DoJ probes Sanofi disclosures on Plavix effectiveness

It's common knowledge now that the Plavix blood thinner is less effective in certain patients. But when did Sanofi ($SNY) know that its star drug didn't work so well in those people? Did the French drugmaker properly disclose any and all of its knowledge on the subject to FDA?

That's the question the U.S. Justice Department is apparently trying to answer. In its 2012 annual report, filed with the Securities and Exchange Commission on Friday, Sanofi disclosed the government probe, offering very little detail. "[T]he U.S. Department of Justice is investigating disclosures to the FDA regarding the variability of response to Plavix," the company stated.

It's not the first time Sanofi and its Plavix partner, Bristol-Myers Squibb ($BMY), have been questioned about those Plavix disclosures. As The Wall Street Journal notes, two state attorneys general have sued the two companies, alleging that they knew--or should have known--since 2003 that some patients don't metabolize Plavix well, and as such don't get the full benefit of the drug. The suits claim that Sanofi and Bristol-Myers keps that information to themselves to protect Plavix sales. Both companies declined to comment for the WSJ and Reuters.

Plavix's effectiveness is compromised in two groups, studies have shown: Patients with a variant of the CYP2C19 gene don't metabolize Plavix well, so they either need a higher dose or a different medication altogether. Patients who use both Plavix and certain heartburn drugs--and other meds that inhibit the same CYP2C19 gene--don't get the full benefit, either.

In 2008, researchers flagged the CYP2C19 gene's effects on Plavix effectiveness, and other studies uncovered the interaction between the drug and heartburn remedies. FDA opened a safety review soon after, and ended up warning about the drug interactions at a cardiology meeting later that year. In 2010, the agency added a black-box warning to flag the differences in Plavix effectiveness for patients with the CYP2C19 variant. That warning suggested that doctors test patients for that variation before prescribing Plavix, but the practice hasn't become widespread.

- see the Sanofi SEC filing
- read the WSJ coverage (sub. req.)

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