Part A: 1. Has a confirmed diagnosis of CD at least 3 months before baseline, based on endoscopy results. 2. Has moderately to severely active CD at Screening, defined as a CDAI score ≥220 and a SES-CD ≥6 (≥4 if isolated ileal disease). 3. Has demonstrated at least 1 of the following (a, b, or c) to at least 1 IL antagonist or at least 1 tumor necrosis factor (TNF) antagonist, at doses approved for the treatment of CD: 1. Inadequate response after completing the full induction regimen; 2. Loss of response (recurrence of symptoms during scheduled maintenance dosing after prior clinical benefit); or 3. Intolerance (a significant adverse event that precluded further use, including but not limited to serious infection including opportunistic infections, malignancy, infusion-related and hypersensitivity reactions including anaphylaxis, and liver injury). Note: Participants with primary nonresponse to ≥2 agents are not eligible. Participants with intolerance to 2 agents may be eligible at the investigator's discretion. Part B: 4. Participant is in clinical remission at Week 26. Note: Participants exhibiting a clinical response (defined as a ≥ 100-point decrease in CDAI) at Week 26 may enter Part B at the investigator's discretion.

1. A current diagnosis of ulcerative colitis or indeterminate colitis. 2. Clinical evidence of a current abdominal abscess or a history of prior abdominal abscess. 3. Known fistula (other than perianal fistula) or phlegmon. 4. Known perianal fistula with abscess. 5. Ileostomy, colostomy, or severe, or symptomatic stenosis of the intestine. 6. Previous extensive colon resection with ≥2 colonic segments remaining, performed ≥ 6 months prior to screening. 7. Short bowel syndrome. 8. Any planned surgical intervention for CD, except for seton placement for perianal fistula without abscess. 9. History or evidence of adenomatous colonic polyps that have not been removed. 10. History or evidence of colonic mucosal dysplasia. 11. Intolerance or contraindication to ileocolonoscopy. 12. Any identified congenital or acquired immunodeficiency (eg, common variable immunodeficiency, human immunodeficiency virus [HIV] infection). 13. Active or latent tuberculosis (TB), regardless of treatment history. 14. A positive test for hepatitis B virus (HBV) as defined by the presence of hepatitis B surface antigen (HBsAg) or hepatitis B core antibody (HBcAb) test. 15. A positive test for hepatitis C virus (HCV), as defined by a positive hepatitis C virus antibody (HCVAb) test and detectable HCV ribonucleic acid (RNA). 16. Primary nonresponse to ≥2 IL antagonists (Cohort 1) or ≥2 TNF antagonists (Cohort 2) for the treatment of CD. 17. Received approved or investigational anti-integrin antibodies (i.e., vedolizumab, natalizumab, efalizumab, etrolizumab, abrilumab [AMG 181], anti- mucosal addressin cell adhesion molecule-1 [MAdCAM-1] antibodies, or rituximab). 18. History of or symptoms of progressive multifocal leukoencephalopathy (PML) in the investigator's opinion. If a participant has symptoms consistent with PML, a PML checklist must be completed and submitted to the PML independent adjudication committee (IAC). If the PML IAC deems the participant to have PML, the participant is ineligible.