Acid Base, Ion Disorders, Lithisasis

Introduction and Aims: Hyperkalaemia is a risk factor for mortality in patients with cardiovascular disease and chronic kidney disease (CKD) (Goyal, 2012; Torlen, 2012) and limits use of renin-angiotensin-aldosterone system inhibitors (RAASi) in these patients. Sodium (or calcium) polystyrene sulfonate (SPS/CPS) has uncertain efficacy and has been associated with substantial adverse events, as well as poor gastrointestinal tolerability, and hence is suboptimal for acute use and unsuitable for chronic use (Harel, 2013; Sterns, 2010). Therefore, there is a need for a hyperkalaemia treatment that rapidly reduces serum potassium (K+) and is safe and well tolerated in these patients. ZS-9, a nonabsorbed cation exchanger designed to specifically entrap excess K +, significantly reduced K+ vs placebo over 48 hr with excellent tolerability in patients with CKD (Ash, 2013). We report acute-phase efficacy in a Phase 3 trial of ZS-9 in patients with hyperkalemia. Methods: Patients (N=753) with serum K+ 5.0-6.5 mmol/L were randomised (1:1:1:1:1) to ZS-9 (1.25g, 2.5g, 5g or 10g) or placebo given three times daily (TID) with meals for 48 hr (acute phase), after which those with K+ ≤4.9 mmol/L (n=542) were re-randomised to ZS-9 or placebo once daily for Day 3-15. Serum K+ was measured at baseline and at predefined intervals, including 1, 4, 24, and 48 hr after the first dose. The acute-phase primary efficacy endpoint was the rate of K+ change over the first 48 hr, using longitudinal modeling to account for all post-baseline data. Results:Mean K+ at baseline was 5.3 mmol/L. Substantial percentages of patients had CKD (60%), a history of heart failure (40%), or diabetes (60%) or were on RAASi therapy (67%). ZS-9 demonstrated significant dose-dependent reductions in K+; the acute-phase primary efficacy endpoint was met for ZS-9 2.5g (p=0.0009), 5g (p<0.0001) and 10g TID (p<0.0001; Fig. 1). There was a significant decrease in K+ by -0.11 mmol/L with ZS-9 10g vs an increase of +0.01 mmol/L with placebo (p=0.009) 1 hr after the first dose. At 48 hr K+ fell by -0.73 mmol/L with 10g TID vs -0.25 mmol/L with placebo (p<0.001); other significant reductions vs placebo are shown in Fig 2. Rates of all adverse events (AEs) and gastrointestinal AEs were not significantly different in the ZS-9 and placebo groups. Conclusions: ZS-9 produced significant dose-dependent reductions in K+ when given TID for 48 hr, with an AE profile similar to placebo. The significant reduction in serum K+ 1 hr after the first ZS-9 10g dose further suggests that ZS-9 is effective in removing K+ from the small intestine fluid, where it is in equilibrium with blood levels. ZS-9 may address an important unmet clinical need by rapidly correcting hyperkalaemia in high-risk patients, many of whom require RAASi for end-organ protection. SP321 PHASE 3, MULTICENTER, RANDOMISED, DOUBLE-BLIND, PLACEBO-CONTROLLED TRIALOF ZS-9: SUBGROUP ANALYSIS STRATIFIED BY BASELINE SERUM POTASSIUM LEVELS