Caremark's (CMX) board rejected an unsolicited cash-and-stock bid from rival Express Scripts (ESRX) and reiterated its support for a planned deal with big drug store chain CVS (CVS).

Nashville, Tenn.-based Caremark said it concluded Express Scripts' proposal "does not constitute, and is not reasonably likely to lead to, a superior proposal" than the all-stock deal the mail-order pharmacy agreed to with Woonsocket, R.I.-based CVS.

CVS said Nov. 1 it would pay $21 billion in stock for Caremark. Express Scripts said last month it would offer $26 billion in cash and stock.

CVS said Monday it expects to close the deal in the first quarter.

"Unlike Caremark's and CVS's decision to enter into a merger from positions of strength and provide plan sponsors and consumers with the products and services they desire, Express Scripts' proposal is reactionary and defensive," Caremark said. "Caremark believes that Express Scripts' interference with the CVS/Caremark merger reflects Express Scripts' concerns about the enhanced competition due to the innovative services created by a CVS/Caremark combination and the change in industry landscape that would result."

St. Louis-based Express Scripts reiterated that it believes its offer is superior and said it remains committed to pursuing the deal.

"Our historical stock price performance has been outstanding and superior to CVS'," Express Scripts said. "As a combined company, Express Scripts and Caremark will have growth opportunities that provide significant upside potential to stockholders of both companies."

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