The FDA has approved tenapanor (Ibsrela, Andrelyx Inc) for the treatment of irritable bowel syndrome with constipation in adult patients.
Tenapanor is a sodium/hydrogen exchanger 3 (NHE3) inhibitor administered as 50mg orall tablets, to be taken twice daily.
The approval is based upon the results of Andrelyx’s phase 3 IBS-C clinical trial program. Studies NCT02686138 and NCT02621892 shared the same initial 12-week treatment program, until continuing for an additional 14 weeks and incorporating a four-week randomized withdrawl, respectively.
The primary endpoints for the trials were the proportion of patients that qualified as responders during the first 12-week treatment period, (i.e. any patient that experienced at least a 30% reduction in weekly average abdominal pain score compared with baseline, and an increase of at least one complete spontaneous bowel movement in weekly average from baseline in the same week for at least six of the 12 treatment weeks).
In trial 1 (NCT02686138) 37% of patients on tenapanor qualified as responders, compared with only 24% on placebo treatment.
In trial 2 (NCT02621892) 27% of patients on tenapanor qualified as responders, compared with only 19% on placebo.
"[Tenapanor] has the potential to provide IBS-C patients and their doctors with a novel mechanism and an innovative approach to managing IBS-C, a highly burdensome and difficult-to-treat condition affecting more than 11 million people in the United States," says Mike Raab, president and chief executive officer of Ardelyx, in a statement.
Tenapanor is contraindicated in patients with known or suspected mechanical gastrointestinal obstruction, and patients less than six years of age. In juvenile rat studies, Tenapanor caused death presumably due to dehydration. Safety and effectiveness of Tenapanor in patients under the age of 18 years has not been established at the time of this release.
Adverse events reported with the use of Tenapanor include diarrhea, abdominal distension, flatulence, and dizziness. If diarrhea occurs, dosing should be suspended and the patient rehydrated.