US FDA calls for new boxed warning on Sanofi-Aventis/Bristol-Myers Squibb's Plavix; seeks comment on improving transparency

The US Food and Drug Administration last Friday called for a new boxed warning to the blockbuster anti-blood clotting drug Plavix (clopidogrel), alerting patients and health care professionals that the drug can be less effective in people who cannot metabolize the compound to convert it to its active form. It also said it is seeking input on how to increase transparency in its interactions with regulated industry.

Plavix originator France's Sanofi-Aventis and marketing partner US drug major Bristol-Myer's Squibb announced the same day that they would add the boxed warning concerns the diminished effectiveness of their drug in patients who have a genetic variation leading to reduced formation of the active metabolite. These patients, who are designated as poor metabolizers, represent, according to the prescribing information, approximately 2% of whites, 4% of blacks and 14% of Chinese. The percentage of poor metabolizers is estimated to be approximately 3% of the population, based on published studies.

Number two best-selling drug