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Background: CpG oligonucleotides (ODNs) are synthetic single-stranded DNA sequences that act as immunostimulants. They have been increasingly used to treat several cancers; however, thrombocytopenia is a potential recognized side effect of some sequences., Objectives: We tested the ability of 2 CpG ODNs (ODN 2395 and ISIS 120704) to induce thrombocytopenia when administered to BALB/c mice and determined mechanisms associated with thrombocytopenia., Methods: BALB/c mice were prebled and then injected with titrated doses of CpG ODNs, and platelet counts were determined. The mice were treated with intravenous immunoglobulin (IVIg) or various inhibitors and antagonists of toll-like receptor 9 (TLR9) and spleen tyrosine kinase (Syk) to determine their effects on thrombocytopenia., Results: Compared with saline-treated mice or mice treated with 2'-O-methoxyethyl-modified antisense ODN, both ODN 2395 and ISIS 120704 induced acute dose-dependent thrombocytopenia within 3 and 24 hours, respectively. The thrombocytopenia was associated with significant increases in plasma monocyte chemoattractant protein 1. IVIg administration significantly rescued the CpG ODN-induced thrombocytopenia, as did treatment with either a Syk inhibitor or TLR9 antagonists. In vitro, CpG ODN could activate human platelets and this correlated significantly with enhanced IVIg- and Syk-dependent phagocytosis by THP-1 monocytes., Conclusion: These results suggest that CpG ODNs induce acute inflammatory-associated (IVIg-sensitive) thrombocytopenia that can be alleviated by Syk- or TLR9-blockade, and an IVIg- and Syk-dependent platelet clearance pathway appears primarily responsible for the thrombocytopenia., Competing Interests: Declaration of competing interests There are no competing interests to disclose., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Abstract: Fostamatinib, a recently approved Syk inhibitor used in adult primary immune thrombocytopenia (ITP), has been shown to be safe and effective in this disorder. However, clinical trial results may not be similarly reproduced in clinical practice. Here, 138 patients with ITP (both primary and secondary) from 42 Spanish centers who had been treated with fostamatinib were evaluated prospectively and retrospectively. The median age of our cohort (55.8% women) was 66 years (interquartile range [IQR], 56-80). The median time since ITP diagnosis at fostamatinib initiation was 51 months (IQR, 10-166). The median number of therapies before fostamatinib initiation was 4 (IQR, 2-5), including eltrombopag (76.1%), romiplostim (57.2%), and IV immunoglobulins (44.2%). Fifty-eight patients (42.0%) had signs/symptoms of bleeding in the month before treatment initiation. Seventy-nine percent of patients responded to fostamatinib with 53.6% complete responses (platelet count > 100 × 109/L). Eighty-three patients (60.1%) received fostamatinib monotherapy, achieving a high response rate (85.4%). The proportion of time in response during the 27-month period examined was 83.3%. The median time to platelet response was 11 days (IQR, 7-21). Sixty-seven patients (48.5%) experienced adverse events, mainly grade 1 to 2; the commonest of which were diarrhea (n = 28) and hypertension (n = 21). One patient had deep venous thrombosis, and one patient developed acute myocardial infarction. Fostamatinib was shown to be effective with good safety profile in patients with primary and secondary ITP across a wide age spectrum in this real-world study., (© 2024 American Society of Hematology. Published by Elsevier Inc. All rights are reserved, including those for text and data mining, AI training, and similar technologies.)

Bullous pemphigoid (BP) is an autoantibody-mediated blistering skin disease characterized by local inflammation and dermal-epidermal separation, with no approved targeted therapy. The Syk tyrosine kinase is critical for various functions of the immune response. Second-generation Syk inhibitors such as entospletinib are currently being tested for hematological malignancies. Our aim was to test the effect of entospletinib in a fully human model system of BP. Incubating BP serum-treated human frozen skin sections with normal human granulocytes and fresh plasma triggered dermal-epidermal separation that was dependent on complement, NADPH oxidase, and protease activity. Entospletinib dramatically reduced dermal-epidermal separation with a half-maximal inhibitory concentration of ≈16 nM. Entospletinib also reduced ROS production, granule release, and spreading of human granulocytes plated on immobilized immune complexes consisting either of a generic antigen-antibody pair or of recombinant collagen type XVII (BPAg2) and BP serum components (supposedly autoantibodies). However, entospletinib did not affect the chemotactic migration of human granulocytes or their responses to nonphysiological stimulation by phorbol esters. Entospletinib had no effect on the survival of granulocytes either. Taken together, entospletinib abrogates dermal-epidermal separation, likely through inhibition of granulocyte responsiveness to deposited immune complexes. Entospletinib or other Syk inhibitors may provide therapeutic benefits in BP., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

