Activist investor Carl Icahn announced late Monday he is abandoning his effort to block the $67 billion acquisition of Express Scripts Holding Co. by Cigna Corp.

In a statement on his website, Icahn said he informed the U.S. Securities and Exchange Commission of his decision.

“In light of the ISS and Glass Lewis recommendations in favor of the Cigna/Express Scripts transaction and the significant stockholder overlap between the two companies, we have informed the SEC that we no longer intend to solicit proxies to vote against the transaction,” Icahn said.

Proxy advisory firm Glass Lewis & Co. last week joined Institutional Shareholder Services in recommending that shareholders of the Bloomfield, Connecticut-based Cigna vote to approve the proposed acquisition of Express Scripts.

Icahn, who has built a stake in Cigna, had urged shareholders to vote against the deal. He said Cigna’s “likely standalone value” is $215 a share and Express Scripts should be valued at less than $60 a share. As a result, he said, “it’s a travesty to complete this deal.”

Icahn also questioned the future of pharmacy benefit managers such as Express Scripts, which work with employers to administer prescriptions. The Trump administration proposed a rule in July scaling back protections that allow rebates between drug manufacturers and insurers and pharmacy benefits managers.

Glass Lewis, according to Cigna, said the deal is “strategically and financially compelling, structured in a reasonable manner from a valuation standpoint for Cigna shareholders.”

When the two companies announced the deal last March, they said the combination will “drive greater affordability,” improve links within health care and prescriptions while simplifying health care for customers.