AstraZeneca partner Ardelyx scores a trial success for GI drug

AstraZeneca's headquarters in London--Courtesy of AstraZeneca

So far at least, AstraZeneca ($AZN) is getting its money's worth from its partnership with Ardelyx ($ARDX). Fresh off an IPO, the biotech reports that its lead drug tenapanor (RDX5791) scored a success in a large Phase IIb trial for irritable bowel syndrome. And that counts as a win for AstraZeneca, which signed a $272 million partnership deal on the drug back in 2012--part of a deal frenzy aimed at repairing a damaged pipeline.

Tenapanor is an NHE3 sodium transport inhibitor program which is designed to force the body to flush sodium through feces rather than urine, sparing kidneys and helping patients with IBS, end-stage renal disease and chronic kidney disease. NHE3 is a protein needed to absorb sodium in the gut.

Shares of Ardelyx surged 20% this morning.

In the Phase IIb IBS study investigators reported a significant increase in bowel movements among patients taking a 50-mg dose--hitting the primary endpoint as well as "most" secondary endpoints. Two lower doses used in the study, though, were not successful in beating out a placebo, which registered a 33% success rate in the trial compared to 60.7% among the patients in the 50-mg drug arm. 

Tenapanor is also in a Phase IIb study for end-stage renal disease as well as a Phase IIa trial for chronic kidney disease. And AstraZeneca is paying the freight on the R&D program as part of their deal, leaving Ardelyx the right to co-promote this drug in the U.S.

"The magnitude of the response to tenapanor in this trial, combined with the fact that the drug was well-tolerated, with only a modest incidence of diarrhea is remarkable," says David Rosenbaum, the biotech's VP of drug research. "In addition, of those subjects who were administered 50 milligrams of tenapanor twice a day, over 65 percent responded that they were 'quite satisfied' or 'very satisfied' with tenapanor versus about 38 percent with placebo, a result that was also statistically significant."

- here's the release (PDF)