(Bloomberg) -- GSK Plc shares surged after the UK pharma company agreed to pay as much as $2.2 billion to resolve about 80,000 US court cases alleging that its old reflux medication Zantac was contaminated with a suspected carcinogen.

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The cases represent about 93% of those against the company involving Zantac, GSK said Wednesday in a statement. Settling them is not an admission of liability, the company said.

Plaintiffs had argued that the company knew that Zantac’s active ingredient, ranitidine, turned into the potential carcinogen NDMA under certain conditions. The US Food and Drug Administration asked companies producing Zantac to remove all ranitidine-based drugs from the US market in 2020.

The stock rose 6% in early London trading, reversing what had been a drop of 4.2% in the last 12 months.

The news “lifts a major investor concern and allows the shares to trade on fundamentals, suggesting upside given GSK’s current significant discount to peers across a range of earnings multiples,” Bloomberg Intelligence’s John Murphy said in a note.

GSK is among a number of companies that made and sold versions of Zantac, and investor concern about the potential settlement value has weighed heavily on the drugmaker’s share price. GSK said it “strongly believes that these settlements are in the best long-term interests of the company and its shareholders as they remove significant financial uncertainty, risk and distraction associated with protracted litigation.”

The settlement value is at the lower end of Jefferies’ estimates, with analyst Peter Welford describing it as nearing the “best case scenario.” The market had been pricing in up to around $30 billion into GSK’s share price over the Zantac litigation, according to Shore Capital’s Sean Conroy.

Plaintiffs decided to settle the case after Delaware’s Supreme Court signaled it might walk back an earlier ruling that went in their favor, according to people familiar with the matter, who asked not to be identified discussing the deliberations.

Other Settlements

Sanofi agreed in April to pay more than $100 million to settle about 4,000 Zantac-related lawsuits. Pfizer Inc. agreed to settle more than 10,000 related cases, Bloomberg reported in May.