More than £4 billion was wiped off the value of GlaxoSmithKline yesterday after researchers in the United States said that Avandia, the diabetes drug that is the group’s second-best-selling product, raised the risk of heart attack by 40 per cent.

The study, undertaken by the Cleveland Clinic in Ohio, analysed the incidence of heart problems in 42 clinical trials involving 15,560 patients who took the drug and 12,283 who were given rival medicines or a placebo. Researchers said that the analysis showed that those using Avandia were 43 per cent more likely to suffer a heart attack.

Steven Nissen, the chairman of cardiovascular medicine at the clinic, said: “The results of this analysis raise serious concerns about the cardiovascular safety of [Avandia].” Details of the study are to be published this week in The New England Journal of Medicine.

Shares in Glaxo, Britain’s largest pharmaceutical company, slumped more than 5 per cent after the report. The decline, from £14.64 to £13.90, was the biggest in four years. The company was valued at £79.6 billion, compared with £83.8 billion at the close of trading on Friday.

BACKGROUND

• GSK plan to beat fakes may be scrapped

• Why Ribena has got a new squeeze

• US Panel allows Glaxo to keep selling Avandia

• US rule on Avandia, with £1.2bn at stake for GSK

• GSK doubles buyback

No company is out of reach of activists

Shareholder activism is going to become one of the overriding themes of the second half of the year

Related Internet Links

• GlaxoSmithKline company information

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GlaxoSmithKline dismissed the study yesterday. “GSK strongly disagrees with the findings, which are based on incomplete evidence and a methodology that the author admits has significant limitations,” the company said.

Dr Nissen acknowledged that the study was imperfect. The data was compiled from a variety of existing sources and researchers did not examine any of the patients or have access to information about their medical condition at the time.

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