Role of Tyrosine Kinase Syk in Thrombus Stabilisation at High Shear

Understanding the pathways involved in the formation and stability of the core and shell regions of a platelet-rich arterial thrombus may result in new ways to treat arterial thrombosis. The distinguishing feature between these two regions is the absence of fibrin in the shell which indicates that in vitro flow-based assays over thrombogenic surfaces, in the absence of coagulation, can be used to resemble this region. In this study, we have investigated the contribution of Syk tyrosine kinase in the stability of platelet aggregates (or thrombi) formed on collagen or atherosclerotic plaque homogenate at arterial shear (1000 s−1). We show that post-perfusion of the Syk inhibitor PRT-060318 over preformed thrombi on both surfaces enhances thrombus breakdown and platelet detachment. The resulting loss of thrombus stability led to a reduction in thrombus contractile score which could be detected as early as 3 min after perfusion of the Syk inhibitor. A similar loss of thrombus stability was observed with ticagrelor and indomethacin, inhibitors of platelet adenosine diphosphate (ADP) receptor and thromboxane A2 (TxA2), respectively, and in the presence of the Src inhibitor, dasatinib. In contrast, the Btk inhibitor, ibrutinib, causes only a minor decrease in thrombus contractile score. Weak thrombus breakdown is also seen with the blocking GPVI nanobody, Nb21, which indicates, at best, a minor contribution of collagen to the stability of the platelet aggregate. These results show that Syk regulates thrombus stability in the absence of fibrin in human platelets under flow and provide evidence that this involves pathways additional to activation of GPVI by collagen.

Targeting SYK of monocyte-derived macrophages regulates liver fibrosis via crosstalking with Erk/Hif1α and remodeling liver inflammatory environment

Liver fibrosis is a danger signal indicating a huge risk of liver cancer occurrence, but there is still no effective clinical means to regulate the progress of liver fibrosis. Although a variety of drugs targeting SYK have been developed for tumors and autoimmune diseases, the mechanism and specific efficacy of SYK’s role in liver fibrosis are not yet clear. Our studies based on chronic CCL4, bile duct ligation, and subacute TAA mouse models show that SYK in monocyte-derived macrophages (MoMFs) is fully dependent on phosphorylation of Erk to up-regulate the expression of Hif1α, thereby forming the crosstalk with SYK to drive liver fibrosis progress. We have evaluated the ability of the small molecule SYK inhibitor GS9973 in a variety of models. Contrary to previous impressions, high-frequency administration of GS9973 will aggravate CCL4-induced liver fibrosis, which is especially unsuitable for patients with cholestasis whose clinical features are bile duct obstruction. In addition, we found that inhibition of MoMFs SYK impairs the expression of CXCL1, on one hand, it reduces the recruitment of CD11bhiLy6Chi inflammatory cells, and on the other hand, it promotes the phenotype cross-dress process of pro-resolution MoMFs, thereby remodeling the chronic inflammatory environment of the fibrotic liver. Our further findings indicate that on the basis of the administration of CCR2/CCR5 dual inhibitor Cenicriviroc, further inhibiting MoMFs SYK may give patients with fibrosis additional benefits.

Preclinical Activity of Selective SYK Inhibitors, Entospletinib and Lanraplenib, Alone or Combined with Targeted Agents in Ex Vivo AML Models with Diverse Mutational Backgrounds

