The contribution of VEGF signalling to fostamatinib-induced blood pressure elevation

Identification of new drugs to counteract anti-spike IgG-induced hyperinflammation in severe COVID-19

Previously, we and others have shown that SARS-CoV-2 spike-specific IgG antibodies play a major role in disease severity in COVID-19 by triggering macrophage hyperactivation, disrupting endothelial barrier integrity, and inducing thrombus formation. This hyperinflammation is dependent on high levels of anti-spike IgG with aberrant Fc tail glycosylation, leading to Fcγ receptor hyperactivation. For development of immune-regulatory therapeutics, drug specificity is crucial to counteract excessive inflammation whereas simultaneously minimizing the inhibition of antiviral immunity. We here developed an in vitro activation assay to screen for small molecule drugs that specifically counteract antibody-induced pathology. We identified that anti-spike-induced inflammation is specifically blocked by small molecule inhibitors against SYK and PI3K. We identified SYK inhibitor entospletinib as the most promising candidate drug, which also counteracted anti-spike-induced endothelial dysfunction and thrombus formation. Moreover, entospletinib blocked inflammation by different SARS-CoV-2 variants of concern. Combined, these data identify entospletinib as a promising treatment for severe COVID-19.

Characterisation of tyrosine kinase inhibitor-receptor interactions at VEGFR2 using sunitinib-red and nanoBRET

Vascular endothelial growth factor (VEGF) is an important mediator of angiogenesis, proliferation and migration of vascular endothelial cells. It is well known that cardiovascular safety liability for a wide range of small molecule tyrosine kinase inhibitors (TKIs) can result from interference with the VEGFR2 signalling system. In this study we have developed a ligand-binding assay using a fluorescent analogue of sunitinib (sunitinib-red) and full length VEGFR2 tagged on its C-terminus with the bioluminescent protein nanoluciferase to monitor ligand-binding to VEGFR2 using bioluminescence resonance energy transfer (BRET). This NanoBRET assay is a proximity-based assay (requiring the fluorescent and bioluminescent components to be within 10nm of each other) that can monitor the binding of ligands to the kinase domain of VEGFR2. Sunitinib-red was not membrane permeable but was able to monitor the binding affinity and kinetics of a range of TKIs in cell lysates. Kinetic studies showed that sunitinib-red bound rapidly to VEGFR2 at 25 °C and that cediranib had slower binding kinetics with an average residence time of 112 min. Comparison between the log K_i values for inhibition of binding of sunitinib-red and log IC₅₀ values for attenuation of VEGF₁₆₅a-stimulated NFAT responses showed very similar values for compounds that inhibited sunitinib-red binding. However, two compounds that failed to inhibit sunitinib-red binding (dasatinib and entospletinib) were still able to attenuate VEGFR2-mediated NFAT signalling through inhibition of downstream signalling events. These results suggest that these compounds may still exhibit cardiovascular liabilities as a result of interference with downstream VEGFR2 signalling.

Clinical Pharmacokinetics and Pharmacodynamics of Fostamatinib and Its Active Moiety R406

Fostamatinib is the first approved spleen tyrosine kinase inhibitor for chronic immune thrombocytopenia. This review summarizes the clinical development, pharmacokinetics, pharmacodynamics, drug–drug interactions, adverse events, and comprehensive analyses of fostamatinib. While integrating these findings, we discuss the fostering and improvement of fostamatinib for further clinical applications. Fostamatinib is designed as a prodrug and cleavage of its active moiety R406 in the intestine. As R406 is the major product in the blood, this review mainly discusses the pharmacokinetics and pharmacodynamics of R406. It is metabolized by cytochrome 3A4 and UGT1A9 in the liver and is dominantly excreted in feces after anaerobic modification by the gut microbiota. As fostamatinib and R406 strongly inhibit the breast cancer resistance protein, the interaction with those substrates, particularly statins, should be carefully monitored. In patients with immune thrombocytopenia, fostamatinib administration started at 100 mg twice daily, and most patients increased to 150 mg twice daily in the clinical trial. Although responders showed a higher R406 concentration than non-responders, the correlation between R406 exposure and achievement of the platelet count as a pharmacodynamic marker was uncertain in the pharmacokinetic/pharmacodynamic analysis. Additionally, R406 concentration was almost halved in patients with a heavy body weight; hence, the exposure-efficacy study for suitable dosing should be continued with post-marketing data. In contrast, the pharmacokinetic/pharmacodynamic analysis for exposure safety revealed that R406 exposure significantly correlated with the incidence of hypertension. Even though the influence of elevated exposure on other toxicities, including diarrhea and neutropenia, is still unclear, careful management is required with dose escalation to avoid toxicity-related discontinuation.

