Efficacy and Safety of Sodium Zirconium Cyclosilicate for Treatment of Hyperkalemia: An 11-Month Open-Label Extension of HARMONIZE

Background: Sodium zirconium cyclosilicate (SZC; formerly ZS-9) is a selective potassium (K + ) binder for treatment of hyperkalemia. An open-label extension (OLE) of the ­HARMONIZE study evaluated efficacy and safety of SZC for ≤11 months. Methods: Patients from HARMONIZE with point-of-care device i-STAT K + 3.5–6.2 mmol/L received once-daily SZC 5–10 g for ≤337 days. End points included achievement of mean serum K + ≤5.1 mmol/L (primary) or ≤5.5 mmol/L (secondary). Results: Of 123 patients who entered the extension (mean serum K + 4.8 mmol/L), 79 (64.2%) completed the study. The median daily dose of SZC was 10 g (range 2.5–15 g). The primary end point was achieved by 88.3% of patients, and 100% achieved the secondary end point. SZC was well tolerated with no new safety concerns. Conclusion: In the HARMONIZE OLE, most patients maintained mean serum K + within the normokalemic range for ≤11 months during ongoing SZC treatment.