Spleen tyrosine kinase (SYK) is a non-receptor tyrosine kinase that mediates integrin and Fc receptor signaling in myeloid cells. SYK has been implicated as an oncogenic driver in acute myeloid leukemia (AML) with aberrant expression of HOXA9 and MEIS1 and cooperates with FLT3 internal tandem duplication to drive leukemogenesis. The oral SYK inhibitor entospletinib (ENTO) has demonstrated clinical activity in HOXA9/MEIS1 driven AML and is currently being investigated in a phase 3 trial of previously untreated patients with nucleophosmin1-mutated (NPM1 mut) AML. Lanraplenib (LANRA) is a next generation oral SYK inhibitor with potency and selectivity comparable to ENTO. In healthy volunteers and patients with autoimmune disease, LANRA has shown pharmacokinetic properties that compare favorably with ENTO. To support the clinical development of LANRA for the treatment of AML, ex vivo treatment of patient-derived AML cells was used to compare its activity to that of ENTO, both as a single-agent and in combination with other AML therapies. First, ENTO and LANRA single-agent activities were evaluated in peripheral blood-derived blasts from 15 AML patients, representing different mutational backgrounds including NPM1, FLT3, PTPN11, and NRAS mutations. AML cells were seeded into 96 well plates and treated with ENTO and LANRA for 6 days. Comparable effects on viability were observed across the 15 models with the 2 compounds, and in 11 of the models, the half maximal inhibitory concentration (IC 50) values were within 2-fold of each other. ENTO had a slightly lower IC 50 value than LANRA in the FLT3-mutated models possibly due to the direct FLT3 inhibitory activity of ENTO. Next, we tested the activity of ENTO and LANRA ex vivo in bone marrow-derived AML blasts from 29 AML patients representing diverse mutational backgrounds, including NPM1, IDH1, FLT3, and RAS mutations as well as MLL rearrangements. The models were treated for 9 days with either ENTO or LANRA, and viability was assessed using Annexin V and 7-aminoactinomycin D staining. Again, ENTO and LANRA showed comparable effects on cell viability with no significant differences between the compounds when compared across the different mutational backgrounds. Both studies suggest the potential for anti-leukemic activity in several different genetically defined subsets of AML. Matrix combination assays were performed by combining ENTO or LANRA with either cytarabine (NPM1 mut), gilteritinib (FLT3 mut), or trametinib (RAS mut) with cell viability and death assessed after a 3-day incubation period. Increased cell death in an additive manner was observed in all combinations tested, with results for ENTO and LANRA being similar, indicating the utility of both compounds in combinatorial treatment paradigms. These results support the clinical evaluation of LANRA in genetically defined subsets of AML. A phase 1b/2 study of LANRA in combination with the selective FLT3 inhibitor gilteritinib, in patients with relapsed or refractory FLT3 mut AML is planned for the end of this year. Disclosures Day: Cyteir Therapeutics: Current equity holder in publicly-traded company, Ended employment in the past 24 months; Kronos Bio, Inc.: Current Employment, Current equity holder in publicly-traded company. Heckman: Novartis: Research Funding; Orion Pharma: Research Funding; Celgene/BMS: Research Funding; Oncopeptides: Consultancy, Research Funding; Kronos Bio, Inc.: Research Funding. Schinzel: Kronos Bio, Inc.: Current Employment, Current equity holder in publicly-traded company. Obholzer: Kronos Bio, Inc.: Current Employment, Current equity holder in publicly-traded company, Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company. Lin: Kronos Bio, Inc.: Current Employment. Kumar: Kronos Bio, Inc.: Current Employment, Current equity holder in publicly-traded company. DiMartino: Kronos Bio, Inc.: Current Employment, Current equity holder in publicly-traded company. Saffran: Kronos Bio, Inc.: Current Employment, Current equity holder in publicly-traded company.

Final Results of a Phase 1/2 Study of SYK Inhibitor Entospletinib in Combination with Obinutuzumab in Patients with Relapsed/Refractory (R/R) Chronic Lymphocytic Leukemia (CLL)

