Spleen Tyrosine Kinase Inhibitor Research Articles

JAK Inhibitors for Atopic Dermatitis: An Update.

Atopic dermatitis (AD) is one of the most common inflammatory skin diseases. AD is driven by barrier dysfunction and abnormal immune activation of Thelper (Th)2, Th22, and varying degrees of Th1 and Th17 among various subtypes. The Janus kinase (JAK)-signal transducer and activator of transcription (STAT) and spleen tyrosine kinase (SYK) pathways are involved in signaling of several AD-related cytokines, such as IFN-γ, IL-4, IL-13, IL-31, IL-33, IL-23, IL-22, and IL-17, mediating downstream inflammation and barrier alterations. While AD is primarily Th2-driven, the clinical and molecular heterogeneity of AD endotypes highlights the unmet need for effective therapeutic options that target more than one immune axis and are safe for long-term use. The JAK inhibitors, which target different combinations of kinases, have overlapping but distinct mechanisms of action and safety profiles. Several topical and oral JAK inhibitors have been shown to decrease AD severity and symptoms. A review of the JAK and SYK inhibitors that are currently undergoing evaluation for efficacy and safety in the treatment of AD summarizes available data on a promising area of therapeutics and further elucidates the complex molecular interactions that drive AD.

Resistance Mechanisms to SYK Inhibition in AML

Alterations in signaling pathways are critical to the pathogenesis of acute myeloid leukemia (AML) and are often driven by aberrant kinases. We previously identified spleen tyrosine kinase (SYK), a non-receptor, cytoplasmic tyrosine kinase, as a druggable target in AML and a critical regulator of FLT3, the most commonly mutated receptor tyrosine kinase in this disease. SYK was initially described as having an important role in B-cell development. More recent studies showed a broader relevance of SYK in hematopoietic signaling. Multiple orally bioavailable SYK inhibitors, including entospletinib (GS-9973) and TAK-659, are currently in Phase I/II clinical trials in patients with AML, with promising results. Targeted therapy, however, is typically associated with the emergence of resistance, and combination therapy is almost always needed for a durable therapeutic response. The aim of our study, therefore, was to identify resistance mechanisms to SYK inhibition in AML and to identify new synergistic drug combinations to overcome them.We conducted a genome-scale, pooled open reading frame (ORF) library screen to investigate the mechanisms of drug resistance to SYK inhibition. We screened the AML cell lines MV4;11 and MOLM-14, which are both highly sensitive to SYK inhibitors, with entospletinib after transduction with the ORF library. Expression of KRAS and HRAS ORFs, as well as other RAS signaling pathway-related proteins, emerged as conferring the strongest resistance to entospletinib in both cell lines. Upon overexpression of NRAS and KRAS in MV4;11 and MOLM-14 cells, both wildtype for RAS, we observed i) upregulation of phospho ERK 1/2, indicating activated RAS signaling, and ii) we confirmed markedly reduced sensitivity to entospletinib. We next screened 12 AML cell lines for sensitivity to entospletinib and found that the presence of activating mutations of the RAS signaling pathway was associated with innate resistance to entospletinib.To further study the mechanism of resistance to SYK inhibition, we generated entospletinib resistant cell lines by exposing MV4;11 cells to increasing concentrations of the drug for five months. In these cells, the entospletinib IC50 shifted from 500 nM to 5 μM, and these cells were also cross resistant to the SYK inhibitor PRT062607. RNA-sequencing showed increased expression of NRAS, KRAS and related pathway genes in entospletinib resistant compared to sensitive parental cells. Accordingly, gene set enrichment analysis revealed significant upregulation of RAS signaling-related gene sets. These findings were confirmed by qPCR and western blot analysis, supporting that the activation of the RAS/MAPK signaling pathway also confers acquired resistance to SYK inhibition in AML.Because RAS mutant AML cells have been reported to be sensitive to MEK inhibition, we next tested whether MEK inhibition using PD0325901 would recapture response to SYK inhibition in RAS/MAPK activated AML cells. Indeed, entospletinib was synergistic with PD0325901 in the MV4;11 entospletinib resistant cells. Moreover, entospletinib was synergistic with PD0325901 in five different AML cell lines, including AML cell lines with RAS pathway mutations. Additionally, this drug combination was synergistic when tested in a patient sample with NRAS G12D, KRAS G12D and PTPN11 G60V mutations.In conclusion, we found that RAS pathway activation results in resistance to entospletinib in AML that may be overcome with the combination of a SYK inhibitor with a MEK inhibitor. DisclosuresNo relevant conflicts of interest to declare.

