a sodium-free, non-absorbed potassium (K+ )-binding polymer approved for the treatment of hyperkalaemia. In PEARL-HF, patiromer 25.2 g (fixed dose) prevented hyperkalaemia in HF patients with or without CKD initiating spironolactone. The current study evaluated the effectiveness of a lower starting dose of patiromer (16.4 g/day) followed by individualized titration in preventing hyperkalaemia and hypokalaemia when initiating spironolactone.

METHODS AND RESULTS

This open-label 8-week study enrolled 63 patients with CKD, serum K+ 4.3-5.1 mEq/L, and chronic HF, who, based on investigator opinion, should receive spironolactone. Eligible patients started spironolactone 25 mg/day and patiromer 16.8 g/day (divided into two doses), with patiromer titrated to maintain serum K+ 4.0-5.1 mEq/L. Mean (standard deviation) serum K+ was 4.78 (0.51) mEq/L at baseline; weekly values were 4.48-4.70 mEq/L during treatment. Serum K+ of 3.5-5.5 mEq/L at the end of study treatment (primary endpoint) was achieved by 57 (90.5%) patients; 53 (84.1%) had serum K+ 4.0-5.1 mEq/L. One patient (1.6%) developed hypokalaemia, and two patients (3.2%) developed hypomagnesaemia. Spironolactone was increased to 50 mg/day in all patients; 43 (68%) patients required one or more patiromer dose titration. Adverse events (AEs) occurred in 36 (57.1%) patients, with a low rate of discontinuations [four (6.3%) patients]. The most common AE was mild to moderate abdominal discomfort [four (6.3%) patients].

CONCLUSIONS

In this open-label study, patiromer 16.8 g/day followed by individualized titration maintained serum K+ within the target range in the majority of patients with HF and CKD, all of whom were uptitrated to spironolactone 50 mg/day, patiromer was well tolerated, with a low incidence of hyperkalaemia, hypokalaemia, and hypomagnesaemia.

Evaluation of the Pharmacodynamic Effects of the Potassium Binder RDX7675 in Mice

INTRODUCTION

Hyperkalemia is a common complication in patients with heart failure or chronic kidney disease, particularly those who are taking inhibitors of the renin-angiotensin-aldosterone system. RDX7675, the calcium salt of a reengineered polystyrene sulfonate-based resin, is a potassium binder that is being investigated as a novel treatment for hyperkalemia. This study evaluated the pharmacodynamic effects of RDX7675 in mice, compared to 2 current treatments, sodium polystyrene sulfonate (SPS) and patiromer.

METHODS

Seven groups of 8 male CD-1 mice were given either standard chow (controls) or standard chow containing 4.0% or 6.6% active moiety of RDX7675, patiromer, or SPS for 72 hours. Stool and urine were collected over the final 24 hours of treatment for ion excretion analyses.

RESULTS

RDX7675 increased stool potassium (mean 24-hour excretion: 4.0%, 9.19 mg; 6.6%, 18.11 mg; both P < .0001) compared with controls (4.47 mg) and decreased urinary potassium (mean 24-hour excretion: 4.0%, 12.05 mg, P < .001; 6.6%, 6.68 mg, P < .0001; vs controls, 20.38 mg). The potassium-binding capacity of RDX7675 (stool potassium/gram of resin: 4.0%, 1.14 mEq/g; 6.6%, 1.32 mEq/g) was greater (all P < .0001) than for patiromer (4.0%, 0.63 mEq/g; 6.6%, 0.48 mEq/g) or SPS (4.0%, 0.73 mEq/g; 6.6% 0.55 mEq/g). RDX7675 and patiromer decreased urinary sodium (mean 24-hour excretion: 0.07-1.38 mg; all P < .001) compared to controls (5.01 mg). In contrast, SPS increased urinary sodium excretion (4.0%, 13.31 mg; 6.6%, 17.60 mg; both P < .0001) compared to controls.

CONCLUSIONS

RDX7675 reduced intestinal potassium absorption and had a greater potassium-binding capacity than patiromer or SPS in mice. The calcium-based resins RDX7675 and patiromer reduced intestinal sodium absorption, unlike sodium-based SPS. These results support further studies in humans to confirm the potential of RDX7675 for the treatment of patients with hyperkalemia.

