This is a four-part Phase 2b study comprised of a 16-week, double-blind, placebo-controlled, Induction Period, a 12-week double-blind, placebo-controlled, Maintenance Period, a 24-week, Open-label Period and a post-treatment 28 week observational safety follow-up period designed to evaluate the short-term efficacy and the short- and long term safety of brazikumab in participants with moderate to severe, active Crohn's disease (CD) who have failed or are intolerant to anti-TNFα therapy as determined by the Investigator.