ClinicalTrials.gg
CompletedNCT04676646REALIZE-KUpdated Jul 9, 2025Results posted

Study to Assess Efficacy and Safety of SZC for the Management of High Potassium in Patients With Symptomatic HFrEF Receiving Spironolactone

A Phase 4 interventional study of Sodium zirconium cyclosilicate and Placebo in Hyperkalaemia and Heart Failure With Reduced Ejection Fraction, sponsored by AstraZeneca. Completed at 89 sites in 8 countries. Open to participants aged 18 Years to 130 Years. Per ClinicalTrials.gov, last updated 2025-07-09.

Sponsored by AstraZeneca · Phase 4, Interventional, and Treatment

Phase
Phase 4
Study type
Interventional
Enrollment
366
Allocation
Randomized
Ages
18 Years to 130 Years
Sex
All
01

Study summary

The main objective of this study is to evaluate the efficacy of SZC as compared with placebo in keeping potassium levels within the normal range (3.5-5.0 mEq/L) while on spironolactone ≥25 mg daily without assistance of rescue therapy for hyperkalaemia (HK).

Read the detailed description

REALIZE-K is a Phase 4, multinational, multicenter, double-blind, placebo-controlled, randomized-withdrawal, parallel-group study that includes the following 3 phases: screening, 4-6 week open-label run-in phase where sodium zirconium cyclosilicate (SZC) and spironolactone will be optimized, followed by a 6-month double-blind, placebo-controlled, randomized withdrawal treatment phase.

Patients meeting the following criteria will enter the 4-6 week open-label run-in phase: symptomatic heart failure with reduced ejection fraction (HFrEF); receiving an angiotensin-converting enzyme inhibitor (ACEi), angiotensin II receptor blocker (ARB), or angiotensin receptor-Neprilysin inhibitor (ARNi); receiving no spironolactone or eplerenone, or receiving low-dose spironolactone (\<25 mg daily); receiving a beta-blocker unless contraindicated; AND with hyperkalemia (sK+ 5.1-5.9 mEq/L) and an eGFR >/= 30 mL/min/1.73m2, OR normokalemic (sK+ 3.5-5.0 mEq/L) and 'at risk' of developing hyperkalemia (ie, history of hyperkalemia within the past 36 months and eGFR >/= 30 mL/min/1.73m2, or sK+ 4.5-5.0 mEq/L and eGFR 30-60 mL/min/1.73m2 and/or age >75 years).

Patients who are normokalemic on SZC and receiving spironolactone >/= 25 mg daily at the end of the open-label run-in phase will enter the 6-month double-blind, placebo-controlled, randomized withdrawal treatment phase. Eligible patients will be randomized 1:1, stratified by run-in phase sK+ cohort.

02

Conditions studied

  • Hyperkalaemia
  • Heart Failure With Reduced Ejection Fraction

Browse trials for

03

In context

Hyperkalemia

133 studies on the registry are indexed under Hyperkalemia; 25 are open to participants now.

This study's enrollment of 366 is above the median of 87 across 102 interventional studies indexed under Hyperkalemia.

Browse Hyperkalemia studies →

Lead sponsor

AstraZeneca is the lead sponsor of 3,499 studies on the registry; 270 are open to participants now.

Of its 368 completed or terminated interventional studies of FDA-regulated products, 178 (48%) have results posted.

Counted across the registry records on this site, refreshed daily.

04

Who can participate

Ages eligible
18 Years to 130 Years
Sexes eligible
All
Accepts healthy volunteers
No

Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.

Inclusion criteria

  • Adults aged ≥18 years
  • Potassium and estimated (eGFR):
  • Cohort 1: sK+ 5.1-5.9 mEq/L at screening/study enrolment and eGFR ≥30 mL/min/1.73 m2; OR
  • Cohort 2: Normokalaemic (sK+ 3.5-5.0 mEq/L) at screening and 'at risk' of developing HK defined as any of the following:
  • Have a history of HK (sK+ >5.0 mEq/L) within the prior 36 months and eGFR ≥30 mL/min/1.73 m2; or
  • sK+ 4.5-5.0 mEq/L and eGFR 30 to 60 mL/min/1.73 m2; or
  • sK+ 4.5-5.0 mEq/L, and age >75 years
  • Symptomatic HFrEF ( [NYHA] class II-IV), which has been present for at least 3 months
  • (LVEF) ≤40%
  • Receiving angiotensin-converting enzyme inhibitor (ACEi), angiotensin II receptor blocker (ARB), or angiotensin receptor-Neprilysin inhibitor (ARNi)
  • Not on or on low-dose spironolactone or eplerenone (\<25 mg daily)
  • Receiving beta-blocker unless

Exclusion criteria

EXCLUSION CRITERIA

  • Heart failure due to restrictive cardiomyopathy, active myocarditis, constrictive pericarditis, hypertrophic (obstructive) cardiomyopathy, or severe stenotic valve disease as a primary cause of HF
  • Current inpatient hospitalisation with unstable HF, defined as any of the following:
  • Systolic blood pressure \<95 mmHg during the 6 hours prior to screening.
  • Intravenous diuretic therapy during the 12 hours prior to screening.
  • Use of intravenous inotropic drugs during the 24 hours prior to screening.
  • Received mechanical circulatory support during the 48 hours prior to screening
  • Previous cardiac transplantation or implantation of a ventricular assistance device (VAD) or similar device, or transplantation or implantation expected after randomisation
Terms in these criteria, in plain language(4)

Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.