Effect of Patiromer on Hyperkalemia Recurrence in Older Chronic Kidney Disease Patients Taking RAAS Inhibitors

BACKGROUND

Older people are predisposed to hyperkalemia because of impaired renal function, comorbid conditions, and polypharmacy. Renin-angiotensin-aldosterone system inhibitors (RAASi), which are recommended to treat chronic kidney disease and heart failure augment the risk. Patiromer, a nonabsorbed potassium binder, was shown in the phase 3 OPAL-HK study to decrease serum potassium in patients with chronic kidney disease taking RAASi. We studied the efficacy and safety of patiromer in a prespecified subgroup of patients aged ≥65 years from OPAL-HK.

METHODS

Chronic kidney disease patients with mild or moderate-to-severe hyperkalemia received patiromer, initially 8.4 g/d or 16.8 g/d, respectively, for 4 weeks (treatment phase, part A). Eligible patients entered an 8-week randomized withdrawal phase (part B) and continued patiromer or switched to placebo.

RESULTS

Mean ± standard error change in serum potassium from baseline to week 4 of part A (primary endpoint) in patients aged ≥65 years was -1.01 ± 0.05 mEq/L (P < .001); 97% achieved serum potassium 3.8-<5.1 mEq/L. The serum potassium increase during the first 4 weeks of part B was greater in patients taking placebo than in those taking patiromer (P < .001). Fewer patients taking patiromer (30%) than placebo (92%) developed recurrent hyperkalemia (serum potassium ≥5.1 mEq/L). Mild-to-moderate constipation occurred in 15% (part A) and 7% (part B) of patients aged ≥65 years. Serum potassium <3.5 mEq/L and serum magnesium <1.4 mg/dL were infrequent (4% each in patients aged ≥65 years in part A).

CONCLUSIONS

Patiromer reduced recurrent hyperkalemia and was well tolerated in older chronic kidney disease patients taking RAASi.

The tolerability and safety profile of patiromer: a novel polymer-based potassium binder for the treatment of hyperkalemia

INTRODUCTION

Hyperkalemia (HK) occurs often among patients with chronic kidney disease (CKD) and heart failure (HF) and those treated with renin-angiotensin-aldosterone system inhibitors (RAASI). Even small deviations from normal potassium levels carry increased risk of mortality. Patiromer is approved for treatment of HK and has been shown in clinical trials to reduce serum potassium among patients with HK and comorbid conditions. Areas covered: We review pooled data from two clinical trials of patiromer in patients with CKD and HK, safety of patiromer in special populations, drug-drug interaction (DDI) studies, and other studies in healthy volunteers. Expert opinion: Potassium must be maintained within a narrow range to avoid increased risk of mortality. Patients with CKD and HF and those receiving RAASI require careful monitoring of potassium levels. Patiromer effectively reduces serum potassium, and gastrointestinal adverse events (AEs) are the most common patiromer-associated AEs. Effective management of HK with patiromer may allow use of RAASI at optimal doses as recommended by treatment guidelines. Future research should examine the potential for potassium binders, including patiromer, to extend use of RAASI in appropriate patient populations.

Use of QSPR Modeling to Characterize In Vitro Binding of Drugs to a Gut-Restricted Polymer

Purpose

Polymeric drugs, including patiromer (Veltassa®), bind target molecules or ions in the gut, allowing fecal elimination. Non-absorbed insoluble polymers, like patiromer, avoid common systemic drug-drug interactions (DDIs). However, the potential for DDI via polymer binding to orally administered drugs during transit of the gastrointestinal tract remains. Here we elucidate the properties correlated with drug-patiromer binding using quantitative structure-property relationship (QSPR) models.

Methods

We selected 28 drugs to evaluate for binding to patiromer in vitro over a range of pH and ionic conditions intended to mimic the gut environment. Using this in vitro data, we developed QSPR models using step-wise linear regression and analyzed over 100 physiochemical drug descriptors.

Results

Four descriptors emerged that account for ~70% of patiromer-drug binding in vitro: the computed surface area of hydrogen bond accepting atoms, ionization potential, electron affinity, and lipophilicity (R² = 0.7, Q² = 0.6). Further, certain molecular properties are shared by nonbinding, weak, or strong binding compounds.

Conclusions

These findings offer insight into drivers of in vitro binding to patiromer and describe a useful approach for assessing potential drug-binding risk of investigational polymeric drugs.

