Phase III trial of RDZ 5792 (tenapanor) meets endpoint in treatment for hyperphosphatemia- Ardelyx

Ardelyx has reported that the Phase III clinical trial evaluating the efficacy and safety of RDZ 5792 (tenapanor) as a treatment for hyperphosphatemia in patients with end-stage renal disease (ESRD) who are on dialysis met its primary endpoint and was generally well-tolerated. The responder population (n=80 out of 164) had a mean reduction in serum phosphorus from baseline to the end of the eight-week treatment period of 2.56 mg/dL, with a reduction of up to 5.7 mg/dL. Notably, in this group, 33 percent of patients had a reduction in serum phosphorus of greater than 3 mg/dL. The study demonstrated a statistically significant difference in serum phosphorus levels from the end of the eight-week treatment period to the end of the four-week randomized withdrawal period between the tenapanor-treated group and the placebo-treated group in the responder patient population (mean -1.01 mg/dL, median of -1.3 mg/dL) and met its primary endpoint (95% CI -1.44, -0.21; LSmean -0.82 mg/dL; p=0.01). Only 7.8 percent of patients discontinued treatment due to GI side effects.

Tenapanor was well-tolerated in the trial. In the eight-week treatment period, the only adverse event that affected more than five percent of patients treated with tenapanor was diarrhea (39 percent), a patient-reported side effect of loosened stool or increased frequency in bowel movements regardless of magnitude. In the four-week randomized withdrawal period, there was a diarrhea rate of 1.2 percent for patients treated with tenapanor compared with 2.4 percent on placebo.