Several recent papers support the involvement of an interaction between stromal cell-derived factor-1 (SDF-1/CXCL12) and its receptor, chemokine receptor CXCR4, in memory T cell migration in the inflamed rheumatoid arthritis (RA) synovium. Analogs of the 14-mer peptide T140 were previously found to be specific CXCR4 antagonists that were characterized as not only HIV-entry inhibitors but also anti-cancer-metastatic agents. In this study, a T140 analog, 4F-benzoyl-TN14003, was proven to inhibit CXCL12-mediated migration of human Jurkat cells and mouse splenocyte in a dose-dependent manner in vitro (IC(50)=0.65 and 0.54 nM, respectively). Furthermore, slow release administration by subcutaneous injection (s.c.) of 4F-benzoyl-TN14003 using an Alzet osmotic pump significantly suppressed the delayed-type hypersensitivity response induced by sheep red blood cells in mice, and significantly ameliorated clinical severity in collagen-induced arthritis in mice. As such, T140 analogs might be attractive lead compounds for chemotherapy of RA.