Longs Drug Stores Corp.'s largest institutional shareholder, Advisory Research Inc., said it will support CVS Caremark Corp.'s $2.7 billion takeover offer.

Advisory Research, which owns 9.2 percent of Longs Drug, is disappointed Walgreen Co. withdrew its $2.8 billion bid Oct. 8, President David Heller said today in a phone interview. The firm said in a statement today it will tender its shares in favor of CVS' cash offer.

Longs Drug directors spurned the Walgreen bid because they thought it posed antitrust risk."In today's environment it would be very difficult to find anyone who would purchase the whole company and could arrange the financing so it would appear to us that CVS may be the only buyer," he said.