(Bloomberg) -- Vir Biotechnology Inc. is replacing Chief Executive Officer George Scangos with Bayer AG executive Marianne De Backer as the infectious disease company seeks a follow-up to its Covid-19 antibody. The shares fell the most in five months. 

Scangos, 74,  who has led the company since its inception in 2017, is retiring after a long career in the industry. He was CEO of Biogen Inc. before taking the top job at Vir where he shepherded the company through the introduction of its only approved medicine, sotrovimab, the Covid antibody developed with GSK Plc. The shares fell as much as 7.7%, the most intraday since August, at the New York market open.

Sotrovimab was pulled from the US market after Covid variants rendered it ineffective, and Vir has since been searching for its next hit. De Backer, 54, is taking over as the company focuses on other infectious diseases like flu and hepatitis B. 

With the exception of the race to develop Covid vaccines and therapies, pharmaceutical companies have largely neglected infectious diseases. Yet there are still millions of people globally who could benefit from treatments for such diseases, which is what Vir is hoping to address if they succeed with any of their experimental medicines.

Read More: After Pandemic Success, Vir Looks for a Follow-Up

“There was nothing magic about this moment,” Scangos said in an interview. “When we have the opportunity to hire someone of Dr. De Backer’s skill sets, experience and demonstrated track record, it’s a good time to go.”

Scangos will retire as CEO in early April but remain an adviser until June and a member of Vir’s board after that, Vir said Wednesday. He plans to stay involved in the biotech industry while spending time with family and traveling. 

De Backer most recently led business development for Bayer’s pharmaceutical division, only weeks ago representing the German drug giant in dozens of meetings at the JPMorgan Healthcare Conference in San Francisco. She previously spent more than 20 years at Johnson & Johnson, including in science and business development roles.

Vir’s board interviewed numerous candidates and was ultimately impressed by De Backer’s science knowledge and business background, as well as her strategic thinking, Scangos said. She is joining Vir at a critical moment for the young company, which needs to find a new drug or drugs to support its growth. Vir now boasts $2.32 billion of cash and plans to share mid-stage trial data from three of its experimental treatments this year. 

(Updates with opening share price in first two paragraphs)

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