Therapeutic resistance and intolerance of Bruton tyrosine kinase (BTK) inhibitors is an emerging need in CLL. SYK is integral to the activation of BTK and the B-cell receptor (BCR) signaling cascade and is overexpressed in CLL. We have shown that BAFF-mediated SYK activation triggered BCR signaling and rendered protection of CLL cells from spontaneous apoptosis in vitro. Single agent small molecule SYK inhibitor entospletinib was efficacious in treatment of patients with R/R CLL. Here we report final results of a single arm, open label, investigator-initiated phase 1/2 clinical trial which evaluated safety and efficacy of entospletinib in combination with obinutuzumab, a glycoengineered monoclonal anti-CD20 antibody, in patients with R/R CLL (NCT03010358). Patients enrolled in the Phase 1 dose-escalation portion of the trial included adults with CLL or non-Hodgkin lymphoma (Phase 1 part only) after ≥1 prior therapy. Patients were enrolled at 2 dose levels to receive entospletinib 200 or 400 mg twice-daily orally according to 3+3 design. The primary endpoint for the phase 1 portion of the study was to determine the RP2D of the combination. All patients received single agent entospletinib as part of a 7-day run-in. Thereafter, patients received entospletinib on days 1-28 of each 28-day cycle continuously, and obinutuzumab intravenously in standard doses for 6 cycles. Once the RP2D was determined, a phase 2 study enrolled patients with R/R CLL only, where complete response (CR) was the primary endpoint. A total of 24 patients (22 CLL, 2 follicular lymphoma) were enrolled. Twelve patients were enrolled in the phase 1 part of the study. The phase 2 part of the study included 17 patients with CLL. Of 6 patients who received entospletinib 200 mg on the Phase 1 part of the study, one patient experienced a DLT (grade 3 asymptomatic AST/ALT abnormalities) attributed to entospletinib. No DLTs were observed among the six patients who received entospletinib 400 mg. Thus, entospletinib 400 mg twice-daily was determined to be the RP2D in combination with obinutuzumab. Efficacy of entospletinib+obinutuzumab was analyzed in the 21 patients with CLL, of which 17 received entospletinib at RP2D (400 mg twice daily). Patients with CLL had a median age of 66 years. Thirteen patients (62%) had TP53 aberration (n=9), complex karyotype (n=6), or NOTCH1 or SF3B1 mutation. The median number of prior therapies was two (range, 1-6). Seven patients had received prior ibrutinib (4 patients discontinued due to intolerance and 2 due to progression). Median follow-up was 31 months. Among the 21 efficacy-evaluable participants with CLL, the ORR was 67% (95%CI, 43-85%). Three patients (14%, 95%CI 3-36%) achieved a CR, and 11 patients (53%) had a partial response (PR). patients with confirmed CR had undetectable MRD in the bone marrow. Median event-free survival was 27.5 months (95%CI: 16 months-NR), treatment duration - 31 months (95%CI: 27-40; Figure). Thirteen patients with high-risk CLL had an ORR of 54% (5 PRs and 2 CRs). Among the eight patients who had previously received kinase inhibitors, ORR was 62.5% (all PRs). Treatment-related adverse events were reported in 96% of patients (Table). Grade 3 or higher AEs occurred in 65%. Neutropenia (43.5%; including 4 patients [17%] who had transient grade 4 neutropenia attributed to obinutuzumab) was the most common grade ≥3 hematologic toxicity. The median onset of neutropenia was 7 days after the first obinutuzumab infusion, median duration was 28 days. Growth factor support was not required and grade ≥3 infection occurred in only 1 patient. Only one patient on study discontinued therapy due to adverse events (recurrent AST/ALT abnormalities which resolved upon cessation of entospletinib). Pharmacodynamic analysis demonstrated that treatment with entospletinib led to rapid downmodulation of pSTAT3 and the anti-apoptotic protein MCL1 in CLL cells. Furthermore, six months of combination therapy was accompanied by a reduction in IFNγ secretion in CD4 + T-cells and a reversal of exhausted phenotype, as evidenced by downregulation of PD-1. Thus, the combination of entospletinib and obinutuzumab shows an acceptable safety profile. Efficacy of this combination (EFS 27.5 months in predominantly high-risk population ) compares favorably with chlorambucil/obinutuzumab in R/R CLL (13 months), thus warranting continued exploration of the regimen. Figure 1 Figure 1. Disclosures Danilov: Genentech: Consultancy, Honoraria, Research Funding; SecuraBio: Research Funding; Bayer Oncology: Consultancy, Honoraria, Research Funding; Takeda Oncology: Research Funding; TG Therapeutics: Consultancy, Research Funding; Bristol-Meyers-Squibb: Honoraria, Research Funding; Rigel Pharm: Honoraria; Abbvie: Consultancy, Honoraria; Beigene: Consultancy, Honoraria; Pharmacyclics: Consultancy, Honoraria; Gilead Sciences: Research Funding; Astra Zeneca: Consultancy, Honoraria, Research Funding. Spurgeon: Bristol Myers Squibb: Other: Institution: Research Grant/Funding; BeiGene: Other: Institution: Research Grant/Funding; AstraZeneca: Other: Institution: Research Grant/Funding; Acerta Pharma: Other: Institution: Research Grant/Funding; Pharmacyclics: Consultancy; Janssen: Consultancy, Other: Institution: Research Grant/Funding; Genentech: Consultancy, Other: Institution: Research Grant/Funding; Karyopharm: Consultancy; Velos Bio: Consultancy, Other: Institution: Research Grant/Funding; Gilead Sciences: Other: Institution: Research Grant/Funding; Ionis: Other: Institution: Research Grant/Funding; Merck & Co., Inc.: Other: Institution: Research Grant/Funding; Fred Hutchinson Cancer Research Center: Other: Data Safety Monitoring Board. Kittai: Abbvie: Consultancy; Bristol-Meyers Squibb: Consultancy; Janssen: Consultancy.

