Fistula is a representative devastating complication in Crohn's patients due to refractory to conventional therapy and high recurrence. In our phase I clinical trial, adipose tissue-derived stem cells (ASCs) demonstrated their safety and therapeutic potential for healing fistulae associated with Crohn's disease. This study was carried out to evaluate the efficacy and safety of ASCs in patients with Crohn's fistulae. In this phase II study, forty-three patients were treated with ASCs. The amount of ASCs was proportioned to fistula size and fistula tract was filled with ASCs in combination with fibrin glue after intralesional injection of ASCs. Patients without complete closure of fistula at 8 weeks received a second injection of ASCs containing 1.5 times more cells than the first injection. Fistula healing at week 8 after final dose injection and its sustainability for 1-year were evaluated. Healing was defined as a complete closure of external opening without any sign of drainage and inflammation. A modified per-protocol analysis showed that complete fistula healing was observed in 27/33 patients (82%) by 8 weeks after ASC injection. Of 27 patients with fistula healing, 26 patients completed additional observation study for 1-year and 23 patients (88%) sustained complete closure. There were no adverse events related to ASC administration. ASC treatment for patients with Crohn's fistulae was well tolerated, with a favorable therapeutic outcome. Furthermore, complete closure was well sustained. These results strongly suggest that autologous ASC could be a novel treatment option for the Crohn's fistula with high-risk of recurrence.

The present study was designed to evaluate the safety and potential of adipose tissue-derived stem cells (ASCs) for the treatment of Crohn's fistula. In this dose escalation study, patients were sequentially enrolled into three dosing groups with at least three patients per group. The first three patients (group 1) were given 1 × 10⁷ cells/ml. After 4 weeks, this dose was deemed safe, and so an additional four patients (group 2) were given 2 × 10⁷ cells/ml. Four weeks later, after which this second dose was deemed safe, a third and final group of three patients were given 4 × 10⁷ cells/ml. Each patient was followed for a minimum of 8 weeks. Patients who showed complete healing at week 8 were followed up for an additional 6 months. Efficacy endpoint was complete healing at week 8 after injection, defined as complete closure of the fistula track and internal and external openings without drainage or signs of inflammation. There were no grade 3 or 4 severity adverse events, and there were no adverse events related to the study drug. Two patients in group 2, treated with 2 × 10⁷ ASCs/ml, showed complete healing at week 8 after injection. Of the three patients enrolled in group 3, treated with 4 × 10⁷ ASCs/ml, one showed complete healing. Outcome in another patient was assessed as partial healing due to incomplete closure of the external opening, although the inside of fistula track was filled considerably and there was no drainage. All three patients with complete healing at week 8 showed a sustained effect without recurrence 8 months after injection. In conclusion, this study demonstrates the tolerability, safety, and potential efficacy of ASCs for the treatment of Crohn's fistula and provides support for further clinical study.

A previous phase II clinical trial of adipose-derived stem cell (ASC) therapy for fistulae associated with Crohn's disease, a devastating condition with a high recurrence rate, demonstrated safety and therapeutic potential with a 1-year sustained response. In the present study, 41 of the 43 phase II trial patients were followed for an additional year, regardless of response in the initial year. At 24 months, complete healing was observed in 21 of 26 patients (80.8%) in modified per protocol analysis and 27 of 36 patients (75.0%) in modified intention-to-treat analysis. No adverse events related to ASC administration were observed. Furthermore, complete closure after initial treatment was well-sustained. These results strongly suggest that autologous ASCs may be a novel treatment option for Crohn's fistulae. Significance: Long-term follow-up of patients with Crohn's fistula found that one or two doses of autologous adipose-derived stem cell therapy achieved complete closure in 80% of the patients at 12 months. After 24 months, 75% of those patients sustained complete closure, showing sustainable safety and efficacy of the treatment.

The somatic POLE P286R mutation defines a unique subclass of colorectal cancer featuring hypermutation, representing a potential genomic biomarker for immunotherapy