Paris-based pharmaceuticals producer Sanofi has filed a patent infringement suit against U.S. drugmaker Eli Lilly, claiming that its U.S. rival infringed four of its patents for the type 2 diabetes drug Lantus. The synthetic insulin is one of the French company's top-selling drugs, with sales of €5 billion in 2012.
Sanofi said the case, to be heard by a U.S. district court in the state of Delaware,
is in response to Lilly's New Drug Application for an insulin glargine drug, filed with the Food and Drug Administration (FDA) in December 2013.

The company said it was informed by Lilly that its filing included a paragraph IV certification challenging six of the seven Sanofi patents listed in the FDA Orange Book for Lantus and Lantus SoloStar products. Lilly also has said it planned to launch its product following expiry of Sanofi's patent on the active ingredient, on Feb. 12, 2015.

Sanofi's legal action triggers an automatic 30-month stay of approval of the Lilly biosimilar by the FDA, effectively keeping it off the U.S. market until mid-2016, more than a year after its previously expected launch date.