New York: Cigna said on Sunday it had rejected a multibillion-dollar buyout deal from rival health care giant Anthem, saying it was “deeply disappointed” in the group’s actions. The board was unanimous in its decision, calling the offer “inadequate” in a letter to Anthem, which had estimated the deal at $53.8 billion including debt when it made it public Saturday. Cigna had previously rejected an offer exceeding $45 billion from Anthem. “We are deeply disappointed with your recent actions,” the letter read. The letter was signed by Cigna’s chairman, Isaiah Harris, and David Cordani, the president, chief executive and director.