Roger SD, Spinowitz BS, Lerma EV, et al. - Whether sodium zirconium cyclosilicate (SZC; formerly ZS-9), selective potassium (K⁺) binder for the treatment of hyperkalemia, has efficacy and safety when evaluated for ≤ 11 months, was tested in this open-label extension (OLE) of the ­HARMONIZE study performed on patients from HARMONIZE with point-of-care device i-STAT K⁺ 3.5–6.2 mmol/L treated with once-daily SZC 5–10 g for ≤ 337 days. The primary endpoint was the achievement of mean serum K⁺ ≤ 5.1 mmol/L and the secondary endpoint was an achievement of mean serum K⁺ ≤ 5.5 mmol/L. Overall 123 patients were included in the extension (mean serum K⁺ 4.8 mmol/L), of these, 79 (64.2%) completed the study. The median daily dose of SZC was 10 g (range 2.5–15 g). The attainment of the primary endpoint was reported in 88.3% of patients and that of the secondary endpoint in 100%. The good tolerability of SZC, with no new safety concerns, was revealed. During ongoing SZC treatment, the mean serum K⁺ within the normokalemic range was maintained for ≤ 11 months in most patients studied in the HARMONIZE OLE.