GFR and eGFR (kidney filtering)

GFR (glomerular filtration rate) is how much blood the kidneys filter each minute. It is usually estimated from a blood test — eGFR, by formulas such as CKD-EPI or MDRD — and some studies ask for it to be measured directly instead. Usually given in mL/min/1.73 m².

Check the method, the units and the minimum the study states. A value of 90 or above is in the normal-or-high range, but kidney damage can show in other tests too.

NYHA class (heart failure)

The New York Heart Association’s four classes of how much heart failure limits physical activity.

I
No limits: ordinary activity causes no undue tiredness or breathlessness.
II
Slight limits: comfortable at rest, ordinary activity causes symptoms.
III
Marked limits: comfortable at rest, less than ordinary activity causes symptoms.
IV
Symptoms even at rest; any activity makes them worse.

Studies set their own limit — many outside heart failure leave out class III–IV, while heart failure studies may ask for a particular class. Check the class this study names.

LVEF (left ventricular ejection fraction)

The share of blood the heart’s main pumping chamber (the left ventricle) pushes out with each beat, measured by an echocardiogram (heart ultrasound) or a MUGA scan. About 50–70% is normal.

Contraindication

A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.

05

Study design

Phase
Phase 4
Primary purpose
Treatment
Allocation
Randomized
Intervention model
Parallel assignment
Masking
Double (Participant, Investigator)
Enrollment
366 participants (actual)

Study arms

  • Experimental
    Open-label run-in phase

    Cohort 1 (4 weeks duration): Patients who are hyperkalemic at study entry will begin SZC 10 g TID for up to 48 hours followed by SZC 10 g once daily to achieve and maintain normokalemia. The SZC dose will be adjusted as needed to maintain normokalemia (dose range = 5 g every other day, to 5-15 g once daily). Cohort 2 (up to 6 weeks duration): Patients who develop hyperkalemia during the uptitration of spironolactone will receive SZC 10 g TID for up to 48 hours followed by SZC 10 g once daily to achieve and maintain normokalemia. The SZC dose will be adjusted as needed to maintain normokalemia (dose range = 5 g every other day, to 5-15 g once daily).

    Drug: Sodium zirconium cyclosilicate · Drug: Placebo · Other: Spironolactone

  • Experimental
    Randomized withdrawal phase (6 months)

    SZC arm and Placebo arm: Patients will continue on the SZC dose they were receiving at the end of the run-in phase. The SZC / Placebo dose will be adjusted as needed to maintain normokalemia (dose range = 5 g every other day, to 5-15 g once daily).

    Drug: Sodium zirconium cyclosilicate · Drug: Placebo · Other: Spironolactone

Interventions

  • Investigational medicinal product

    Also known as: SZC

  • DrugPlacebo

    Placebo comparator

  • OtherSpironolactone

    Background intervention. During the run-in phase, spironolactone will be initiated/uptitrated up to a maximum of 50 mg per day. During the randomized withdrawal phase the spironolactone dose at the end of the run-in phase will be maintained.

06

What researchers measure

Primary outcomes

  1. Participants Who Achieved Response, Defined as Serum Potassium (sK+) Within 3.5 to 5.0 mEq/L, Spironolactone Greater Than or Equal to 25 mg Daily, no Rescue Therapy for Hyperkalaemia

    The median percentages of participants having a response are presented. Response means all three requirements were met. Non-response was indicated for participants lost to follow-up, including death. The treatment effect was analysed using a generalised estimating equation (GEE) model with a binomial family and a log link, a dependent variable of response per visit, fixed independent variables of randomised treatment, subject recruitment country, a per visit indicator variable and open-label period cohort. The common odds ratio was derived together with two-sided 95% confidence intervals.

    Time frame: From Month 1 (Visit 9) to Month 6 (Visit 14), up to 6 months

Secondary outcomes

  1. Participants Who Achieved Response, Defined as sK+ Within 3.5-5.0 mEq/L, on the Same Dose of Spironolactone as Randomisation, no Rescue Therapy for Hyperkalaemia

    The median percentages of participants who achieved a response are presented. Response means all three requirements were met. Non-response was indicated for participants lost to follow-up, including death. The analysis was performed using a GEE model with a binomial family and a log link, a dependent variable of response per visit, fixed independent variables of randomised treatment, subject recruitment country, a per visit indicator variable and open-label period cohort. The common odds ratio was derived together with two-sided 95% confidence intervals.

