July 29 (Reuters) - British drugmaker GSK said on Monday it has

agreed to confidentially settle a lawsuit in Illinois that alleged its

discontinued heartburn drug Zantac caused cancer, the latest in a series of

settlements to end costly litigation.

First approved in 1983, Zantac, sold at different times by GSK, Pfizer ( PFE )

, Sanofi and Boehringer Ingelheim, became the world's

best-selling medicine in 1988 and one of the first to top $1 billion in annual

sales.

The companies together are facing thousands of petitions against them

including more than 70,000 lawsuits in Delaware.

Lawsuits began piling up after the U.S. Food and Drug Administration in

2020 asked manufacturers to pull the drug off the market over concerns that

ranitidine, an active ingredient in the drug, could degrade into a

cancer-causing chemical over time or when exposed to heat.

GSK did not admit any liability and said it would vigorously defend itself

in any other Zantac cases.

The company's shares were up 0.8% in the early trade.