Ardelyx Receives Complete Response Letter for Kidney Disease Therapy

The FDA is requesting an additional study to demonstrate tenapanor lowers serum phosphorus.

Ardelyx has received a Complete Response Letter (CRL) from the FDA for its NDA for tenapanor. The therapy is under review for the control of serum phosphorus in adult patients with chronic kidney disease (CKD) on dialysis. Regulators noted that data submitted indicate the treatment effect is small and of unclear clinical significance.

Additionally, the FDA noted that for the application to be approved, Ardelyx needs to conduct an additional well-controlled trial demonstrating clinical relevance on its effect on serum phosphorus. There were no safety, clinical pharmacology/biopharmaceutics, CMC or non-clinical issues identified in the CRL.

“We are saddened by this communication from the FDA and what it means for the patients and the physicians who treat them,” Mike Raab, president and chief executive officer of Ardelyx, said in a statement. “We continue to believe tenapanor represents an important, first-in-class treatment option for patients with elevated phosphorus. We do not agree with the FDA's subjective assessment on the clinical relevance of the treatment effect of tenapanor in our studies, which met all clinical endpoints agreed upon by the FDA. In our view, the serum phosphorus lowering data generated with tenapanor in all of our clinical studies is meaningful and clinically significant."

On July 19, the company issued an update indicating the FDA thought there were deficiencies in the NDA related to the size of the treatment effect and its clinical relevance.

In April, the FDA extended the PDUFA review period for tenapanor to July 29, 2021. The agency had requested the company to submit additional analyses in light of tenapanor’s novel mechanism of action. Ardelyx has submitted its NDA in June 2020.