PARIS The U.S. Department of Justice (DoJ) is investigating disclosures to the Food & Drug Administration (FDA) about the variable response that certain patients may have to blood-thinner Plavix, Sanofi said in its annual report.
The French drugmaker said it had became aware of the probe in June 2012 and was cooperating with the DoJ.
Plavix, once the world's second-best selling drug, was co-marketed by Sanofi and U.S. drugmaker Bristol-Myers Squibb before it lost patent protection in May 2012.
The U.S. FDA added a so-called boxed warning to Plavix in 2010 to highlight that the drug could be less effective in certain patients who could not metabolize it properly.
A Sanofi spokeswoman declined to elaborate on the statement in the annual report.
The DoJ and Bristol Myers Squibb were not immediately available for comment.