Clinical efficacy of leflunomide in primary Sjogren's syndrome is associated with regulation of T-cell activity and upregulation of IL-7 receptor α expression

Objectives To investigate whether the immunomodulatory capacities of leflunomide are associated with clinical efficacy in the treatment of primary Sjogren's syndrome (SS) in a phase II pilot study. Methods Peripheral blood mononuclear cells from 13 primary SS patients were obtained at baseline and after 24 weeks of leflunomide treatment. Ex-vivo production of interleukin (IL) 1 beta and tumour necrosis factor alpha (TNF alpha) and of interferon (IFN), IL-4, as well as TNF alpha ELISA measured production on T-cell and monocyte stimulation. In addition, the authors investigated the ability of leflunomide to influence systemic levels of inflammatory cytokines, as well as T-cell activation markers and the expression of IL-7 receptor alpha by flow cytometry. Correlations between changes in cytokine levels and changes in clinical response parameters were studied. Results Ex-vivo production of IL-1 beta and TNF alpha was decreased at 24 weeks in the whole patient group, whereas IFN and IL-4 production were not significantly changed. However, a significant decrease in T-cell-stimulated IFN and TNF alpha production was observed in clinical responders, but not in non-responders. Moreover, significant correlations were found between increased sialometry values and decreased IFN and TNF alpha production. In addition, leflunomide reduced levels of inflammatory serum cytokines and CD40L expression, whereas it upregulated IL-7R alpha expression on CD4 T cells with persistent serum IL-7 concentrations. Conclusions Leflunomide treatment suppressed cytokine release from circulating immune cells. Inhibition of T-helper 1 cell cytokine production was related to clinical efficacy. This suggests that selective T-cell targeting might be a relevant therapeutic strategy in primary SS, possibly enhancing clinical efficacy and safety.