The Express Scripts Holding Company (ESRX) is a Fortune 100 company that provides pharmacy benefit management services to health plans, employers, and government programs. It is the largest pharmacy benefit manager in the United States, and is headquartered in St. Louis, Missouri. The company's services
From Wikipedia
Express Scripts Holding Company is a pharmacy benefit management (PBM) organization. In 2017 it was the 22nd-largest company in the United States by total revenue as well as the largest pharmacy benefit management (PBM) organization in the United States. Express Scripts had 2016 revenues of $100.752 billion. Since December 20, 2018, the company has been a direct subsidiary of Bloomfield, Connecticut-based Cigna.