    Time frame: From Month 1 (Visit 9) to Month 6 (Visit 14), up to 6 months

  2. Participants Who Achieved Response, Defined as Spironolactone Greater Than or Equal to 25 mg Daily

    The median percentages of participants who achieved a response are presented. Response means that the requirement was met. Non-response was indicated for subjects lost to follow-up, including death. The analysis was performed using a GEE model with a binomial family and a log link, a dependent variable of response per visit, fixed independent variables of randomised treatment, subject recruitment country, a per visit indicator variable and open-label period cohort. The common odds ratio was derived together with two-sided 95% confidence intervals.

    Time frame: From Month 1 (Visit 9) to Month 6 (Visit 14), up to 6 months

  3. Time to First Hyperkalaemia (sK+ Greater Than 5.0mEq/L) Episode

    The time to first hyperkalaemia episode for participants on SZC compared to placebo during the randomised-withdrawal period, with hyperkalaemia defined as sK+ greater than 5.0 mEq/L as assessed by central laboratory, is presented in median time (days). The analysis was performed using a Cox regression model including randomised treatment group and subject recruitment country, adjusted for the stratification factor (hyperkalaemia vs normokalaemia at study entry). Placebo group used as reference level in Cox model.

    Time frame: From randomisation to the end of treatment (EOT) visit, up to 6 months

  4. Time to First Instance of Decrease or Discontinuation of Spironolactone Dose Due to Hyperkalaemia

    The time to first instance of decrease or discontinuation of spironolactone dose due to hyperkalaemia is presented in median time (days). The analysis was performed using a Cox regression model, adjusted for the stratification factor (hyperkalaemia vs normokalaemia at study entry).

    Time frame: From randomisation to the EOT visit, up to 6 months

  5. Kansas City Cardiomyopathy Questionnaire Clinical Summary Score (KCCQ-CSS) at EOT

    The KCCQ is a 23-item instrument measuring, from the patients' perspectives, their heart failure-related symptoms, physical and social limitations, self-efficacy, and health-related quality of life (QoL) over the prior 2 weeks. It was scored as follows: Physical Limitation (items 1a-f), Symptom Stability (item 2), Symptom Frequency (items 3, 5, 7, and 9), Symptom Burden (items 4, 6, and 8), Self Efficacy (items 10 and 11), QoL (items 12, 13, and 14), and Social Limitation (items 15a-d). Scores were calculated by summing the responses within each domain and by taking the average. Scale scores were transformed to a 0 to 100 range, with 0 implying the lowest level of functioning and 100 for the highest level of functioning. The CSS was calculated as the average of Physical Limitation Score and Total Symptom Score (TSS) and the TSS was calculated as the average of Symptom Frequency and Symptom Burden Scores. The change from randomisation in KCCQ-CSS is reported.

    Time frame: At EOT visit (approximately 6 months post-randomisation)

Other outcomes

  1. Location and Severity of Peripheral Oedema

    The location and severity of peripheral oedema that occurred during the randomised-withdrawal phase are presented. Participants with multiple peripheral oedema events were counted only once. The location of oedema is not mutually exclusive so multiple locations may apply for each participant.

    Time frame: During the randomised-withdrawal period and up to 14 days after discontinuation of SZC or placebo, up to 6.5 months

07

Results

Posted Jul 9, 2025

Participant flow

Open-label Run-in Phase
Participant flow — Open-label Run-in Phase
MilestoneOpen-label Run-in PhaseRandomized-withdrawal Phase - SZC GroupRandomized-withdrawal Phase - Placebo Group
Started36600
Completed20300
Not completed16300
Withdrew: Adverse event300
Withdrew: Death300
Withdrew: Study-specific withdrawal criteria200
Withdrew: Failure to meet randomization criteria14400
Withdrew: Lost to follow-up100
Withdrew: Withdrawal by subject800
Withdrew: Withdrawn from study due to withdrawal by co-investigator100
Withdrew: Withdrawn from study due to withdrawal by pi100
Randomised-withdrawal Phase
Participant flow — Randomised-withdrawal Phase
MilestoneOpen-label Run-in PhaseRandomized-withdrawal Phase - SZC GroupRandomized-withdrawal Phase - Placebo Group
Started0102101
Completed08887
Not completed01414
Withdrew: Adverse event055
Withdrew: Death012
Withdrew: Development of study-specific withdrawal criteria024
Withdrew: Lost to follow-up010
Withdrew: Withdrawn from study due to pd - wrong doses of spironolactone010
Withdrew: Withdrawn from study due to spironolactone was stopped on may 28, related hyperkalaemia010
Withdrew: Withdrawn from study due to the participant did not have enough medication by issues in iwrs001
Withdrew: Withdrawn from study due to the patient was random by mistake on this date he was an olrif010
Withdrew: Withdrawal by subject022

