Iguratimod is effective in refractory rheumatoid arthritis patients with inadequate response to methotrexate-cyclosporin A-hydroxychloroquine-prednisone

Decreased Expression of IL-35 and Its Receptor Contributes to Impaired Megakaryopoiesis in the Pathogenesis of Immune Thrombocytopenia

Recent findings have shown that the level of interleukin-35 (IL-35) is abnormal in several autoimmune diseases. Nonetheless, whether IL-35 participates in the pathogenesis of immune thrombocytopenia (ITP) remains unclear. The current study investigates whether IL-35 modulates megakaryopoiesis. The results show that IL-35 receptors are progressively expressed on bone marrow megakaryocytes during the in vitro differentiation of CD34+ progenitors. IL-35 increases the number of megakaryocyte colony-forming units through the Akt pathway. The level of bone marrow IL-35 is reduced in ITP patients, and the decreased level of IL-35 may inhibit megakaryopoiesis. Then, the potential causes of decreased IL-35 in ITP patients are explored. The primary type of cell that secretes IL-35, known as IL-35-producing regulatory T cells (iTr35), is reduced in ITP patients. Bone marrow mesenchymal stem cells (MSCs) from ITP patients exhibit an impaired capability of inducing iTr35 due to enhanced apoptosis, which may contribute to the reduced level of bone marrow IL-35 in ITP patients. Iguratimod promotes megakaryocyte development and differentiation by elevating the expression of IL-35 receptors on megakaryocytes. Iguratimod improves response rates and reduces bleeding symptoms in corticosteroid-resistant ITP patients.

Iguratimod as an alternative therapy for systemic sclerosis and prevention of the occurrence of ischemic digital ulcer

Objectives

This study aimed to assess the effectiveness of iguratimod (IGU) as an alternative treatment for systemic sclerosis (SSc), especially in the prevention of ischemic digital ulcers (DUs).

Methods

We constructed two cohorts from the Renji SSc registry. In the first cohort, SSc patients receiving IGU were observed prospectively with effectiveness and safety. In the second cohort, we picked up all the DU patients with at least a 3-month follow-up to investigate the prevention of IGU on ischemic DU.

Results

From 2017 to 2021, 182 SSc patients were enrolled in our SSc registry. A total of 23 patients received IGU. With a median follow-up of 61 weeks (IQR: 15-82 weeks), the drug persistence was 13/23. In total, 91.3% of the patients (21/23) became free of deterioration in the last visit with IGU. Of note, 10 patients withdrew from the study due to the following reasons: two patients withdrew due to deterioration, three due to incompliance, and five due to mild-to-moderate side effects. All the patients with side effects recovered fully after stopping IGU. Of note, 11 patients had ischemic DU, and 8 out of 11 (72.7%) patients had no new occurrence of DU during the follow-up. In the second cohort of 31 DU patients receiving a combination of vasoactive agents with a median follow-up of 47 weeks (IQR, 16-107 weeks), IGU treatment was protective of new DU occurrence (adjusted risk ratio = 0.25; 95% CI, 0.05-0.94; adjusted odds ratio = 0.07; and 95% CI, 0.01-0.49).

Conclusion

Our study for the first time describes the potential of IGU possibly as an alternative treatment for SSc. To our surprise, this study provides a hint that IGU treatment can be used for the prevention of the occurrence of ischemic DU and merits further investigation.

Iguratimod as a New Drug for Rheumatoid Arthritis: Current Landscape

Iguratimod (IGU) is a novel synthetic small molecule disease modified anti-rheumatic drug approved only in Japan and China up to date. IGU plays an important immunomodulatory role in the synovial tissue of rheumatoid arthritis by inhibiting the production of immunoglobulins and cytokines and regulating T lymphocyte subsets. IGU also regulates bone metabolism by stimulating bone formation while inhibiting osteoclast differentiation, migration, and bone resorption. In clinical trials, IGU was shown to be superior to placebo and not inferior to salazosulfapyridine. Combined therapy of IGU with other disease-modifying anti-rheumatic drugs showed significant improvements for disease activity. IGU has good efficacy and tolerance as an additional treatment for rheumatoid arthritis patients with inadequate response to methotrexate and biological disease-modifying anti-rheumatic drugs. In this review, we summarize current landscape on the mechanism of action of IGU and its clinical effectiveness and safety. It is expected that further translational studies on IGU will pave the road for wider application of IGU in the treatment of autoimmune diseases other than rheumatoid arthritis.

