Mesenchymal stromal cells in the treatment of perianal fistulas in Crohn's disease.

Significant unmet needs remain in patients with Crohn's disease and perianal fistulas. Mesenchymal stromal cells have potent immunomodulatory actions. The Phase II studies reported efficacy of local injection of mesenchymal stromal cells to achieve closure of fistulas. A Phase III trial demonstrated that in patients with Crohn's disease and refractory complex perianal fistulas, a single injection of 120 × 106 cells was superior to local injection of placebo associated with the same surgical procedure, in obtaining closure of the fistula tracts together with absence of abscesses >2 cm, 24 weeks after the injection, a stringent combined primary end point. The benefit over placebo was sustained 52 weeks after the single injection. The therapy is safe with adverse events limited to local pain.