Patients with IBD, both UC and CD, who fulfil the inclusion and exclusion criteria will be included consecutively:

• Retrospective cohort Patients treated with IBD from January 2015 to June 2024 will be included.
• Prospective cohort Consecutive patients with IBD who are starting, from clinical practice, new biological/small molecule therapies, failure (already exposed) to a mechanism of action (for anti TNF-alpha, more than one molecule is allowed), and who belong to the Lazio Regional Health System.

Eligible subjects will be identified among patients belonging to the IBD Unit of the Digestive Diseases Centre (CEMAD) of the Foundation and to all the other IBD Units of all the centres specified in Annex 1. Based on the number of patients referred to the clinics, we estimate 112 patients per month, the time for recruitment is 24 months.

Potential study participants will receive oral and written information about the study. Patients who agree to participate in the study will be asked to sign a written informed consent according to GCP.

Multicenter, ambispectic observational study with drug

Inclusion Criteria:

1. Age 18 to 70 years
2. Patients with a previous diagnosis of CD or UC at least 3 months before baseline.
3. Patients who have already failed at least one advanced (biological or small molecule) therapy for IBD and who have experienced failure to at least one mechanism of action (failure is defined as primary failure, secondary failure, or intolerance).
4. Patients who have already started a new advanced therapy for IBD based on clinical practice indication (primary loss of response, secondary loss of response, intolerance to the previous drug) since at least 1 week and up to 8 weeks after starting it.
5. Written informed consent certifying the willingness of the subject to participate to the study.

Exclusion Criteria:

1. Age < 18 years.
2. Patients with diagnosis of indeterminate colitis.
3. Patients naive to advanced (biological or small molecule) therapy for IBD.
4. Refusal to sign written informed consent certifying the willingness of the subject to participate to the study.

Patients with IBD, both UC and CD, who meet the inclusion and exclusion criteria