March 28 (Bloomberg) -- Teva Pharmaceutical Industries Ltd., the world's largest generic-drug maker, was forbidden from beginning sales of a generic version of Eisai Co.'s biggest product, the Aricept Alzheimer's treatment.

A judge in Newark, New Jersey, granted Eisai's request to bar the generic drug until the trial for Eisai's patent- infringement suit against Teva can be held. Petah Tikva, Israel- based Teva is expecting U.S. Food and Drug Administration approval to begin sales as early as next month.

``There is no doubt that Teva has infringed Eisai's valid patent, and Eisai will likely prevail at trial in demonstrating the enforceability of that patent over Teva's inequitable conduct defense,'' U.S. District Judge Harold Ackerman said in an opinion issued today.

The FDA first approved Aricept tablets in 1996. The drug is Tokyo-based Eisai's biggest product, with $2.16 billion in worldwide sales in the year ended in March 2007, or 38 percent of revenue, according to data compiled by Bloomberg.

Teva received tentative approval from the FDA in January, and could receive final approval April 26, following a delay required under federal drug law because of the patent litigation.

Teva American depositary receipts, each representing one ordinary share, fell 63 cents to $46.01 at 4 p.m. New York time in Nasdaq Stock Market composite trading.

The case is Eisai Co. v. Teva Pharmaceuticals USA Inc., 05cv5727 and 07cv5489, U.S. District Court for the District of New Jersey (Newark).

To contact the reporter on this story: Susan Decker in Washington at sdecker1@bloomberg.net.

Last Updated: March 28, 2008 16:03 EDT