Efficacy and safety of iguratimod on patients with primary Sjögren’s syndrome: a randomized, placebo-controlled clinical trial

Objective: To evaluate the clinical efficacy and safety of iguratimod for the treatment of primary Sjögren's syndrome (pSS) and explore its possible mechanism of action.Method: We conducted a randomized, placebo-controlled clinical trial in 66 pSS patients. Patients were randomized in a 2:1 ratio to receive oral iguratimod for 24 weeks or matching placebo. The primary endpoint was the EULAR Sjögren's Syndrome Patient Reported Index (ESSPRI). Secondary endpoints included mental discomfort visual analogue scale (VAS) score, patient global assessment (PGA), EULAR Sjögren's Syndrome Disease Activity Index (ESSDAI), Schirmer's test values, unstimulated whole salivary flow, erythrocyte sedimentation rate (ESR), and immunoglobulin G (IgG). The proportions of B cells in peripheral blood and levels of serum B-cell activating factor (BAFF) were measured at baseline and week 24 in the iguratimod group. All adverse events were recorded during the trial period.Results:ESSPRI improved more in the iguratimod than in the placebo group (p = 0.016). Mental discomfort VAS score, PGA, Schirmer's test, ESR, and IgG also improved more in the iguratimod than in the placebo group (all p < 0.05). Adverse events were reported 13.6% of the iguratimod group. Levels of BAFF and proportions of plasma cells in patients decreased significantly after iguratimod treatment. The proportions of peripheral plasma cells had positive correlations with both serum IgG and BAFF.Conclusion: Iguratimod improved some dryness symptoms and disease activity in pSS patients, and reduced the level of BAFF and percentage of plasma cells over 24 weeks. Iguratimod seems to be an effective and safe treatment for pSS.