(Adds details, background, shares)
April 24 (Reuters) - Pharmacy benefit manager Express Scripts Holding Co said on Monday its PBM contract with major customer Anthem Inc was unlikely to be extended following its expiration in late 2019.
Shares of the largest U.S. pharmacy benefit manager (PBM) fell about 15 percent to $57.50 after the bell.
Last month, a federal judge dismissed two of the six counterclaims that Express Scripts raised in health insurer Anthem's $15 billion lawsuit claiming it charged too much for drugs.
Anthem had sued Express Scripts in March 2016, accusing it of excessive pricing and operational failures. It also sought the right to terminate its 10-year contract with Express Scripts.
Anthem accounted for about 18 percent of Express Scripts' revenue in the first quarter ended March 31.
(Reporting by Sweta Singh and Divya Grover in Bengaluru; Editing by Martina D'Couto)