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2677 Iguratimod Could Correct the Defective IL-35-Mediated Megakaryopoiesis in Immune ThrombocytopeniaClinically Relevant Abstract

Program: Oral and Poster Abstracts
Session: 501. Hematopoietic Stem and Progenitor Cells and Hematopoiesis: Basic and Translational: Poster II
Hematology Disease Topics & Pathways:
Bleeding and Clotting, Diseases, thrombocytopenias
Sunday, December 10, 2023, 6:00 PM-8:00 PM

Xuan Cai1*, Ruoyun Gui1*, Jin Wu, MD1*, Chen-Cong Wang2*, Xiaolu Zhu, MD3*, Haixia Fu, MD4*, Kai-yan Liu, MD, PhD5 and Xiaohui Zhang, MD6*

1Peking University People's Hospital, Beijing, CHN
2Peking University People's Hospital, Peking University Institute of Hematology, Beijing, China
3Peking University People’s Hospital, Beijing, China
4Peking University People’s Hospital, Peking University Institute of Hematology, Beijing, Beijing, China
5Peking University People's Hospital, Beijing, China
6Peking University Institute of Hematology, Peking University people hospital, Beijing, China


IL-35 is an inhibitory cytokine of the IL-12 family, and comprises an EBI3 subunit and a p35 subunit. Previous data indicated that serum levels of IL-35 were significantly lower in immune thrombocytopenia (ITP) patients than in healthy controls. Moreover, the concentration of plasma IL-35 in ITP patients achieving complete response returned to normal, but was not corrected in those who failed to achieve response. However, the underlying pathological function of IL-35 in impaired megakaryopoiesis in ITP remains unexplored. Our study aimed to evaluate the immunoregulatory role of IL-35 in megakaryocytes (MKs) differentiation. Iguratimod, a traditional therapy for inflammatory disorders, has been demonstrated to promote megakaryopoiesis. The effect of iguratimod on the treatment of ITP was retrospectively reviewed.


Bone marrow samples were obtained from newly-diagnosed primary ITP patients and healthy donors. CD34+ cells from ITP patients and healthy donors were differentiated into MKs with and without IL-35 to determine the mechanism of IL-35 in megakaryopoiesis. Iguratimod was added to the culture medium of MKs to determine its function in MKs differentiation. Additionally, ITP mouse model was established to further validate the function of IL-35.


In comparison with healthy controls, ITP patients showed lower bone marrow levels of IL-35. IL-35 receptor expression was progressively induced on bone marrow MKs from healthy controls during the differentiation of CD34+ progenitors. In contrast, MKs from ITP patients exhibited defective expression of the IL-35 receptor. We then determined the effect of IL-35 on the megakaryocytic potential of CD34+ progenitor cells in culture medium containing TPO. IL-35 increased the number of medium-sized and large-sized colonies, and increased the total number of CD41+ cells. In IL-35-treated MKs, higher levels of Akt phosphorylation were observed. Pretreatment with LY294002, an inhibitor of Akt phosphorylation, blocked the differentiation of MKs induced by IL-35. LY294002 inhibited proplatelet formation and aggregation of β1-tubulin in MKs stimulated by IL-35. Flow cytometry analysis revealed that platelet production decreased in the LY294002 pretreatment group. These results demonstrated that IL-35 can enhance the proliferation and differentiation of MKs through Akt pathways. The decreased level of bone marrow IL-35 may partially explain the defective megakaryopoiesis in ITP.

We then explored the potential causes of the decreased IL-35 levels in ITP. Flow cytometry analysis showed that the percentage of bone marrow iTr35 cells, the primary sources of IL-35, was significantly lower in ITP patients. Furthermore, we cocultured CD4+ T cells with MSCs from healthy controls and ITP patients, respectively. The percentage of iTr35 cells was lower when cultured with ITP-MSCs. These results showed that ITP-MSCs exhibited an impaired capability of inducing iTr35 cells, which might contribute to the reduced level of bone marrow IL-35 in ITP patients.

We further investigated the effects of iguratimod on the differentiation of CD34+ progenitors into MKs. When CD34+ cells were cultured with TPO alone, the addition of iguratimod upregulated the expression of IL-35 receptors on MKs from ITP patients and a murine model of this disease, and consequently promoted the formation of MK colonies. In the retrospective study of iguratimod, a total of 68 adult patients with corticosteroid-resistant primary ITP were included. Initial response was achieved in 42/68 (62%) patients, and complete response was achieved in 25/68 (37%) patients. In patients who achieved initial response, the median time to response was 28 days. Sustained response at 6 months was seen in 35/68 (51%). Bleeding symptoms were reduced from 37/68 (54%) patients at baseline to 14/68 (21%) patients at 6 months. Most adverse events were mild (grade 1-2), and there were no grade 4 or worse adverse events in our patients. The most common adverse events were elevated ALT, gastrointestinal disorders, and nausea.


ITP-MSCs exhibited an impaired capability of inducing iTr35 cells, which contributed to the reduced level of bone marrow IL-35 in ITP. IL-35 promoted MKs differentiation through the Akt pathway. Iguratimod promoted megakaryopoiesis by inducing the expression of IL-35 receptors on MKs. Iguratimod had good efficacy and safety in the treatment of ITP.

Disclosures: No relevant conflicts of interest to declare.

*signifies non-member of ASH