Tenapanor Helps Patients With Kidney Disease on Dialysis Achieve, Maintain Normal Serum Phosphorus Levels: Presented at NKF

By Eric Ramos

CHICAGO -- April 7, 2021 -- Treatment with tenapanor, either alone or in combination with sevelamer, helps patients with chronic kidney disease (CKD) who are on dialysis achieve and maintain normal serum phosphorus levels, according to a study presented at the Virtual National Kidney Foundation (NKF) 2021 Spring Clinical Meetings.

“Tenapanor increases the proportion of patients with a serum phosphorus level within the normal range, up to 47.4%, which is better than the 29% with standard care as shown in the DOPPS [Dialysis Outcomes and Practice Patterns] April 2020,” reported David P. Rosenbaum, MD, Ardelyx, Inc., Fremont, California.

Tenapanor, an investigational, first-in-class, non-binder therapy that targets the primary pathway of phosphate absorption, was investigated in the phase 3 PHREEDOM trial, where patients with CKD or end-stage renal disease on dialysis were randomised to receive tenapanor, alone or in combination with sevelamer. Patients who completed the PHREEDOM trial were then eligible to enrol in the long-term, open-label extension NORMALIZE study.

A total of 172 patients were enrolled in NORMALIZE -- 110 from the tenapanor arm and 62 from the combination group. Patients initially randomised to tenapanor continued to receive tenapanor, either alone or in combination with sevelamer, depending on their serum phosphorus levels. Patients initially randomised to tenapanor and sevelamer continued to receive the same combination treatment, with the sevelamer dose adjusted based on serum phosphorus levels.

Patients were monitored for safety and efficacy with in-office and telephone visits for up to 18 months. The primary endpoint was the proportion of patients who achieved a normal serum phosphorus level (2.5-4.5 mg/dL) at 18 months.

Patients had a mean serum phosphorus reduction from 7.27 mg/dL at baseline of PHREEDOM to 4.94 mg/dL at the last post-baseline serum phosphorus assessment in NORMALIZE, with a mean serum phosphorus reduction of 2.33 mg/dL.

“The proportion of patients achieving a serum phosphorus level ≤4.5 mg/dL consistently doubled -- up to 47.4% -- from baseline of NORMALIZE at post-baseline visits through the evaluation period up to 18 months,” said Dr. Rosenbaum.

The only adverse event reported in >5% of patients was diarrhoea, with an incidence rate of 23.3%. Two patients experienced diarrhoea that led to study drug discontinuation.

Funding for this study was provided by Ardelyx.

[Presentation title: A Long-Term, Open Label Study to Evaluate the Ability of Tenapanor Alone or in Combination With Sevelamer to Achieve Normal Serum Phosphorus in Patients With CKD on Dialysis (NORMALIZE)]

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