Japan’s Eisai has filed a lawsuit against Teva, after receiving notice that the generic drugmaker plans to launch a copycat version of Eisai’s Alzheimer’s disease treatment Aricept (donepezil) in the USA.

Eisai filed the lawsuit against Teva in the US District Court for the District of New Jersey, alleging that Teva’s filing of an Abbreviated New Drug Application for a donepezil infringes a composition of matter patent on the drug that is not due to expire in the USA until November 25, 2010.

Aricept is a major earner for Eisai, bringing in revenues of 163 billion yen for the year ended March 2005 with sales projected to rise to 188 billion yen this year. It is also marketed by Pfizer, which reported sales of $255 million in the first nine months of this year.

- Meanwhile, Teva has been granted final US regulatory approval for a generic version of Purdue Pharma's Oxycontin (oxycodone) tablets, an opioid analgesic for the treatment of moderate to severe pain. Teva said shipments of its generic will start immediately. Purdue's product had total annual sales of about $1.2 billion.