A federal court judge in Indiana yesterday upheld Eli Lilly's patent on Zyprexa, a schizophrenia treatment among the top-selling prescription drugs in the US last year. US District Judge Richard Young ruled Ivax, Dr. Reddy's Laboratories and Teva Pharmaceutical Industries can't sell generic versions of Zyprexa before 2011. Lilly sued the three generic companies to protect the patent after the generic companies claimed that it was invalid because Zyprexa is too similar to other chemical compounds with expired patents. "We have always been very confident that our patents are valid and enforceable and today's court ruling sends a clear message on the strength of those patents," said Sidney Taurel, chairman, president and chief executive officer of Lilly. Zyprexa generated US sales of 2.4 billion and accounted for a $4.4 billion of Lilly's revenue last year. The drug has been Lilly's top seller since generic competition emerged in 2001 to the company's Prozac antidepressant.