Randomised, Double-blind, Placebo-controlled Trial of CCR9-targeted Leukapheresis Treatment of Ulcerative Colitis Patients.

Background and Aims: Ulcerative colitis patients display increased numbers of circulating pro-inflammatory monocyte human leukocyte antigen-DR [HLA-DRhi] monocytes expressing high levels of the gut-homing C-C chemokine receptor 9 [CCR9] and tumour necrosis factor [TNF]-alpha. The aim of this first-in-human, double-blind, randomised, placebo-controlled trial was to evaluate selective removal of circulating CCR9-expressing monocytes by leukapheresis in patients with moderate to severe ulcerative colitis, with regards to safety, tolerability, and immunological response. Methods: Patients with ulcerative colitis were treated every second day with leukapheresis during five sessions with a C-C chemokine ligand 25 [CCL25; CCR9 ligand] column or a placebo column. Results: No major safety concerns were raised and the procedure was well tolerated. Pro-inflammatory HLA-DRhi cells decreased significantly in the active treatment group [p = 0.0391] whereas no statistically significant change was seen in the placebo group [p = 0.4688]. There was a significant decrease of HLA-DRhi monocytes in the active group compared with the placebo group when corrected for the imbalance in weight between the groups [p = 0.0105]. Mayo score decreased in the active group [p = 0.0156] whereas the change in the placebo group was not significant [p = 0.1250]. Mayo score = 3 was observed in five out of 14 patients [35.7%] in the active group compared with one out of eight [12.5%] receiving placebo. The number of responders in the active treatment group was eight out of 14 patients [57.1%], whereas in the corresponding placebo group three out of eight patients [37.5%] responded to placebo. A dose-response correlation was observed between the blood volume processed and clinical outcome. Conclusion: This clinical induction trial using CCL25-tailored leukapheresis demonstrates a safe and effective removal of activated monocytes with a clinical effect in patients with ulcerative colitis.