Relypsa announced positive top-line results for Part A of a two-part pivotal Phase 3 clinical trial evaluating patiromer for the treatment of hyperkalemia. Patiromer is a non-absorbed, potassium-binding polymer designed for the binding and removal of potassium from the GI tract, particularly the colon. It has been formulated as a dry, odorless powder for suspension in small amounts of water.

Part A is a single-blind, single-arm trial in 243 patients with hyperkalemia and chronic kidney disease (CKD) who received patiromer and were also being treated with renin angiotensin aldosterone system (RAAS) inhibitor medications. The primary endpoint of Part A was the change in serum potassium from Part A baseline to Part A week 4. 

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Part B, the placebo controlled randomized withdrawal part of the study, was designed to provide additional evidence of the efficacy of patiromer in treating hyperkalemia and to assess the need for chronic dosing. Patients from Part A whose baseline serum potassium level was greater than or equal to 5.5 mEq/L at enrollment and whose serum potassium level was controlled at week 4 were eligible for Part B. These patients were then randomized into two groups; one to continue on patiromer, and a second to receive placebo for an additional eight weeks. The primary endpoint for Part B is the between group difference in the change in serum potassium from Part B baseline to Part B week 4.

The primary endpoint for Part A was the change in serum potassium from baseline to week 4, which showed a statistically significant reduction of 1.01 mEq/L (P<0.001). 

The company expects to report primary endpoint results from Part B of this trial in the fourth quarter of 2013.

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