Updated Preliminary Results of a Phase 1b Dose Escalation and Dose Expansion Study of Tirabrutinib in Combination with Entospletinib in Patients with B-Cell Lymphoma

Introduction: Tirabrutinib (TIRA; GS/ONO-4059) is a selective Bruton's tyrosine kinase (BTK) inhibitor. Entospletinib is a selective inhibitor of spleen tyrosine kinase (SYK). Both have single agent activity in lymphoma and updated results from the combination of TIRA+ENTO from this ongoing phase 1b study (NCT02457598) are reported here.Methods: Patients with previously treated non-germinal-center B-cell type (non-GCB) diffuse large B-cell lymphoma (DLBCL) or two prior lines of therapy for follicular lymphoma (FL), small lymphocytic lymphoma (SLL), mantle cell lymphoma (MCL), marginal zone lymphoma (MZL), or Waldenstrom's macroglobulinemia (WM) and no prior exposure to targeted inhibitors were eligible for enrollment. Patients were enrolled using a 3+3 dose escalation design with either ENTO 200mg or 400mg QD and doses of TIRA ranging from 20mg to 160mg QD. Cohorts were subsequently enrolled at multiple dose levels to evaluate disease-specific safety and efficacy.Results: As of March 5, 2018, 72 patients have enrolled on the combination. The median age was 67.5 years (range: 30-90) and the disease subtypes for patients enrolled were non-GCB DLBCL (n=32), FL (18), MZL (5), WM (7), SLL (2), MCL (8). No maximum tolerated dose and no dose-response relationship was observed with daily dosing of both agents at the dose levels evaluated.For patients with non-GCB DLBCL (n=32), the median number of prior therapies is 3 (range 1-7). The median duration of treatment is 8 weeks (range 2-98.1) with 6 patients still on treatment. 6/27 (22%) of the evaluable patients achieved a response; best overall response is shown in table 1.For patients with indolent NHL (n=40), the median number of prior therapies is 3 (range 1-6). The median duration of treatment is 36 weeks (range 0.1-116), with 29 patients still on treatment. 19/31 (61%) of the evaluable patients achieved a response with best overall response by indication shown in table 1.The most common treatment-emergent adverse events (AEs) are listed in table 2. Of the 71 patients who have received treatment on study, AEs led to treatment interruption or discontinuation of both study drugs in 10 and 1 patients, respectively. There have been 4 deaths on study, all due to disease progression.Conclusion: Once-daily dosing of TIRA up to 160 mg in combination with ENTO up to 400 mg QD was safe and well tolerated. Early results show activity in combination across all indications treated. DisclosuresSalles:Novartis: Consultancy, Honoraria; Epizyme: Honoraria; Abbvie: Honoraria; Servier: Honoraria, Other: Advisory Board; Celgene: Honoraria, Other: Advisory Board, Research Funding; Pfizer: Honoraria; Merck: Honoraria; F. Hoffmann-La Roche Ltd: Consultancy, Honoraria, Research Funding; Gilead: Honoraria, Other: Advisory Board; BMS: Honoraria, Other: Advisory Board; Morphosys: Honoraria; Acerta: Honoraria; Janssen: Honoraria, Other: Advisory Board; Servier: Honoraria; Takeda: Honoraria; Amgen: Honoraria. Dyer:Gilead Sciences, Inc.: Honoraria, Research Funding. Hodson:Gilead Sciences, Inc.: Research Funding. Ysebaert:Roche: Consultancy, Research Funding; Gilead Sciences, Inc.: Consultancy, Research Funding; Janssen: Consultancy, Research Funding. Cartron:Sanofi: Honoraria; Celgene: Consultancy, Honoraria; Janssen: Honoraria; Roche: Consultancy, Honoraria; Gilead Sciences: Honoraria. Davies:Acerta Pharma: Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead Sciences, Inc.: Honoraria, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; GSK: Research Funding; ADC-Therapeutics: Research Funding; Janssen: Honoraria; Karyopharma: Membership on an entity's Board of Directors or advisory committees. Danilov:Aptose Biosciences: Research Funding; Gilead Sciences: Consultancy, Research Funding; Verastem: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; Bayer Oncology: Consultancy, Research Funding; Takeda Oncology: Research Funding; TG Therapeutics: Consultancy; Astra Zeneca: Consultancy. Fegan:Roche: Honoraria; Abbvie: Honoraria; Gilead Sciences, Inc.: Honoraria; Napp: Honoraria; Janssen: Honoraria. Huang:Gilead Sciences, Inc.: Employment. Mitra:Gilead Sciences, Inc.: Employment. Rule:Roche: Honoraria; AstraZeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Gilead Sciences, Inc.: Membership on an entity's Board of Directors or advisory committees; Celltrion: Membership on an entity's Board of Directors or advisory committees; Kite: Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Honoraria, Research Funding, Speakers Bureau. Morschhauser:Janssen: Other: Scientific Lectures; Epizyme: Consultancy; Roche: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees.