Outcome measures

PrimaryParticipants Who Achieved Response, Defined as Serum Potassium (sK+) Within 3.5 to 5.0 mEq/L, Spironolactone Greater Than or Equal to 25 mg Daily, no Rescue Therapy for Hyperkalaemia

The median percentages of participants having a response are presented. Response means all three requirements were met. Non-response was indicated for participants lost to follow-up, including death. The treatment effect was analysed using a generalised estimating equation (GEE) model with a binomial family and a log link, a dependent variable of response per visit, fixed independent variables of randomised treatment, subject recruitment country, a per visit indicator variable and open-label period cohort. The common odds ratio was derived together with two-sided 95% confidence intervals.

Time frame:
From Month 1 (Visit 9) to Month 6 (Visit 14), up to 6 months
Reported as:
Number · Percentage of participants
Participants Who Achieved Response, Defined as Serum Potassium (sK+) Within 3.5 to 5.0 mEq/L, Spironolactone Greater Than or Equal to 25 mg Daily, no Rescue Therapy for Hyperkalaemia
Percentage of participantsRandomized-withdrawal Phase - SZC GroupRandomized-withdrawal Phase - Placebo Group
Participants Who Achieved Response, Defined as Serum Potassium (sK+) Within 3.5 to 5.0 mEq/L, Spironolactone Greater Than or Equal to 25 mg Daily, no Rescue Therapy for Hyperkalaemia72.135.7
Statistical analysis
  • Randomized-withdrawal Phase - SZC Group vs Randomized-withdrawal Phase - Placebo Group · GEE model · p = <0.001 · Odds ratio (or): 4.45 · 95% CI 2.89 to 6.86An odds ratio greater than 1 indicated increased odds of response on SZC compared to placebo.
SecondaryParticipants Who Achieved Response, Defined as sK+ Within 3.5-5.0 mEq/L, on the Same Dose of Spironolactone as Randomisation, no Rescue Therapy for Hyperkalaemia

The median percentages of participants who achieved a response are presented. Response means all three requirements were met. Non-response was indicated for participants lost to follow-up, including death. The analysis was performed using a GEE model with a binomial family and a log link, a dependent variable of response per visit, fixed independent variables of randomised treatment, subject recruitment country, a per visit indicator variable and open-label period cohort. The common odds ratio was derived together with two-sided 95% confidence intervals.

Time frame:
From Month 1 (Visit 9) to Month 6 (Visit 14), up to 6 months
Reported as:
Number · Percentage of participants
Participants Who Achieved Response, Defined as sK+ Within 3.5-5.0 mEq/L, on the Same Dose of Spironolactone as Randomisation, no Rescue Therapy for Hyperkalaemia
Percentage of participantsRandomized-withdrawal Phase - SZC GroupRandomized-withdrawal Phase - Placebo Group
Participants Who Achieved Response, Defined as sK+ Within 3.5-5.0 mEq/L, on the Same Dose of Spironolactone as Randomisation, no Rescue Therapy for Hyperkalaemia58.222.9
Statistical analysis
  • Randomized-withdrawal Phase - SZC Group vs Randomized-withdrawal Phase - Placebo Group · GEE model · p = <0.001 · Odds ratio (or): 4.58 · 95% CI 2.78 to 7.55An odds ratio \>1 indicated increased odds of response on SZC compared to placebo.
SecondaryParticipants Who Achieved Response, Defined as Spironolactone Greater Than or Equal to 25 mg Daily

The median percentages of participants who achieved a response are presented. Response means that the requirement was met. Non-response was indicated for subjects lost to follow-up, including death. The analysis was performed using a GEE model with a binomial family and a log link, a dependent variable of response per visit, fixed independent variables of randomised treatment, subject recruitment country, a per visit indicator variable and open-label period cohort. The common odds ratio was derived together with two-sided 95% confidence intervals.

Time frame:
From Month 1 (Visit 9) to Month 6 (Visit 14), up to 6 months
Reported as:
Number · Percentage of participants
Participants Who Achieved Response, Defined as Spironolactone Greater Than or Equal to 25 mg Daily
Percentage of participantsRandomized-withdrawal Phase - SZC GroupRandomized-withdrawal Phase - Placebo Group
Participants Who Achieved Response, Defined as Spironolactone Greater Than or Equal to 25 mg Daily81.449.5
Statistical analysis
  • Randomized-withdrawal Phase - SZC Group vs Randomized-withdrawal Phase - Placebo Group · GEE model · p = <0.001 · Odds ratio (or): 4.33 · 95% CI 2.50 to 7.52An odds ratio greater than 1 indicated increased odds of response on SZC compared to placebo.
SecondaryTime to First Hyperkalaemia (sK+ Greater Than 5.0mEq/L) Episode

The time to first hyperkalaemia episode for participants on SZC compared to placebo during the randomised-withdrawal period, with hyperkalaemia defined as sK+ greater than 5.0 mEq/L as assessed by central laboratory, is presented in median time (days). The analysis was performed using a Cox regression model including randomised treatment group and subject recruitment country, adjusted for the stratification factor (hyperkalaemia vs normokalaemia at study entry). Placebo group used as reference level in Cox model.

