The public motion outlines the non-disclosure and confidentiality agreements that Walgreens and Theranos entered into beginning in April 2010. "If confidential information subject to the NDA and/or the Confidentiality provision of the Agreement were publicly disseminated, Theranos might claim that Walgreens potentially could be in breach of the NDA and/or the Agreement," the motion reads.

Walgreens just filed a $140 million lawsuit against @theranos in Delaware. — John Carreyrou (@JohnCarreyrou) November 8, 2016

While there's no word on the focus of the lawsuit, there's plenty of turbulent history for Walgreens to choose from. Theranos was once a blood-testing start-up poised to reach the stars, but in 2015 the safety and accuracy of its methods came under fire. The Food and Drug Administration shut down all Theranos testing aside from Herpes in October 2015, and in July this year US regulators banned CEO Elizabeth Holmes from running a lab for two years.

Walgreens ended its relationship with Theranos in June, after months of warnings that the start-up had to clean up its act.

In October, an investor who poured $100 million into Theranos sued the company, alleging it had fed financiers a "series of lies."