A Study to Evaluate the Effect of Sodium Zirconium Cyclosilicate on Chronic Kidney Disease (CKD) Progression in Participants With CKD and Hyperkalaemia or at Risk of Hyperkalaemia

This is a Phase 3, international, randomised withdrawal, double-blind, parallel-group, placebo-controlled study, to evaluate the effect of SZC as adjunct to RAASi therapy (lisinopril or valsartan) in slowing CKD progression in participants with CKD and hyperkalaemia or at risk of hyperkalaemia.

Specifically, the study will include participants with hyperkalaemia (S-K \> 5.0 to ≤ 6.5 mmol/L by central laboratory) who are on adequate or limited RAASi therapy due to hyperkalaemia, and participants with normokalaemia (S-K ≥ 3.5 to ≤ 5.0 mmol/L by central laboratory) who are on limited RAASi therapy due to high risk of hyperkalaemia. High risk of hyperkalaemia is defined as (1) participants with a previous medical history or record of hyperkalaemia within the prior 24 months who are on limited RAASi therapy despite indication in CKD; (2) participants in whom RAASi therapy is indicated in CKD but are on limited RAASi therapy and have S-K ≥ 4.7 to ≤ 5.0 mmol/L; and (3) participants in whom RAASi therapy has been discontinued or reduced to suboptimal doses because of hyperkalaemia.

A participant is expected to be in the study for approximately 28 months, which includes up to 13 days for the screening period, 27 months for the intervention period, and 1 week for follow-up. The 27-month intervention period of the study consists of 3 phases, an initiation phase (up to 72 hours), a run-in phase (3 months/up to Day 90), and a maintenance phase (24 months/104 weeks).

The initial dose of SZC will be administered to participants during the initiation phase. No changes will be made to the ACEi or ARB therapy at this stage. As soon as possible after the participant is confirmed to be normokalaemic at the end of the initiation phase, the participant will enter the run-in phase. Participants will receive open-label SZC and either lisinopril or valsartan. The aim of the run-in phase is to increase ACEi or ARB therapy stepwise to their maximum doses. After a 3-month run-in period for RAASi dose optimization while on SZC, participants will be randomized to SZC or placebo and followed during the subsequent 24 months of maintenance phase for efficacy and safety assessments.