Ardelyx asserts kidney drug is back on track

Dive Brief:

  • After years of setbacks, Ardelyx on Feb. 15 released the latest Phase 3 clinical results for its lead candidate  tenapanor, a kidney disease drug, saying it met the primary endpoint for treating hyperphosphatemia (a disorder causing an elevated level of serum phosphorus in the blood) in patients with end-stage renal disease who are on dialysis.
  • Tenapanor  also was generally well-tolerated by the 219 patients in the placebo-controlled study, Ardelyx said, though diarrhea – which felled an earlier trial of the drug for a different population – was self-reported in 39% of patients in the eight-week trial period. And 7.8% of patients discontinued treatment due to diarrhea.
  • Former partners AstraZeneca and Sanofi both exited work on tenapanor’s development after previous clinical trial failures.

Dive Insight:

In the just-reported trial, 33% of patients had a reduction in serum phosphorus of greater than 3 mg/dL, Fremont, Calif.-based Ardelyx said. Buoyed by these results, which initially boosted its shares by about 9% Feb. 15, Ardelyx said it will begin a second, longer Phase 3 trial of tenapanor for treating hyperphosphatemia in ESRD patients on dialysis by mid-2017.

The company added that details on the just-completed Phase 3 trial will be presented at the American Society of Nephrology Kidney Week in New Orleans this fall.

Unlike other therapies, Ardelyx touted tenapanor as offering better results using fewer oral doses than binder treatments.

"My patients are often required to take more than 19 pills per day, of which, nearly half are phosphate binders. The efficacy of tenapanor with only a few small pills, combined with its GI tolerability, has the potential to change the way in which we treat our patients in the future," said trial investigator Geoff Block, the director of clinical research at Colorado Kidney Care.

But skeptics remain. One critic, for example, asserted that Ardelyx has "selectively reported results from its latest late-stage tenapanor study." He said Ardelyx restricted its analysis to responders (patients who showed at least a 1.2 mg/dL drop in serum phosphate after the initial eight-week treatment period), which showed a statistically significant difference in the pooled treatment group versus placebo in the four-week withdrawal period. But he said these results imply that 51% of the participants failed to respond during the eight-week initial treatment period.

In 2015, Ardelyx’s Phase 2B study found a higher-than-acceptable rate of diarrhea from tenapanor in hyperphosphatemic patients with chronic kidney disease on hemodialysis, though the drug did reduce serum phosphate levels.

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