Updated Preliminary Results of a Phase 1b Dose Escalation and Dose Expansion Study of Tirabrutinib Alone or in Combination with Idelalisib or Entospletinib in Patients with Previously Treated Chronic Lymphocytic Leukemia

Updated Preliminary Results of a Phase 1b Dose Escalation and Dose Expansion Study of Tirabrutinib Alone or in Combination with Idelalisib or Entospletinib in Patients with Previously Treated Chronic Lymphocytic Leukemia

Fostamatinib, a Spleen Tyrosine Kinase Inhibitor, for the Treatment of Warm Antibody Autoimmune Hemolytic Anemia: Initial Results of the Multicenter, Open-Label Extension Period of the Soar Phase 2 Study

▪Background: Warm antibody autoimmune hemolytic anemia (wAIHA) is a rare and often serious disease characterized by antibody-mediated destruction of red blood cells (RBCs). Activation of Fc receptors on macrophages in turn activates spleen tyrosine kinase (SYK), which triggers a signaling cascade leading to phagocytosis of the antibody-bearing cells. Fostamatinib, a SYK inhibitor, markedly improved Hgb levels in 9 of 17 (53%) patients with wAIHA during a phase 2, open-label, multicenter study. This abstract reports the results of ongoing fostamatinib treatment as of 2 July 2018 in patients who completed the 24-week treatment period and rolled over into the extension period of the study.Methods: Eligible adult patients had primary or secondary wAIHA and had failed more than one prior treatment for wAIHA. Patients had to have hemoglobin (Hgb) <10 g/dL, an IgG-positive direct antiglobulin test, haptoglobin <10 mg/dL, and lactate dehydrogenase (LDH) >ULN. In order to enter the extension period of the study, patients had to have [1] met the primary efficacy endpoint (Hgb >10 g/dL with an increase of ≥2 g/dL from baseline by Week 24 without rescue therapy or RBC transfusion) OR have shown a beneficial trend during the 24-week treatment period and [2] tolerated study drug. Fostamatinib 150mg BID (or the dose taken at the end of the 24-week treatment period, if a dose reduction had occurred) was taken orally with no food restriction, and patients were seen every 6 weeks during the extension period.Results: Six patients have entered the extension period including 5 who had met the primary efficacy endpoint and 1 who showed a beneficial trend at Week 24 (and had a response at Week 30). One patient had lymphoproliferative disease. Prior AIHA treatment included splenectomy (1), steroids (6), and rituximab (2). The median duration of disease was 1.9 years (range 0.4-15.7). The mean age was 58.7 years (range 30-86), 5 were female, all were white, and 4 were Hispanic or Latino. At baseline the median Hgb was 9.1 g/dL (range: 8.6-9.5); the median lactate dehydrogenase was 273 U/L (range 233-781); the median reticulocyte count was 252.2 x109/L (range 7.8-350.0); and the median haptoglobin was 7.0 mg/dL (range 7.0-9.0). The direct antiglobulin test was positive for IgG in 5 patients at screening.Median Hgb levels increased over the course of the study. See figure. Four of 6 patients had an ongoing response as of the data cutoff date, and none has had rescue therapy or an RBC transfusion. All 6 patients had ≥1 adverse event (AE) during the study, including noninfectious diarrhea in 1 (treatment-related), hepatic disorders in 3 (treatment-related in 2; treatment interrupted in 1), and hypertension in 1 (not related). One patient had a serious AE (inappropriate antidiuretic hormone secretion), which was not related to fostamatinib. To date, no new safety signals have been detected.Summary/Conclusion: Patients with wAIHA continued to display markedly improved Hgb levels during the extension period of the study. Side effects were manageable and consistent with those previously reported with fostamatinib in other conditions. [Display omitted] DisclosuresKuter:ONO: Consultancy; Protalex: Research Funding; Rigel: Consultancy, Research Funding; BMS: Research Funding; Pfizer: Consultancy; Novartis: Consultancy; Amgen Inc.: Consultancy; Principia: Research Funding; Bioverativ: Consultancy, Research Funding; Argenx: Consultancy; Syntimmune: Consultancy; Dova Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees. Arnold:Amgen: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; UCB: Consultancy; UCB: Consultancy; Bristol Myers Squibb: Research Funding; Novartis: Consultancy, Research Funding; Bristol Myers Squibb: Research Funding. Boxer:Incyte: Speakers Bureau; Rigel: Speakers Bureau; AbbVie: Speakers Bureau. Broome:Bioverativ: Honoraria; Alexion: Honoraria. Field:Prolong: Research Funding; Ironwood: Consultancy, Research Funding; Incyte: Research Funding. Lowe:Rigel: Consultancy. Tong:Rigel: Employment, Equity Ownership. Zayed:Rigel: Employment, Equity Ownership. Duliege:Rigel: Employment, Equity Ownership.

