Eli Lilly and Co., whose best-selling schizophrenia drug Zyprexa survived a United Kingdom court challenge by generic makers two years ago, lost a bid to dismiss another lawsuit over the medicine’s patent in Britain.

Judge Christopher Floyd in the High Court in London on Tuesday denied Lilly’s request for a judgment without trial against Neopharma Ltd., the closely held company that has European marketing rights for the generic version of the drug known chemically as olanzapine. One of Neopharma’s three claims in the case was dismissed.

While Floyd agreed Neopharma should be allowed to introduce “fresh evidence” in the dispute, he said the company was unlikely to succeed and ordered it to post a $321,400 security to pay Lilly’s legal fees if it loses.

The disputed patent held by Indianapolis-based Lilly was upheld by the U.K. Court of Appeal in December 2009, against a challenge by the Indian generic-drug maker Dr. Reddy’s Laboratories Ltd. The drug survived a parallel U.S. challenge in 2006 and went on to generate worldwide sales last year of more than $5 billion.

“This decision granting summary judgment for part of the case and security for costs for the remainder of the case in these circumstances, is unprecedented,” said Mark Sudwell, a U.K.-based spokesman for Eli Lilly. The ruling “confirms Lilly’s confidence in the strength of the olanzapine patent.”

Neopharma, which currently has no operations, briefly sold its generic version of the drug in Britain in 2008, before a court injunction forced it to stop. The case was put on hold until the Dr. Reddy’s lawsuit was resolved.

Neopharma’s lawyer, Antony Watson, argued the case should go to trial because he will introduce claims against the patent that haven’t yet been addressed in the U.K. Lilly claims those arguments were rejected by courts in the Czech Republic, Slovakia, Canada and the U.S. and needn’t be heard.