Relypsa Offers Data Published in New England Journal of Medicine for Pivotal Phase 3 Program of Patiromer FOS

Relypsa, Inc. RLYP, a biopharmaceutical company, announced that results from the pivotal Phase 3 program of the company's lead product candidate, Patiromer for Oral Suspension (Patiromer FOS), were published today in New England Journal of Medicine. The program was conducted under Special Protocol Assessment to evaluate the safety and efficacy of Patiromer FOS for the treatment of hyperkalemia (HK) in chronic kidney disease (CKD) patients on renin-angiotensin-aldosterone system (RAAS) inhibitor therapy. Hyperkalemia is a serious condition defined as abnormally elevated potassium levels in the blood. Lead author, Matthew R. Weir, M.D. Professor and Director, Division of Nephrology, University of Maryland School of Medicine, commented, "Hyperkalemia remains our primary concern in patients on kidney- and cardio-protective RAAS therapy. We are pleased to have these exciting results for Patiromer FOS published in New England Journal of Medicine. The rigor of the Phase 3 program gives me confidence in the clinical evidence which I believe sufficiently supports the company's application to gain approval of Patiromer FOS as a treatment for hyperkalemia." Last month, the company announced that it had submitted a New Drug Application to the FDA for Patiromer FOS for the treatment of HK. If approved, Patiromer FOS is positioned to be the first new treatment for HK in over 50 years and the first ever studied long-term as a therapy for up to 12 months. All endpoints were met in the two-part Phase 3 program consisting of a treatment phase, which was designed to assess the ability of Patiromer FOS to correct hyperkalemia, and a placebo-controlled randomized maintenance phase designed to evaluate the effect of continued treatment with Patiromer FOS on potassium control and ability of patients to continue RAAS inhibitor therapy compared to placebo. In the treatment phase, among 237 evaluable patients receiving Patiromer FOS, the mean change in the serum potassium level was −1.01 mEq/L (P<0.001). At week 4, 76% (95% confidence interval) of the patients were within the target potassium level (3.8 to < 5.1 mEq/L). Subsequently, 107 patients were randomly assigned to Patiromer FOS (55 patients) or placebo (52 patients) for the maintenance phase. Of note during this phase, the Patiromer FOS group had no change in median potassium from baseline, but in the placebo group, median serum potassium increased (P<0.001). Further, a recurrence of hyperkalemia (serum potassium level ≥ 5.5 mEq/L) occurred in 60% of the patients in the placebo group as compared with 15% in the Patiromer FOS group through week 8 (P<0.001). In a pre-specified analysis, 44% patients in the placebo group as compared with 94% in the Patiromer FOS group were still receiving RAAS inhibitor therapy at the end of the study.  Mild-to-moderate constipation was the most common adverse event (11% of the patients in the treatment phase and 4% in the Patiromer FOS group in the maintenance phase). Importantly, there was no evidence of drug-induced edema or urinary tract infections. The hypokalemia rate over the 4 week treatment period was low (3%) and no patients in the maintenance phase experienced hypokalemia. No serious drug-related adverse events were reported in either the treatment or maintenance phases.  Phase 3 Patiromer FOS Program Background The two-part Phase 3 clinical program was conducted under an agreed upon special protocol assessment (SPA) with the U.S. Food and Drug Administration (FDA).  Part A, the treatment phase in which all participants received Patiromer FOS, was a single-blind, single-arm trial in 243 patients with hyperkalemia and CKD who were also being treated with RAAS inhibitor medications.  The FDA-agreed upon primary endpoint of Part A under the SPA was the change in serum potassium from Part A baseline to Part A Week 4.  The secondary endpoint was the proportion of patients with a serum potassium level in the target range of 3.8 to < 5.1 mEq/L at Part A Week 4. Part B, the placebo-controlled randomized maintenance phase part of the trial, was designed to provide additional evidence of the efficacy of Patiromer FOS 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 Part A Week 4 were eligible for Part B.  These patients were then randomized into two groups; one to continue on Patiromer FOS for an additional eight weeks, and a second to receive placebo for eight weeks.  The primary endpoint for Part B was the between group difference in the change in serum potassium from Part B baseline to Week 4 of Part B or to an earlier time point when the subject first has serum potassium less than 3.8 mEq/L or greater than or equal to 5.5 mEq/L.