Cyclophosphamide-free Mobilisation Increases Safety While Preserving the Efficacy of Autologous Haematopoietic Stem Cell Transplantation in Refractory Crohn's Disease Patients.

Background and Aim Autologous haematopoietic stem cell transplantation [AHSCT] is a therapeutic option for refractory Crohn's disease [CD]. However, high adverse event rates related to chemotherapy toxicity and immunosuppression limit its applicability. This study aims to evaluate AHSCT's safety and efficacy using a cyclophosphamide [Cy]-free mobilisation regimen.Methods A prospective, observational study included 14 refractory CD patients undergoing AHSCT between June 2017 and October 2022. The protocol involved outpatient mobilisation with G-CSF 12-16 mu g/kg/daily for 5 days, and optional Plerixafor 240 mu g/d [1-2 doses] if the CD34 + cell count target was unmet. Standard conditioning with Cy and anti-thymocyte globulin was administered. Clinical, endoscopic, and radiological assessments were conducted at baseline and during follow-up.Results All patients achieved successful outpatient mobilisation [seven patients needed Plerixafor] and underwent transplantation. Median follow-up was 106 weeks (interquartile range [IQR] 52-348). No mobilisation-related serious adverse events [SAEs] or CD worsening occurred. Clinical and endoscopic remission rates were 71% and 41.7% at 26 weeks, 64% and 25% at 52 weeks, and 71% and 16.7% at the last follow-up, respectively. The percentage of patients who restarted CD therapy for clinical relapse and/or endoscopic/radiological activity was 14% at 26 weeks, 57% at 52 weeks, and 86% at the last follow-up, respectively. Peripheral blood cell populations and antibody levels post-AHSCT were comparable to Cy-based mobilisation.Conclusions Cy-free mobilisation is safe and feasible in refractory CD patients undergoing AHSCT. Although relapse occurs in a significant proportion of patients, clinical and endoscopic responses are achieved upon CD-specific therapy reintroduction. Graphical Abstract