Correction of serum potassium with sodium zirconium cyclosilicate in Japanese patients with hyperkalemia: a randomized, dose–response, phase 2/3 study

Background Sodium zirconium cyclosilicate (SZC) is an oral potassium binder approved to treat hyperkalemia in adults in a number of countries, including Japan. Methods This phase 2/3, randomized, double-blind, placebo-controlled, dose–response study (ClinicalTrials.gov: NCT03127644) was designed to determine the efficacy and safety of SZC in Japanese adults with hyperkalemia. Patients with serum potassium (sK + ) concentrations ≥ 5.1– ≤ 6.5 mmol/L were randomized 1:1:1 to SZC 5 g, SZC 10 g, or placebo three times daily for 48 h (six doses total). The primary efficacy endpoint was the exponential rate of change in sK + over 48 h. The proportion of patients with normokalemia (sK + 3.5–5.0 mmol/L) at 48 h and adverse events (AEs) were also evaluated. Results Overall, 103 patients (mean age, 73.2 years; range 50–89 years) received SZC 5 g ( n = 34), SZC 10 g ( n = 36), or placebo ( n = 33). The exponential rate of sK + change from 0 to 48 h versus placebo was − 0.00261 (SZC 5 g) and – 0.00496 (SZC 10 g; both P < 0.0001). At 48 h, the proportions of patients with normokalemia were 85.3%, 91.7%, and 15.2% with SZC 5 g, SZC 10 g, and placebo, respectively. No serious AEs were reported. Hypokalemia (sK + < 3.5 mmol/L) occurred in two patients in the SZC 10 g group; normokalemia was re-established within 6 days and no treatment-related AEs were reported. Conclusion SZC is effective and well tolerated in Japanese patients with hyperkalemia.