Time frame:
From randomisation to the end of treatment (EOT) visit, up to 6 months
Reported as:
Median · Days
Time to First Hyperkalaemia (sK+ Greater Than 5.0mEq/L) Episode
DaysRandomized-withdrawal Phase - SZC GroupRandomized-withdrawal Phase - Placebo Group
Time to First Hyperkalaemia (sK+ Greater Than 5.0mEq/L) Episode65.0 (35.00 to 98.00)9.0 (8.00 to 13.00)
Statistical analysis
  • Randomized-withdrawal Phase - SZC Group vs Randomized-withdrawal Phase - Placebo Group · Regression, Cox · p = <0.001 · Hazard ratio (hr): 0.51 · 95% CI 0.37 to 0.71A hazard ratio less than 1 favors SZC to be associated with a longer time to first hyperkalaemia episode than placebo.
SecondaryTime to First Instance of Decrease or Discontinuation of Spironolactone Dose Due to Hyperkalaemia

The time to first instance of decrease or discontinuation of spironolactone dose due to hyperkalaemia is presented in median time (days). The analysis was performed using a Cox regression model, adjusted for the stratification factor (hyperkalaemia vs normokalaemia at study entry).

Time frame:
From randomisation to the EOT visit, up to 6 months
Reported as:
Median · Days
Time to First Instance of Decrease or Discontinuation of Spironolactone Dose Due to Hyperkalaemia
DaysRandomized-withdrawal Phase - SZC GroupRandomized-withdrawal Phase - Placebo Group
Time to First Instance of Decrease or Discontinuation of Spironolactone Dose Due to HyperkalaemiaNA (NA to NA)NA (NA to NA)
Statistical analysis
  • Randomized-withdrawal Phase - SZC Group vs Randomized-withdrawal Phase - Placebo Group · Regression, Cox · p = 0.006 · Hazard ratio (hr): 0.37 · 95% CI 0.17 to 0.73A hazard ratio less than 1 favored SZC to be associated with a longer time to first instance of a decrease of spironolactone dose due to hyperkalaemia than placebo.
SecondaryKansas City Cardiomyopathy Questionnaire Clinical Summary Score (KCCQ-CSS) at EOT

The KCCQ is a 23-item instrument measuring, from the patients' perspectives, their heart failure-related symptoms, physical and social limitations, self-efficacy, and health-related quality of life (QoL) over the prior 2 weeks. It was scored as follows: Physical Limitation (items 1a-f), Symptom Stability (item 2), Symptom Frequency (items 3, 5, 7, and 9), Symptom Burden (items 4, 6, and 8), Self Efficacy (items 10 and 11), QoL (items 12, 13, and 14), and Social Limitation (items 15a-d). Scores were calculated by summing the responses within each domain and by taking the average. Scale scores were transformed to a 0 to 100 range, with 0 implying the lowest level of functioning and 100 for the highest level of functioning. The CSS was calculated as the average of Physical Limitation Score and Total Symptom Score (TSS) and the TSS was calculated as the average of Symptom Frequency and Symptom Burden Scores. The change from randomisation in KCCQ-CSS is reported.

Time frame:
At EOT visit (approximately 6 months post-randomisation)
Reported as:
Least squares mean · Score on a scale
Kansas City Cardiomyopathy Questionnaire Clinical Summary Score (KCCQ-CSS) at EOT
Score on a scaleRandomized-withdrawal Phase - SZC GroupRandomized-withdrawal Phase - Placebo Group
Kansas City Cardiomyopathy Questionnaire Clinical Summary Score (KCCQ-CSS) at EOT71.27 ± 2.5772.27 ± 2.36
Statistical analysis
  • Randomized-withdrawal Phase - SZC Group vs Randomized-withdrawal Phase - Placebo Group · t-test, 2 sided · p = 0.724 · Least-squares mean difference: -1.01 · 95% CI -6.64 to 4.63A least-squares mean difference greater than 0 favors SZC compared to placebo.
Other pre-specifiedLocation and Severity of Peripheral Oedema

The location and severity of peripheral oedema that occurred during the randomised-withdrawal phase are presented. Participants with multiple peripheral oedema events were counted only once. The location of oedema is not mutually exclusive so multiple locations may apply for each participant.

