The St. Louis company had said recently it expected to close the deal early in the second quarter. Shareholders from both companies have already approved the acquisition, but the Federal Trade Commission is still reviewing it.
Express Scripts spokesman Brian Henry says he can't comment on whether his company's announcement means regulatory approval of the deal is likely. He says discussions with the FTC are private.
Pharmacy benefits managers, or PBMs, run prescription drug plans for employers, government agencies and other clients, using their large purchasing power to negotiate lower drug prices. They make money by reducing costs for health plan sponsors and members.