Dialysis: add-on tenapanor cuts serum phosphate in phase 3 trial

  • Ardelyx

  • International Clinical Digest
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  • Adding tenapanor to phosphate binders significantly reduced serum phosphorus in a phase 3 trial of dialysis-dependent patients with refractory hyperphosphataemia, according to a company news release.

Why this matters

  • Minimally absorbed tenapanor reduces phosphorus uptake by inhibiting intestinal sodium/hydrogen exchanger 3 (NHE3).

Study design

  • AMPLIFY double-blind, randomised trial of 236 dialysis-dependent patients with hyperphosphataemia (5.5-10 [mean, 6.8] mg/dL) despite a stable phosphate binder regimen.
  • Participants received add-on placebo or tenapanor (30 mg twice daily, titrated based on need and tolerance).
  • Funding: Ardelyx.

Key results

  • Primary endpoint: mean reduction in serum phosphorus at 4 weeks was significantly greater with tenapanor vs placebo (−0.84 vs −0.19 mg/dL; P=.0004).
    • Weekly decreases ranged from −0.84 to −1.21 mg/dL (P≤.0004).
  • Secondary endpoints:
    • 49.1% of tenapanor-treated patients achieved serum phosphorus
    • FGF23 levels, associated with cardiovascular risk, were reduced by 22%-24% with tenapanor vs placebo (P≤.0027).
  • Discontinuation rates were 4.3% with tenapanor vs 2.5% with placebo.
    • Discontinuation for loose stools/diarrhea: 2.6% vs 0.8%.
  • Loose stools/diarrhoea were the most common adverse event (placebo-adjusted rate, 36%).
    • Cases occurred primarily in the first 5 days and were transient in nature.


  • The source of these data is a news release issued by Ardelyx, Inc. of Fremont, California. Results of the AMPLIFY study have not been published in a peer-reviewed journal.

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