SANOFI-AVENTIS FILES SUIT TO BLOCK GENERIC AMBIEN

Sanofi-aventis has filed a patent infringement lawsuit in federal court to block the manufacturing and marketing of zolpidem tartrate, a generic version of its blockbuster sleep drug Ambien CR.

The company filed the suit Feb. 5 in the U.S. District Court for the Middle District of North Carolina after generic firm Synthon Pharmaceuticals filed an abbreviated new drug application (ANDA) to market zolpidem tartrate extended-release tablets in 6.25- and 12.5-mg doses. The ANDA challenges claims in the brand company's '531 patent that cover a specific pharmaceutical controlled-release dosage form used to release zolpidem and/or its related salts over a period of time, according to court papers. Synthon says that those patent claims are invalid and unenforceable.

Sanofi holds three unexpired patents related to Ambien and Ambien CR. The '531 patent expires Dec. 1, 2019, with pediatric exclusivity extending through June 1, 2020. Its '938 patent, originally set to expire in October 2006, won FDA pediatric exclusivity and now expires April 21 of this year.

Sales of Ambien generated approximately $1.4 billion for the company during the first nine months of 2006, the company reports.