A Multicenter, Open Phase II Study to Assess the Effect and Safety of "Low Dose" Photodynamic Therapy in Patients With Moderate to Severe Active Distal Ulcerative Colitis

Subsequently, the following algorithm will apply: >3 clinical responders at SD8, then another 10 patients, the second cohort, will be exposed to the same PDT dose intensity <3 clinical responders, without adverse proctosigmoidoscopic observations at SD8, then the second cohort, will be exposed to the next higher PDT dose intensity 15 J/cm2 <3 clinical responders, with adverse proctosigmoidoscopic observations at SD8, then the second cohort, will be exposed to the next lower PDT dose intensity 5 J/cm2 The safety will be continuously evaluated throughout the study. The screening phase consists of 1 week (SD-7 - SD0), the treatment phase of 4 weeks (SD1-SD29), and the follow-up evaluation phase of 4 weeks (SD30-SD57), equating to an overall duration of 9 weeks per patient. It is foreseen to have at least 3 participating investigational sites to complete accrual of the first cohort in 3 months, and the second cohort, if appropriate in an additional 3 months. In case of low recruitment, extra sites will be asked for participation. Hence the study duration from study initiation until last patient whom completed the study is 8 months to reach the primary analysis of the study. The follow-up analysis will be completed about 3 months later. Stopping rules: Requirement for prohibited medication or surgical procedure Requirement to increase the dose of permitted medication SAE thought to be attributable to PDT Grade III and IV toxicities (CTC v3.0) thought to be attributable to PDT Patients request to be withdrawn Lost to follow-up Investigational Medicinal Device: All patients will drink 50 ml orange juice containing 15 mg/kg 5-aminolevulinic acid (5-ALA). After 3 hours, the lesions will be illuminated with red light at 635 nm using a cylindrical light diffuser (Model RD, Medlight SA) in a white diffusing inflatable balloon catheter (model CDB OEB, Medlight SA) at a fluence rate of 65.5 mW/cm2 over 153 seconds resulting in a total light dose of 10 J/cm2. The first cohort will be treated at a ligh