Electronic supplementary material

The online version of this article (10.1007/s11095-018-2356-y) contains supplementary material, which is available to authorized users.

Evidence in support of hyperkalaemia management strategies: A systematic literature review

BACKGROUND

Hyperkalaemia is a potentially life-threatening condition that can be managed with pharmacological and non-pharmacological approaches. With the recent development of new hyperkalaemia treatments, new information on safe and effective management of hyperkalaemia has emerged.

OBJECTIVES

This systematic literature review (SLR) aimed to identify all relevant comparative and non-comparative clinical data on management of hyperkalaemia in adults. Our secondary aim was to assess the feasibility of quantitatively comparing randomised controlled trial (RCT) data on the novel treatment sodium zirconium cyclosilicate (ZS) and established pharmacological treatments for the non-emergency management of hyperkalaemia, such as the cation-exchangers sodium/calcium polystyrene sulphonate (SPS/CPS).

METHODS

MEDLINE, Embase and the Cochrane Library were searched on 3^rd April 2017, with additional hand-searches of key congresses and previous SLRs. Articles were screened by two independent reviewers. Eligible records reported interventional or observational studies of pharmacological or non-pharmacological management of hyperkalaemia in adults.

RESULTS

Database searches identified 2,073 unique records. Two hundred and one publications were included, reporting 30 RCTs, 29 interventional non-RCTs and 43 observational studies. Interventions investigated in RCTs included ZS (3), SPS/CPS (3), patiromer (4) and combinations of temporising agents (6 RCTs). A robust and meaningful indirect treatment comparison between ZS and long-established cation-binding agents (SPS/CPS) was infeasible because of heterogeneity between studies (including time points and dosing) and small sample size in SPS/CPS studies.

CONCLUSIONS

Despite hyperkalaemia being associated with several chronic diseases, there is a paucity of high-quality randomised evidence on long-established treatment options (SPS and CPS) and a limited evidence base for hyperkalaemia management with these agents.

Palatability and physical properties of potassium-binding resin RDX7675: comparison with sodium polystyrene sulfonate

Background

Hyperkalemia is a potentially life-threatening condition that patients with heart failure or chronic kidney disease, especially those taking renin–angiotensin–aldosterone system inhibitors, are at high risk of developing. Sodium polystyrene sulfonate (SPS), a current treatment, binds potassium within the gastrointestinal tract to reduce potassium absorption. However, poor palatability limits its long-term use. RDX7675, a novel potassium binder in development for the treatment of hyperkalemia, is a calcium salt of a reengineered polystyrene sulfonate-based resin designed to have enhanced palatability. Here, the physical properties and palatability of RDX7675 and SPS are compared.

Methods

RDX7675 and SPS particle sizes were measured using wet dispersion laser diffraction. Palatability was assessed in a randomized, crossover, healthy volunteer study with two visits. At visit 1 (open label), volunteers evaluated high-viscosity, intermediate-viscosity, and water-reconstituted formulations of RDX7675 (all vanilla flavor), and an equivalent reconstituted SPS (Resonium A^®). At visit 2 (single-blind), volunteers evaluated RDX7675 as a high-viscosity formulation in vanilla, citrus, and mint flavors, and as intermediate-viscosity, low-viscosity, and reconstituted formulations in citrus flavor. Volunteers used a “sip and spit” technique to rate overall acceptability and seven individual characteristics from 1 (“dislike everything”) to 9 (“like extremely”).

Results

RDX7675 particles were smaller than SPS particles, with a narrower size range (RDX7675, 80%, 14–52 µm; SPS, 11.3–124.2 µm), and had a smooth, spherical shape, in contrast to the shard-like SPS particles. Reconstituted RDX7675 was considered superior to SPS for five of the seven palatability characteristics and for overall acceptability (median, visit 1: reconstituted RDX7675, 5.0; SPS, 4.0). High-viscosity vanilla was the most highly rated RDX7675 formulation (median overall acceptability, visit 2: 7.0).

Conclusion

The smaller, more uniformly shaped, spherical particles of RDX7675 resulted in improved palatability over SPS when reconstituted in water. The overall results are promising for future patient acceptability of RDX7675 treatment.

Evaluation of the Potential for Drug Interactions With Patiromer in Healthy Volunteers

INTRODUCTION

Patiromer is a potassium-binding polymer that is not systemically absorbed; however, it may bind coadministered oral drugs in the gastrointestinal tract, potentially reducing their absorption.

