Pharma giant GSK plunges 9% after U.S. court allows scientific testimony in Zantac lawsuits

LONDON — Shares of British pharmaceuticals giant GSK plunged 9% Monday, after a U.S. court ruled that scientific evidence could be presented as a stack of lawsuits relating to the discontinued heartburn drug Zantac move forward.

The Delaware State Court late on Friday ruled that plaintiffs' expert witnesses could testify in the roughly 75,000 cases alleging the once-popular drug ranitidine — sold under the brand name Zantac in the U.S. — may cause cancer.

"This case has always been about getting the science in front of a jury," Brent Wisner, lawyer at the firm Wisner Baum which is representing many of the plaintiffs, said in a statement.

The dispute has been rumbling for years and involves numerous pharmaceutical firms. Zantac was sold by GSK as a prescription drug in the 1980s before transitioning to an over-the-counter medicine, and following its patent expiry in the 1990s has been sold by companies including France's Sanofi, U.S. firm Pfizer and Germany's Boehringer Ingelheim.

The drug was withdrawn from European and U.S. markets in 2019 and 2020 after regulators conducted a safety review which raised concerns it contained a probable carcinogen called NDMA.

The companies involved deny there is a scientific consensus that the drug can be linked to any later development of cancers.

In a statement Friday, GSK said it disagreed with the latest Delaware ruling and would immediately seek an appeal.

It said the decision contradicted the federal court's multi-district litigation ruling in December 2022, which dismissed all cases alleging five cancer types. It added that the court decision only related to whether the methodology used by the plaintiffs' experts was sufficiently reliable to be presented as evidence at trial.

"Following