FILE PHOTO: A screen displays the share price for pharmaceutical maker AbbVie on the floor of the New York Stock Exchange July 18, 2014. REUTERS/Brendan McDermid/File Photo

(Reuters) - AbbVie Inc ABBV.N said on Friday that William Chase stepped down as chief financial officer and will retire from the company in mid-2019, and the U.S. drugmaker promoted controller, Robert Michael, to the CFO role.

Michael, 48, will report to Chase, who as of Friday becomes executive vice president of finance and administration.

The move came as a surprise and raises questions as the company faces new competition for its top drug, the rheumatoid arthritis treatment Humira, Credit Suisse analyst Vamil Divan wrote in a research note.

“We do not believe the Street had been expecting a CFO transition and, in fact, had expected a transition at the CEO level before one with the CFO,” Divan wrote.

AbbVie said in a filing with the U.S. Securities and Exchange Commission that Chase, who was 50 at the time AbbVie filed its annual report in February, had informed it that he planned to retire from the company. AbbVie did not put out a news release on the transition.

In an internal email to all AbbVie employees seen by Reuters, Chief Executive Officer Richard Gonzales thanked Chase for "helping to shape" the company. He said Chase was retiring after more than 30 years with the company and its predecessor, Abbott Laboratories. ABT.N Abbott split into two companies at the beginning of 2013.

AbbVie said on Thursday it had settled a patent dispute with Fresenius Kabi Oncology Ltd FRES.M3 over a proposed biosimilar rival to Humira, in the latest such settlement.

Humira, the world’s biggest-selling prescription drug with sales expected to reach $20 billion this year, began facing competition from biosimilar versions in Europe earlier this week.

AbbVie shares were down 1 percent at $88.86 in afternoon trading.