Roger SD, Spinowitz BS, Lerma EV, et al. - Sodium zirconium cyclosilicate (SZC; formerly ZS-9), selective potassium (K⁺) binder for the treatment of hyperkalemia, was assessed for its safety as well as effectiveness for ≤ 11 months in this open-label extension (OLE) of the ­HARMONIZE study. For ≤ 337 days, once-daily SZC 5–10 g was administered to patients from HARMONIZE with point-of-care device i-STAT K⁺ 3.5–6.2 mmol/L. The primary endpoint was the achievement of mean serum K⁺ ≤ 5.1 mmol/L and the secondary endpoint was achievement of mean serum K⁺ ≤ 5.5 mmol/L. The study was completed by 79 (64.2%) of 123 patients who joined the extension (mean serum K⁺ 4.8 mmol/L). The median daily dose of SZC was 10 g (range 2.5–15 g). The achievement of the primary endpoint in 88.3% of patients and of secondary endpoint in 100% was documented. Findings revealed good tolerability of SZC with no new safety concerns. During ongoing SZC treatment in the HARMONIZE OLE, mean serum K⁺ was maintained within the normokalemic range for ≤ 11 months in most cases.