Michael M. Morrissey hit the road last summer charged with one of the most daunting tasks in his career: to convince investors and analysts to keep the faith in Exelixis, the South San Francisco-based biotechnology company he suddenly found himself leading. Within a span of 10 days, two major events had rocked the firm: Its most lucrative partnership, a licensing deal with Bristol-Myers Squibb for the cancer drug XL184, had dissolved after BMS shifted strategy, and its chief executive officer, George A. Scangos, had abruptly left to head up Biogen Idec.
