Aug 7 (Reuters) - The third trial over claims that

discontinued heartburn drug Zantac ended in a mistrial on

Wednesday when jurors could not agree about whether

pharmaceutical company Boehringer Ingelheim was responsible for

an Illinois man's cancer, according to the plaintiff's lawyer.

Martin Gross alleged in his lawsuit in state court in

Chicago that he developed prostate cancer from a carcinogenic

contaminant called NDMA found in the drug. The mistrial means

that he can take his case to trial again.

Boehringer Ingelheim said in a statement that it was

"disappointed" that the jury had not reached a verdict and that

"the  totality of the scientific  evidence" supports "only one

conclusion: Zantac does not cause any type of cancer."

First approved by U.S. regulators in 1983, Zantac became the

world's best-selling medicine in 1988 and one of the first to

top $1 billion in annual sales. It was sold at different times

by Boehringer Ingelheim, GSK, Pfizer ( PFE ) and Sanofi

, all of which have faced thousands of lawsuits.

Two such cases previously went to trial, both ending in

verdicts for the defense - one for Boehringer Ingelheim and GSK

in May, and the other for GSK on Monday.

Sanofi has agreed to settle about 4,000 cases against it,

while Pfizer ( PFE ) has reportedly agreed to settle more than 10,000.

The companies have also settled some individual cases before

trial.

The majority of the lawsuits are in Delaware state court,

where a judge in June allowed more than 70,000 cases to go

forward after rejecting the defendants' bid to keep key

plaintiffs' expert witnesses out of court on the grounds that

their scientific methods were not reliable. The companies are

appealing that ruling.

The litigation began after the U.S. Food and Drug

Administration in 2020 asked manufacturers to pull the drug off

the market over concerns that ranitidine, the active ingredient

in Zantac and generic versions of the drug, could degrade into

NDMA over time or when exposed to heat.

The drugmakers have said the cases are meritless. They won a

significant victory in 2022, when a Florida federal judge ruled

against about 50,000 cases, finding that the alleged cancer link

was not supported by sound science. Some of those cases are

being appealed.