- In its latest pipeline setback, Ardelyx Inc. is discontinuing development of its Phase 3 hyperkalemia drug due to patients experiencing an "unexpected" side effect during treatment.
- The Fremont, California-based biotech was evaluating its drug, called RDX7675, as a therapy for hyperkalemia, a condition where potassium levels in the blood are higher than normal. While RDX7675 did show meaningful potassium-lowering activity in a Phase 2 onset-of-action study, at least some patients taking it also had decreased serum bicarbonate.
- Those lower bicarbonate levels would limit RDX7675's commercial viability, according to Ardelyx. In scrapping the program, the biotech expects to save $40 million over the following two years, which should give it enough capital to operate into 2019.
Ardelyx's announcement is noteworthy given that, just three months ago, the biotech announced it was axing 28% of its workforce and delaying early-stage programs to concentrate resources around its two late-stage candidates.
But with RDX7675 shelved, there's now one such drug left. Tenapanor, a sodium–hydrogen exchanger 3 inhibitor, is in Phase 3 testing for both end-stage renal disease (ESRD) hyperphosphatemia and irritable bowel syndrome with constipation (IBS-C).
In addition to the RDX7675 announcement, Ardelyx revealed on Tuesday it received feedback from the Food and Drug Administration about a second registrational study for tenapanor in hyperphosphatemia. That trial will begin enrollment soon, and will include an active control arm to assess the drug's safety.
Investors, however, haven't developed a very positive attitude toward tenapanor.
In 2015, the drug failed a Phase 2a clinical trial assessing it as a treatment for Stage 3 chronic kidney disease patients with type 2 diabetes mellitus and albuminuria. Earlier this year, tenapanor hit the primary endpoint of the late-stage T3MPO-1 study of IBS-C patients; yet those patients also demonstrated much higher levels of diarrhea than participants in the placebo group, raising concerns about how its efficacy and safety may stack up to other drugs on the market like Allergan plc and Ironwood Pharmaceuticals Inc.'s Linzess (linaclotide).
Like many biopharmas, though, Ardelyx still has optimism in its drug.
"If approved, tenapanor would be the first non-phosphate binder treatment available for hyperphosphatemia in ESRD patients who are on dialysis, who currently rely on highly burdensome and difficult-to-take binders for treatment," Ardelyx's Chief Development Officer David Rosenbaum said in a Tuesday statement.
"In the first Phase 3 study, tenapanor, with just a few small pills, achieved the primary endpoint of meaningfully reducing serum phosphorus and was well-tolerated," he added. "The second Phase 3 trial is a crucial step toward advancing tenapanor to the market, and we look forward to beginning enrollment. In our view, tenapanor has the potential to dramatically improve phosphorus management and change the way patients are treated."
Ardelyx is also planning to direct attention and resources to RDX013, a preclinical, potassium secretagogue also being looked at for the hyperkalemia indication.
Ardelyx stock opened at $5.75 per share on Tuesday, up 2.7% from close-of-market Monday. Shares continued to climb in Tuesday morning trading too, reaching $5.95 apiece at one point.