Losing patent protection on Prozac in 2001 could have sent Eli Lilly and Company into a major depression. In 2000 the drug was the company's bestseller, bringing in $2.6 billion, or 24 percent of Lilly's total revenue. But in August 2001, Barr Laboratories Inc started selling generic Prozac. The next year, global sales of the branded drug dropped 63 percent.

Thanks to Zyprexa, Lilly's Prozac withdrawal was a bit less severe. Introduced to the U.S. market in 1996 as a treatment for schizophrenia, Zyprexa took on new life in 2000 after receiving FDA approval for the treatment of bipolar disorder. By 2004, Zyprexa generated $4.4 billion, nearly 32 percent of Lilly's revenue, and the company's total profits surpassed Prozac levels.

But that same year, Zyprexa's story started to echo Prozac's, beginning with a lawsuit filed in federal district court in Indianapolis--the same court that heard the Prozac patent litigation. Lilly even brought in the same trial lawyer--Charles Lipsey, a partner at Finnegan, Henderson, Farabow, Garrett & Dunner. At trial Lipsey faced Jeffrey Ward and Thomas Heneghan, partners at Michael Best & Friedrich, who represented the three drugmakers that sought to make generic Zyprexa--Dr. Reddy's Laboratories, Ltd., Teva Pharmaceuticals USA, Inc., and Zenith Goldline Pharmaceuticals, Inc. (which was later acquired by Teva in January 2006).

So far, Lilly has managed to hang on to Zyprexa's patent. In April 2005 federal district court judge Richard Young ruled that the patent was valid and would be infringed by a generic. This past spring, the U.S. Court of Appeals for the Federal Circuit heard the generic drug companies' appeal. Lipsey and William Mentlik, a name partner at Westfield, New Jersey, IP boutique Lerner, David, Littenberg, Krumholz & Mentlik, presented oral arguments on behalf of Lilly and the generics, respectively. A decision is expected within the year.

In the Prozac patent case, Lipsey also won round one in a summary judgment ruling. The trouble came on appeal, when a three-judge panel at the Federal Circuit overturned the ruling.

For Lipsey, getting the call from Lilly general counsel Robert Armitage to lead the Zyprexa case was a signal that Lilly didn't consider the Prozac loss a result of bad lawyering. Still, Lipsey says, "I badly didn't want to see the result repeated and worked very hard to try to avoid that."

There is a key difference in the Zyprexa litigation that Lipsey hopes will lean in his client's favor: The Prozac loss dealt with a secondary patent on the drug, covering the effects of Prozac on the body's serotonin uptake. The Zyprexa patent at issue is the drug's original, basic patent. These are almost always upheld in court, Lipsey says. But ultimately "it's in the lap of the gods," he adds.

Michael Best's Ward, however, believes that errors in the district court's decision might be in his favor. "We have some very good points on appeal," he says. "I'm optimistic that the judges will overturn."