Eli Lilly and Company has filed a 500-million dollar international lawsuit against the Canadian government.

Lilly says Canada unfairly shortened the life of patents for its best-selling drugs.  The case was filed Thursday under the rules of the North American Free Trade Agreement.
Lilly says Canadian courts unfairly threw out the patents when challenged by the generic drug manufacturers.

The legal fight will move to the next stage after the two sides failed to settle their differences during a 90-day consultation process which ends Friday.