Fostamatinib for the treatment of warm antibody autoimmune hemolytic anemia: Phase 2, multicenter, open-label study

Patients with relapsed warm antibody autoimmune hemolytic anemia (wAIHA) have limited treatment options. Fostamatinib is a potent, orally administered spleen tyrosine kinase inhibitor approved in the United States and Europe for the treatment of adults with chronic immune thrombocytopenia (ITP). This phase 2 study evaluated the response to fostamatinib, administered at 150 mg BID orally with or without food in adults with wAIHA and active hemolysis with hemoglobin (Hgb) <10 g/dL who had failed at least one prior treatment. Hemoglobin levels and safety assessments were performed at visits every 2 weeks. The primary endpoint was Hgb >10 g/dL with an increase of ≥2 g/dL from baseline by week 24 without rescue therapy or red blood cell transfusion. Eleven of 24 (46%) patients achieved the primary endpoint. Increases in median Hgb were detected at week 2 and sustained over time. Median lactate dehydrogenase levels and reticulocyte counts generally declined over time with little change in median haptoglobin levels. The most common adverse events (AEs) were diarrhea (42%), fatigue (42%), hypertension (27%), dizziness (27%), and insomnia (23%). AEs were manageable and consistent with the fostamatinib safety database of over 3900 patients across multiple diseases (rheumatoid arthritis, B-cell lymphoma, COVID-19, and ITP). No new safety signals were detected. Fostamatinib may be a promising therapeutic option for wAIHA. A randomized, double-blind, phase 3 study is nearing completion.

Evaluating fostamatinib disodium as a treatment option for immune thrombocytopenia in adult patients

INTRODUCTION

Immune thrombocytopenia (ITP) is an autoimmune bleeding disorder characterized by increased platelet destruction and decreased platelet production, leading to thrombocytopenia with or without bleeding manifestations. The majority of patients experiencing treatment need will eventually need secondary treatment following first line therapy with steroids. In 2018, the oral spleen tyrosine kinase inhibitor fostamatinib received US Food and Drug Administration approval for ITP patients with an insufficient response to a previous treatment.

AREAS COVERED

This review outlines pharmacological characteristics of fostamatinib and provides an overview of its efficacy and safety results in phase II and III trials, followed by the expert opinion of the authors.

EXPERT OPINION

Increasing knowledge on the role of different players and mechanisms in the pathophysiology of autoimmune disorders in general and of ITP in particular, has led to the development of several new treatment options, as illustrated by the introduction of fostamatinib in the treatment of ITP. However, lacking direct comparison with other recent treatment options (in particular thrombopoietin receptor agonists), its use should be evaluated critically taking into account the unique toxicity and potential drug-drug interaction profile.

In silico Analysis of Publicly Available Transcriptomics Data Identifies Putative Prognostic and Therapeutic Molecular Targets for Papillary Thyroid Carcinoma

Background

Purpose

Methods

Results

Conclusion

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 Acquity^TM 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.

Fostamatinib: A Review in Chronic Immune Thrombocytopenia

Fostamatinib (Tavalisse^®; Tavlesse^®) is the first spleen tyrosine kinase (Syk) inhibitor approved for the treatment of chronic immune thrombocytopenia (ITP) in adult patients who have had an insufficient response to previous treatment. By inhibiting Syk activation in macrophages, fostamatinib blocks autoantibody-mediated platelet phagocytosis. In the placebo-controlled phase III FIT1 and FIT2 trials, 24 weeks of oral fostamatinib therapy increased platelet count in previously treated adults with ITP. A significantly higher proportion of patients achieved stable response with fostamatinib than with placebo in FIT1, but not in FIT2; however, pooled analyses of the two studies showed that fostamatinib produced significantly higher stable and overall response rates than placebo. Interim findings from the ongoing FIT3 open-label extension study suggested that the efficacy of fostamatinib was maintained with long-term treatment (up to 62 months; median duration 6 months), including in patients receiving fostamatinib as second- or later-line treatment. Fostamatinib had a generally manageable tolerability profile in all three FIT studies, with no serious safety risks. Fostamatinib therefore provides an alternative treatment option for chronic ITP in adult patients with an insufficient response to previous treatment.

