HARMONIZE Asia: A Phase III Randomized Study to Investigate the Efficacy and Safety of Sodium Zirconium Cyclosilicate in Patients with Hyperkalemia in China

Purpose Sodium zirconium cyclosilicate (SZC) is an oral potassium (K+)-lowering therapy for adults with hyperkalemia. HARMONIZE Asia (ClinicalTrials.gov identifier: NCT03528681) evaluated the efficacy and safety of SZC in Chinese patients with hyperkalemia. Methods This Phase III, randomized, double-blind, placebo-controlled study recruited patients with serum K+ (sK+) ≥5.1 mmol/L at 35 sites in China. Patients received SZC 10 g three times daily (TID) for 24 or 48 hours during an open-label initial phase (OLP). Those patients achieving normokalemia (sK+ 3.5–5.0 mmol/L inclusive) entered a 28-day randomized (2:2:1) treatment phase (RTP) and received SZC 5 g, SZC 10 g, or placebo once daily. The primary endpoint was mean sK+ during RTP Days 8 to 29. Secondary endpoints included mean change in sK+ during the OLP, the proportion of patients who achieved normokalemia at the end of the OLP, the proportion that maintained normokalemia during the RTP, and time to recurrence of hyperkalemia. Findings In total, 270 patients received SZC 10 g TID during the OLP; 256 (94.8%) completed the OLP. During the OLP, mean sK+ decreased by 1.1 mmol/L from baseline (5.9 mmol/L; P < 0.001) and 87.4% of patients achieved normokalemia. During the RTP, SZC 5 g and 10 g reduced mean sK+ versus placebo in a dose-dependent manner (each P < 0.001); least-squares means (95% confidence interval [CI]) sK+ were 4.9 mmol/L (4.7, 5.0), 4.4 mmol/L (4.3, 4.6), and 5.2 mmol/L (5.1, 5.4) for SZC 5 g, 10 g, and placebo, respectively. At RTP end, the proportions of patients who maintained normokalemia were 58.8% (SZC 5 g; odds ratio vs placebo, 2.5 [95% CI: 1.1, 6.1; P = 0.035]), 76.5% (SZC 10 g; odds ratio vs placebo, 6.3 [95% CI: 2.6, 15.3; P < 0.001]), and 36.8% for placebo. Risk of recurrent hyperkalemia was reduced by 61.0% and 84.0% with SZC 5 g and SZC 10 g, respectively, versus placebo (each P < 0.001). During the RTP, the incidence of adverse events was numerically higher with SZC 5 g (50.0% of patients) and 10 g (44.0%) versus placebo (36.0%); driven primarily by peripheral edema and constipation. Implications Both SZC doses demonstrated clinically relevant and statistically significant, dose-dependent efficacy in managing sK+ levels in Chinese patients with hyperkalemia, compared with placebo. SZC tolerability was broadly aligned with the known safety profile of SZC.