Study to Evaluate the Efficacy and Safety of Filgotinib in the Treatment of Perianal Fistulizing Crohn's Disease

Key Inclusion Criteria: * Males or non-pregnant, non-lactating females, ages 18 to 75 years, inclusive based on the date of screening visit * Diagnosis of Crohn's disease (CD) with a minimum duration of CD of at least 3 months * Has draining perianal fistulae as a complication of CD, confirmed by magnetic resonance imaging (MRI) at screening * Previously demonstrated an inadequate clinical response, loss of response to, or intolerance of at least 1 of the following agents (depending on current country treatment recommendations/guidelines): * Antibiotics AND/OR * Immunomodulators AND/OR * Tumor necrosis factor α (TNFα) Antagonist * Is willing and able to undergo MRI per protocol requirements * Is willing and able to undergo flexible sigmoidoscopy per protocol requirements Key Exclusion Criteria: * Presence of current rectovaginal anovaginal or enterovesicular fistulae * Presence of ulcerative colitis (UC), indeterminate colitis, ischemic colitis, fulminant colitis, or toxic mega-colon * History of total proctocolectomy, total colectomy, presence of ileostomy or colostomy, or likely requirement for surgery during the study * Use of any prohibited concomitant medications as described in the study protocol * Active tuberculosis (TB) or history of latent TB that has not been treated Note: Other protocol defined Inclusion/Exclusion criteria may apply.