First-in-class phosphate absorption inhibitor approved by FDA

The US Food and Drug Administration (FDA) has approved XPHOZAH ^® (tenapanor), the first and only phosphate absorption inhibitor.

Ardelyx’s first-in-class oral treatment is indicated to reduce serum phosphorus in adults with chronic kidney disease (CKD) on dialysis as add-on therapy in patients who have an inadequate response to phosphate binders or who are intolerant to phosphate binder therapy.

About the approved phosphate absorption inhibitor

XPHOZAH acts locally in the gut to inhibit the sodium hydrogen exchanger 3 (NHE3). As a result, it reduces phosphate absorption through the paracellular pathway, the primary pathway of phosphate absorption, according to Ardelyx.

“The approval of XPHOZAH is an important milestone for patients on dialysis… it represents a new mechanism and new option for patients who, despite treatment with phosphate binders, continue to have elevated phosphorus,” stated Mike Raab, President and Chief Executive Officer of Ardelyx.

Clinical evidence supporting FDA-approval

Approval of the phosphate absorption inhibitor XPHOZAH was based on data from 1,000 patients in three Phase III clinical trials (PHREEDOM, BLOCK and AMPLIFY) evaluating the efficacy and safety of XPHOZAH. It was investigated both as monotherapy and in combination with phosphate binder therapy. Overall, the data showed that XPHOZAH significantly reduced elevated serum phosphorus in patients receiving maintenance hemodialysis.

However, in the trials, the only observed adverse reaction for the treatment was diarrhoea. This reportedly occurred in 43 to 53 percent of patients; in at least five percent of XPHOZAH-treated patients with chronic kidney disease on dialysis across trials. Most XPHOZAH-treated patients experienced mild-to-moderate reactions that resolved over time, or with dose reduction.

Further to the three Phase III trials for XPHOZAH, Ardelyx also declared that it has completed two open-label clinical trials (OPTIMIZE and NORMALIZE) to evaluate different options for integrating the treatment into clinical practice.

XPHOZAH is expected to be available to eligible patients in the US in November 2023.