Phase I Study of Novel SYK Inhibitor TAK-659 in Combination with R-CHOP for Front-Line Treatment of High Risk Diffuse Large B-Cell Lymphoma

Background: DLBCL is highly heterogeneous in underlying biology and clinical behavior. Several high-risk disease features and poor prognostic factors are associated with a higher propensity for refractory disease or relapse after standard R-CHOP therapy; these subset patients require novel strategies to improve upon outcomes. Single-agent TAK-659, a novel oral SYK inhibitor, has demonstrated efficacy in heavily pre-treated DLBCL (Gordon et al., Clin Cancer Res, 2020). We report results of a phase I single institution, single arm dose escalation study that assessed safety of 1 st line treatment with R-CHOP and adjunctive TAK-659 for treatment naïve high-risk DLBCL. Methods: Patients aged ≥18 years, ECOG 0-2 with untreated stage I-IV DLBCL with high-risk features defined as, ABC/non-GCB subtype, high-intermediate or high-risk NCCN-IPI (score ≥4), MYC gene rearranged by FISH including double hit lymphoma (DHL), double expressing DLBCL (DEL; overexpression of MYC ≥40% AND BCL2 ≥50% by IHC respectively), or previously treated transformed low-grade lymphoma without prior exposure to anthracycline, were eligible. Patients were treated with R-CHOP for 1 cycle on or off study followed by combined treatment with R-CHOP and TAK-659 for an additional 5 cycles on study. TAK-659 was dosed daily with dosing escalated from 60mg (dose level 1), to 80mg (dose level 2) to 100mg (dose level 3) based on a 3+3 design. The primary objective was to determine the safety and establish the maximum tolerated dose of TAK-659 when combined with R-CHOP in the front-line treatment of high-risk DLBCL. Secondary objectives were to assess preliminary efficacy of this combination as determined by overall response rate (ORR) by PET-CT (Lugano 2014 criteria), progression free survival (PFS), overall survival (OS) and establish the pharmacokinetics of TAK-659 according to dose. Results: 12 pts were enrolled from Dec 2019 to Nov 2021. The median age was 64 yrs (range 25-75); 8 (67%) had stage III/IV disease, 4 (33%) with high risk NCCN-IPI ≥ 4. Histology included 7 (58%) with de novo DLBCL (4 GCB, 3 non-GCB subtype DLBCL) including 7 (58%) with DEL, 3 (25%) with transformed FL, 1 (8%) with Richter's and 1 (8%) with DHL. Dose level 3 (100 mg) was established as the MTD. PKs were measured pre- and post-dose D1 and D15 of cycle 2; Cuzick's test signaled an increase in AUC by dose level on D1 (p = 0.01) but not on D15 (Fig 1). ORR was 100% (CR 92%; Fig 2). With a median follow-up of 14.2 months, 1 pt had primary refractory disease (ABC and DEL), 2 pts with CR subsequently progressed (1 non-GC DLBCL, 1 Richter's) and 1 died of cardiogenic shock unrelated to study drug. The 12-month PFS and OS rates were 82% and 90% respectively with estimated 18-month PFS and OS rates of 68% and 90% respectively. The most common treatment related adverse events (TRAEs) attributed to TAK-659 were lymphopenia (n=12, 100%), infection (6=, 50%), AST elevation (n = 12, 100%) and ALT elevation (n = 10, 83%) (Table). Incidence and severity of transaminitis was consistent with prior reports for this agent. Most common grade 3/4 toxicities were hematologic. Median number of cycles of TAK-659 delivered was 5 (range 3-5). TRAEs led to TAK-659 dose modifications in 8 (67%) pts, though none at dose level 1: 2 (17%) required permanent dose reductions (both for lung infections), while 5 (42%) required discontinuation (4 for infection, and 1 for febrile neutropenia). R-CHOP administration was delayed in 2 pts because of TAK-659 related TRAEs. Aside from dose modifications of vincristine for peripheral neuropathy, no additional dose modifications for R-CHOP were needed. Infections