Cigna Corp. shareholders on Friday voted in favor of the health insurer's proposed $52 billion acquisition of pharmacy benefit manager Express Scripts Holding Co., although the deal still needs clearance from antitrust authorities.

The vote in favor of the merger was on expected lines after activist investor Carl Icahn walked away last week from his 11th-hour attempt to rally shareholders to reject the deal.

The U.S. Department of Justice is still conducting an antitrust review of the combination that is not expected to close until later this year.

According to the preliminary results, about 90 percent of the votes cast were in favor of the merger, the health insurer said.

Cigna expects the merger to close by end of 2018.

The insurer agreed to buy Express Scripts in March saying the two companies could save more on healthcare costs for clients if they better coordinated medical care with prescriptions.

But since then Express Scripts has come under stiffer opposition from the Trump administration, lawmakers and drug makers as being a middleman that drives up drug costs. Icahn had argued that Cigna was overpaying given prospects for reduced profits.

He backed down after shareholder advisory groups recommended that shareholders vote for the deal.

Express Scripts shareholders also approved the deal, with about 78 percent of outstanding shares of Express Scripts voted for the deal.

Cigna's plan for the acquisition comes as Express Scripts' major rival CVS Health and Aetna Inc move forward on their own merger. Cigna's deal to be bought by Anthem Inc fell apart last year after it failed to pass antitrust review.

Cigna shares slipped 0.10 percent, while Express Scripts rose 0.47 percent.