Novo Nordisk, the Danish pharmaceutical group focused on diabetes care, has begun legal action in the US to block the launch of a new insulin product produced by its French rival Sanofi-Aventis.

Novo Nordisk is seeking an injunction because it claims Sanofi-Aventis' Solo-Star injection pen combined with Lantus insulin - recently approved by the US Food & Drug Administration - infringes the patents on its NovoPen 4.