In a complaint filed on 2 September in a federal district court in Delaware, Novo Nordisk alleged that Sanofi-Aventis' OptiClik, approved by the Food and Drug Administration in August 2004, infringes patents covering its FlexPen device.
The case should go to court in 2007.
Novo Nordisk said it developed the first insulin pen in 1985 and has amassed a large patent portfolio covering the device.
"As a pioneer in diabetes treatment for 80 years, we have amassed a large patent portfolio that we are committed to defending," said Martin Soeters, president of Novo Nordisk's US subsidiary, in a statement.
Novo, which was the first company to introduce an insulin pen injection system in 1985, accused Sanofi-Aventis 'of wilful and deliberate patent infringement'.
The Danish company is seeking an injunction to prevent Sanofi-Aventis and its US, German, and Swiss affiliates from selling the OptiClik device, or an agreement that would make Sanofi-Aventis pay Novo royalties on OptiClik's profits.
Novo claims its FlexPen is the leading insulin delivery device in the US.
The OptiClik pen system is Sanofi-Aventis' only US Food and Drug Administration (FDA)-approved insulin delivery device and is used with all its US insulin products.
Ypsomed affected The OptiClik system was licensed to Sanofi-Aventis by Swiss company Ypsomed, and shares in the latter company dipped on news of the Novo lawsuit.
Ypsomed's core business is pen injector systems, and the company said in its last financial statement that the strong growth seen in that business - up 43 per cent to CHF 186 million in the 2004/05 fiscal year - was in part a result of the launch in January 2005 of Sanofi-Aventis' OptiClik-delivered Lantus (insulin glargine) product.
In a statement, Ypsomed said it: "does not currently possess detailed information with respect to [Novo's] claim," while noting that Sanofi-Aventis has rejected the claims of infringement as unjustified.
The US market for insulin is currently valued at about $2 billion per year, according to Novo.
Approximately a fifth of all US diabetics who need to take insulin to control the disease use pen injectors, up from about 5 per cent five years ago.
External links to companies or organisations mentioned in thisstory: Novo Nordisk Sanofi-Aventis Ypsomed