July 20 (Reuters) - Ironwood Pharmaceuticals Inc said on Thursday its potential blockbuster drug for gastroesophageal reflux disease (GERD) not controlled by current medicines significantly reduced heartburn severity and regurgitation frequency, meeting the main goals of a midstage trial.
In the eight-week, 282-patient trial the experimental drug, IW-3718, was given on top of widely used drugs for the painful condition, such as Prilosec or Nexium, and compared with those taking just the standard treatments, known as proton pump inhibitors (PPI).
At the highest tested dose - 1,500 milligrams twice a day - IW-3718 plus a PPI led to a 58 percent decrease from baseline in weekly heartburn severity versus a 46 percent reduction for PPI alone, a difference deemed statistically significant and clinically meaningful, Ironwood reported.
The Ironwood drug also led to a 55.4 percent mean decrease in weekly episodes of regurgitation in which acid rises into the throat, burning the esophagus. That compared with a decrease of 38 percent for PPI alone.
There were no serious adverse side effects reported, with constipation the most common side effect.
Drugs like AstraZeneca Plc's Nexium are highly effective in neutralizing stomach acid, but millions of people are still not getting adequate relief. IW-3781 works on bile acid rising from the small intestines, intercepting and trapping it before it reaches the esophagus.
There are currently no approved treatments that help patients still suffering from GERD despite taking PPIs.
The data "provide strong evidence that bile plays a key role in uncontrolled GERD and that IW-3718 may bring a much-needed new approach to treating these patients," Dr Michael Vaezi, one of the study's researchers from Vanderbilt University Medical Center, said in a statement.
An estimated 10 million Americans and more than 60 million globally suffer from uncontrolled GERD, the company said.
"We expect this drug to be north of $2 billion in (annual) sales opportunity. It's a very big category," Chief Executive Peter Hecht told Reuters.
The condition is one of the leading causes of emergency room visits because sufferers believe they are having a heart attack, Hecht said.
"When we talk to patients, payers, doctors they say anything will help," Hecht added.
The company said it will discuss the data with regulators and plans to begin pivotal Phase III testing of the 1,500 mg dose in the second half of 2018.
Ironwood owns full rights to the drug and said it expects patent protection into the mid-2030s. (Reporting by Bill Berkrot in New York; Editing by Matthew Lewis)