Investigating Potential Mechanism(s) By Which ASO-Based Drugs Cause Thrombocytopenia

IntroductionAntisense oligonucleotides (ASOs) are a new class of single-stranded DNA based drugs that hold great therapeutic promise for their disease modifying potential in a wide range of genetic diseases. Preclinical toxicology studies in monkeys, as well as late stage clinical trials in humans, have upon repeated dosing, reported events of ASO sequence-specific lowering of platelet counts (mild to severe thrombocytopenia) (Henry et al. Nucleic acid therapeutics 2017). The underlying cause of this platelet decrease is still unclear in humans. We have investigated if the thrombocytopenia associated with ASOs is due to either impaired platelet production and/or destruction of platelets (clearance) due to increased platelet reactivity (activation/aggregation status). Preliminary data from mouse derived fetal liver megakaryocytes suggest that pro-platelet production does not seem to be reduced by ASOs and hence in the current study we hypothesized that the ASO-induced thrombocytopenia is due to increased clearance of platelets from the circulation.MethodsIn the current study we explored how ASOs affect platelet aggregation in platelet rich plasma (PRP) and platelet-leukocyte aggregates in whole blood (WB) obtained from healthy volunteers after informed consent. PRP or WB was treated with a clinically relevant concentration of ASO (5µM) corresponding to expected maximum plasma concentration levels, or a 20x-supra-therapeutic concentration (100µM). Four ASOs were tested: two CpG-rich phosphorothioate deoxyoligonucleotide (PS ODN) sequences: 818290 and 120704, and two non-CpG 2'-MOE containing sequences: 104838 and 501861. 818290 was included as a positive control since it has been shown to cause direct platelet activation (Flierl et al. JEM 2015). 104838 have been reported to cause moderate, dose dependent drops in platelet counts in monkeys and humans, with platelet sequestration in the liver and spleen (Narayanan PK, et al. Toxicol Sci. 2018). 501861 has triggered sporadic severe thrombocytopenia in select monkeys. ASO treated PRP was analyzed for platelet aggregation using 96-well optimul aggregometry (Lordkipanidzé et al. Blood 2014) in the presence of vehicle (PBS) or 6 concentrations of thrombin receptor activating peptide-6 (0.08-80µM,TRAP6). In a separate experiment, PRP was incubated with ASOs plus the spleen tyrosine kinase (Syk) inhibitor PRT-060318 (10µM). ASO treated WB was incubated with fluorescently labelled CD41/61 antibody to label platelets and a leukocyte-specific antibody CD14, and platelet-leukocyte aggregates were analyzed by FACS according to (Gerrits et al. Curr. Protoc. 2016).ResultsThe two non-CpG rich 2'-MOE ASO sequences 104838 and 501861 did not affect platelet aggregation at either concentration (5µM + 100µM) (Figure 1 A+B). Whilst the two CpG-rich PS ODN ASOs (818290 and 120704) triggered spontaneous platelet aggregation in PRP at 100µM (Figure 1 C+D), that was normalized by co-incubating these ASOs with a Syk inhibitor (Figure 2). 5µM of ASO treatment triggered a significant increase in platelet-leukocyte aggregates in WB for all the ASOs tested (Figure 3).ConclusionWe have shown that the two CpG-rich PS ODN ASOs (818290 and 120704) triggered spontaneous platelet aggregation in PRP at 100µM. This effect was inhibited by a Syk inhibitor. 818290 has previously been identified to activate platelets through a Syk-dependent, GPVI receptor mediated mechanism (Flierl et al. JEM 2015). Here, we report for the first time that the aggregatory effects of 120704 have been identified to be Syk dependent as well, possibly through a similar interaction with platelet GPVI receptors.We have also presented novel data that therapeutically relevant concentrations of all the ASOs tested cause an increase in platelet-leukocyte aggregates in WB. Based on these data we highlight the importance of screening ASOs in multi-cellular assays, not just PRP, since there was no effect of the ASOs 104838 or 501861 on platelet aggregation. Enhanced formation of platelet-leukocyte aggregates could be one contributing factor for increased platelet clearance, explaining ASO-induced thrombocytopenia. Further investigation into the ASO-induced interactions between platelets and immune cells are warranted. Defining the mechanisms by which ASO-based drugs cause low platelet count may yield strategies to manage this drug-induced thrombocytopenia in patients. [Display omitted] DisclosuresThon:Platelet Biogenesis: Employment, Equity Ownership, Other: Co-founder, Patents & Royalties. Henry:Ionis Pharmaceuticals: Employment. Narayanan:Ionis Pharmaceuticals: Employment. Italiano:Platelet Biogenesis: Equity Ownership, Other: Co-founder, Patents & Royalties.

A study of pyrazolo-benzimidazole derivatives as spleen tyrosine kinase inhibitors: an in-silico approach

