Objective. To analyze the relationship between the type I interferon (IFN) signature and clinical response to rituximab in rheumatoid arthritis (RA) patients.Methods. Twenty RA patients were treated with rituximab (cohort 1). Clinical response was defined as a decrease in the Disease Activity Score evaluated in 28 joints (DAS28) and as a response according to the European League Against Rheumatism (EULAR) criteria at week 12 and week 24. The presence of an IFN signature was analyzed in peripheral blood mononuclear cells by measuring the expression levels of 3 IFN response genes by quantitative polymerase chain reaction analysis. After comparison with the findings in healthy controls, patients were classified as having an IFN high or an IFN low signature. The data were confirmed in a second independent cohort (n ‫؍‬ 31). Serum IFN␣ bioactivity was analyzed using a reporter assay.Results. In cohort 1, there was a better clinical response to rituximab in the IFN low signature group. Consistent with these findings, patients with an IFN low signature had a significantly greater reduction in the DAS28 and more often achieved a EULAR response at weeks 12 and 24 as compared with the patients with an IFN high signature in cohort 2 versus cohort 1. The pooled data showed a significantly stronger decrease in the DAS28 in IFN low signature patients at weeks 12 and 24 as compared with the IFN high signature group and a more frequent EULAR response at week 12. Accordingly, serum IFN␣ bioactivity at baseline was inversely associated with the clinical response, although this result did not reach statistical significance.Conclusion. The type I IFN signature negatively predicts the clinical response to rituximab treatment in patients with RA. This finding supports the notion that IFN signaling plays a role in the immunopathology of RA.

Objectives The exact underlying mechanism of rituximab treatment in patients with RA is poorly defined and knowledge about the effect of B cell depletion on immune cells in secondary lymphoid organs is lacking. We analysed lymphoid tissue responses to rituximab in RA patients. Methods Fourteen RA patients received 2 × 1000 mg rituximab intravenously, and lymph node (LN) biopsies were obtained before and 4 weeks after the first infusion. Tissues were examined by flow cytometry, immunohistochemistry and quantitative PCR. LN biopsies from five healthy individuals (HC) served as controls. Results LN biopsies of RA patients showed increased frequencies of CD21 + CD23 + IgD high IgM variable follicular B cells and CD3 + CD25 + CD69 + early activated, tissue resident T cells when compared with HCs. After treatment, there was incomplete depletion of LN B cells. There was a significant decrease in CD27 − IgD + naïve B cells, and CD27 + IgD + unswitched memory B cells including the CD27 + IgD + IgM + subset and follicular B cells. Strikingly, CD27 + IgD − switched memory B cells persisted in LN biopsies after rituximab treatment. In the T cell compartment, a significant decrease was observed in the frequency of early activated, tissue resident T cells after rituximab treatment, but late activated T cells persisted. B cell proliferation inducing cytokine IL-21 was higher expressed in LN biopsies of RA patients compared with HC and expression was not affected by rituximab treatment. Conclusion Rituximab does not cure RA, possibly due to persistence of switched memory B cells in lymphoid tissues suggesting that factors promoting B cell survival and differentiation need to be additionally targeted.

Objective. To investigate the safety, tolerability, pharmacokinetics, and efficacy of apilimod mesylate, an oral interleukin-12 (IL-12)/IL-23 inhibitor, in patients with rheumatoid arthritis (RA).Methods. We performed a phase IIa, randomized, double-blind, placebo-controlled proof-of-concept study of apilimod, in combination with methotrexate, in 29 patients with active RA ( Results. While only mild adverse events were observed in stages 1 and 2, in stage 3, all patients experienced headache and/or nausea. Among apilimodtreated patients (100 mg/day), there was a small, but significant, reduction in the DAS28 on day 29 and day 57 compared with baseline. ACR20 response was reached in only 6% of patients on day 29 and 25% of patients on day 57, similar to the percentage of responders in the placebo group. Increasing the dosage (100 mg twice a day) did not improve clinical efficacy. Consistent with clinical results, apilimod did not have an effect on expression of synovial biomarkers. Of importance, we also did not observe an effect of apilimod on synovial IL-12 and IL-23 expression. Conclusion. Our results do not support the notion that IL-12/IL-23 inhibition by apilimod is able to induce robust clinical improvement in RA.Rheumatoid arthritis (RA) is a chronic inflammatory disease affecting synovial tissue. Activated immune cells are important in orchestrating synovial inflammation by producing several cytokines, including interleukin-12 (IL-12) and IL-23 (1). IL-12 is a heterodimeric cytokine (p70) formed by 2 subunits, p40 and p35 (2). The structure of the more recently discovered heterodimeric IL-23 is closely related to that of IL-12 and shares the p40 subunit, but IL-23 contains p19, a unique subunit (3). IL-12 acts in the initial inflammation phase by promoting differentiation of naive CD4ϩ T cells to interferon-␥-producing Th1 cells. IL-23 induces proliferation of effector memory T cells and plays a critical role in the pathogenesis of RA by inducing IL-17-producing T cells (4). Animal studies confirm this finding, as IL-23-deficient (p19 Ϫ/Ϫ ) mice and mice lacking IL-12 and IL-23 (p40 Ϫ/Ϫ ) are resistant to collagen-induced arthritis (4).Apilimod mesylate (STA-5326), an orally administered small molecule, inhibits the production of IL-12 and IL-23. It selectively prevents nuclear translocation of c-Rel, a member of the Rel/NF-B family of transcription factors, thereby reducing both p35 and p40 ClinicalTrials.gov identifier: NCT00642629.

Presence of lymphocyte aggregates is a dynamic phenomenon related to the degree of synovitis and can be detected in different forms of early arthritis. This feature does not appear to be related to clinical outcome.