Boehringer Ingelheim, the world’s largest private pharmaceutical company, was hit with an antitrust class action alleging that the company is using expired patents to delay competition between brand name and generic inhalers.

The lawsuit, filed Monday in Connecticut federal court, was followed Tuesday by the Federal Trade Commission’s announcement that it sent warning letters to 10 companies, including Boehringer Ingelheim, disputing the “accuracy or relevance” of patent listings in the Food and Drug Administration’s Orange Book.