Time frame:
During the randomised-withdrawal period and up to 14 days after discontinuation of SZC or placebo, up to 6.5 months
Reported as:
Number · Participants
Location and Severity of Peripheral Oedema
ParticipantsRandomized-withdrawal Phase - SZC GroupRandomized-withdrawal Phase - Placebo Group
Location of oedema: pedal oedema1310
Location of oedema: ankle oedema1713
Location of oedema: pretibial oedema115
Location of oedema: thigh oedema10
Severity of pedal oedema - right side: trace43
Severity of pedal oedema - right side: mild15
Severity of pedal oedema - right side: moderate71
Severity of pedal oedema - right side: severe00
Severity of pedal oedema - left side: trace45
Severity of pedal oedema - left side: mild24
Severity of pedal oedema - left side: moderate71
Severity of pedal oedema - left side: severe00
Severity of ankle oedema - right side: trace44
Severity of ankle oedema - right side: mild56
Severity of ankle oedema - right side: moderate71
Severity of ankle oedema - right side: severe00
Severity of ankle oedema - left side: trace46
Severity of ankle oedema - left side: mild56
Severity of ankle oedema - left side: moderate81
Severity of ankle oedema - left side: severe00
Severity of pretibial edema - right side: trace21
Severity of pretibial edema - right side: mild42
Severity of pretibial edema - right side: moderate51
Severity of pretibial edema - right side: severe00
Severity of pretibial edema - left side: trace12
Severity of pretibial edema - left side: mild32
Severity of pretibial edema - left side: moderate71
Severity of pretibial edema - left side: severe00
Severity of thigh edema - right side: trace00
Severity of thigh edema - right side: mild00
Severity of thigh edema - right side: moderate10
Severity of thigh edema - right side: severe00
Severity of thigh edema - left side: trace00
Severity of thigh edema - left side: mild00
Severity of thigh edema - left side: moderate10
Severity of thigh edema - left side: severe00

Adverse events

Collected over Open-label Run-in Phase (OLP): includes treatment-emergent adverse events (TEAEs) that occurred during the OLP and all AEs which occurred prior to first dose of SZC which worsen in severity following dosing during the OLP, up to 4-6 weeks Randomised-withdrawal Phase (RWP): includes TEAEs that occurred during the RWP and up to 14 days after discontinuation of SZC/placebo and all AEs which occurred prior to first dose which worsen in severity following dosing during the RWP, up to 6.5 months. Non-serious events are listed at a 5% frequency threshold.

Adverse event summary by group
GroupDeathsSeriousOther
Open-label Run-in Phase7/362 (1.9%)11/362 (3%)9/362 (2.5%)
Randomized-withdrawal Phase - SZC Group2/101 (2%)23/101 (22.8%)20/101 (19.8%)
Randomized-withdrawal Phase - Placebo Group2/101 (2%)22/101 (21.8%)25/101 (24.8%)
Most frequent serious events
Showing 10 of 40
Most frequent serious events
EventOpen-label Run-in PhaseRandomized-withdrawal Phase - SZC GroupRandomized-withdrawal Phase - Placebo Group
Cardiac failureCardiac disorders4/36212/1014/101
HyperkalaemiaMetabolism and nutrition disorders0/3622/1013/101
PneumoniaInfections and infestations1/3622/1011/101
Acute kidney injuryRenal and urinary disorders0/3620/1012/101
Sudden cardiac deathGeneral disorders0/3621/1010/101
Dengue feverInfections and infestations0/3621/1011/101
Lower respiratory tract infectionInfections and infestations0/3620/1011/101
OsteomyelitisInfections and infestations0/3621/1011/101
Pulmonary sepsisInfections and infestations0/3620/1011/101
Respiratory tract infectionInfections and infestations0/3621/1010/101
Most frequent other events
Most frequent other events
EventOpen-label Run-in PhaseRandomized-withdrawal Phase - SZC GroupRandomized-withdrawal Phase - Placebo Group
HyperkalaemiaMetabolism and nutrition disorders6/36212/10123/101
Oedema peripheralGeneral disorders3/3626/1012/101
HypokalaemiaMetabolism and nutrition disorders0/3626/1010/101

Baseline characteristics

Age, Continuous
Age, Continuous(Years)Randomized-withdrawal Phase - SZC GroupRandomized-withdrawal Phase - Placebo GroupTotal
Mean72.5 ± 7.8869.2 ± 10.4670.9 ± 9.39
Age, Customized
Age, Customized(Participants)Randomized-withdrawal Phase - SZC GroupRandomized-withdrawal Phase - Placebo GroupTotal
18-64 years183250
65-84 years7963142
>=85 years5611
Sex: Female, Male
Sex: Female, Male(Participants)Randomized-withdrawal Phase - SZC GroupRandomized-withdrawal Phase - Placebo GroupTotal
Female262652
Male7675151
Ethnicity (NIH/OMB)
Ethnicity (NIH/OMB)(Participants)Randomized-withdrawal Phase - SZC GroupRandomized-withdrawal Phase - Placebo GroupTotal
Hispanic or Latino402767
Not Hispanic or Latino6274136
Unknown or Not Reported000
Race/Ethnicity, Customized
Race/Ethnicity, Customized(Participants)Randomized-withdrawal Phase - SZC GroupRandomized-withdrawal Phase - Placebo GroupTotal
White9194185
Black or African American5510
Asian000
Native Hawaiian or Other Pacific Islander000
American Indian or Alaskan Native000
Other628
Not Reported000
Country
Country(Participants)Randomized-withdrawal Phase - SZC GroupRandomized-withdrawal Phase - Placebo GroupTotal
BRA311950
CAN71623
CZE31316
ESP332659
GBR9413
HUN5510
POL81018
USA6814
Type 2 diabetes at baseline
Type 2 diabetes at baseline(Participants)Randomized-withdrawal Phase - SZC GroupRandomized-withdrawal Phase - Placebo GroupTotal
Yes272552
No7576151
08