encountered included bacterial and opportunistic infections (1 each for PJP, CMV and aspergillosis) and 1 case of COVID. Growth factor prophylaxis and anti-fungal therapy were not mandated; PJP prophylaxis was advised for CD4 counts < 200 at initial diagnosis. Conclusion: TAK-659, a novel SYK inhibitor combined with R-CHOP in pts with newly diagnosed high-risk DLBCL including DLBCL transformed from follicular lymphoma and DEL produces high CR rates; survival at 12 months appears promising. A dose of 60 mg was well tolerated, did not require dose modifications and maintained a similar AUC to the MTD of 100 mg with ongoing treatment. Opportunistic infections were noted with this treatment combination suggesting that patients should receive aggressive anti-microbial prophylaxis with future evaluation of this combination. Figure 1 Figure 1. Disclosures Karmali: BeiGene: Consultancy, Speakers Bureau; Morphosys: Consultancy, Speakers Bureau; Kite, a Gilead Company: Consultancy, Research Funding, Speakers Bureau; Takeda: Research Funding; Karyopharm: Consultancy; EUSA: Consultancy; Janssen/Pharmacyclics: Consultancy; AstraZeneca: Speakers Bureau; BMS/Celgene/Juno: Consultancy, Research Funding; Genentech: Consultancy; Epizyme: Consultancy; Roche: Consultancy. Ma: Beigene: Research Funding, Speakers Bureau; Juno: Research Funding; AstraZeneca: Honoraria, Research Funding, Speakers Bureau; Loxo: Research Funding; Janssen: Research Funding, Speakers Bureau; Abbvie: Honoraria, Research Funding; TG Therapeutics: Research Funding; Pharmacyclics: Research Funding, Speakers Bureau. Winter: BMS: Other: Husband: Data and Safety Monitoring Board; Agios: Other: Husband: Consultancy; Actinium Pharma: Consultancy; Janssen: Other: Husband: Consultancy; Epizyme: Other: Husband: Data and Safety Monitoring Board; Gilead: Other: Husband: Consultancy; Ariad/Takeda: Other: Husband: Data and Safety Monitoring Board; Karyopharm (Curio Science): Honoraria; Merck: Consultancy, Honoraria, Research Funding; Novartis: Other: Husband: Consultancy, Data and Safety Monitoring Board. Gordon: Zylem Biosciences: Patents & Royalties: Patents, No royalties; Bristol Myers Squibb: Honoraria, Research Funding. OffLabel Disclosure: TAK-659 will be discussed for the treatment of DLBCL (not FDA approved for this indication)

Eco-Friendly UPLC–MS/MS Method for Determination of a Fostamatinib Metabolite, Tamatinib, in Plasma: Pharmacokinetic Application in Rats

Fostamatinib is a prodrug of the active metabolite tamatinib, which is a spleen tyrosine kinase (Syk) inhibitor used in the treatment of primary chronic adult immune thrombocytopenia and rheumatoid arthritis. A highly sensitive, rapid, reliable, and green method was developed and validated using ultra-performance liquid chromatography and tandem mass spectrometry (UPLC–MS/MS) for quantification of tamatinib in rat plasma. Ibrutinib was used as internal standard and liquid–liquid extraction was applied using tert-butyl methyl ether. The analyte was separated on an AcquityTM CSH C18 (2.1 mm × 100 mm, 1.7 µm) column using mobile phase consisting of 10 mM ammonium acetate and acetonitrile (10:90) and the flow rate was 0.25 mL/min. Electrospray ionization (ESI) was carried out in positive mode. Quantitation of tamatinib and the IS was performed using multiple reaction monitoring mode with precursor-to-product transitions of m/z 471.1 > 122.0 and m/z 441.1 > 84.0, respectively. The calibration range was 0.1–1000.0 ng/mL and the linearity of the method was ≥0.997. The developed method greenness was investigated. All principal parameters for the method, including linearity, accuracy, precision, recovery, and stability, were within acceptable ranges. Tamatinib pharmacokinetic study in rats was successfully carried out using the developed method.

