GSK shares slump as US judge says experts can testify in Zantac cases

GSK shares were down almost 10% on Monday after a US court ruled that jury trials could hear expert witnesses in 70,000 cases brought by cancer sufferers claiming its Zantac heartburn drug caused their condition.

A judge in the Delaware State Court ruled that scientific experts would be able to testify there is a link between the plaintiffs' illnesses and their exposure to probable human carcinogens, through the Zantac drug.

GSK and other companies who marketed Zantac, including Boehringer Ingelheim and Sanofi dispute the claims. The UK firm on Monday said it would appeal the ruling immediately.

"Following the 16 epidemiological studies looking at human data regarding the use of ranitidine, the scientific consensus is that there is no consistent or reliable evidence that ranitidine increases the risk of any cancer," GSK said in a statement on Monday.

AJ Bell investment director Russ Mould said investors had "reached a point of some comfort" on the Zantac issue as a series of US lawsuits linking the heartburn drug to cancer "appeared to be running out of steam".

“In the short term this just pours more uncertainty over the investment case. An uncomfortable comparison for GSK management can be drawn with AstraZeneca, which has left its counterpart for dust in recent times and is forging ahead with ambitious growth targets.”

Reporting by Frank Prenesti for Sharecast.com