In its 13-year history, Theranos's biggest coup was its partnership with the Walgreens drugstore chain. Announced in 2013, the deal involved opening in-store blood testing centers at 40 locations and was supposed to be the first step in building the then-obscure start-up into a true competitor of established giants Quest Diagnostics and LabCorp.

But as allegations began to surface that Theranos's much-touted pinprick technology might not be what the company claimed, Walgreens began distancing itself from the growing scandal. In January, Walgreens said it had stopped sending clinical tests to a Theranos lab in Newark while government regulators were reviewing the company. In June, the chain told Theranos that it would terminate the partnership and close all of their Theranos Wellness Centers in Arizona — “effective immediately.”

Now Walgreens Boots Alliance is suing Theranos, seeking $140 million in damages. The lawsuit was filed in federal court in Wilmington, Del., under seal, according to Reuters.

Elizabeth Holmes, the embattled chief executive of Theranos who has been sanctioned by government regulators because of issues at the company, said in a statement that the company is “disappointed” that Walgreens filed the lawsuit and appeared to be threatening a countersuit. Holmes said Theranos will seek to hold Walgreens “responsible” for the damage it has caused the company and its investors.

“Over the years, Walgreens consistently failed to meet its commitments to Theranos. Through its mishandling of our partnership and now this lawsuit, Walgreens has caused Theranos and its investors significant harm,” Holmes said, vowing to “respond vigorously” to the allegations.

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