Safety of Allogeneic Adipose Tissue-Derived Mesenchymal Stem Cells for the Treatment of Complex Perianal Fistulas Not Associated With Crohn's Disease: A Phase I Clinical Trial

BACKGROUND: Anal fistula treatment aims to eradicate the fistula, preserve the sphincter, prevent recurrence, and allow an early return to daily activities for the patient. Because of the difficulty of achieving these goals, stem cell-based therapy has emerged for the treatment of complex perianal fistula with promising results. OBJECTIVE: The objective of this study was to evaluate the safety of allogeneic mesenchymal stem cells in the treatment of complex anal fistula in patients without Crohn's disease. DESIGN: This was a prospective nonrandomized phase I clinical trial. SETTINGS: This study was conducted at a second-level hospital. PATIENTS: Twenty consecutive patients diagnosed with a complex fistula were included. INTERVENTIONS: All patients received 40 x 10(6) allogeneic mesenchymal stem cells. In patients with 2 tracts, 20 x 10(6) stem cells were applied on each tract. MAIN OUTCOME MEASURES: The patients were discharged 24 hours after the procedure and were evaluated at 1, 2, 4, 8, 16, and 24 weeks after the application. The long-term follow-up was performed 1 year after the procedure. RESULTS: The procedure was performed in a total of 20 patients from October 1, 2016, to October 31, 2017; 1 patient was eliminated from the final data analysis. No adverse effects were reported within the first 24 hours, and all the patients were discharged asymptomatic. Three patients (15%) presented with perianal abscess. In 1 patient, the abscess appeared at the fourth week, and, in the other 2 patients, the abscess was diagnosed at week 8. Complete closure was achieved in 13 (69%) patients. LIMITATIONS: This was a nonrandomized controlled trial. CONCLUSION: The use of allogeneic mesenchymal stem cells as a treatment is a safe option for the management of complex perianal fistula not associated with Crohn's disease. See Video Abstract at http://links.lww.com/ DCR/B443.