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

Eur J Heart Fail. 2015 Oct;17(10):1050-6. doi: 10.1002/ejhf.300. Epub 2015 Jun 16.


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.

Keywords: RAAS; ZS-9; heart failure; hyperkalaemia.

Publication types

  • Clinical Trial, Phase III
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Double-Blind Method
  • Heart Failure / blood*
  • Humans
  • Hyperkalemia / blood
  • Hyperkalemia / drug therapy*
  • Potassium / blood*
  • Silicates / therapeutic use*


  • Silicates
  • sodium zirconium cyclosilicate
  • Potassium