Sanofi SA and Regeneron Pharmaceuticals Inc have developed a new injectable drug called Dupixent (known chemically as dupilumab).  Dupixent is said to be a very important drug for the treatment of eczema that causes extreme itching to the skin, with annual sales estimated to exceed $5 billion by 2023.

Sanofi SA and Regeneron Pharmaceuticals Inc decided to pre-emptively sue Amgen Inc to prove that their eczema drug Dupixent, awaiting a U.S. approval decision, does not infringe Amgen’s patent for a failed asthma treatment as they plan to start selling Dupixent as soon as FDA approval is achieved.

The lawsuit is a pre-emptive measure  to eliminate any potential obstacle Amgen might seek to raise against the planned commercialization of Dupixent which is expected to gain FDA approval very shortly.