Eli Lilly and Co., the Indianapolis-based drugmaker whose best-selling schizophrenia medicine Zyprexa survived a patent challenge in Britain two years ago, has asked a U.K. judge to reject a parallel lawsuit by a closely held generics company.

Neopharma Ltd., which holds European marketing rights for generic olanzapine, should have its revived claim dismissed without a trial because it can’t realistically prove the patent is invalid, Lilly’s lawyer said Monday in London. Neopharma sold the generic in the U.K. in 2008 before a temporary court injunction forced it to stop.

Neopharma’s claim that “the patent is invalid has no prospect of success, having already been rejected in a number of courts around the world,” Lilly’s lawyer, Thomas Mitcheson, said in court papers outlined in Monday’s hearing.

The Court of Appeal in London affirmed the patent’s validity in December 2009, in a challenge by India’s Dr. Reddy’s Laboratories Ltd. Eli Lilly had already won a similar case in the U.S. The drug accounted for more than $5 billion in sales for the company last year, or about 22 percent of its global revenue. The drug’s European patent expires in the U.K. on Sept. 26, while its U.S. protection ends in October.

Neopharma’s lawyer, Antony Watson, said the case must go to trial because he will introduce “fresh evidence” and because the lawsuit involves new claims that haven’t been addressed in the U.K. The patent should be revoked because the development is too “obvious” to experts in the field, he said.

The specific argument made by Neopharma was already rejected by courts in the Czech Republic, Slovakia, Canada and the U.S., Eli Lilly said in its filing.