Shares of Legend Biotech fell 14% Monday after the company announced that CEO Ying Huang stepped down and left the board. Legend said in a regulatory filing that Huang's resignation was not the result of a disagreement with the company, but didn't say anything more about why he left.

Huang didn't immediately respond to messages seeking comment. The board named Alan Bash-president of the unit responsible for Legend's main drug-as interim CEO while it searches for a permanent successor.

Legend, based in New Jersey, sold $1.9 billion of that drug, Carvykti, last year. The therapy is made by removing a patient's own immune cells, reprogramming them in a lab to attack cancer and infusing them back into the body. Legend co-develops and sells Carvykti with Johnson & Johnson under a 2017 deal. The companies split profits equally outside China, while Legend keeps 70% of profits inside China.

Oppenheimer analyst Kostas Biliouris said the leadership change was a mixed signal for investors. Huang had brought deep experience to the role, he said, but "investors have been unhappy with the recent stock performance." Prior to news of Huang's departure Monday, Legend's shares were down 23% since the start of the month.