A landscape for drug-target interactions based on network analysis

In this work, we performed an analysis of the networks of interactions between drugs and their targets to assess how connected the compounds are. For our purpose, the interactions were downloaded from the DrugBank database, and we considered all drugs approved by the FDA. Based on topological analysis of this interaction network, we obtained information on degree, clustering coefficient, connected components, and centrality of these interactions. We identified that this drug-target interaction network cannot be divided into two disjoint and independent sets, i.e., it is not bipartite. In addition, the connectivity or associations between every pair of nodes identified that the drug-target network is constituted of 165 connected components, where one giant component contains 4376 interactions that represent 89.99% of all the elements. In this regard, the histamine H1 receptor, which belongs to the family of rhodopsin-like G-protein-coupled receptors and is activated by the biogenic amine histamine, was found to be the most important node in the centrality of input-degrees. In the case of centrality of output-degrees, fostamatinib was found to be the most important node, as this drug interacts with 300 different targets, including arachidonate 5-lipoxygenase or ALOX5, expressed on cells primarily involved in regulation of immune responses. The top 10 hubs interacted with 33% of the target genes. Fostamatinib stands out because it is used for the treatment of chronic immune thrombocytopenia in adults. Finally, 187 highly connected sets of nodes, structured in communities, were also identified. Indeed, the largest communities have more than 400 elements and are related to metabolic diseases, psychiatric disorders and cancer. Our results demonstrate the possibilities to explore these compounds and their targets to improve drug repositioning and contend against emergent diseases.

Systematic analysis of molecular mechanisms of heart failure through the pathway and network-based approach

AIMS

The molecular networks and pathways involved in heart failure (HF) are still largely unknown. The present study aimed to systematically investigate the genes associated with HF, comprehensively explore their interactions and functions, and identify possible regulatory networks involved in HF.

MAIN METHODS

The weighted gene coexpression network analysis (WGCNA), crosstalk analysis, and Pivot analysis were used to identify gene connections, interaction networks, and molecular regulatory mechanisms. Functional analysis and protein-protein interaction (PPI) were performed using DAVID and STRING databases. Gene set variation analysis (GSVA) and receiver operating characteristic (ROC) curve analysis were also performed to evaluate the relationship of the hub genes with HF.

KEY FINDINGS

A total of 5968 HF-related genes were obtained to construct the co-expression networks, and 18 relatively independent and closely linked modules were identified. Pivot analysis suggested that four transcription factors and five noncoding RNAs were involved in regulating the process of HF. The genes in the module with the highest positive correlation to HF was mainly enriched in cardiac remodeling and response to stress. Five upregulated hub genes (ASPN, FMOD, NT5E, LUM, and OGN) were identified and validated. Furthermore, the GSVA scores of the five hub genes for HF had a relatively high areas under the curve (AUC).

SIGNIFICANCE

The results of this study revealed specific molecular networks and their potential regulatory mechanisms involved in HF. These may provide new insight into understanding the mechanisms underlying HF and help to identify more effective therapeutic targets for HF.

The prognostic significance of inflammation-based scores in patients with ampullary carcinoma after pancreaticoduodenectomy

Background

Growing evidence indicates that the systemic inflammatory response plays an important role in cancer development and progression. Several inflammatory markers have been reported to be associated with clinical outcomes in patients with various types of cancer. This study was designed to evaluate the prognostic value of inflammatory indexes in patients with ampullary cancer (AC) who underwent pancreaticoduodenectomy (PD).

Methods

We retrospectively reviewed the data of 358 patients with AC who underwent PD between 2009 and 2018. R software was used to compare the area under the time-dependent receiver operating characteristic (ROC) curves (AUROCs) of the inflammation-based indexes, including the neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), modified Glasgow Prognostic Score (mGPS), prognostic nutritional index (PNI) and prognostic index (PI), in terms of their predictive value for survival. The survival differences of these indexes were compared by the Kaplan-Meier method and univariate and multivariate analyses were performed to determine the prognostic factors of disease-free survival (DFS) and overall survival (OS).

Results

The estimated 1-, 2-, and 3-year OS and DFS rates were 83.9, 65.8, and 55.2% and 58.0, 42.8, and 37.8%, respectively, for the entire cohort. The survival differences were significant in terms of OS and DFS when patients were stratified by these inflammation-based indexes. The comparisons of the AUROCs of these inflammation-based indexes illustrated that NLR and PI displayed the highest prognostic value, compared to the other indexes. When NLR and PI were combined, NLR-PI showed even higher AUROC values and was identified as a significant prognostic factor for OS and DFS.