Transitioning From Thrombopoietin Agonists to the Novel SYK Inhibitor Fostamatinib: A Multicenter, Real-World Case Series

Fostamatinib is an oral spleen tyrosine kinase (SYK) inhibitor used for the treatment of adult patients with chronic immune thrombocytopenia (ITP) who have had an insufficient response to a previous treatment. Clinical and operational barriers may exist that warrant bridging or switching from thrombopoietin receptor agonists (TPO-RAs), such as volatility or unpredictability of platelets, adverse events, and quality of life or patient preference. While fostamatinib demonstrated durable platelet responses, the safety and efficacy in combination, bridging, and/or switching with TPO-RAs is not well documented. The objective of this article is to provide guidance from real-world case studies for a safe and effective strategy for the transitioning of patients from TPO-RAs to fostamatinib, with some degree of overlap between the two agents. Currently, the evidence does not exist to guide the safe and effective use of combination therapy or transition between therapies in ITP. This case series highlights the importance to further understand the complexities of managing this disease, as well as successfully combining, bridging, and/or switching patients over to fostamatinib without the need for rescue therapy or increase in adverse events. The need for real-world evidence that guides providers on the safety and efficacy of short- and long-term combination therapy of fostamatinib and TPO-RAs is crucial. The rationale for combination therapy is to target different pathways, platelet destruction, and production without added toxicities. Additionally, gradual tapering off of TPO-RAs may provide a more favorable clinical outcome when switching to fostamatinib. The need for additional data is necessary to provide clinicians with guidance when managing patients with ITP.

Acute Kidney Injury Induced Lupus Exacerbation Through the Enhanced Neutrophil Extracellular Traps (and Apoptosis) in Fcgr2b Deficient Lupus Mice With Renal Ischemia Reperfusion Injury

Renal ischemia is the most common cause of acute kidney injury (AKI) that might be exacerbate lupus activity through neutrophil extracellular traps (NETs) and apoptosis. Here, the renal ischemia reperfusion injury (I/R) was performed in Fc gamma receptor 2b deficient (Fcgr2b-/-) lupus mice and the in vitro experiments. At 24 h post-renal I/R injury, NETs in peripheral blood neutrophils and in kidneys were detected using myeloperoxidase (MPO), neutrophil elastase (NE) and citrullinated histone H3 (CitH3), as well as kidney apoptosis (activating caspase-3), which were prominent in Fcgr2b-/- mice more compared to wild-type (WT). After 120 h renal-I/R injury, renal NETs (using MPO and NE) were non-detectable, whereas glomerular immunoglobulin (Ig) deposition and serum anti-dsDNA were increased in Fcgr2b-/- mice. These results imply that renal NETs at 24 h post-renal I/R exacerbated the lupus nephritis at 120 h post-renal I/R injury in Fcgr2b-/- lupus mice. Furthermore, a Syk inhibitor attenuated NETs, that activated by phorbol myristate acetate (PMA; a NETs activator) or lipopolysaccharide (LPS; a potent inflammatory stimulator), more prominently in Fcgr2b-/- neutrophils than the WT cells as determined by dsDNA, PAD4 and MPO. In addition, the inhibitors against Syk and PAD4 attenuated lupus characteristics (serum creatinine, proteinuria, and anti-dsDNA) in Fcgr2b-/- mice at 120 h post-renal I/R injury. In conclusion, renal I/R in Fcgr2b-/- mice induced lupus exacerbation at 120 h post-I/R injury partly because Syk-enhanced renal NETs led to apoptosis-induced anti-dsDNA, which was attenuated by a Syk inhibitor.