TAK-603 selectively suppresses Th1-type cytokine production and inhibits the progression of adjuvant arthritis.

We have shown that TAK-603, a new anti-rheumatic drug, is more effective in animal models in which cellular immunity plays a central role. Here, we studied the effect of the drug on Th1 cytokines, which are dominantly produced in this type of immune reaction, in an in vitro system and an in vivo model. We established Th1- and Th2-dominant T-cell lines, and studied the effect of TAK-603 on their cytokine production. Th1 cell lines were BALB/c mouse allo-reactive T cells and C57BL mouse mite antigen-reactive T cells, and the Th2 cell line was BALB/c mouse ovalbumin-reactive T cells. TAK-603 suppressed the production of Th1 cytokines [interferon-gamma (IFN-gamma) and interleukin-2 (IL-2)] and not that of Th2 cytokines (IL-4, IL-5) in these cell lines. Furthermore, selective suppression of Th1 cytokine production was also observed in the T-cell clones obtained from the ovalbumin-reactive T-cell line. To investigate the effect on cytokine production in animal models of arthritis, we analysed the expression of cytokine messenger RNA using reverse transcription-polymerase chain reaction. In adjuvant arthritis rats, Th1-dominant cytokine production was observed both in the arthritic joint and the spleen, and the time-course paralleled the progression of arthritis. On the other hand, in type-II collagen-induced arthritis, in which TAK-603 has little effect, Th1-dominant cytokine production was not observed and Th2 cytokines were shown to be more important. The adjuvant arthritis rats treated with TAK-603 (6.25 mg/kg/day, per os) showed significantly lower cytokine mRNA expression both locally and systemically. These data suggest that TAK-603 selectively suppresses Th1 cytokine production, which is consistent with its effect on cellular immunity in animal models.