Lucy Turnbull has stepped down as chair of cancer drug maker Prima Biomed.

The biotech, which this week changed its name to Immutep (ASX: PRR), is now led by Dr Russell Howard, the current chair of NeuClone which makes cheaper biologic drugs.

Ms Turnbull’s final interest notice came in late on Wednesday. The former Lord Mayor of Sydney and wife of PM Malcolm Turnbull owns or controls 20.4 million shares in the company.

Ms Turnbull quit last Friday, announcing the news in her chairwoman’s address to shareholders.

“I am delighted that Dr Russell Howard will become the company’s chair effective from tomorrow,” Ms Turnbull said.

“After careful consideration, due to my extensive professional and personal commitments I feel the time is right for me to step down.”

CEO Marc Voigt says Dr Howard had been on the board since May 2013.

“His strong scientific background and knowledge of the industry and company made him a natural successor as chair,” he told Stockhead.

“While Lucy’s decision to step down was made immediately prior to the AGM, in light of her demanding schedule the handover to Dr Russell had been planned for some time.”