P1004: EFFECT AND MOLECULAR MECHANISM OF TQ05105, A NOVEL SMALL MOLECULE INHIBITOR OF JAK2 IN MYELOPROLIFERATIVE NEOPLASM

Abstract

Background: The JAK2V617F gene mutation leads to upregulation of the JAK/STAT signaling pathway, which causes excessive bone marrow cell proliferation, elevated inflammatory cytokines, constitutional symptoms and shortened survival in myeloproliferative neoplasms (MPN) patients. The JAK1/2 kinase inhibitor ruxolitinib can dramatically improve disease-related symptoms, but side effect such as anemia and thrombocytopenia limit its use in a substantial proportion of patients. Several JAK2 kinase inhibitor III Clinical trials have yielded unsatisfactory outcomes recently. TQ05105 is a new small molecule inhibitor that targets JAK2 kinase. Aims: We aim to investigate the effect and molecular mechanism of TQ05105 on MPN cell lines and mouse models. Methods: We systematically measured the function of TQ05105 in MPN cell lines, including UKE1 and SET2 cells, by performing proliferation, apoptosis and colony-forming assays. RT-PCR and inflammatory factor multi-assay kit was used to detect the secretion of inflammatory factors such as TNF-α, IL-1β, MCP-1 in mRNA level and protein level respectively. CFU-E and BFU-E assays were performed on MPN cell lines and primary cells. In vivo, TQ05105 was evaluated in JAK2V617F Jak2V617F transplant mouse model and MPL515 retroviral mouse model. Mice were orally administrated with placebo, 25 mg/kg (bid) and 50 mg/kg (bid) every day for 4 weeks. Flow cytometry analysis was performed to determine the proportion of different hematopoietic progenitor cell populations. In addition, HE staining and Gomori staining was used to detect the changes in the spleen and bone marrow. Results: In UKE1 and SET2 cell lines, TQ05105 can inhibit the proliferation and induced cell apoptosis, notably reduce the expression of cytokines, including TNF-α, IL-1 and MCP-1. According to Western blot results, the phosphorylation of JAK/STAT signaling pathway associated proteins JAK2, STAT3 and STAT5 were significantly suppressed by TQ05105. Furthermore, compared to the control group, TQ05105 can strongly limit the ability of UKE1 cell lines, SET2 cell lines and primary cells from MPN patients (PMF, PV, ET) to form BFU-E and CFU-GM. TQ05105 can striking reduce mouse spleen volume, along with favorable impact on leukocyte and erythrocyte counts in Jak2V617F transplant mouse model. The proportion of stem and progenitor cells, especially CMPs and MEPs, was considerably reduced in mice after treatment with TQ05105. HE staining showed remarkably Spleen response such as recovering structure, reduced infiltration of erythrocytes and suppressed proliferation of megakaryocytes. MPLW515L retroviral mouse model recapitulated the feature of myelofibrosis, application of TQ05105 in this model resulted in reduction of the spleen volume, extramedullary hematopoiesis, leukocyte and platelets count, bone marrow fibrosis and decreased fraction of CMPs and MEPs. Summary/Conclusion: TQ05105, as a novel small molecule JAK2 inhibitor, can inhibit cell proliferation, induce cell apoptosis and decrease inflammatory cytokines by affecting the JAK/STAT signaling pathway. In vivo experiments further proved that TQ05105 can reduce spleen size and improve disease-related symptoms of MPN, indicating that it is a promising therapeutic drug for MPN.