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.

GSK shares jumped as much as 6.5% on Thursday after the British drugmaker struck a $2.2 billion settlement over U.S. lawsuits that alleged its discontinued heartburn drug Zantac caused cancer.

GSK has agreed to pay $2.2bn to settle about 80,000 Zantac lawsuits in the US. In a statement released after the close of markets on Wednesday, the pharmaceuticals firm said it had reached an agreement with 10 firms who represent 93% of the Zantac (ranitidine) state court product liability cases pending against it in the US.