UC is a chronic, idiopathic form of intestinal inflammatory disease (IBD) that affects the colon, most commonly afflicting adults aged 30-40 years and resulting in disability and lower quality of life (1). It is characterized by relapsing and remitting mucosal inflammation, starting in the rectum and extending to proximal segments of the colon. Although biologic therapies have provided clinical benefits to patients, these goals are still poorly met, due to the limited knowledge of the underlying mechanisms of immunopathology and the lack of predictive biomarkers that would allow proper patient stratification.

The hypothesis of this study is that by identifying new biomarkers in blood, stool and tissue that (i) predict response (or non-response) to therapy prior to the start of treatment and (ii) predict response to therapy in the early phase of treatment will allow to find the right treatment for the right patient (personalized medicine).

Inclusion Criteria:

• Male and female patients ≥ 18 years of age (at the time of signing the ICF)
• Established diagnosis of ulcerative colitis with a minimum disease duration of 3 months
• Moderate to severe active UC defined by Mayo Score ≥ 6
• Moderate to severe active UC defined by endoscopy score of ≥2
• Indication to start any biological or small molecule agent (anti-TNF, anti- IL12/23, anti-integrin and JAK-inhibitors)
• In case of treatment with corticosteroid: stable dose for at least 3 weeks prior to baseline, dosage ≤ 20 mg prednisone
• Indication for an endoscopy for the assessment of disease activity as for standards of care and current guidelines
• Able to comply with the study procedures
• Person affiliated to or beneficiary of a social security plan
• Person informed about study organization and able to sign informed consent form

Exclusion Criteria:

• Diagnosis of indeterminate colitis, microscopic colitis, ischaemic colitis, infectious colitis, radiation colitis

• Absolute contraindications to endoscopy procedures or complication during previous endoscopy

• Bleeding disorders

• Indication for surgery for UC

• Rectal topical therapy (enemas or suppositories) ≤ 2 weeks prior to baseline

• Treatment with > 20 mg prednisone within 3 weeks prior to baseline

• Anaemia (haemoglobin < 10 g/dl) at baseline

• Any circumstances which could contradict a study participation and lead the Investigator to assess the patient as unsuitable for study participation for any other reason

• Person referred in articles L.1121-5, L. 1121-7 and L.1121-8 of the Public Health Code:

  • Pregnant, parturient or breastfeeding woman
  • Minor person (non-emancipated)
  • Adult person under legal protection (any form of public guardianship)
  • Adult person incapable of giving consent and not under legal protection

• Person deprived of liberty for judicial or administrative decision, person under psychiatric care as referred in articles L. 3212-1 and L. 3213-1

Patients with moderate to severe active UC with an indication to start a biologic treatment.