METHODS

Twelve randomized, open-label, 3-period, 3-sequence crossover studies were conducted in healthy volunteers to evaluate the effect of patiromer (perpetrator drug) on absorption and single-dose pharmacokinetics (PK) of drugs (victims) that might be commonly used with patiromer. Subjects received victim drug alone, victim drug administered together with patiromer 25.2 g (highest approved dose), and victim drug administered 3 hours before patiromer 25.2 g. The primary PK endpoints were area under the curve (AUC), extrapolated to infinity (AUC0-∞), and maximum concentration ( Cmax). Results were reported as 90% confidence intervals (CIs) about the geometric mean AUC0-∞ and Cmax ratios with prespecified equivalence limits of 80% to 125%.

RESULTS

Overall, 370 subjects were enrolled, with 365 receiving ≥1 dose of patiromer; 351 subjects completed the studies and all required treatments. When coadministered with patiromer, the 90% CIs for AUC0-∞ remained within 80% to 125% for 9 drugs (amlodipine, cinacalcet, clopidogrel, furosemide, lithium, metoprolol, trimethoprim, verapamil, and warfarin). The AUC0-∞ point estimate ratios for levothyroxine and metformin with patiromer coadministration were ≥80%, with the lower bounds of the 90% CIs at 76.8% and 72.8%, respectively. For ciprofloxacin, the point estimate for AUC0-∞ was 71.5% (90% CI: 65.3-78.4). For 8 of 12 drugs, point estimates for Cmax were ≥80% with patiromer coadministration; for ciprofloxacin, clopidogrel, metformin, and metoprolol, the point estimates were <80%. When patiromer was administered 3 hours after each victim drug, the 90% CIs for AUC0-∞ and Cmax for each drug were within the prespecified 80% to 125% limits.

CONCLUSION

For 9 of the 12 drugs coadministered with patiromer, there were no clinically significant drug-drug interactions. For 3 drugs (ciprofloxacin, levothyroxine, and metformin), a 3-hour separation between patiromer and their administration resulted in no clinically significant drug-drug interactions.

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.

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.

Effectiveness of patiromer in the treatment of hyperkalemia in chronic kidney disease patients with hypertension on diuretics

OBJECTIVE

Recurrent hyperkalemia frequently limits use of renin-angiotensin-aldosterone system inhibitors (RAASi) in chronic kidney disease (CKD) patients with hypertension, diabetes, and/or heart failure. Patiromer is a sodium-free, nonabsorbed potassium (K)-binding polymer approved by the US Food and Drug Administration for the treatment of hyperkalemia. This post-hoc analysis of OPAL-HK examined the effectiveness and safety of patiromer in reducing serum K in hyperkalemic CKD patients on RAASi, with hypertension, receiving diuretic therapy versus those not on diuretics.

METHODS

Depending on the degree of hyperkalemia at baseline, CKD patients with serum K from 5.1 to less than 6.5 mmol/l on RAASi (n = 243) were assigned to a patiromer of total dose 8.4 or 16.8 g, divided twice daily. Changes in serum K, and tolerability and safety were assessed over 4 weeks in patients on and not on diuretics.

RESULTS

At baseline, 132 patients used diuretics and 111 were not on diuretics, mean age was 64.3 and 64.0 years, respectively, and 63 and 51% were men. Similar reductions in serum K were seen over 4 weeks in both subgroups. At week 4, serum K fell by -0.95 ± 0.04 mmol/l with any diuretic and -1.04 ± 0.05 mmol/l with no diuretic. Patiromer was well tolerated, with mild-to-moderate constipation reported as the most common adverse event (7.6 and 14.4% of patients on any diuretic or no diuretic, respectively). Hypokalemia (s-K <3.5 mEq/l) was reported in 2.3% of patients on any diuretic and in 3.7% not on diuretics.

CONCLUSION

The serum K-lowering efficacy and safety profile of patiromer in hyperkalemia patients with CKD was not compromised by diuretic therapy.