In an effort to contribute designing of improved anticancer molecules, in-silico prediction data including pharmacophore hypothesis, 3D-QSAR model, and molecular docking studies were performed on 55 compounds collected from literature. Tyrosine kinase has been used as a target enzyme as it plays a vital role in spleen cancer. The 3VF8 protein was selected for our molecular docking studies which is a crystal structure of spleen tyrosine kinase Syk catalytic domain with pyrazolylbenzimidazole inhibitor. A five-point pharmacophore was developed using 55 molecules having IC50 ranging from 13.2 to 0.83 μM. The best predictive pharmacophoric hypothesis ADRRR_2 was characterised by survival score 6.096, R2 = 0.8103, Q2 = 0.6169, F value = 20.3, RMSE = 0.45, Pearson-r = 0.4678, SD = 0.1905, and stability = 0.323 with a four-component PLS factor. In molecular docking studies, the compounds Bnz34, Bnz41, Bnz44, and Bnz45 showed interactions with MET448, LEU377, LEU307, LEU501, GLY378, LEU453, and LEU454 residues; these compounds have low-binding energies and a good in vivo activity. The pharmacophoric feature R5 is involved in hydrogen-bonding interaction whereas R7 is involved in aromatic hydrogen-bonding interactions with LEU377, GLY378, LEU501, LEU453, and LEU454 respectively. These results explained that one hydrogen acceptor, one hydrogen donor, and three aromatic rings are crucial for spleen tyrosine kinase inhibition.

New biologics in the treatment of urticaria.

Symptomatic management of chronic spontaneous urticaria (CSU) basically depends on second-generation H1 antihistamines and omalizumab. Omalizumab is a game changer in the management, but still there is a need for new targets and new biologics targeting new pathways in the treatment which will provide long-lasting remission, which will be given orally and which will be cheaper. This review will focus on new biologics that are underway of production or are already under use for different disorders but could be beneficial for the treatment of Chronic urticaria. In this review, the treatment targets are classified according to the cells which are involved in the pathogenesis of CSU. Those are mast cells/basophils, B cells, T cells and eosinophils. The treatments that are under clinical trials for CSU are anti-IgE treatments such as ligelizumab, molecules targeting intracellular signaling pathways such as spleen tyrosine kinase inhibitors, surface inhibitory molecules such as siglec-8, anti-IL-1s such as canakinumab, Bruton kinase (BTK) inhibitors such as GDC-0853 and anti-IL-5s such as benralizumab and mepolizumab. The ongoing clinical trials on new targets of treatment hold new hopes not only for a better care of the disease but also a better understanding of the pathomechanisms lying underneath.

Discovery of potent and selective Spleen Tyrosine Kinase inhibitors for the topical treatment of inflammatory skin disease

The discovery and lead optimisation of a novel series of SYK inhibitors is described. These were optimised for SYK potency and selectivity against Aurora B. Compounds were profiled in a human skin penetration study to identify a suitable candidate molecule for pre-clinical development. Compound 44 (GSK2646264) was selected for progression and is currently in Phase I clinical trials.

Fostamatinib in chronic immune thrombocytopenia: a profile of its use in the USA.

Oral fostamatinib is an orally administered small molecule spleen tyrosine kinase (SYK) inhibitor approved for the treatment of adults with chronic immune thrombocytopenia (ITP) who have an inadequate response to a previous treatment. Fostamatinib has a unique mechanism of action, whereby its active metabolite targets the SYK-mediated pathway of platelet destruction. In clinical trials, fostamatinib provided durable responses in adults with chronic ITP who had not responded or had relapsed following treatment with one or more prior ITP therapies, including corticosteroids, thrombopoietin receptor agonists, rituximab, and/or splenectomy. Most patients who respond to fostamatinib maintain platelet counts of > 50 × 109/L for periods of ≥ 12 months. The most common adverse events reported with fostamatinib in clinical trials were diarrhea, hypertension, nausea, and increased transaminase levels.

Effects of GS-9876, a novel spleen tyrosine kinase inhibitor, on platelet function and systemic hemostasis

IntroductionSpleen tyrosine kinase (SYK) mediates signal transduction in multiple hematopoietic cells, including platelets. SYK signals downstream of immunoreceptors and SYK inhibition may ameliorate disease pathology in multiple autoimmune disorders; however, the impact of SYK inhibition in platelets and its potential relevance to bleeding is not fully understood. These studies evaluated the effect of an oral SYK inhibitor, GS-9876, on platelets in vitro and in vivo, and the impact of GS-9876 plus non-steroidal anti-inflammatory drugs (NSAIDs) on platelet aggregation. Material and methodsThe effect of GS-9876 on platelet activation, aggregation, and binding was characterized by western blotting, aggregometry, fluorescence-activated cell sorting, and microscopy techniques. The effect of GS-9876 on in vivo bleeding time (BT) was determined in cynomolgus monkeys and humans. ResultsGS-9876 inhibited glycoprotein VI (GPVI)-induced phosphorylation of linker for activation of T cells and phospholipase Cγ2, platelet activation and aggregation in human whole blood, and platelet binding to collagen under arterial flow. Ex vivo, GPVI-stimulated platelet aggregation was inhibited in GS-9876-treated monkeys without a concomitant increase in BT. Similarly, orally administered GS-9876 did not increase BT in humans. No in vitro additive effects on inhibition of platelet aggregation were observed with GS-9876 plus NSAIDs in human blood. ConclusionsGS-9876 inhibited SYK activity in platelets via the GPVI receptor without prolonging BT in monkeys or humans. Furthermore, GS-9876 did not increase inhibition of platelet aggregation by NSAIDs in vitro, suggesting that these agents can potentially be combined without increasing bleeding risk in humans.

