Preventive effect of a novel antifolate, MX-68, in murine systemic lupus erythematosus (SLE)

We evaluated the preventive effects of a novel nonpolyglutamatable antifolate, MX-68, on two experimental murine models of systemic lupus erythematosus (SLE); NZBxNZW F1 (BWF1) mice and chronic graft-versus-host disease (GVHD) mice, in comparison with classical antifolate methotrexate (MTX). The oral administration of 2 mg/kg MX-68, three times a week from 12 to 40 or 60 weeks of age, significantly delayed the onset of proteinuria and prolonged the life-span of BWF1 mice. The elevation of serum blood urea nitrogen (BUN) and cholesterol levels resulting from the development of lupus nephritis was also inhibited. However, MX-68 did not suppress the increase of serum anti-DNA or anti-TNP antibodies or total IgG isotype (IgG1, IgG2 and IgG3) levels. In chronic GVHD mice, MX-68 given three times a week from the day of first cell injection, for 9 weeks, dose-dependently delayed the appearance of proteinuria. The elevation of BUN and cholesterol levels was also inhibited. Furthermore, in the 4 mg/kg MX-68 group, the production of IgG anti-DNA and anti-TNP antibodies was significantly inhibited, but this was not observed in the 2 mg/kg MX-68 and the 4 mg/kg MTX groups. These beneficial effects of MX-68 were much greater than those of MTX in both models. These results suggest that MX-68 might be a more useful drug for the treatment of SLE.