Indianapolis-based Eli Lily and Co. said a federal court judge has upheld a patent protecting one of its best-selling drugs, the cancer treatment Alimta.

A trial on the drug's compound patent, which protects its chemical makeup, started Nov. 8 and ended Monday with a ruling from the U.S. District Court for the District of Delaware, Lilly said. Generic drugmaker Teva Pharmaceuticals Industries Ltd. had challenged the patent, which protects Alimta until July 2016.

Alimita was Lilly's third-best-selling drug in the third quarter, trailing only the antipsychotic Zyprexa and the antidepressant Cymbalta. Revenue from Alimta climbed 21 percent, to $560.3 million, in the quarter, as sales in Japan rose. Alimta rang up $1.64 billion in sales during the first three quarters of 2010.

It was a welcome court win after a difficult few months for Lilly, which is facing a wave of patent expirations in coming years.

In August, a federal judge in New Jersey ruled that the company's method-of-use patent for attention deficit hyperactivity drug Strattera is invalid; Lilly is appealing that decision.  The previous month, a federal appeals court upheld a ruling that invalidated a patent on cancer drug Gemzar, which generates $750 million in U.S. sales each year.

A generic version of Gemzar launched Monday.

Gemzar is the first of several blockbuster Lilly drugs that will see their patents expire by 2013. Generic versions of Zyprexa, Cymbalta, Evista and Strattera could zap nearly half of Lilly's current sales, putting great pressure on the company to find new drugs to take their place.

Alimta is a chemotherapy drug used to treat advanced nonsquamous non-small cell lung cancer and malignant pleural mesothelioma, a cancer that affects the inside lining of the chest cavity.

Lilly said last month its third-quarter profit jumped 38 percent to $1.3 billion, as international sales climbed. But, aside from court challenges, the company also faces patent expirations for some of its key products. That includes Zyprexa next year and Cymbalta in 2013.

Analysts who follow Lilly question how it will make up for the lost revenue. Company leaders have repeatedly expressed confidence in their pipeline of drugs under development, and they also point to growth opportunities in the animal health business and emerging international markets.