Spleen tyrosine kinase from Nile tilapia (Oreochromis niloticus): Molecular characterization, expression pattern upon bacterial infection and the potential role in BCR signaling and inflammatory response

Spleen tyrosine kinase (SYK), a member of non-receptor tyrosine kinase family, plays an important role in immune responses against pathogen infection, which is capable of activating B cells signaling pathway and regulating inflammatory response. In this study, Nile tilapia (Oreochromis niloticus) ortholog (OnSYK) was identified and characterized at expression pattern against bacterial infection, function in B cells activation pathway and inflammatory response. The cDNA of OnSYK ORF contained 1851 bp of nucleotide sequence encoding polypeptides of 616 amino acids. The deduced OnSYK protein was highly homologous to other species SYK, containing two SH2 domains and a TyrKc domain. Spatial mRNA expression analysis revealed that OnSYK had wide tissue distribution and was highly expressed in the liver. After challenge of Streptococcus agalactiae (S. agalactiae) in vivo, mRNA expression of OnSYK was significantly up-regulated in the head kidney, spleen and liver. The up-regulation of OnSYK transcript was also displayed in the head kidney and spleen leukocytes stimulation with S. agalactiae and LPS in vitro, which was confirmed at protein level in the head kidney leukocytes by FACS analysis. In addition, after induction with mouse anti-OnIgM monoclonal antibody in vitro, the expressions of OnSYK and its downstream molecules (OnLYN, OnBLNK and OnAP-1) were significantly up-regulated in the head kidney leukocytes, and pharmacological inhibition of SYK activity with inhibitor (P505-15) significantly attenuated the expressions of OnLYN, OnBLNK and OnAP-1. Moreover, upon LPS challenge, the expressions of OnSYK, OnTNF-α, OnIL-6 and OnAP-1 were also up-regulated in the head kidney monocytes/macrophages. After treatment with SYK inhibitor (BAY 61–3606), the expressions of OnTNF-α, OnIL-6 and OnAP-1 were inhibited in the LPS-challenged head kidney monocytes/macrophages. Taken together, the results of this study indicated that OnSYK, playing potential roles in BCR signaling and inflammatory response, was likely to get involved in host defense against bacterial infection in Nile tilapia.

Tofacitinib and TPCA-1 exert chondroprotective effects on extracellular matrix turnover in bovine articular cartilage ex vivo

ObjectiveCurrently, there are no disease-modifying osteoarthritis drugs (DMOADs) approved for osteoarthritis. It is hypothesized that a subtype of OA may be driven by inflammation and may benefit from treatment with anti-inflammatory small molecule inhibitors adopted from treatments of rheumatoid arthritis. This study aimed to investigate how small molecule inhibitors of intracellular signaling modulate cartilage degradation and formation as a pre-clinical model for structural effects. DesignBovine cartilage explants were cultured with oncostatin M (OSM) and tumour necrosis factor α (TNF-α) either alone or combined with the small molecule inhibitors: SB203580 (p38 inhibitor), R406 (Spleen tyrosine kinase (Syk) inhibitor), TPCA-1 (Inhibitor of κB kinase (Ikk) inhibitor), or Tofacitinib (Tofa) (Janus kinases (Jak) inhibitor). Cartilage turnover was assessed with the biomarkers of degradation (AGNx1 and C2M), and type II collagen formation (PRO-C2) using ELISA. Explant proteoglycan content was assessed by Safranin O/Fast Green staining. ResultsR406, TPCA-1 and Tofa reduced the cytokine-induced proteoglycan loss and decreased AGNx1 release 3.7-, 43- and 32-fold, respectively. SB203580 showed no effect. All inhibitors suppressed C2M at a concentration of 3 µM. TPCA-1 and Tofa increased the cytokine reduced PRO-C2 3.5 and 3.7-fold, respectively. ConclusionUsing a pre-clinical model we found that the inhibitors TPCA-1 and Tofa inhibited cartilage degradation and rescue formation of type II collagen under inflammatory conditions, while R406 and SB203580 only inhibited cartilage degradation, and SB203580 only partially. These pre-clinical data suggest that TPCA-1 and Tofa preserve and help maintain cartilage ECM under inflammatory conditions and could be investigated further as DMOADs for inflammation-driven osteoarthritis.

