P718 A Phase I Study of Ex Vivo Expanded Allogeneic Bone Marrow Derived Mesenchymal Stem Cells for the Treatment of Pediatric Perianal Fistulizing Crohn’s Disease

Abstract Background Background: Mesenchymal stem cells have been used for the treatment of perianal Crohn’s fistulizing disease by direction injection. However, no studies to date have included pediatric patients. Objective To determine safety and efficacy of mesenchymal stem cells for pediatric perianal fistulizing Crohn’s disease. Methods Design: Phase I safety trial Settings Tertiary inflammatory bowel disease referral center Patients Crohn’s patients aged 13-17 with perianal fistulizing disease. Intervention 75 million mesenchymal stem cells were administered with a 22G needle by direct injection after curettage and primary closure of the fistula tract. A repeat injection of 75 million mesenchymal stem cells at 3 months was given if complete clinical and radiographic healing were not achieved. Main outcomes measures Adverse and serious adverse events at post procedure day 1, week 2, week 6, month 3, month 6 and month 12. Clinical healing, radiographic healing per magnetic resonance imaging, and patient reported outcomes at the same time points. Results Results: A total of 7 pediatric patients were enrolled and treated (6 male; median age of 16.7 years). There were no adverse or serious adverse events reported related to investigational product. At six months, 83% had complete clinical and radiographic healing. The perianal Crohn’s disease activity index, Wexner incontinence score, and VanAssche score had all decreased at six months. Limitations Single institution and open label. Conclusion Bone marrow derived mesenchymal stem cells offer a safe, and likely effective, alternative treatment approach for pediatric perianal fistulizing Crohn’s disease.