Ardelyx's Hail Mary attempt to save the FDA application for its kidney drug seems to have worked, as the agency has granted the struggling biotech a hearing for tenapanor.
The FDA has agreed to convene the Cardiovascular and Renal Drug Advisory Committee to consider the application, which was rejected last summer and again on appeal in February. Ardelyx is seeking approval for tenapanor to control serum phosphorus in adult patients with chronic kidney disease (CKD) who are on dialysis.
The FDA’s Office of New Drugs in the Center for Drug Evaluation and Research agreed to Ardelyx's second level appeal in an interim response letter, the company said April 25. The letter said that the agency believed input from the committee would be valuable in considering the clinical meaningfulness of the phosphate-lowering effect seen with tenapanor during a phase 3 trial. The FDA's Office of New Drugs will then have 30 days from the meeting to respond to Ardelyx's appeal. No date has been set for the meeting.
While the FDA agreed that tenapanor lowered phosphate according to the late-stage clinical program, the benefit was deemed “small and of unclear clinical significance.” In a complete response letter, the agency asked for another trial, prompting Ardelyx to lay off 65% of its staff and appeal the rejection.
If this appeal is successful, Ardelyx can refile the application without conducting the study. But the biotech plans to submit new analyses of existing phase 3 results and an assessment of tenapanor’s benefits and risks, plus a proposed label for the therapy.
Ardelyx needed this last-ditch effort to work, as the company ended September 2021 with just $142 million in the bank. That number had dwindled to $116.7 million as of December 31, 2021, according to a fourth-quarter earnings report issued in February.
Meanwhile, Ardelyx has been working on launching tenapanor, marketed as Ibsrela, in irritable bowel syndrome with constipation. If approved for the kidney disease indication, Ardelyx plans to market it as Xphozah.
Analysts from Piper Sandler called the FDA's move a "clear positive," but the odds are still stacked against tenapanor in kidney disease. The granting of a hearing gives the firm "no reason to believe [the FDA] ... has changed its tune." Throughout the laborious regulatory process, Piper Sandler said nephrologists have been "champing at the bit" for access to tenapanor, which has a novel mechanism of action.
If approved in this indication, Piper Sandler sees $800 million in sales potential within five years of launch for Ardelyx.
"Bottom line—we like this development, but we think it’s prudent to wait and see," Piper Sandler said. "Today’s update provides a glimmer of hope for tenapanor’s future as a renal therapy, but given FDA’s record on the tenapanor approval process, we remain comfortable on the sidelines for the time being."
Ardelyx's shares opened up 36% to hit $1.02 on Monday morning, compared to a prior close of 74 cents. Prior to the complete response letter in July 2021, the company was trading in the $8 range.