Federal regulators are challenging patents on 20 brand name drugs, including the blockbuster weight-loss injection Ozempic, in the latest action by the Biden administration targeting industry practices that drive up pharmaceutical prices.

The Federal Trade Commission on Tuesday sent warning letters to 10 drugmakers, taking issue with patents on popular drugs for weight loss, diabetes, asthma and other reparatory conditions. The letters allege that certain patents filed by Novo Nordisk, GlaxoSmithKline, AstraZeneca and seven other companies are inaccurate or misleading.

Brand-name drugmakers use patents to protect their medicines and stave off cheaper, generic medicines. Most blockbuster drugs are protected by dozens of patents covering various ingredients, manufacturing processes and intellectual property. Generic drugmakers can only launch their own cheaper versions if the patents have expired or are successfully challenged in court.

“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,” said FTC Chair Lina Khan, in a statement.