A Two-Part, Single-Blind, Phase 3 Study Evaluating the Efficacy and Safety of Patiromer for the Treatment of Hyperkalemia (OPAL)

The purpose of this study was to evaluate the efficacy and safety of patiromer (investigational drug) in the treatment of hyperkalemia (high serum potassium). The study also evaluated the effect of withdrawing patiromer treatment and assessed whether chronic treatment with patiromer prevented the recurrence of hyperkalemia. The safety of patiromer treatment was also evaluated.

There were two parts in the study, Part A and Part B. Part A was an assessment of 4 weeks of dosing with patiromer in the treatment of hyperkalemia; Part B was a randomized, placebo-controlled, 8-week assessment of the withdrawal of patiromer in participants with a baseline serum potassium at the beginning of Part A ≥ 5.5 mEq/L who responded to the 4 weeks of treatment with patiromer during Part A. All participants received patiromer during Part A; Part B participants were randomized to continue patiromer or switch to placebo. Total study participation was up to 14 weeks (including up to 2 weeks of follow up). The dose of patiromer could be titrated based on participant's serum potassium response.