Gene variant reduces Plavix effectiveness

Shares in Sanofi-Aventis dropped 4.3% to 44.50 euros on December 23, 2008, after three separate studies identified a genetic variant that  impairs patient response to its blockbuster anti-clotting drug Plavix  (clopidogrel).

The $8.5-billion a year agent, which is marketed with US drug major  Bristol-Myers Squibb, was less effective in young patients carrying the  CYP2C19*2 genetic variant.

In data that appeared in The Lancet, the detrimental effect of  CYP2C19*2, as measured using a composite endpoint of death, myocardial  infarction and urgent coronary revascularization, persisted from six  months after clopidogrel initiation up to the end of follow-up  (p=0.009). After multivariable analysis, the variant was the only  independent predictor of cardiovascular events (p=0.0006).