Electrolyte and Acid-Base Disorders in Chronic Kidney Disease and End-Stage Kidney Failure

The kidneys play a pivotal role in the regulation of electrolyte and acid-base balance. With progressive loss of kidney function, derangements in electrolytes and acid-base inevitably occur and contribute to poor patient outcomes. As chronic kidney disease (CKD) has become a worldwide epidemic, medical providers are increasingly confronted with such problems. Adequate diagnosis and treatment will minimize complications and can potentially be lifesaving. In this review, we discuss the current understanding of the disease process, clinical presentation, diagnosis and treatment strategies, integrating up-to-date knowledge in the field. Although electrolyte and acid-base derangements are significant causes of morbidity and mortality in CKD and end-stage renal disease patients, they can be effectively managed through a timely institution of combined preventive measures and pharmacological therapy. Exciting advances and several upcoming outcome trials will provide further information to guide treatment and improve patient outcomes.

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.

Effect of Patiromer on Urinary Ion Excretion in Healthy Adults

BACKGROUND AND OBJECTIVES

Patiromer is a nonabsorbed potassium-binding polymer that uses calcium as the counterexchange ion. The calcium released with potassium binding has the potential to be absorbed or bind phosphate. Because binding is not specific for potassium, patiromer can bind other cations. Here, we evaluate the effect of patiromer on urine ion excretion in healthy adults, which reflects gastrointestinal ion absorption.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We analyzed the effect of patiromer on urine potassium, sodium, magnesium, calcium, and phosphate in two studies. Healthy adults on controlled diets in a clinical research unit were given patiromer up to 50.4 g/d divided three times a day for 8 days (dose-finding study) or 25.2 g/d in a crossover design as daily or divided (two or three times a day) doses for 18 days (dosing regimen study). On the basis of 24-hour collections, urinary ion excretion during the baseline period (days 5-11) was compared with that during the treatment period (days 13-19; dose-finding study), and the last 4 days of each period were compared across regimens (dosing regimen study).

RESULTS

In the dose-finding study, patiromer induced a dose-dependent decrease in urine potassium, urine magnesium, and urine sodium (P<0.01 for each). Patiromer at 25.2 g/d decreased urine potassium (mean±SD) by 1140±316 mg/d, urine magnesium by 45±1 mg/d, and urine sodium by 225±145 mg/d. Urine calcium increased in a dose-dependent manner, and urine phosphate decreased in parallel (both P<0.01). Patiromer at 25.2 g/d increased urine calcium by 73±23 mg/d and decreased urine phosphate by 64±40 mg/d. Urine potassium, urine sodium, and urine magnesium were unaffected by dosing regimen, whereas the increase in urine calcium was significantly lower with daily compared with three times a day dosing (P=0.01). Urine phosphate also decreased less with daily compared with two or three times a day dosing (P<0.05).

CONCLUSIONS

In healthy adults, patiromer reduces urine potassium, urine sodium, urine magnesium, and urine phosphate, while modestly increasing urine calcium. Compared with divided dosing, administration of patiromer once daily provides equivalent reductions in urine potassium, urine sodium, and urine magnesium, with less effect on urine calcium and urine phosphate.

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).

Patiromer: A Review in Hyperkalaemia

Patiromer (Veltassa(™)) for oral suspension is a sodium-free potassium binder that is approved in the USA for the treatment of hyperkalaemia. In clinical trials, patiromer significantly reduced serum potassium levels from baseline to week 4 in patients with chronic kidney disease (CKD) and mild to severe hyperkalaemia (OPAL-HK), or CKD, mild to moderate hyperkalaemia and type 2 diabetes mellitus (AMETHYST-DN), who were receiving renin-angiotensin-aldosterone system inhibitors (RAASis; drugs that inhibit the renal excretion of potassium). Among patients in OPAL-HK who had moderate to severe hyperkalaemia at baseline and normokalaemia on patiromer and RAASis at week 4, continuing patiromer for a further 8 weeks maintained reductions in potassium levels more effectively than switching to placebo (i.e. withdrawing patiromer); consequently, fewer patiromer than placebo recipients experienced recurrent hyperkalaemia during this period. Furthermore, almost all patiromer (vs. less than half of placebo) recipients were still receiving RAASi therapy at the end of this trial. In AMETHYST-DN, the significant reduction from baseline in serum potassium levels seen at week 4 was sustained for up to 52 weeks. Patiromer was generally well tolerated in these trials, with no treatment-related serious adverse events or deaths. Commonly occurring treatment-related adverse events include mild to moderate constipation and hypomagnesaemia, and there is a low risk of hypokalaemia. In conclusion, oral patiromer is a useful new option for patients with hyperkalaemia.