Study locations

89 sites
  • Research Site
    Fairhope, Alabama 36532, United States
  • Research Site
    Los Angeles, California 90033, United States
  • Research Site
    Torrance, California 90502, United States
  • Research Site
    Evanston, Illinois 60202, United States
  • Research Site
    Hazel Crest, Illinois 60429-2196, United States
  • Research Site
    Oak Lawn, Illinois 60453, United States
  • Research Site
    Kansas City, Missouri 64111, United States
  • Research Site
    New York, New York 10029, United States
  • Research Site
    Winston-Salem, North Carolina 27157, United States
  • Research Site
    Greenville, South Carolina 29605, United States
  • Research Site
    Houston, Texas 77054, United States
  • Research Site
    Falls Church, Virginia 22042, United States
  • Research Site
    Belo Horizonte, 30110-017, Brazil
  • Research Site
    Bragança Paulista, 12916-542, Brazil
  • Research Site
    Brasília, 70390-700, Brazil
  • Research Site
    Brasília, 71615-907, Brazil
  • Research Site
    Campina Grande do Sul, 83430-000, Brazil
  • Research Site
    Campinas, 13060-080, Brazil
  • Research Site
    Canoas, 92425-020, Brazil
  • Research Site
    Joinville, 89201-490, Brazil
  • Research Site
    Porto Alegre, 90020-090, Brazil
  • Research Site
    Porto Alegre, 90035-000, Brazil
  • Research Site
    Porto Alegre, 90035-903, Brazil
  • Research Site
    Ribeirão Preto, 14026-020, Brazil
  • Research Site
    Salvador, 41810-011, Brazil
  • Research Site
    Santa Cruz do Sul, 96835-090, Brazil
  • Research Site
    São Paulo, 01321-001, Brazil
  • Research Site
    São Paulo, 04556-100, Brazil
  • Research Site
    São Paulo, 05652-9000, Brazil
  • Research Site
    São Paulo, 08270-070, Brazil
  • Research Site
    Votuporanga, 15500-003, Brazil
  • Research Site
    Cambridge, Ontario N1R 6V6, Canada
  • Research Site
    Kitchener, Ontario N2N 1B2, Canada
  • Research Site
    Scarborough Village, Ontario M1B 4Z8, Canada
  • Research Site
    Scarborough Village, Ontario M1S 4N6, Canada
  • Research Site
    Toronto, Ontario M5B1M8, Canada
  • Research Site
    Whitby, Ontario L1N 5T2, Canada
  • Research Site
    Montreal, Quebec H1T 1C8, Canada
  • Research Site
    Montreal, Quebec H2X 3E4, Canada
  • Research Site
    Québec, Quebec G1R 2J6, Canada
  • Research Site
    Terrebonne, Quebec J6V 2H2, Canada
  • Research Site
    Brandýs nad Labem, 250 01, Czechia
  • Research Site
    Broumov, 55001, Czechia
  • Research Site
    Hradec Králové, 500 02, Czechia
  • Research Site
    Jaroměř, 55101, Czechia
  • Research Site
    Louny, 440 01, Czechia
  • Research Site
    Ostrava, 708 52, Czechia
  • Research Site
    Uherské Hradiště, 68601, Czechia
  • Research Site
    Budapest, 1122, Hungary
  • Research Site
    Budapest, 1204, Hungary
  • Research Site
    Zalaegerszeg, 8900, Hungary
  • Research Site
    Gdynia, 81-157, Poland
  • Research Site
    Lodz, 90-553, Poland
  • Research Site
    Lodz, 91-002, Poland
  • Research Site
    Lódz, 93-513, Poland
  • Research Site
    Skórzewo, 60-185, Poland
  • Research Site
    Żarów, 58-130, Poland
  • Research Site
    A Coruña, 15006, Spain
  • Research Site
    Almería, 4009, Spain
  • Research Site
    Barcelona, 8035, Spain
  • Research Site
    Barcelona, 8041, Spain
  • Research Site
    Bilbao (Vizcaya), 48013, Spain
  • Research Site
    Granada, 18007, Spain
  • Research Site
    Huelva, 21005, Spain
  • Research Site
    Jaén, 23007, Spain
  • Research Site
    Lleida, 25198, Spain
  • Research Site
    Madrid, 28041, Spain
  • Research Site
    Majadahonda, 28222, Spain
  • Research Site
    Murcia, 30120, Spain
  • Research Site
    Palma de Mallorca, 07010, Spain
  • Research Site
    Palma de Mallorca, 07198, Spain
  • Research Site
    Pamplona, 31008, Spain
  • Research Site
    Sabadell, 08208, Spain
  • Research Site
    Salamanca, 37007, Spain
  • Research Site
    Santiago de Compostela, 15706, Spain
  • Research Site
    Seville, 41009, Spain
  • Research Site
    Seville, 41013, Spain
  • Research Site
    Valencia, 46010, Spain
  • Research Site
    Valencia, 46026, Spain
  • Research Site
    Zaragoza, 50009, Spain
  • Research Site
    Ashington, NE63 9JJ, United Kingdom
  • Research Site
    Bridgend, CF31 1RQ, United Kingdom
  • Research Site
    Bristol, BS105NB, United Kingdom
  • Research Site
    Glasgow, G4 0SF, United Kingdom
  • Research Site
    Leicester, LE3 9QP, United Kingdom
  • Research Site
    Liverpool, L9 7AL, United Kingdom
  • Research Site
    Manchester, M13 9WL, United Kingdom
  • Research Site
    Newport, NP20 2UB, United Kingdom
  • Research Site
    Sheffield, S5 7AU, United Kingdom
09

