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STORY: Shares of drugmaker GSK dropped more than 9% Monday (June 3).

Investors were spooked after a U.S. judge allowed more than 70,000 lawsuits to go forward.

The suits allege GSK's discontinued heartburn drug Zantac caused cancer.

The British company said it disagreed with the ruling and would immediately appeal.

Monday's share drop wiped out nearly $8.90 billion of the company's market value.

J.P. Morgan analysts said the potential liability GSK could face is likely higher than the $2-$3 billion figure assumed by the market.

The judge ruled late Friday (May 31) expert witnesses can testify in court that the drug may cause cancer.

Former Zantac makers, including GSK, Pfizer, Boehringer Ingelheim and Sanofi had argued the witnesses' opinions lacked scientific support.

GSK has settled a series of lawsuits related to Zantac, including several in California, over the last year.

Although last month, a Chicago jury rejected an Illinois woman’s claim Zantac caused her colon cancer.