The obligate intracellular parasite Leishmania binds several receptors to trigger uptake by phagocytic cells, ultimately resulting in visceral or cutaneous leishmaniasis. A series of signaling pathways in host cells, which are critical for establishment and persistence of infection, are activated during Leishmania internalization. Thus, preventing Leishmania uptake by phagocytes could be a novel therapeutic strategy for leishmaniasis. However, the host cellular machinery mediating promastigote and amastigote uptake is not well understood. Here, using small molecule inhibitors of Mitogen-activated protein/Extracellular signal regulated kinases (MAPK/ERK), we demonstrate that ERK1/2 mediates Leishmania amazonensis uptake and (to a lesser extent) phagocytosis of beads by macrophages. We find that inhibiting host MEK1/2 or ERK1/2 leads to inefficient amastigote uptake. Moreover, using inhibitors and primary macrophages lacking spleen tyrosine kinase (SYK) or Abl family kinases, we show that SYK and Abl family kinases mediate Raf, MEK, and ERK1/2 activity and are necessary for uptake. Finally, we demonstrate that trametinib, a MEK1/2 inhibitor used to treat cancer, reduces disease severity and parasite burden in Leishmania-infected mice, even if it is started after lesions develop. Our results show that maximal Leishmania infection requires MAPK/ERK and highlight potential for MAPK/ERK-mediated signaling pathways to be novel therapeutic targets for leishmaniasis., Competing Interests: Declaration of competing interest The authors have no competing financial interests., (Copyright © 2024 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.)

Hidradenitis suppurativa is a disease in great need of novel therapies. Given the heterogeneous nature of the disease and the variable response to therapies, biomarkers are essential to predict response to therapies and increase our understanding of disease pathogenesis. Our recent phase 2 clinical trial of spleen tyrosine kinase antagonism using fostamatinib in hidradenitis suppurativa demonstrated a 75% clinical response, with the greatest benefit in individuals with elevated serum inflammation and IgG. In this study, we present results of an in-depth serum proteomic analysis in this patient cohort identifying downregulation of IL-12B as well as B-cell-associated proteins CCL19 and CCL20 and IFN-γ-mediated proteins CXCL10 and CX3CL1. Clinical responders demonstrated greater reduction in serum IL-17A, IL-6, IL-8, and CX3CL1 compared with clinical nonresponders. Baseline levels of CCL28 were associated with clinical response to fostamatinib therapy at week 12. Overall, this suggests that fostamatinib, by targeting B-cell receptor and Fc receptor activity in B cells, monocytes, and macrophages, has a significant molecular impact on the inflammatory serum proteome of hidradenitis suppurativa. In addition, potential therapeutic biomarkers may aid in patient selection for targeted therapy., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

There is evidence that major components of the fungi cell wall not only define fungal properties and survival but also are responsible for their biological activities. Some data indicate that structural components of the fungal cell wall exert stimulatory/modulatory effects on immunocompetent cells acting as pathogen-associated molecular patterns (PAMPs). Fungal components can influence the activity of certain immune cell populations by affecting cell maturation and proliferation, promoting phagocytosis, cytotoxic activity, and cell migration, as well as production of various mediators. However, there is little information available concerning the impact of fungal-derived components on peripheral blood mononuclear cell (PBMC) activation. The aim of this study was to determine whether certain fungi-associated molecules, i.e., β-(1,3)-glucans (zymosan and curdlan) and mannan activate in vitro human PBMCs to synthesize cytokines, including chemokines. We documented that PBMCs, in response to stimulation with zymosan, curdlan, and mannan, express cytokines IFN-γ and GM-CSF, and chemokine CCL3, both at protein and transcript levels, as well as cytokine IL-1β and chemokine CXCL8, at mRNA level. Our observations support the idea that fungal-derived components can activate immune cells, including PBMCs, by stimulation of cytokine/chemokine production. A thorough understanding of this interaction is of prime importance since it influence both pathophysiological and immune processes as well as anti-fungal defense mechanisms., (Copyright © 2020 Elsevier GmbH. All rights reserved.)

