CCR9 Inhibition in the treatment of Colonic Inflammation (2009)

PURPOSE: While CCR9-mediated migration of immune cells from the circulation into inflamed small intestine has been well documented, the role of this chemokine receptor in colonic inflammation has remained largely uninvestigated. This study describes the presence of the CCR9 chemokine ligand (TECK) in human colon samples from healthy and IBD subjects. It also describes the key role played by CCR9/TECK in the spontaneous development of colitis in a genetic mouse model and the effective treatment of this condition with CCR9 antagonists. METHODS: Human colon biopsy samples, obtained from commercial sources and representative of healthy and IBD subjects, were obtained from commercial sources and analyzed for TECK content by northern blotting and IHC. Groups of mdr1a -/-mice, which spontaneously develop inflammatory colitis, were sacrificed at regular time intervals prior to and during the onset of disease and analyzed for TECK expression within the colon as well as levels of CCR9 cells in the periphery. The ability to modify disease progression in the mdr1a -/-mice was evaluated by treatment with the CCR9 antagonists, CCX282-B and CCX025, both of which are in clinical development for treatment of IBD. CCX282-B was evaluated both in a therapeutic mode (treatment started after the onset of clinical signs) and a prophylactic mode (treatment initiated before the onset of clinical signs). Vehicle-treated mdr1a -/-mice and wt FVB mice were used as controls in all studies. RESULTS: TECK protein was readily detectable by IHC in human colon samples from both normal and IBD donors. The presence of TECK in the colon was confirmed by northern blot analysis. TECK levels in the colon of asymptomatic mdr1a -/-mice were significantly increased compared to control FVB mice (0.2 0.09 pg/g protein and 0.04 0.006 pg/g protein, respectively; p0.05) and furthermore, in mice displaying severe symptoms, TECK levels were significantly increased compared to asymptomatic animals (16.51 3.9 pg/g protein; p0.05 vs asymptomatic mice). In addition to the increased levels of TECK present in the diseased colon, an increase in circulating CCR9 CD4 T-cells was noted in mdr1a -/-mice versus wild type controls. Chronic treatment of mdr1a -/-mice with CCX025 (50 mg/kg/day) resulted in a normalization of body weight gain compared to vehicle-treated animals (n25/group; 29.3 2.9 grams vs 26.3 4.0 grams, respectively; p 0.007). mdr1a -/-mice treated with CCX025 had a significant survival advantage compared to vehicle treated animals (4% mortality vs 28% mortality at 30 weeks of age). While vehicle-treated mdr1a -/-mice had an incidence of established diarrhea of 40% by 30 weeks, treatment with CCX025 resulted in a significantly lower incidence of only 4%. A similar benefit was observed in mdr1a -/- mice treated with CCX282-B, following therapeutic as well as prophylactic intervention. CONCLUSION: Our results clearly establish the presence of the CCR9 chemokine TECK in human colon. We also provide conclusive evidence for the role of CCR9 in the pathogenesis of colonic inflammation in the mdr1a -/-mouse colitis model and establish the therapeutic benefit associated with chronic administration of CCR9 antagonists in inflammatory colitis.