Study of the 12-month Efficacy of Stem Cell Injection in Crohn's Disease With Complex Ano-perineal Fistula

Ano-perineal (or ano-rectal) fistulas are a frequent and major complication of Crohn's disease. Indeed, they indicate a greater severity of the disease. In addition, they have a major impact on the quality of life of patients. Finally, these fistulas are difficult to cure, especially when they are complex. Indeed, medical treatment with anti-TNF drugs can only cure them in one third of cases. Various obturation treatments have been proposed in addition to medical treatment such as advancement flap, injection of biological glue, placement of a plug, intersphincter ligation of the fistulous path or laser but with still insufficient healing rates. The injection of mesenchymal stem cells of adipose origin was first proposed for this indication in 2003. Since then, numerous studies have been published on the subject. Most importantly, an international multicenter randomized double-blind phase 3 controlled trial demonstrated the superiority of allogeneic stem cells over placebo with a therapeutic effect maintained at one year follow-up. The trial involved selected patients with Crohn's disease and one or more complex ano-perineal fistulas refractory to conventional treatments. This treatment has a high cost and its practical modalities are constraining (manufacturing, delivery, constrained time between the factory and the injection). However, this study is the first to have demonstrated in such a rigorous way the effectiveness of a local treatment on complex ano-perineal fistulas of Crohn's disease. These allogeneic mesenchymal stem cells have therefore been granted marketing authorization in Europe and have been commercialized in several European countries including France during the summer of 2020 under the trade name ALOFISEL®. They are indicated for complex ano-perineal fistulas that have not responded to at least one conventional biological treatment, in the context of inactive or less active Crohn's disease. The main objective of the study is to evaluate the rate