Relypsa Reports Strong Part B Results

Relypsa, Inc. has reported positive results on both the primary and secondary efficacy endpoints in a trial of patiromer for the treatment of hyperkalemia. The results cover Part B, the placebo-controlled randomized withdrawal portion of its two-part Phase III trial.

The results demonstrate that, after having treated hyperkalemia and controlled serum potassium in the treatment phase (Part A) of the trial, hyperkalemia recurred at any time during Part B in significantly more subjects randomized to placebo than in subjects who continued to receive patiromer, supporting chronic dosing in order to maintain serum potassium levels in the normal range. Taken together with the positive results from the previously reported Part A data, the Part B data indicate that patiromer is an effective treatment for hyperkalemia, the company reports.

The two-part trial was conducted under an agreed upon special protocol assessment (SPA) with the FDA. Part A, in which all participants received patiromer, was a single-blind, single-arm trial in 243 subjects with hyperkalemia and chronic kidney disease (CKD) who were also being treated with renin angiotensin aldosterone system (RAAS) inhibitor medications. Part A met both the primary and secondary efficacy endpoints, with results that were both statistically significant and clinically meaningful.

Part B was designed to provide additional evidence that chronic administration with patiromer maintains control of serum potassium levels and that once patiromer treatment is withdrawn, hyperkalemia recurs. Subjects from Part A whose baseline serum potassium level was at least 5.5 mEq/L at enrollment and whose serum potassium level was controlled at week 4 were eligible for Part B. These subjects were then randomized into two groups: one to continue on patiromer and the second to receive placebo for an additional eight weeks.

The company expects to report results within the next few weeks from its 52-week phase IIb clinical trial, known as AMETHYST-DN, which evaluated the safety and efficacy of patiromer in reducing hyperkalemia in 306 patients with CKD who were being treated with RAAS inhibitors.