The most litigated rodent in the world of science this week plagued the European Patent Office. It reacted by narrowing the Oncomouse patent, a controversial method for producing genetically engineered animals with a predisposition to cancer.

The story began in 1984, when the President and Fellows of Harvard College applied for a US patent for the Oncomouse, also known as the Harvard Mouse. At that time, it had already been established in the US that a living organism could be patentable and the Oncomouse was hailed by some as a breakthrough in cancer research; but it outraged animal rights groups. They appealed several times against the US patent, ultimately without success.

In 1985, Harvard College applied for a European patent entitled "Method for producing transgenic animals". It was initially rejected, being deemed an "animal variety" and therefore excluded from Europe's morality rules on patentability.

However, in May 1992, the EPO Appeal Board granted the patent in respect of "non-human mammalian animals" for 11 member states of the European Patent Organisation after balancing animal suffering against the potential benefits to mankind.

Seventeen oppositions against the patent, filed in 1992 and 1993 by various animal rights groups, led to the decision in November 2001 to maintain the patent in respect of "transgenic rodents". Several appeals against that decision lodged in March 2003 were heard by the Technical Board of Appeal. This week, it decided to restrict the patent further to "transgenic mice".

The full reasons for the appeal decisions have still to be published.

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