References and documents

Publications

  • Kosiborod MN, Cherney DZI, Desai AS, Testani JM, Verma S, Chinnakondepalli K, Dolling D, Patel S, Dahl M, Eudicone JM, Friberg L, Ouwens M, Antunes MO, Connelly KA, Madrini V Jr, Kuthi L, Lala A, Lorenzo M, Guimaraes PO, Marcos MC, Merkely B, Nunez J, Squire I, Vaclavik J, Wranicz J, Petrie MC. Sodium Zirconium Cyclosilicate for Management of Hyperkalemia During Spironolactone Optimization in Patients With Heart Failure. J Am Coll Cardiol. 2025 Mar 18;85(10):971-984. doi: 10.1016/j.jacc.2024.11.014. Epub 2024 Nov 18. PubMed 39566872 ↗
  • Kosiborod MN, Cherney D, Connelly K, Desai AS, Guimaraes PO, Kuthi L, Lala A, Madrini V Jr, Merkely B, Villota JN, Squire I, Testani JM, Vaclavik J, Verma S, Wranicz J, Dahl M, Eudicone JM, Friberg L, Petrie MC. Sodium Zirconium Cyclosilicate in HFrEF and Hyperkalemia: REALIZE-K Design and Baseline Characteristics. JACC Heart Fail. 2024 Oct;12(10):1707-1716. doi: 10.1016/j.jchf.2024.05.003. Epub 2024 May 13. PubMed 38878009 ↗

Study documents

PDFs hosted by the registry, ClinicalTrials.gov.

Individual participant data

Plan to share: Yes — Qualified researchers can request access to anonymized individual patient-level data from AstraZeneca group of companies sponsored clinical trials via the request portal. All request will be evaluated as per the AZ disclosure commitment: https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure. Yes, indicates that AZ are accepting requests for IPD, but this does not mean all requests will be shared.

Supporting information: Study protocol, Statistical analysis plan

Time frame: AstraZeneca will meet or exceed data availability as per the commitments made to the EFPIA Pharma Data Sharing Principles. For details of our timelines, please rerefer to our disclosure commitment at https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure.

Access criteria: When a request has been approved AstraZeneca will provide access to the deidentified individual patient-level data in an approved sponsored tool . Signed Data Sharing Agreement (non-negotiable contract for data accessors) must be in place before accessing requested information. Additionally, all users will need to accept the terms and conditions of the SAS MSE to gain access. For additional details, please review the Disclosure Statements at https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure.

Data sharing details ↗ · astrazenecagroup-dt.pharmacm.com

10

Updates

Tracking since Sep 25, 2026
No changes since tracking began. The registry record was last updated on Jul 9, 2025, before this site started recording changes on Sep 25, 2026. Its history is on ClinicalTrials.gov ↗
11

Registry details

Key details

Study ID
NCT04676646
Lead sponsor
AstraZeneca
Responsible party
Sponsor
First posted
Dec 21, 2020
Start date
Mar 8, 2021
Primary completion
Jul 15, 2024
Completion
Jul 15, 2024
Results posted
Jul 9, 2025
Last update
Jul 9, 2025

Oversight

Data monitoring committee
Yes
FDA-regulated drug
Yes
FDA-regulated device
No
View the source record on ClinicalTrials.gov ↗

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Studies of the drug tested here: Sodium zirconium cyclosilicate

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