The legal battle between US pharma giant Eli Lilly and Dr Reddy's Laboratories, which had filed two abbreviated new drug applications seeking permission to market a generic version of the former's blockbuster drug Zyprexa (generic name: olanzaprine), is expected to begin by the latter part of this year.

Zyprexa, an over $3-billion drug in Eli Lilly's portfolio, is used in the treatment of schizophrenia, and is currently Eli Lilly's largest selling product globally. Its patents are valid till 2011.

A successful outcome in the trial, in addition to the US FDA approval (still awaited), could give Dr Reddy's a 180-day exclusivity to market certain dosage forms of the product in the US before the expiry of the patent, and may result in a windfall for the company.

Dr Reddy's spokesperson declined to comment on the issue. Rajiv Gulati, chairman & managing director, Eli Lilly & Company (India) also declined to comment.

According to information from Eli Lilly's website, Dr Reddy's had filed two separate ANDAs under para 4, covering certain dosage forms of olanzaprine in mid 2001.

In both instances, Eli Lilly had filed patent infringement suits against Dr Reddy's, claiming that the challenge to their patents for the drug is "without merit".

In addition to Dr Reddy's, two other companies -- Zenith Goldline Pharmaceuticals and Teva Pharmaceuticals -- have also filed ANDAs to market the generic versions of Zyprexa, according to the information available on Eli Lilly's website.

Of these, Zenith had filed the ANDA before Dr Reddy's. However, the dosage form details of Zenith's filing are not known.

According to Eli Lilly's website, "We currently expect a trial date to be scheduled for the fourth quarter of 2003. We believe that the generic manufacturers' patent claims are without merit and we expect to prevail in this litigation. However, it is not possible to predict or determine the outcome of this litigation."

The two pending filings for olanzaprin are only two of the ANDA filings by Dr Reddy's. In the company's 2001-02 annual report, K Anji Reddy, chairman of the company, put the number of pending ANDAs at 13, which represented a potential annual market of $11 billion.