As the aim to discover orally SYK inhibitors for solid tumor treatment, a series of novel derivatives based on imidazo[1,2-a]pyrazine scaffold were designed, synthesized and evaluated. Structure-activity relationship study of both enzymatic and cellular assays led to the identification of compound 12f. The novel SYK inhibitor 12f showed potent antitumor activity against solid tumors with favorable drug-like properties of lipophilicity and solubility. 12f could induce cell apoptosis of ovarian and lung cancer cell lines. In SKOV3 xenograft mouse model, oral administration of 12f led to significant tumour regression without obvious toxicity. 12f improved the limited response of traditional SYK inhibitors in solid tumors in vitro and in vivo. Taken together, this compound may act as a promising lead compound for further development of new SYK inhibitors for solid tumor therapy., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background: Entospletinib (GS-9973) is an oral, selective inhibitor of spleen tyrosine kinase. Entospletinib monotherapy was evaluated in a multicenter, phase II study of subjects with relapsed or refractory B-cell malignancy., Patients and Methods: The study included 43 patients with relapsed or refractory diffuse large B-cell lymphoma (DLBCL). The participants received 800 mg of the original, monomesylate formulation of entospletinib twice daily as a starting dose; the doses could be reduced because of toxicity throughout the study., Results: No patient achieved a complete or partial response, 5 patients (12%) had stable disease, and 26 patients (60%) had progressive disease. Progression-free survival (PFS) at 16 weeks was 3.6% (95% confidence interval [CI], 0.3%-15.3%), and the median PFS was 1.5 months (95% CI, 1-1.7 months). The independent review committee-assessed nodal response for 27 evaluable patients showed a reduced tumor burden in 6 patients (22%). The median duration of entospletinib treatment for these 6 patients was 9 weeks (range, 3-24 weeks). One patient (4%) had a decrease of ≥ 50% in the sum of the product of the nodal diameters. The treatment-emergent adverse events occurring in ≥ 20% of the cohort were fatigue, nausea, decreased appetite, constipation, dyspnea, diarrhea, dehydration, cough, insomnia, and peripheral edema. The common laboratory abnormalities occurring in ≥ 20% of the subjects were lymphocytopenia, anemia, creatinine (chronic kidney disease), increased aspartate aminotransferase, hypoalbuminemia, total bilirubin, hyponatremia, leukopenia, increased alanine aminotransferase, increased alkaline phosphatase, and hyperglycemia., Conclusion: Entospletinib monotherapy at 800 mg twice daily demonstrated limited activity in patients with advanced, relapsed DLBCL., (Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.)

Aims: Immune and inflammatory responses mediated by immunoglobulin (Ig) G are largely responsible for the pathogenesis of autoimmune diseases. Spleen tyrosine kinase (Syk) plays a pivotal role in the IgG-mediated responses; therefore, Syk has emerged as a new therapeutic target for the treatment of autoimmune diseases. In this study, we investigated the inhibitory actions of JTE-852, a novel Syk inhibitor, on IgG-mediated cellular responses and autoimmune reactions in vivo., Main Methods: We examined mediator secretion from human monocytes. We also conducted rat models of reversed cutaneous anaphylaxis (RCA) and reversed passive Arthus (RPA), which are classified as type II and type III hypersensitivities, respectively. In a rat collagen-induced arthritis (CIA) model, JTE-852 or methotrexate was administered preventively (before the onset of arthritis) or therapeutically (after the onset of arthritis)., Key Findings: JTE-852 blocked secretion of reactive oxygen species and tumor necrosis factor-α from monocytes stimulated by IgG crosslinking. In the RCA and RPA models, JTE-852 also suppressed edema and dye leakage, respectively. In the CIA model, JTE-852 showed both preventive and therapeutic effects against joint swelling and bone erosion; on the other hand, methotrexate did not show the therapeutic effect., Significance: JTE-852 attenuates IgG-mediated responses and signs in animal model of autoimmune diseases. JTE-852 is thus a promising candidate for a novel, orally available drug for the treatment of autoimmune diseases., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Band 3 (also known as the anion exchanger, SLCA1, AE1) constitutes the major attachment site of the spectrin-based cytoskeleton to the erythrocyte's lipid bilayer and thereby contributes critically to the stability of the red cell membrane. During the intraerythrocytic stage of Plasmodium falciparum 's lifecycle, band 3 becomes tyrosine phosphorylated in response to oxidative stress, leading to a decrease in its affinity for the spectrin/actin cytoskeleton and causing global membrane destabilization. Because this membrane weakening is hypothesized to facilitate parasite egress and the consequent dissemination of released merozoites throughout the bloodstream, we decided to explore which tyrosine kinase inhibitors might block the kinase-induced membrane destabilization. We demonstrate here that multiple Syk kinase inhibitors both prevent parasite-induced band 3 tyrosine phosphorylation and inhibit parasite-promoted membrane destabilization. We also show that the same Syk kinase inhibitors suppress merozoite egress near the end of the parasite's intraerythrocytic lifecycle. Because the entrapped merozoites die when prevented from escaping their host erythrocytes and because some Syk inhibitors have displayed long-term safety in human clinical trials, we suggest Syk kinase inhibitors constitute a promising class of antimalarial drugs that can suppress parasitemia by inhibiting a host target that cannot be mutated by the parasite to evolve drug resistance., (© 2017 by The American Society of Hematology.)

