The controversial diabetes pill failed to significantly slow plaque buildup in the arteries compared with an older drug, Pfizer’s Glucotrol, according to a study presented at the American Heart Association meeting. The new study tested Avandia against Glucotrol in 672 people in 19 countries who Type 2 diabetes with a high risk for heart problems and many were very overweight.

After 18 months, those who took Avandia had an 0.21 percent reduction in plaque in a heart artery, while the Glucotrol patients experienced an 0.43 percent increase in plaque. The results did not achieve statistical significance, although Avandia did show a significant advantage in a secondary endpoint that measured total volume of blood vessel blockage.

“This study supports but does not prove the hypothesis that (Avandia) has greater anti-atherosclerotic effect than (Glucotrol) in patients with type 2 diabetes,” according to Richard Nesto, lead investigator of the study, who presented the data at the AHA meeting.

Once a blockbuster, Avandia sales have declined after a May 2007 study in The New England Journal of Medicine suggested the diabetes pill may raise the risk of heart attacks and heart-related deaths. The FDA subsequently pushed for a stricter warning label and the American Diabetes Association recently said patients should avoid using it until safety questions are resolved.

“This is now the second study that was unable to show a beneficial effect,” says James Stein, director of preventive cardiology at the University of Wisconsin-Madison, who had no role in the research. “People really shouldn’t be using this to treat diabetes” because safer and more effective medicines are available.

An earlier study that tested Takeda’s Actos against a drug similar to Glucotrol did find a statistically significant reduction in plaque progression, researchers noted. Glaxo issued a statement saying it was encouraged by findings from the study. But the lack of conclusive proof that Avandia stalls atherosclerosis progression and the comparison to Actos data will likely do little to remove the cloud hanging over the medicine.

Sources: Reuters, Forbes and the Associated Press