Efficacy of cx601 (darvadstrocel) for the treatment of perianal fistulizing Crohn's disease-A prospective nationwide multicenter cohort study.

Background: The use of mesenchymal stem cells is considered a novel and promising therapeutic option for patients with perianal fistulizing Crohn's disease; however, data on its clinical application remain scarce. This multicenter nationwide study aimed to assess the clinical efficacy of mesenchymal stem cells in closing complex anal fistulas.

Methods: In this study 14 Crohn's disease patients (3 males, 11 females) with complex anal fistulas treated in 3 tertiary hospitals in Austria were included between October 2018 and April 2021. Injection of 120 million allogeneic expanded adipose-derived mesenchymal stem cells (Cx601-darvadstrocel) was performed in each patient. Closure of the external fistula opening without secretion by external manual compression was defined as treatment success.

Results: The median age of the patient population at the time of surgery was 32 years (range 26-53 years) with a median body mass index of 21.7 kg/m² (range 16.7-26.6 kg/m²). Of the patients 12 (86%) received monoclonal antibodies (infliximab, adalimumab, ustekinumab, vedolizumab) at the time of surgery. The median number of complex fistulas was 1.4 (range 1-2), The median operative time was 20 min (range 6-50 min) with no perioperative complications. After a median follow-up of 92 weeks, we found successful fistula closure in 57.1% (n = 8) of treated patients. The perianal disease activity index did not improve significantly from initially 7 to a median of 6 after 52 weeks (p = 0.495).

Conclusion: Darvadstrocel is a safe, minimally invasive surgical technique without significant perioperative complications. Clinical success can be expected in about half of the treated patients.