An advisory group is set to meet Monday to discuss the cardiovascular safety of GlaxoSmithKline's type 2 diabetes drug Avandia, and the drug may be in for a rough time.

The meeting will pit GSK's own analysis of Avandia (rosiglitazone) clinical trials against an appraisal of several studies conducted by independent reviewers. The reviewers' report, released this week as part of a 436-page FDA briefing document, “largely confirms concerns first raised in May” by Dr Steven Nissen in The New England Journal of Medicine, according to The New York Times. Nissen's meta-analysis found that patients taking Avandia face a 43% higher risk of heart attacks than those taking other diabetes drugs or no medication, while the FDA report pegged the Avandia odds ratio at 38% for ischemic events.

Moreover, the new report said the risk of heart attack doubles when Avandia is added to insulin. A similar risk was not found with patients taking Takeda's Actos (pioglitazone).

GSK's chief medical officer is set to make the case for Avandia's safety. Across multiple sources of data, “there is no consistent or systematic evidence that rosiglitazone increases the risk of myocardial infarction or cardiovascular death” compared to other diabetes drugs, the company said in its own brief issued ahead of the meeting.

A review of both documents “make it seem unlikely Avandia will remain unscathed,” said Forbes. The panel could suggest pulling Avandia off the market or recommend the FDA sit on its hands due to the conflicting studies. Perhaps more likely, the group could recommend placing additional warnings on the drug or that its use be restricted, particularly with those also taking insulin. In February the same group of advisors recommended Avandia's label should get a “black box” warning about ischemic risk.

Doctors have already voted with their prescription pads, sending GSK's market share in the PPAR class of drugs down to 33% from 51% before Nissen's report, according to IMS Health data cited by The Wall Street Journal. Actos now commands 67% of that market, compared to 49% in January. Last year Avandia had global sales of $3.38 billion—comprising 7% of GSK's total sales.