1 Project summary 1.1 Rational. Accent 1 study has demonstrated the superiority of Infliximab over placebo in a systematic treatment strategy of Crohn 's disease every 8 weeks during one year. However the optimal strategy beyond one year of treatment is not established. Particularly, the need for carrying on systematic treatment with infliximab in all the patients has not been demonstrated.

1.2 Primary objective. Determine factors associated with a low risk of clinical relapse after stopping infliximab in CD patients in remission (CDAI<150) and regularly treated with infliximab for at least one year.

1.3 Main objective and main judgement criteria. Determine predictive factors for relapse within one year after stopping infliximab. Main judgement criteria is the clinical relapse after stopping infliximab. Clinical relapse is defined either by a CDAI>250 or by a CDAI between 150 and 250 if this CDAI is confirmed over two consecutive weeks with an increase of at least 70 points over baseline for the two consecutive measures.

1.4 Secondary objectives and judgement criteria. Determine the time to-relapse Determine predictive factors for short-term relapse (<2 months)after stopping infliximab.

Determine response to infliximab retreatment in these patients. Determine tolerance to infliximab retreatment in these patients. Determine predictive factors for an absence of response to retreatment. Determine predictive factors for infliximab retreatment intolerance. Determine sustained response in the retreated patients.

1.5 Type of study Open-label prospective study of stopping regular treatment. Inclusion period: minimum one year, possibly prolonged to reach 100 patients. Patients will be followed up every two months for at least 18 months after stopping infliximab.

1.6 Justification of the number of patients Number of patients to include is at least 100. This recruitment should be reached within one year. This number should allow to disclose predictive factors associated with a relative risk of at least 2 if this factor is equilibrated (50% at risk patients) or 3 is this factor is disequilibrated (90% at risk patients).

Inclusion criteria:

• Crohn's disease.
• Age > 18 years.
• Patient written informed consent.
• Patient having been treated with infliximab for confirmed Crohn's disease with active intestinal lesions.
• Patient treated with infliximab for at least 1 year, associated with an immunosuppressor for at least one year, with a maximum interval between 2 infliximab infusions of 3 months.
• Patient with continuous remission without steroids for at least 6 months, except IV steroids for infusion reaction prophylaxis.
• CDAI<150.
• Contraception all over the study.

Exclusion criteria:

• Patient having experienced an severe acute infusion reaction to infliximab, defined by an anaphylactoïd reaction (drop in blood pressure, bronchospasm, dyspnea) requiring the arrest of the infliximab infusion.
• Patient having experienced a severe delayed infusion reaction to infliximab, defined by fever, arthralgia, myalgia, requiring a steroid treatment.
• Patient with dominant perianal disease and absence of active intestinal disease at the time of infliximab induction.
• Patient with active perianal disease at the time of inclusion.
• Patient with stoma.
• Patient with debilitating extra-intestinal manifestation at the time of inclusion.
• Non cooperating subjects.
• Pregnant or lactating women.