Mercaptopurine Therapy in Ulcerative Colitis

Inclusion Criteria:

1. Confirmed diagnosis of UC by endoscopy and histopathology

2. Patients between 18 and 80 years of age

3. Active disease, despite oral treatment with at least 2g/day 5-ASA

4. Treatment with oral corticosteroids is required

Exclusion Criteria:

1. Prior treatment with thiopurines

2. Prior treatment with biologics (e.g. anti-TNF agents and vedolizumab)

3. Current pregnancy (a pregnancy test will be performed if necessary according to thetreating physician)

4. Chronic Obstructive Pulmonary Disease (COPD)

5. Acute coronary heart disease

6. (Bacterial) gastroenteritis has to be treated first

7. Coagulation disorders

8. Active malignancy

9. History of colonic dysplasia/cancer

10. Extensive colonic resection, i.e. subtotal colectomy with <15 cm colon in situ

11. Concomitant therapy with drugs interfering with MP metabolism, like allopurinol,ribavirin or anti-epileptics.

12. Known systemic fungal infections or parasitic infections have to be treated first

13. Known duodenal or ventricular ulcus

14. Substance abuse, such as alcohol (> 80 gram/day - one standard glass contains 10 gramof alcohol), I.V. drugs and inhaled drugs. If the subject has a history of substanceabuse, to be considered for inclusion into the protocol, the subject must haveabstained from using the abused substance for at least 2 years. Subjects receivingmethadone within the past 2 years are also excluded

15. Positive tuberculosis screen (when a screening is performed at the discretion of thetreating physician)

16. Active hepatitis B virus or hepatitis C virus infection defined as a positiveanti-HCV, HBsAg and/or anti-HBcore screening.

17. Leucopenia (Neutrophil count < 1,8x10^9/L)

18. Thrombopenia (Platelets < 90x10^9/L)

19. Elevated liver enzymes (>2x ULN)

20. Abnormal renal function (eGFR< 30 mL/min)

21. Other conditions which in the opinion of the investigator may interfere with thesubject's ability to comply with the study procedure