Apple's stock price is also down amid soaring anxiety in the markets over the spread of the coronavirus.
The U.S. Supreme Court on Monday refused to hear Apple's appeal of a 2016 federal court verdict that hit the iPhone maker with a $302 million penalty in a patent infringement case.
The amount rose to $439.7 million as the case dragged on.
The patents, for secure networks, were violated by Apple when it incorporated the technology into its iPhones and iPads through a pair of features, FaceTime and VPN on Demand, VirnetX charged.
The U.S. Court of Appeals for the Federal Circuit last year upheld the 2016 jury verdict, triggering Apple's appeal to the Supreme Court.
Apple had argued that the verdict and the damages were unfair, saying the amount awarded to VirnetX was well above the actual value of the technology at issue.
In addition, the U.S. Patent and Trademark Office, at the request of Apple and other companies, reviewed the validity of the patents and axed key parts of them.
The legal loss comes as shares of Apple were hammered Monday over growing concern about the impact of the coronavirus on the tech giant's sales.
Apple's stock fell 4.1% to $300.24. The company last week said it wouldn't meet its revenue forecast for the current quarter due to supply disruptions in China from the coronavirus, known as Covid-19.