(Bloomberg) -- Another prominent shareholder advisory firm has come out in support of Cigna Corp.’s $54 billion takeover of pharmacy benefits manager Express Scripts Holding Co., dealing another blow to activist investor Carl Icahn’s efforts to block the transaction.

Glass Lewis & Co. urged Cigna shareholders to vote in favor of the deal at an Aug. 24 shareholder meeting, despite the billionaire investor’s arguments that the takeover would be a “travesty.”

"We find the proposed merger both strategically and financially compelling, structured in a reasonable manner from a valuation standpoint for Cigna shareholders," Glass Lewis said in its report late Friday.

The recommendation is in line with that of Institutional Shareholder Services Inc., which also came out in support of the deal Friday.

Representatives for Cigna and Icahn were not immediately available for comment outside of regular business hours. Brian Henry, a spokesman for Express Scripts, said the company was pleased with the results of Glass Lewis report.

Uphill Battle

Cigna, based in Bloomfield, Connecticut, agreed in March to the cash-and-stock deal for St. Louis-based Express Scripts with the goal of bringing two branches of the health-care services sector under one roof, saving money for clients of the combined company.

Icahn owns a 0.56 percent stake in Cigna. He came out against the deal this week, saying the insurer is “dramatically overpaying” for Express Scripts. While he has acknowledged he faces an uphill battle to help block the deal, the billionaire investor has urged Cigna investors to vote against it, based in part on the threat posed by Amazon.com Inc. to Express Scripts’s future.

The activist investor said he believed Cigna would be better served by pursuing a multiyear partnership with a firm such as Express Scripts rather than a takeover, and instead use its cash to buy back shares. He said he believes Cigna could be worth $250 a share on a standalone basis and that Express Scripts, which he holds a short position in, would be worth less than $60 a share.

Glass Lewis said in its report that it believed the merger was set at a reasonable price, and would create a more diverse and integrated business model in the evolving health-care space.

"The board appears to have thoroughly considered the company’s strategic and transaction alternatives in the evolving and consolidating industry and reasonably determined that pursuing a transformative combination with Express Scripts represents the best opportunity to enhance shareholder value," it said.

--With assistance from Zachary Tracer.

To contact the reporter on this story: Scott Deveau in New York at sdeveau2@bloomberg.net

To contact the editors responsible for this story: Elizabeth Fournier at efournier5@bloomberg.net, Keith Campbell, John Deane

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