The drug: Plavix
The companies: Sanofi/Bristol-Myers Squibb
Estimated worldwide sales for 2012: $5.11 billion

Things are looking grim for Bristol-Myers Squibb ($BMY) and Sanofi's ($SNY) top-selling blood thinner Plavix. In the first quarter of this year, Plavix was the best-selling drug in America, jumping 3% to $1.62 billion. Then, May, the generics arrived.

And sales immediately slumped. BMS' Plavix revenues nosedived by 60% during the second quarter, thanks to those copycat rivals. Co-pay discounts may have kept some Plavix users on the branded version, but Bristol-Myers wasn't expecting much; it pulled back from actively promoting the drug or the co-pay program. Now, Plavix revenue is expected to drop more than $4 billion this year, falling well short of the $9.3 billion Plavix brought in last year.

The decline in sales prompted Sanofi and Bristol-Myers to rework their Plavix deal. Under a new agreement inked this month, Sanofi grabs worldwide Plavix rights, except for the U.S. and Puerto Rico. Bristol-Myers will hang on to those at least through 2018.

For more:
Sanofi, Bristol revamp Plavix partnership for post-patent world
Plavix tops U.S. sales ranks, but not for long
AZ puts Brilinta up for another head-to-head fight with Plavix
With Plavix gone generic, payers aim to cut Effient, Brilinta