Eli Lilly's $15B battle for longer Alimta monopoly hits court today

Showdown day has come for Eli Lilly and Alimta. The company goes to court today to fight for 5 years of additional exclusivity on its top-selling lung cancer drug. If Lilly ($LLY) succeeds in defending a method-of-use patent, Alimta will be covered till 2022--and the Indianapolis-based drugmaker could reap $15 billion in additional sales.

Lilly's patent on Alimta's active ingredient runs out in 2017. But the company also patented Alimta's use in combination with folic acid and vitamin B12. That combo helps prevent serious side effects, and it's specified on the FDA-approved label. Generic challengers Teva Pharmaceutical Industries ($TEVA) and Fresenius Kabi contend that any nutritionist would conclude that the vitamins could stave off those potentially fatal side effects. If the court buys that argument, then the patent would fail the "obviousness" test.

But Lilly claims two major points--that its own scientists and the FDA both resisted the idea at first and that proving it worked saved the drug from the R&D trash bin, The Wall Street Journal reports. "The significant scientific research that Lilly performed in support of the vitamin-dosage regimen patent deserves intellectual property protection," a spokesman told the Journal.

Lilly needs a win here, for reasons that really are patently obvious. Its sales are already suffering on the loss of Zyprexa exclusivity; the atypical antipsychotic brought in $4.6 billion in 2011, but just $1.7 billion last year. Its new top seller, Cymbalta, goes off patent in December, putting another $5 billion in annual sales at risk. And Alimta is now Cymbalta's backup player, with $2.6 billion in 2012 sales--and peak expectations topping $3 billion. Five more years of exclusivity would give Lilly more time to develop and launch new drugs to take its older products' place.

Other major drugmakers suffering their own patent-cliff losses are trying to defend secondary patents. As the WSJ notes, it's expensive to fight that sort of fight, and victory is far from certain, but the battle could be worth it, considering the scale of generic erosion for blockbuster products. Added to Pfizer's ($PFE) successful defense of a secondary patent on Viagra--which gave the company another 7 years of exclusivity in the U.S.--the Lilly case could raise new hopes.

- read the WSJ piece (sub. req.)

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