Abstract 3844: TAK-659, a SYK kinase inhibitor, demonstrates preclinical antitumor activity in solid tumor models

Abstract TAK-659 is a highly potent, reversible inhibitor of spleen tyrosine kinase (SYK) and fms related tyrosine kinase 3 (FLT3) that is currently being investigated in Phase I and II clinical trials. SYK is expressed ubiquitously in hematopoietic cells, and abnormal function of SYK has been implicated in several types of hematopoietic malignancies, including diffuse large B-cell lymphoma (DLBCL), chronic lymphocytic leukemia (CLL), and peripheral T-cell lymphoma (PTCL). Although there are considerable data supporting a role for SYK signaling in hematological cancers, data on the relevance of SYK in solid tumors are emerging. The literature suggests that SYK expression plays a role in the growth of breast and ovarian cancers, and the pancreatic adenocarcinoma microenvironment has been shown to be B-cell rich, giving us a basis to explore the activity of TAK-659 in these indications. Furthermore, ovarian cancer patients with recurrent disease have been shown to have an increase in pSYK at the time of relapse versus at diagnosis, suggesting a role for SYK in chemoresistance. The ability of TAK-659 to inhibit ex vivo colony formation of cells with the ability to grow anchorage independently in semi-solid medium was examined in 31 different human tumor xenografts. TAK-659 showed concentration-dependent inhibition of tumor colony growth in 5/31 tumor models tested, including gastric, breast, and ovarian cancers. Pre-clinically, TAK-659 has exhibited significant antitumor activity in a number of mouse xenograft models of solid tumors. We demonstrate here that daily oral administration of TAK-659 at 60mg/kg over 21 days leads to significant antitumor activity in primary human tumor models of gastric, pancreatic, triple negative breast (TNBC), and ovarian cancers, all of which express pSYK. Significant anti-tumor activity was also observed in the HCC70 TNBC xenograft model which does not express total SYK, demonstrating that TAK-659 may have anti-tumor effects beyond the inhibition of pSYK signaling. A decrease in myeloid derived suppressor cells was seen following TAK-659 treatment in this xenograft model, suggesting an immunomodulatory response may be driving the antitumor activity. Taken together, these data along with published information support the rationale for the investigation of TAK-659 in solid tumor cancer indications. Citation Format: Jessica J. Sappal, Matthew Theisen, Zhongmin Xiang, Stephen Tirrell, Rudy Christmas, Jie Yu, Mengkun Zhang, Karuppiah Kannan. TAK-659, a SYK kinase inhibitor, demonstrates preclinical antitumor activity in solid tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3844.

Abstract 819: High response rates with entospletinib in patients with t(v;11q23.3);KMT2A rearranged acute myeloid leukemia and acute lymphoblastic leukemia

Abstract Introduction: Targeted therapy for KMT2A (mixed lineage leukemia [MLL]) rearranged acute leukemia (AL) is lacking. KMT2A regulates leukemic stem cell transcription factors HOXA9 and MEIS1. Spleen tyrosine kinase (SYK) signaling induces MEIS1 in conjunction with HOXA9. We hypothesize that this regulatory loop may be sensitive to SYK inhibition with Entospletinib (ENTO) a highly selective, oral SYK inhibitor. In this analysis, we evaluate the efficacy of ENTO in patients with acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) with t(v;11q23.3) KMT2A/MLL gene rearrangements. Methods: Patients with KMT2A rearranged AL in two different clinical trials were included. AML patients (NCT02343939) received ENTO 400mg BID monotherapy for up to 14 days prior to and with induction chemotherapy (cytarabine 100 mg/m2 for 7 days plus daunorubicin 60 mg/m2 for 3 days) if previously untreated, or ENTO monotherapy alone if relapsed/refractory (R/R). R/R B-ALL patients received ENTO monotherapy for 7 days prior to and with vincristine and dexamethasone in a phase 1 study (NCT02404220). Results: 18 patients with KMT2A rearranged AL were treated. Untreated AML (n=10) patients had a median age of 49 years. One patient was in a morphologic leukemia-free state after ENTO monotherapy (before chemotherapy). After induction chemotherapy plus ENTO, seven patients had morphologic (CR) and cytogenetic (CRc) remission, but two of them had incomplete count recovery (CRi). The composite CR rate (CR/CRi/CRc) was 90%: 5 CRc, 3 CRi (CR/CRc with incomplete count recovery), and 1 CR. Six patients underwent allogeneic stem cell transplantation (SCT) in CR1. After median follow-up of 9.9 months one patient who achieved CR relapsed, with persistence of t (6;11) and an NRAS mutation. Median overall survival and event-free survival have not been reached. In R/R AML (n=6), patients had a median age of 48 years, with 2 median prior therapies. One had CR and one had CRi (but normal cytogenetics) and both received SCT. In all, 3 AML patients (1 newly diagnosed, 2 R/R) responded to ENTO monotherapy alone. In R/R ALL (n=2), median age was 59 years. Both patients had t (4;11) along with other cytogenetic abnormalities with 2 prior therapies. Both patients achieved CR with loss of KMT2A on cytogenetic testing, and one patient received SCT. Overall, ENTO was safe and well tolerated, even in combination with chemotherapy. Conclusions: KMT2A rearranged AL is sensitive to ENTO with CR observed on monotherapy in AML and high response rates in AL patients treated with combination therapy. This represents the first documentation of CR with small molecule monotherapy (n=3) in this genetic subgroup, which typically portends a poor prognosis. Correlative biomarker studies evaluating HOXA9/MEIS1 in patients with t(v;11q23.3) KMT2A rearranged leukemia treated with ENTO are pending. Citation Format: Alison R. Walker, John C. Byrd, William Blum, Tara Lin, Howland E. Crosswell, Danjie Zhang, Jie Gao, Arati V. Rao, Mark D. Minden, Wendy Stock. High response rates with entospletinib in patients with t(v;11q23.3);KMT2A rearranged acute myeloid leukemia and acute lymphoblastic leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 819.

