Influence of Smoking Cessation or Switching to THS on Disease Activity in IBD Patients.

Inclusion criteria: For all patients: 1. Patient has signed the ICF (Informed Consent Form) and is able to understand the information provided in the ICF. Patient can sign or not the optional ICF on long-term biobanking of samples. 2. 19 years ≤ patient's age ≤ 75 years old 3. Patients who were diagnosed with UC or CD. 4. Patient's disease activity is mild to moderate (PMS ≤ 6; CDAI: ≤ 300) and has not changed for at least the last 3 months, as judged by the Investigator. a 5. Patient is ready to comply with the study procedures (including readiness to accept smoking abstinence and/or use of THS). 6. Patient has smoked at least 5 commercially available and/or "roll your own cigarette" every day (no cigarette brand restriction) for at least the last 1 year, based on self-reporting. Smoking status will be verified based on a urinary cotinine test (i.e., cotinine ≥ 200 ng/mL). Specific to patients who prefer to continue using nicotine-containing and tobacco product after having been advised to quit smoking: 7. Not intending to quit using THS or smoking cigarettes within the next 6 months (to be checked at V2). Specific to patients who prefer to stop smoking cigarettes: 8. Any patient who is willing to attempt quitting cigarette smoking Exclusion criteria: For all patients: 9. Patients with severe disease activity (PMS \> 5; CDAI \> 300), as judged by the Investigator. 10. Female patients who are pregnant or breast-feeding 11. Female patients who are planning to become pregnant during the next 8 months 12. Patients with a history of recent and current alcohol and substance abuse 13. Patient is ineligible as judged by the Investigator to participate in the study for any reason (e.g., medical, psychiatric and/or social reason), including any abnormal safety laboratory values obtained at screening that are judged as clinically significant by the investigator. 14. Patient is legally incompetent, or physically or mentally incapable of giving consent (e.g., emergency situation, under guardianship, prisoners, or patients who are involuntarily incarcerated). 15. Patient with any major illness/condition or evidence of an unstable clinical condition (e. g. renal, hepatic, hematologic, gastrointestinal \[except the disease under study\], endocrine, cardiovascular, pulmonary, immunologic, or local active infection/infectious illness) that, in the investigator's judgment, could impact study results. 16. The patient has colorectal carcinoma or high-grade dysplasia adenoma. 17. As per the investigator's judgment, the patient has medical conditions which require or will require in the course of the study, a medical intervention (e. g. start of treatment, surgery, hospitalization), which may interfere with the study participation and/or study results. 18. Any other clinically significant medical condition, which as per the judgment of the PI would jeopardize the safety of the patient. 19. Clinically significant ECG alterations that will not allow patient to participate in the study, per Investigator's discretion