The binding and activation of macrophages by microscopic aggregates of oxLDL in the intima of the arteries may be an important step towards atherosclerosis leading to heart attack and stroke. Microbeads coated with oxLDL were used to activate, capture and isolate the oxLDL receptor complex from the surface of live cells. Analysis of the resulting tryptic peptides by liquid chromatography and tandem mass spectrometry revealed the Spleen Tyrosine Kinase (SYK), and many of SYK's known interaction network including Fc receptors (FCGR2A, FCER1G and FCGR1A) Toll receptor 4 (TLR4), receptor kinases like EGFRs, as well as RNA binding and metabolism proteins. High-intensity precursor ions (∼9*E3 to 2*E5 counts) were correlated to peptides and specific phosphopeptides from long isoform of SYK (SYK-L) by the SEQUEST, OMSSA and X!TANDEM algorithms. Peptides or phosphopeptides from SYK were observed with the oxLDL-microbeads. Pharmacological inhibitors of SYK activity significantly reduced the engulfment of oxLDL microbeads in the presence of serum factors, but had little effect on IgG phagocytosis. Anti SYK siRNA regulated oxLD engulfment in the context of serum factors and or SYK-L siRNA significantly inhibited engulfment of oxLDL microbeads, but not IgG microbeads., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Although agents targeting B-cell receptor signaling have provided practice-changing results in relapsed chronic lymphocytic leukemia (CLL) and non-Hodgkin lymphoma (NHL), they require prolonged administration and provide incomplete responses. Given synergistic preclinical activity with phosphatidylinositol 3-kinase δ and spleen tyrosine kinase inhibition, this phase 2 study evaluated the safety and efficacy of the combination of idelalisib and entospletinib. Eligible patients with relapsed or refractory CLL or NHL underwent intrapatient dose escalation with each agent. With a median treatment exposure of 10 weeks, 60% and 36% of patients with CLL or follicular lymphoma, respectively, achieved objective responses. However, the study was terminated early because of treatment-emergent pneumonitis in 18% of patients (severe in 11 of 12 cases). Although most patients recovered with supportive measures and systemic steroids, 2 fatalities occurred and were attributed to treatment-emergent pneumonitis. Increases of interferon-γ and interleukins 6, 7, and 8 occurred over time in patients who developed pneumonitis. Future studies of novel combinations should employ conservative designs that incorporate pharmacodynamics/biomarker monitoring. These investigations should also prospectively evaluate plasma cytokine/chemokine levels in an attempt to validate biomarkers predictive of response and toxicity. This trial was registered at www.clinicaltrials.gov as #NCT01796470., (© 2016 by The American Society of Hematology.)

Renal fibrosis results from an excessive accumulation of extracellular matrix that occurs in most types of chronic kidney disease. Among the many fibrogenic factors that regulate renal fibrotic processes, transforming growth factor-β1 (TGF-β1) and inflammation after injury play critical roles. Spleen tyrosine kinase (Syk) is important for signaling processes implicated in autoimmune, inflammatory, and allergic diseases. We examined the effects of Syk inhibition on renal fibrosis in vivo and on TGF-β1-induced renal fibroblast activation in vitro. A unilateral ureteral obstruction (UUO) model was induced in male B6 mice. Mice with UUO were administered a Syk inhibitor or saline intraperitoneally 1 day before UUO surgery and daily thereafter. Both kidneys were harvested 7 days after surgery for further analysis. For the in vitro experiments, NRK-49F rat fibroblasts were pre-incubated with a Syk inhibitor before TGF-β1 stimulation. The inhibitory effects of Syk inhibition on signaling pathways down-stream of TGF-β1 were analyzed. In the UUO mouse model, administration of a Syk inhibitor attenuated extracellular matrix protein deposition and expression of α-smooth muscle actin, type I collagen, and fibronectin in a dose-dependent manner. In addition, macrophage infiltration in UUO kidney was reduced by Syk inhibition. Pre-incubation of NRK-49F cells with a Syk inhibitor suppressed TGF-β1-induced myofibroblast activation. Furthermore, inhibitory effects of Syk inhibition on TGF-β1-mediated myofibroblast activation were associated with down-regulation of MAPK-p38. These results suggest that Syk inhibition reduces tubulointerstitial fibrosis in UUO mice and inhibits TGF-β1-induced kidney myofibroblast activation. Syk inhibition could have therapeutic potential for the treatment of renal tubulointerstitial fibrosis., (Copyright © 2016 Elsevier Ltd. All rights reserved.)