Hyperkalemia is characterized by elevated serum potassium, which increases a patient's risk of cardiac arrhythmia and sudden death. At particular risk are heart failure patients, especially those with an underlying chronic kidney disease being treated with aldosterone antagonists. Although these drugs have shown life-saving benefits in multiple large outcome studies, their use is limited by the occurrence or fear of hyperkalemia.

Professor Bertram Pitt from the Division of Cardiovascular Medicine, University of Michigan School of Medicine, USA, who was steering committee chairman of the PEARL-HF (Parallel Evaluation of RLY5016 in Heart Failure), said: "The PEARL-HF trial demonstrates that RLY5016 effectively and safely lowers serum potassium and prevents hyperkalemia in patients with heart failure or heart failure with underlying renal impairment, even those using renin-angiotensin-aldosterone system antagonists. Currently, the risk of hyperkalemia has limited the use of these RAAS inhibitors, which exposes patients to further cardiac risk. These trial data are therefore very significant."

PEARL-HF was a multicentre, randomized, double blind, placebo-controlled trial, designed to evaluate the efficacy, safety and tolerability of RLY5016 in the prevention of hyperkalemia in heart failure patients. The study tested a total of 104 patients over four weeks; 55 with a therapeutic dose of RLY5016 and 49 with placebo. Patients with a serum potassium level of 4.3-5.1 mEq/L and chronic kidney disease currently taking one or more heart-failure therapies, or patients with a documented history of hyperkalemia that led to the discontinuation of a heart failure therapy, were also given a daily 25-50 mg dose of the aldosterone antagonist spironolactone.

The primary endpoint was the measured change from baseline in serum potassium. Efficacy was also evaluated by the proportion of patients with hyperkalemia and the proportion of patients whose spironolactone dose could be increased.

Results showed that RLY5016 significantly reduced the incidence of hyperkalemia compared to the placebo (7% vs. 25%, p=0.015). It also increased the proportion of patients whose spironolactone dose could be increased (91 percent vs. 74 percent, p=0.019). RLY5016 seemed well tolerated by patients, with a withdrawal rate from the study due to an adverse event of 7% (compared to 6% with the placebo), and there were no drug-related serious adverse events.