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New Potassium Binder Shows Promise in Hyperkalemia Study

Phase III program planned for later this year

Positive results have been reported from an open-label clinical study evaluating the pharmacodynamic activity of RDX022 (Ardelyx, Inc.) in healthy adult volunteers. The study demonstrated that RDX022, an investigational potassium binder for the treatment of hyperkalemia, effectively binds potassium in the gastrointestinal tract, supporting plans to proceed with a phase III clinical program, which is expected to begin in the second half of 2016.

In the study, four cohorts participated in a two-day treatment-free baseline period followed by a four-day treatment period. Each cohort consisted of 12 subjects who received RDX022 and three subjects who received a similar dose of sodium polystyrene sulfonate (SPS), for a total of 60 subjects.

RDX022 was administered at 4.6 g twice daily (9.2 g/day), 6.9 g twice daily (13.8 g/day), 4.6 g three times daily (13.8 g/day), and 9.2 g three times daily (27.5 g/day), and resulted in a mean increase of fecal potassium from baseline of 888 mg/day, 1,791 mg/day, 1,408 mg/day, and 1,670 mg/day, respectively. RDX022 was generally well tolerated at all doses and demonstrated results comparable with those observed with SPS. Other fecal electrolytes were monitored during the study and no unexpected changes were observed; in particular, fecal magnesium remained unchanged from baseline.

RDX022 is an investigational oral, nonabsorbed, potassium-binding polymer based on polystyrene sulfonate (Kayexalate, Concordia Pharmaceuticals), a well-characterized polymer. In a randomized, crossover study conducted to evaluate various oral formulations of RDX022 in healthy subjects, RDX022 consistently outperformed SPS in all aspects of the taste assessments, including mouth feel, texture, and flavor.

In the second half of 2016, Ardelyx, Inc., expects to initiate a phase III clinical study in patients with chronic kidney disease, with or without heart failure, who are taking drugs that inhibit the renin–angiotensin–aldosterone system and who have been diagnosed with hyperkalemia, a common adverse effect that occurs in patients taking those drugs.

Source: Ardelyx, Inc.; January 5, 2016.

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