Identification of pyrazolopyridine derivatives as novel spleen tyrosine kinase inhibitors.

Inhibition of spleen tyrosine kinase (Syk) is a promising strategy for the treatment of various allergic and autoimmune disorders such as asthma, rheumatoid arthritis, and allergic rhinitis. Previously, a Syk inhibitor with novel indazole scaffold was discovered by structure-based virtual screening. Herein, the structure-activity relationship of the indazole Syk inhibitors was investigated. Several new inhibitors demonstrated potent activity against Syk. In particular, compound 18c showed good Syk inhibitory activity (IC50 = 1.2 µM), representing a good lead compound for further optimization.

Role of Hepatic Deposited Immunoglobulin G in the Pathogenesis of Liver Damage in Systemic Lupus Erythematosus.

The onset of hepatic disorders in patients with systemic lupus erythematosus (SLE) is frequent; however, the etiology and liver pathogenesis of SLE remain unknown. In the present study, the role of hepatic deposited immunoglobulin G (IgG) in SLE-derived liver damage was investigated. From a retrospective analysis of the medical records of 404 patients with lupus and from experimental studies on mice models, we found that liver dysfunction is common in SLE and liver damage with IgG deposition spontaneously develops in lupus-prone mice. Liver injury was recreated in mice by injecting IgG from lupus serum intrahepatically. The inflammation intensity in the liver decreased with IgG depletion and the lupus IgG-induced liver inflammation in FcγRIII-deficient mice was comparatively low; while, inflammation was increased in FcγRIIb-deficient mice. Macrophages, Kupffer cells, natural killer cells, and their products, but not lymphocytes, are required for the initiation of SLE-associated liver inflammation. Blocking IgG signaling using a spleen tyrosine kinase (Syk) inhibitor suppressed the liver damage. Our findings provided evidence of spontaneously established liver damage in SLE. They also suggested that hepatic-deposited lupus IgG is an important pathological factor in the development of liver injury and that hepatic inflammation is regulated by the Syk signaling pathway. Thus, Syk inhibition might promote the development of a therapeutic strategy to control liver damage in patients with SLE.

Crystal Structures of Spleen Tyrosine Kinase in Complex with Two Novel 4-Aminopyrido[4,3-d] Pyrimidine Derivative Inhibitors.

Spleen tyrosine kinase (SYK) is a cytosolic non-receptor protein tyrosine kinase. Because SYK mediates key receptor signaling pathways involving the B cell receptor and Fc receptors, SYK is an attractive target for autoimmune disease and cancer treatments. To date, representative oral SYK inhibitors, including fostamatinib (R406 or R788), entospletinib (GS-9973), cerdulatinib (PRT062070), and TAK-659, have been assessed in clinical trials. Here, we report the crystal structures of SYK in complex with two newly developed inhibitors possessing 4-aminopyrido[4,3-D]pyrimidine moieties (SKI-G-618 and SKI-O-85). One SYK inhibitor (SKI-G-618) exhibited moderate inhibitory activity against SYK, whereas the other inhibitor (SKI-O-85) exhibited a low inhibitory profile against SYK. Binding mode analysis indicates that a highly potent SYK inhibitor might be developed by modifying and optimizing the functional groups that interact with Leu377, Gly378, and Val385 in the G-loop and the nearby region in SYK. In agreement with our structural analysis, one of our SYK inhibitor (SKI-G-618) shows strong inhibitory activities on the β-hexosaminidase release and phosphorylation of SYK/Vav in RBL-2H3 cells. Taken together, our findings have important implications for the design of high affinity SYK inhibitors.

An Open-label, Phase II Trial of Entospletinib (GS-9973), a Selective Spleen Tyrosine Kinase Inhibitor, in Diffuse Large B-cell Lymphoma

BackgroundEntospletinib (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 MethodsThe 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. ResultsNo 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. ConclusionEntospletinib monotherapy at 800 mg twice daily demonstrated limited activity in patients with advanced, relapsed DLBCL.

Fostamatinib: First Global Approval

Rigel Pharmaceuticals are developing the spleen tyrosine kinase (SYK) inhibitor fostamatinib (TAVALISSE™) as a treatment for immune thrombocytopenia (ITP), autoimmune haemolytic anaemia and IgA nephropathy. Based on positive results in the phase III FIT clinical trial program, the drug was recently approved in the US as a treatment for thrombocytopenia in adult patients with chronic ITP who have had an insufficient response to a previous treatment. This article summarizes the milestones in the development of fostamatinib leading to this first approval.