Walgreens had been a key partner for Theranos, which promised a device that could perform a wide range of blood tests, essentially replicating a full-scale lab. The deal with Walgreens, regarded as Theranos’s most visible and potentially lucrative partner, involved in-store testing centers at 40 locations. But when its vision collapsed, after it was alleged that Theranos had been running many of its tests on standard equipment, Walgreens sued the start-up seeking $140 million.