The goal of this observational study is to determine if, as with other therapeutics such as anti-TNF, trough levels of Risankizumab are correlated with clinical and biological remission in patients with moderate to severe Crohn's disease. As part of their regular biological surveillance, trough levels of Risankizumab were mesured and clinical and biological data were collected to determine if biological and clinical remission criteria were met.

The treatment of chronic inflammatory bowel disease has undergone a number of therapeutic revolutions in recent years, with the emergence of new biotherapies. These include RISANKIZUMAB, an anti-IL23 p19, whose ADVANCE , MOTIVATE and FORTIFY studies have demonstrated its efficacy in the induction and maintenance phases of Crohn's disease. Reimbursement in France for this indication is expected in the final quarter of 2024.

While for first-line molecules such as anti-TNF alpha, the relationship between serum levels and clinical remission is accepted and allows to guide the therapeutic strategy for patients, it has yet to be demonstrated for new molecules of interest.

We enrolled patients with moderate to severe Crohn's disease on Risankizumab in four centers. Trough levels of Risankizumab were mesured as a part of their regular medical surveillance routine. For each consultation, biological and clinical data were collected to determine wether patients were in remission (according to our primary outcome) or not. Data were collected up to 18 months since the introduction of Risankizumab.

The objectives of this study were also to identify factors of primary or secondary failure of treatment, to determine clinical reponse rate, to evaluate tolerance and persistence of treatment.

Inclusion Criteria:

• Age ≥18 years
• Patients with moderate to severe Crohn's disease
• Failure of at least one immunosuppressant and one anti-TNF alpha agent
• Patients on Risankizumab
• No opposition to study participation

Exclusion Criteria:

• Age < 18 years
• UC
• Unclassified colitis
• Risankizumab prescribed to prevent post-operative relapse
• Any contraindication to Risankizumab
• Refusal to participate in study

Patients with moderate to severe Crohn's disease on Risankizumab