Iguratimod dose dependently inhibits the expression of citrullinated proteins and peptidylarginine deiminases 2 and 4 in neutrophils from rheumatoid arthritis patients

INTRODUCTION

Anti-citrullinated protein antibodies (ACPAs) play an important role in rheumatoid arthritis (RA). Citrullinated proteins (CPs), which are produced by post-translational modification via peptidylarginine deiminase (PAD), are the target antigen of ACPAs and promote the generation thereof. Herein, we investigated whether iguratimod (IGU) affects the generation of CPs via PAD.

METHODS

Neutrophils and peripheral blood mononuclear cells (PBMCs) were isolated from three patients diagnosed with RA and treated with various concentrations of IGU, methotrexate (MTX), or dexamethasone (DXM) or without any drugs as a control for 8 h. The levels of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, and IL-8 in culture supernatants were tested by ELISA. CPs were measured by western blot, and the expression of PAD2 and PAD4 in cells was detected by qRT-PCR and western blot.

RESULTS

PAD2 and PAD4 expressions in neutrophils but not in PBMCs were decreased by IGU at both the protein and mRNA levels (P < 0.05). CP expression in neutrophils but not in PBMCs was also inhibited by IGU. The inhibitory effect of IGU was dose-dependent. IGU, MTX, and DXM dose dependently decreased the secretion of TNF-α, IL-1β, IL-6, and IL-8 in neutrophils and PBMCs (P < 0.05); the inhibitory effect of IGU was not significantly different from that of MTX and DXM.

CONCLUSIONS

IGU inhibited the expression of CPs by downregulating PADs in neutrophils from RA patients, and the effect was comparable to that of MTX and DXM at appropriate concentrations. These findings may provide guidance for more appropriate treatment of RA.Key Points• Iguratimod inhibited citrullinated protein expression in neutrophils from rheumatoid arthritis patients similarly to methotrexate and dexamethasone at appropriate concentrations.• The inhibitory effect was mediated by downregulation of peptidylarginine deiminases, providing insight into the mechanism of iguratimod as a treatment for rheumatoid arthritis.• This study may guide rheumatoid arthritis treatment and facilitate identification of other therapeutic targets.

Autoimmune diseases in China

Autoimmune diseases, such as rheumatoid arthritis, systematic lupus erythematosus and Sjögren's syndrome, are a group of diseases characterized by the activation of immune cells and excessive production of autoantibodies. Although the pathogenesis of these diseases is still not completely understood, studies have shown that multiple factors including genetics, environment and immune responses play important roles in the development and progression of the diseases. In China, there are great achievements in the mechanisms of autoimmune diseases during the last decades. These studies provide new insight to understand the diseases and also shed light on the development of novel therapy.

Iguratimod represses B cell terminal differentiation linked with the inhibition of PKC/EGR1 axis

Background

This study aimed to explore the molecular mechanism and clinical relevance of iguratimod in the regulation of human B cell terminal differentiation.

Methods

An in vitro human antibody-secreting cell (ASC) differentiation system was established to test the effect of iguratimod. B cell phenotype and key transcription factors (TFs) relevant to ASC differentiation were analyzed through flow cytometry and qPCR. The COX-2 activity was measured by enzyme immunoassay (EIA). RNA sequencing was used to identify potential targets of iguratimod. We enrolled six treatment-naive rheumatoid arthritis (RA) patients whose blood samples were collected for phenotypic and molecular studies along with 12-week iguratimod monotherapy.

Results

Iguratimod inhibited human ASC generation without affecting B cell activation and proliferation. Iguratimod showed only weak COX-2 activity. Gene set enrichment analysis (GSEA) identified that protein kinase C (PKC) pathway was targeted by iguratimod which was confirmed by PKC activity detection. Furthermore, early growth response 1 (EGR1), a target of PKC and a non-redundant TF for ASC differentiation, was found to be the most downregulated gene in iguratimod-treated B cells. Lastly, iguratimod monotherapy decreased peripheral ASCs and was associated with improved disease activity. The expression of major ASC-related TFs, including EGR1, was similarly downregulated in patient blood samples.

Conclusions

Iguratimod inhibits ASC differentiation both in vitro and in RA patients. Our study suggests that PKC/EGR1 axis, rather than COX-2, is critically involved in the inhibitory effect by iguratimod on human ASC differentiation. Iguratimod could have a broader application to treat B cell-related autoimmune diseases in clinics.

Electronic supplementary material

The online version of this article (10.1186/s13075-019-1874-2) contains supplementary material, which is available to authorized users.