Why CCR2 and CCR5 blockade failed and why CCR1 blockade might still be effective in the treatment of rheumatoid arthritis

The aim of this study was to provide more insight into the question as to why blockade of CCR1, CCR2, and CCR5 may have failed in clinical trials in rheumatoid arthritis (RA) patients, using an in vitro monocyte migration system model. Monocytes from healthy donors (HD; n = 8) or from RA patients (for CCR2 and CCR5 antibody n = 8; for CCR1 blockade n = 13) were isolated from peripheral blood and pre-incubated with different concentrations of either anti-CCR1, anti-CCR2, or anti-CCR5 blocking antibodies (or medium or isotype controls). In addition, a small molecule CCR1 antagonist (BX471) was tested. Chemotaxis was induced by CCL2/MCP-1 (CCR2 ligand), CCL5/RANTES (CCR1 and CCR5 ligand), or by a mix of 5 RA synovial fluids (SFs), and cellular responses compared to chemotaxis in the presence of medium alone. Anti-CCR2 antibody treatment blocked CCL2/MCP-1-induced chemotaxis of both HD and RA monocytes compared to isotype control. Similarly, anti-CCR5 antibody treatment blocked CCL5/RANTES-induced chemotaxis of RA monocytes. While neither CCR2 nor CCR5 blocking antibodies were able to inhibit SF-induced monocyte chemotaxis, even when both receptors were blocked simultaneously, both anti-CCR1 antibodies and the CCR1 antagonist were able to inhibit SF-induced monocyte chemotaxis. The RA synovial compartment contains several ligands for CCR1, CCR2, and CCR5 as well as other chemokines and receptors involved in monocyte recruitment to the site of inflammation. The results suggest that CCR2 and CCR5 are not critical for the migration of monocytes towards the synovial compartment in RA. In contrast, blockade of CCR1 may be effective. Conceivably, CCR1 blockade failed in clinical trials, not because CCR1 is not a good target, but because very high levels of receptor occupancy at all times may be needed to inhibit monocyte migration in viv

CCR5 blockade in rheumatoid arthritis: a randomised, double-blind, placebo-controlled clinical trial

Objective C-C chemokine receptor type 5 (CCR5), a chemokine receptor expressed on T cells and macrophages, and its ligands are found in inflamed synovial tissue (ST) of patients with rheumatoid arthritis (RA). The rationale for testing CCR5 blockade in patients with RA was supported by the effects of a CCR5 antagonist in collagen-induced arthritis in rhesus monkeys. The effects of CCR5 blockade in patients with active RA were explored. Methods In this phase Ib randomised, placebo-controlled trial, treatment with an oral CCR5 inhibitor (SCH351125) in patients with active RA was evaluated. Clinical efficacy was assessed using European League Against Rheumatism and American College of Rheumatology response criteria. ST biopsies were taken before and after 28 days of treatment, and analysed for CCR5+ cells. In a subset of patients, MRIs of an inflamed joint were obtained before and after treatment. Results In all, 32 patients were included; 20 received SCH351125 and 12 placebo. Three patients who received SCH351125 did not complete the study due to adverse events; none of these were serious. No improvement was observed in the active treatment group compared to placebo. Results were consistent for clinical evaluation, ST analysis and MRI. Conclusion This proof of concept study does not support the use of CCR5 blockade as a therapeutic strategy in patients with active R