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

The lawsuit, filed last month in Connecticut federal court, was followed 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.

"By filing bogus patent listings, pharma companies block competition and inflate the cost of prescription drugs, forcing Americans to pay sky-high prices for medicines they rely on," FTC Chair Lina M. Khan said in a news release. "By challenging junk patent filings, the FTC is fighting these illegal tactics and making sure that Americans can get timely access to innovative and affordable versions of the medicines they need."