This is a multi-center study that explores the relationship between recapture of response with escalation to weekly adalimumab and trough adalimumab concentration before escalation in patients experiencing lack of response (LOR).

Inclusion Criteria:

• Documented diagnosis of Crohn's Disease.
• Treatment with adalimumab, for a minimum of 16 weeks, as per clinical practice, at a dose of 160 mg at week 0, 80 mg at week 2, and then 40 mg q2w with a documented response as defined by the investigator.
• Current evidence of active inflammatory disease/LOR defined as the presence of active inflammation (confirmed with a CRP ≥ 5 mg/L and/or a fecal calprotectin ≥ 250µg/g.
• Ability of subject to participate fully in all aspects of this clinical trial.
• Written informed consent must be obtained and documented.

Exclusion Criteria:

• Primary non-responders to 16 weeks of adalimumab therapy.
• Received any investigational drug within the 16 weeks of adalimumab therapy.
• Serious underlying disease other than CD that, in the opinion of the investigator, may interfere with the subject's ability to participate fully in the study.
• History of alcohol or drug abuse that, in the opinion of the investigator, may interfere with the subject's ability to comply with the study procedures.
• Stools positive for Clostridium difficile.
• Pregnant or lactating women.
• Current enrolment in any other interventional research study.
• Presence of perianal or abdominal abscess.

Participants will be enrolled from approximately 15 to 20 investigative sites in Canada where such Therapeutic Drug Monitoring/Anti-Adalimumab Antibody (TDM/AAA) testing at the point of patient LOR and pre-dose escalation to Every Week (EW) occurs.