Study Background and Disease Burden
Patients with end-stage kidney disease undergoing maintenance hemodialysis frequently suffer from predialysis hyperkalemia, a condition defined by elevated serum potassium levels, typically 5.5 mmol/l or higher before dialysis sessions. Hyperkalemia is clinically significant due to its strong association with cardiac arrhythmias and increased risk of sudden cardiac death, stroke, and other cardiovascular complications. Managing serum potassium in hemodialysis patients is challenging because of fluctuating potassium levels related to dietary intake, residual kidney function, and dialytic clearance. Sodium zirconium cyclosilicate (SZC) is a novel oral potassium binder with the potential to maintain normokalemia safely and effectively between dialysis sessions. The DIALIZE-Outcomes trial was designed to evaluate whether SZC’s potassium-lowering effect could translate into improved arrhythmia-related cardiovascular outcomes in this vulnerable population, addressing a major unmet medical need.
Study Design
The DIALIZE-Outcomes trial was a randomized, double-blind, placebo-controlled study including 2690 adult patients undergoing thrice-weekly maintenance hemodialysis who had predialysis hyperkalemia (serum potassium ≥5.5 mmol/l). Participants were randomized 1:1 to receive either oral SZC or placebo. SZC was initiated at 5 grams once daily on nondialysis days and titrated weekly over four weeks, adjusting between 0 and 15 grams to target normokalemia (serum potassium 4.0–5.0 mmol/l). The treatment period extended to 12 months or until the occurrence of a primary outcome event or study discontinuation.
The primary endpoint was a composite of sudden cardiac death, stroke, or arrhythmia-related events leading to hospitalization, medical intervention, or emergency department visits. Secondary endpoints included the individual components of the composite cardiovascular outcomes and outcomes related to potassium control, such as achievement and maintenance of normokalemia. Safety, including adverse events and the incidence of hypokalemia, was monitored throughout the trial.
Key Findings
The trial enrollment of 2690 participants supported robust statistical power, but the study was terminated early due to unexpectedly low event rates—approximately 33% of the planned number of primary outcome events—and a high rate of medication discontinuation, which diminished the strength and generalizability of the results.
Efficacy on Primary and Secondary Outcomes: The data revealed no statistically significant difference between SZC and placebo groups in relation to the primary composite endpoint. Specifically, 8.8% (119 patients) in the SZC group experienced the primary composite events compared to 8.9% (119 patients) in the placebo group (hazard ratio 0.98, 95% confidence interval 0.76–1.26). Similarly, individual cardiovascular outcomes showed no significant treatment effect.
Potassium Control: SZC demonstrated significantly superior efficacy in maintaining normokalemia at 12 months. Seventy-four percent (495 patients) of the SZC-treated group achieved normokalemia versus 47% (293 patients) in the placebo arm, with an odds ratio of 3.36 (95% confidence interval 2.64–4.26), underscoring SZC’s potassium-lowering potency.
Safety Profile: Serious adverse events occurred at a comparable frequency in both groups (SZC 38.6%, placebo 37.6%). Hypokalemia was infrequent but more common in the SZC group (3.0%) compared to placebo (1.4%). This safety profile is consistent with SZC’s mechanism of selectively binding potassium in the gastrointestinal tract.
Expert Commentary
The DIALIZE-Outcomes trial offers valuable insights though it did not demonstrate a cardiovascular benefit despite effective potassium control. This outcome highlights the complex pathophysiology of cardiovascular risk in hemodialysis patients, suggesting that hyperkalemia is only one of numerous modifiable and non-modifiable risk factors. Early trial termination and low event numbers limit definitive conclusions; hence, the possibility of a type II error exists, where a true effect might have gone undetected.
Also, the high discontinuation rate may reflect challenges in adherence or tolerability in the chronic hemodialysis population, an important consideration for clinical practice. Current guidelines recommend potassium binders primarily to achieve biochemical control; however, translating biochemical improvements to hard clinical endpoints remains uncertain.
Future research should explore integrated strategies combining potassium management with multifaceted cardiovascular interventions. Additionally, mechanistic studies could elucidate whether and how serum potassium fluctuations contribute synergistically with other factors to arrhythmic risk.
Conclusion
The randomized DIALIZE-Outcomes trial demonstrated that sodium zirconium cyclosilicate effectively maintains normokalemia in patients on maintenance hemodialysis with predialysis hyperkalemia, yet it did not reduce the incidence of arrhythmia-related cardiovascular events. This disconnect underscores the complexity of cardiovascular risk management in end-stage kidney disease and points to the necessity of comprehensive approaches beyond potassium lowering alone.
Clinicians should consider SZC’s role as a valuable tool for potassium control while continuing vigilance for cardiovascular events through established preventive measures. The data call for ongoing research to identify strategies that translate potassium regulation into tangible cardiovascular benefits for this high-risk population.
References
Fishbane S, Dember LM, Jadoul M, Kovesdy CP, Guzman N, Kordzakhia G, Lisovskaja V, Sekar P, Wessman P, Al-Shurbaji A, Herzog CA. The randomized DIALIZE-Outcomes trial evaluated sodium zirconium cyclosilicate in hemodialysis. Kidney Int. 2025 Oct;108(4):686-694. doi: 10.1016/j.kint.2025.06.016. Epub 2025 Jul 4. PMID: 40618849.
We also referenced current KDIGO guidelines and prevailing literature on hyperkalemia management in dialysis populations for contextual understanding and interpretation of the trial results.
