By Brendan Pierson

(Reuters) -GSK has agreed to pay up to $2.2 billion to settle most pending U.S. state court lawsuits claiming that a discontinued version of the heartburn drug Zantac caused cancer, the company announced on Wednesday.

The settlement with ten plaintiffs' law firms resolves about 80,000 cases, or 93% of pending cases nationwide, the company said. It did not admit wrongdoing as part of the deal.

The litigation began after the U.S. Food and Drug Administration in 2020 asked manufacturers to pull Zantac drug off the market over concerns that its active ingredient, ranitidine, could degrade into NDMA, a carcinogen, over time or when exposed to heat.

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.

A drug currently sold under the name Zantac uses a different active ingredient and contains no ranitidine.

(Reporting by Aatrayee Chatterjee in Bengaluru; Editing by Aurora Ellis)