Regulators looking into the proposed CVS-Aetna tie-up are expected to require the divestiture of assets related to Medicare drug coverage as a way of addressing competitive issues, the Journal reported, citing sources familiar with the department's evaluation process. CVS has the largest market share in the Medicare drug-plan business, with 6.1 million members, the newspaper reported, citing an analysis by Wells Fargo. Aetna is the fifth-biggest Part D seller, with 2.2 million members. To preserve competition where CVS and Aetna sell Part D plans head-to-head, the Justice Department will require the companies to sell off parts of their Part D business to one or more companies that would compete with the newly merged firm, people familiar with the matter told the Journal.