Alexion Pharmaceuticals

RANK459

The company is best known for its development of Soliris, a drug used to treat a rare blood disorder. Alexion makes its debut on the Fortune 500 this year, but its stay may be short. In December 2020, UK-based pharma giant AstraZeneca announced plans to purchase it for $39 billion. Shareholders of both companies have approved the deal, though a review of the purchase by U.K. regulators, announced in May, may become a stumbling block.