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Sodium zirconium cyclosilicate successfully increased the rate of mineralocorticoid receptor antagonist (MRA) treatment optimization among patients with heart failure with reduced ejection fraction (HFrEF) and established hyperkalemia or high risk for hyperkalemia. Whether this result will have a positive influence on clinical outcomes remains to be seen.

“Although MRAs reduce the risk for morbidity and mortality in patients with HFrEF, they are underused, partially because of the risk for hyperkalemia,” explained Prof. Mikhail Kosiborod, MD, from the University of Missouri, in Missouri¹. To overcome this issue, the REALIZE-K trial (NCT04676646) tested whether sodium zirconium cyclosilicate has the potential to enable the optimization of the MRA spironolactone in the population. The study randomly assigned 203 participants with HFrEF and hyperkalemia or at high risk for hyperkalemia 1:1 to sodium zirconium cyclosilicate plus spironolactone or a placebo plus spironolactone. The primary endpoint was the percentage of participants with an optimal treatment response, defined as normokalemia, a spironolactone dose of at least 25 mg per day, and no use of rescue medication.

At 6 months, 71.2% of the participants in the experimental arm had achieved an optimal treatment response compared with 35.7% of those in the placebo arm (OR 4.45; 95% CI 2.89–6.86; P<0.001). However, the authors did not see a difference in KCCQ-CSS between the study groups at 6 months (difference -1.01 point; 95% CI -6.64 to 4.63; P=0.72).

Serious AE rates were comparable (23% vs 22%), albeit there were more cases of cardiac failure in the experimental arm (12% vs 4%). “All events of cardiac failure in the experimental arm were resolved or resolving, at the end of the study,” added Dr. Kosiborod.

“Although sodium zirconium cyclosilicate effectively enabled optimization of MRA use in patients with HFrEF and hyperkalemia, we did not see an impact on clinical outcomes,” concluded Dr. Kosiborod.

Medical writing support was provided by Robert van den Heuvel.
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