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Stocks making the biggest moves premarket: CI, BHC, MNK, DF, MAR, Z & more

Peter Schacknow

The health insurer's $54 billion deal to buy pharmacy benefits manager Express Scripts ESRX will be opposed by activist investor Carl Icahn , who issued an open letter to Cigna shareholders. Icahn calls the deal a "folly" and that it carries a "ridiculous" price tag, and adds that Amazon.com AMZN represents an "existential threat" to pharmacy benefit managers. Mallinckrodt MNK – The British drugmaker earned an adjusted $1.78 per share for its latest quarter, 30 cents a share above consensus estimates.