Plavix Genetic Variation Problems Lead to DOJ Probe

The U.S. Justice Department (DOJ) is investigating whether Sanofi and Bristol-Myers Squibb failed to adequately disclose information that was known about variations in the effectiveness of Plavix, their blockbuster blood thinner that has been found to not be effective among individuals with certain gene variants.

Disclosure about the investigation came in a Sanofi annual report (PDF) filed last week with the U.S. Securities and Exchange Commission (SEC), indicating that the DOJ is reviewing “disclosures to the FDA regarding the variability of response to Plavix.” However, the Sanofi has known about the investigation since June 2012, and indicates that it has been cooperating with the DOJ.

Plavix (clopidogrel) is a blood thinner that is designed to prevent blood platelets from sticking together to form clots. After it was introduced, Plavix became a widely used blockbuster medication, generating annual sales of over $6 billion for Bristol Myers Squibb Co. and Sanofi-Aventis.

In August 2009, researchers from the University of Maryland identified a gene variant found in about one-third of the population that may signal a reduced effectiveness of Plavix. People with the CYP2C19 variant have reduced functioning of a liver enzyme that is supposed to convert Plavix from its inactive form to its active form, potentially making Plavix ineffective at reducing the risk of blood clots.

While Plavix has been promoted as being better at its job than aspirin, and costs many times more than aspirin, questions have been raised about the effectiveness of Plavix for many patients and whether it actually provides any benefit over aspirin.

There are between 2.5 million and 3 million Plavix prescriptions handed out each month in the U.S., and concerns have emerged that many of these may be unnecessary due to genetic resistance to Plavix.

The drug makers currently face a number of Plavix lawsuits filed throughout the country by former users of the medication, which allege that Plaintiffs suffered various injuries as a result of their unnecessary use of Plavix, such as gastrointestinal bleeding, severe ulcers and a rare blood disorder known as thrombotic thrombocytopenic purpura (TTP).

All of the complaints involve similar allegations against Bristol-Myers Squibb and Sanofi-Aventis, makers of the blockbuster blood thinner, arguing that inadequate warnings were provided about the risk of potential Plavix side effects while the drug makers overstated the efficacy of the medication.

Last month, a panel of federal judges centralized and consolidated all Plavix lawsuits filed in federal court system in the U.S. District Court for the District of New Jersey as part of a multidistrict litigation (MDL). The claims will be handled by U.S. District Judge Freda L. Wolfson for pretrial proceedings.