Ardelyx Announces NDA Acceptance of Tenapanor

Ardelyx announced the U.S. Food and Drug Administration (FDA) has accepted its New Drug Application (NDA) of tenapanor for the control of serum phosphorus in adult patients with chronic kidney disease (CKD) on dialysis.

"The acceptance of our NDA is extremely exciting as it represents the next critical step towards bringing to market a completely new approach to the management of hyperphosphatemia, an area where a significant unmet need exists," said Mike Raab, president, and chief executive officer of Ardelyx. "With potential approval in the second quarter of 2021, we continue to advance commercial preparations for the launch of tenapanor, a first-in-class, non-binder therapy that targets the primary pathway of phosphorus absorption. This is a special time for the Ardelyx team as we have a clear mission – that we can and should do better for patients. We believe that with tenapanor, we have discovered and developed a therapy that will truly advance care for patients on dialysis."

The FDA has set a Prescription Drug User Fee Act (PDUFA) goal date of April 29, 2021.

"I look forward to the prospect of having a novel approach to treating hyperphosphatemia, a condition known to be associated with higher morbidity and mortality in patients with chronic kidney disease on dialysis," said Dr. Kam Kalantar-Zadeh, Chief, Division of Nephrology and Hypertension and Kidney Transplantation, University of California, Irvine, School of Medicine. "I believe innovations that enable us to block phosphorus via the primary pathway of absorption will help us more consistently and effectively manage phosphorus, so we can do better for our patients."

The NDA is supported by three successful Phase 3 trials involving over 1,000 patients that evaluated the use of tenapanor, which included: two monotherapy trials, including a long-term study, to control serum phosphorus in patients with CKD on dialysis, and one trial using a dual-mechanism approach in dialysis patients who had difficult-to-control hyperphosphatemia (≥5.5 mg/dL) despite phosphate binder therapy.

Tenapanor, discovered and developed by Ardelyx, is a first-in-class, proprietary, oral medicine for which an NDA is under review by the FDA for the control of serum phosphorus in adult patients with CKD on dialysis. Tenapanor has a unique mechanism of action and acts locally in the gut to inhibit the sodium hydrogen exchanger 3 (NHE3). This results in a conformational change of the epithelial cell junctions, thereby significantly reducing paracellular uptake of phosphate at the primary pathway of phosphate absorption. Ardelyx is conducting NORMALIZE, an ongoing extension study of the PHREEDOM Phase 3 monotherapy study, which is designed to evaluate the ability of tenapanor, as monotherapy or in combination with sevelamer, to achieve serum phosphorus levels in the normal range (2.5 – 4.5 mg/dL) in patients with chronic kidney disease (CKD) on dialysis. Planned analyses have demonstrated that the use of tenapanor as a foundational approach, as monotherapy or in combination with sevelamer carbonate, produces a significant phosphorus-lowering effect.  After ~20 months of treatment with tenapanor alone or with low doses of sevelamer, patients exhibited a mean serum phosphorus reduction of 2.33 mg/dL, from a mean baseline phosphorus of 7.27 mg/dL at the beginning of the PHREEDOM trial to a mean of 4.94 mg/dL.

Hyperphosphatemia is a serious condition resulting in an abnormally elevated level of phosphorus in the blood that is estimated to affect more than 745,000 dialysis patients in major developed countries. The kidney is the organ responsible for regulating phosphorus levels, but when kidney function is significantly impaired, phosphorus is not adequately eliminated from the body. As a result, hyperphosphatemia is a nearly universal condition among people with CKD on dialysis. Despite treatment with phosphate binders (the only approved therapy for hyperphosphatemia), approximately 70% of CKD patients on dialysis continue to experience elevated phosphorus levels at any point in time (Spherix Global Insights: RealWorld Dynamix, Dialysis 2018). Phosphorus levels greater than 5.5 mg/dL have been shown to be an independent risk factor for cardiovascular morbidity and mortality in patients requiring dialysis (Block 2004), and internationally recognized treatment guidelines recommend lowering elevated phosphate levels toward the normal range (<4.6mg/dL).