This study investigated whether GV1001 may be useful for treating rheumatoid arthritis (RA). Two collagen-induced arthritis (CIA) experiments showed that therapeutic, but not preventive, GV1001 treatment reduced the severity of joint inflammation in CIA. The third CIA experiment indicated that, compared to vehicle treatment, therapeutic GV1001 treatment was associated with a significantly smaller area under the curve for the overall clinical joint score over the 98 day observation period (p < 0.05). GV1001 treatment was also associated with lower Day 98 serum IL-6 levels (p < 0.01) and histological joint scores (p < 0.05). Moreover, splenocytes harvested from the GV1001-treated mice exhibited lower basal and collagen-stimulated production of IFN-gamma and IL-6 on Days 49 and 98 than the splenocytes from vehicle-treated mice. The fourth and fifth experiments indicated that earlier treatment resulted in a better response. In addition, human (THP-1) and murine (RAW 264.7) macrophages and fibroblast-like synoviocytes (FLS) from RA patients were used for in vitro analyses. GV1001 treatment of lipopolysaccharide-stimulated macrophages derived from THP-1 and RAW 264.7 monocytes significantly reduced TNF-alpha and IL-6 secretion (THP-1: all p < 0.05; RAW 264.7: all p < 0.01). However, GV1001 treatment did not affect IL-6 expression in TNF alpha-stimulated RA FLS. GV1001 reduced the clinical joint scores, serum IL-6 levels, and histological joint scores of mice with CIA. In addition, GV1001 lowered the collagen-stimulated IFN-gamma and IL-6 production of murine T-cells and reduced the TNF-ot and IL-6 production of macrophages in vitro. Thus, GV1001 may ameliorate joint inflammation by modifying T-cell reactions to the triggering autoantigen and by reducing macrophage cytokine production. (C) 2017 The Author(s). Published by Elsevier B.V.