The European Patent Office, answering a generic drug maker's challenge, withdrew a patent on Britain-based AstraZeneca PLC's heartburn treatment, Nexium.

AstraZeneca officials said they were disappointed with the patent office's decision, but had other patents and intellectual property measures that protected the drug in Europe, the Wall Street Journal said. The ruling involved the drug's chemical composition. The patent was due to expire in 2014.

The generic drug maker Ratiopharm International GmbH of Germany challenged the patent, which led to the EPO's decision. Ratiopharm has not indicated its plans regarding a generic form of Nexium.

Generic drug makers are challenging Nexium's patents in the United States.

AstraZeneca said Nexium's $4.6 billion in worldwide sales accounted for about a fifth of the company's third-quarter revenue.

Copyright 2006 by United Press International