The CEO of Biogen Idec, James Mullen, will be leaving the company in June after "seven turbulent years," says Fierce Biotech. During his tenure, Mullen oversaw the approval and marketing of Tysabr, to treat multiple sclerosis, which was then linked to rare, deadly brain infections. He also faced criticisms from investor Carl Icahn, including on the company's record of product development record, adds the Wall Street Journal.