UK drug giant GlaxoSmithKline has again come out in defence of its diabetes drug Avandia, this time sending a letter to The Lancet outlining the clinical evidence which indicates that the drug’s safety is indeed comparable to other therapies on the market.

Last week, GSK’s stock was rocked by a meta-analysis of Avandia (rosiglitazone) studies published in the New England Journal of Medicine that suggested it might significantly increase the risk of heart attacks. But in his letter to The Lancet, Ronald Krall, Chief Medical Officer of GSK, said that, while the study found that patients were 43% more likely to suffer a heart attack, it failed to disclose the total percentage number of events. “The actual number of heart attacks represents a very low frequency of events – 0.6% for both Avandia and the control group,” he stressed.

Mounting evidence in support of Avandia

Furthermore, Krall points to two other trials – ADOPT and DREAM – which, he claims, show that the number of ischemic cardiovascular events with Avandia is comparable to the two gold standard therapies - metformin or a sulfonylurea and a placebo. And findings from a soon-to-be-published study, using a managed care database of more than 30,000 diabetes patients in a real-world setting, paint a similar picture, he said.

Krall’s perhaps final nail in the coffin was the fact that the independent safety monitoring board keeping an eye on the cardiovascular profile of Avandia in the 4,500-patient RECORD trial has assessed interim data and deemed that the study should continue.

The authors of the NEJM study themselves admit certain limitations of their study and said their findings could be due to chance, and analysts expressed a fair amount of scepticism right from the start. Nevertheless, GSK’s stock fell more than 6% in the first two days after the news broke, and scripts for the drug took a nosedive in America.

Damage limitation

Given the potential damage article from the NEJM article, analysts at Collins Stewart believe there is probably going to be a short-term knock on effect on Avandia growth. However, they say, going forward, the rosiglitazone-containing combination products Avandamet and Avandaryl - which aren’t affected by any negative safety perceptions – “will likely drive new growth for the Avandia franchise.”

And GSK’s latest damage-limitation move seems to have gone some way in restoring investor confidence in Avandia - the drugmaker’s shares rose nearly 2% following the following the news.