Kaul said he agreed with the advisory panel's decision. "Because of the uncertainty, you can't pull a drug off the market. You have to be absolutely certain that there is substantial risk associated with it," he said.
GlaxoSmithKline said it stands behind the drug. "Across the extensive dataset for Avandia, GlaxoSmithKline believes there is no consistent or systematic evidence that Avandia increases the risk of heart attack or cardiovascular death in comparison to other anti-diabetic medicines," the company said in a prepared statement.
Nissen, for his part, said that a more detailed analysis by the FDA that was used by the advisory panel during its deliberations has confirmed the risk of heart attack with Avandia. This more thorough FDA research has left his original study "no longer relevant," he said.
"The FDA presented a more statistically powerful patient-level analysis at the advisory board meeting on rosiglitazone (Avandia)," he said. "This is a far more accurate approach when you have access to patient data, which we did not. The FDA confirmed a 40 percent increase in risk, virtually identical to our findings reported in the New England Journal of Medicine. Further study-level analysis will not yield any important insights," he added.
Kaul, however, disagreed with Nissen that the FDA's analysis confirmed a risk of heart attack from Avandia. According to Kaul, the FDA study looked at both serious and non-serious heart-related events.
"There was not a statistically significant difference between serious and non-serious events, which is exactly what we found," Kaul said. "There was substantial uncertainty associated with those risk estimates. You couldn't say one way or the other whether the risk was increased or decreased. When they looked at myocardial infarction [heart attack], they did not find a statistically significant increased risk," he added.
Kaul agreed that there is a heart-attack risk with Avandia, but the size of the risk is uncertain. "It's no longer statistically significant when you look at myocardial infarction," he said. "But, if tomorrow there is evidence to suggest increased risk, we will be the first ones to acknowledge it."
