Express Scripts, a pharmacy benefits management (PBM) company, has signed a definitive agreement to acquire WellPoint's NextRx subsidiaries for $4.675 billion, which includes consideration for the value of a future tax benefit for Express Scripts based on the structure of the transaction.

The Indianapolis-based WellPoint said its NextRx subsidiaries provide PBM services to approximately 25 million Americans and manage more than 265 million adjusted prescriptions annually. The transaction includes a 10-year contract for the St. Louis-based Express Scripts to provide services to WellPoint, a health benefits company, following closing of the transaction.

The transition to Express Scripts' platform and products will be staged to maintain consistency of benefits and pharmacy services to members, according to the companies. WellPoint will retain control of medical policy, formulary and integrated disease management, and will work alongside Express Scripts to offer pharmacy management and data analytics.

The transaction is expected to close in the second half of 2009, subject to customary closing conditions and the expiration of the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act.