CLINICAL TRIAL / NCT03345823

Inclusion Criteria: For Substudy 1: - Participant who achieve clinical response in Study M14-431 or Study M14-433. - Participant completes study procedures in the parent study. The final endoscopy for Studies M14-431 or M14-433 may be missing, if the endoscopy cannot be performed during the COVID-19 pandemic. For Substudy 2: - Participant completes Substudy 1. The Week 52 endoscopy may be missing, if the endoscopy cannot be performed during the COVID-19 pandemic. - Participant who achieved clincal response at the time descibed in the protocol and completes study procedures in the parent study/ substudy. For Substudy 3: - Participant is an ongoing participant in Substudy 2 for at least 12 months. - Participant is in stable remission for at least 6 months defined as: 1. CDAI < 150 2. CRP < 5 mg/L and FCP < 250 mg/kg AND 3. Participant has not been on locally acting (rectal or suppository) or systemic corticosteroids for CD => 90 days prior to the entry of Substudy 3. Exclusion Criteria: For Substudies 1,2 and 3: - Participant is considered by the investigator, for any reason, to be an unsuitable candidate for the study. - Participant who has a known hypersensitivity to upadacitinib or its excipients, or had an adverse event during Studies M14-431 and M14-433 or Substudy 1 or 2 of Study M14-430 that in the investigator's judgment makes the participant unsuitable for this study. - Participant at the final visit of M14-431 or M14-433 with any active or chronic recurring infections based on the investigator's assessment that makes the participant an unsuitable candidate for the study. Participants with serious infections undergoing treatment may be enrolled BUT NOT dosed until the infection treatment has been completed and the infection is resolved, based on the investigator's assessment. - Participants with high grade colonic dysplasia or malignancy diagnosed at the endoscopy performed at the final visit of Studies M14-431, M14-433 or Substudy 1 or 2 of Study M14-430 (Week 52). For Substudy 3 only: - Total SES-CD >4 and/or subscore >1 in any segment in the Substudy 2 annual ileo-colonoscopy, if performed within 6 months prior to Week 0 of Substudy 3. - Received any new medication or increase of the dose of current concomitant medication for the treatment of CD in the past 3 months.