Conclusion

Specific inflammatory indexes, such as NLR, PLR and dNLR, were found to be able to predict the OS or DFS of patients. As a novel inflammatory index, the level of NLR-PI, which can be regarded as a more useful prognostic index, exhibited strong predictive power for predicting the prognosis of patients with AC after the PD procedure.

Identification of a novel series of azabenzimidazole-derived inhibitors of spleen tyrosine kinase

Spleen Tyrosine Kinase (SYK) is a well-studied enzyme with therapeutic applications in oncology and autoimmune diseases. We identified an azabenzimidazole (ABI) series of SYK inhibitors by mining activity data of 86,000 compounds from legacy biochemical assays with SYK and other homologous kinases as target enzymes. A structure-based design and hybridization approach was then used to improve the potency and kinase selectivity of the hits. Lead compound 23 from this novel ABI series has a SYK IC₅₀ = 0.21 nM in a biochemical assay and inhibits growth of SUDHL-4 cells at a GI₅₀ = 210 nM.

Experimental and Clinical Evidence of Endothelial Dysfunction in Inflammatory Bowel Disease

The endothelium has a crucial role in proper hemodynamics. Inflammatory bowel disease (IBD) is mainly a chronic inflammatory condition of the gastrointestinal tract. However, considerable evidence points to high cardiovascular risk in patients with IBD. This review positions the basic mechanisms of endothelial dysfunction in the IBD setting (both clinical and experimental). Furthermore, we review the main effects of drugs used to treat IBD in endothelial (dys)function. Moreover, we leave challenging points for enlarging the therapeutic arsenal for IBD with new or repurposed drugs that target endothelial dysfunction besides inflammation.

INSPIRE: A European training network to foster research and training in cardiovascular safety pharmacology

Safety pharmacology is an essential part of drug development aiming to identify, evaluate and investigate undesirable pharmacodynamic properties of a drug primarily prior to clinical trials. In particular, cardiovascular adverse drug reactions (ADR) have halted many drug development programs. Safety pharmacology has successfully implemented a screening strategy to detect cardiovascular liabilities, but there is room for further refinement. In this setting, we present the INSPIRE project, a European Training Network in safety pharmacology for Early Stage Researchers (ESRs), funded by the European Commission's H2020-MSCA-ITN programme. INSPIRE has recruited 15 ESR fellows that will conduct an individual PhD-research project for a period of 36 months. INSPIRE aims to be complementary to ongoing research initiatives. With this as a goal, an inventory of collaborative research initiatives in safety pharmacology was created and the ESR projects have been designed to be complementary to this roadmap. Overall, INSPIRE aims to improve cardiovascular safety evaluation, either by investigating technological innovations or by adding mechanistic insight in emerging safety concerns, as observed in the field of cardio-oncology. Finally, in addition to its hands-on research pillar, INSPIRE will organize a number of summer schools and workshops that will be open to the wider community as well. In summary, INSPIRE aims to foster both research and training in safety pharmacology and hopes to inspire the future generation of safety scientists.

Role of the Spleen Tyrosine Kinase Pathway in Driving Inflammation in IgA Nephropathy

Summary: IgA nephropathy is the most common type of primary glomerulonephritis worldwide. At least 25% of patients may progress to kidney failure requiring dialysis or transplantation. Treatment of IgA nephropathy using generalized immunosuppression is controversial, with concerns regarding the balance of safety and efficacy in a nonspecific approach. This review describes the recent scientific evidence, and a current clinical trial, investigating whether spleen tyrosine kinase (SYK) may be a novel and selective therapeutic target for IgA nephropathy. SYK, a cytoplasmic tyrosine kinase, has a pivotal role as an early intermediate in intracellular signal transduction cascades for the B-cell receptor and the immunoglobulin Fc receptor, and thus is critical for B-cell proliferation, differentiation, and activation, and for mediating proinflammatory responses after Fc-receptor engagement in various cell types. In renal biopsy specimens of patients with IgA nephropathy, increased expression and phosphorylation of SYK were detected, and this correlated with the histologic features of mesangial and endocapillary proliferation. In cell culture studies, patient-derived IgA1 stimulated mesangial cell SYK activation, cell proliferation, and cytokine production, and these responses were attenuated by pharmacologic or molecular inhibition of SYK. A global, randomized, double-blind, placebo-controlled trial investigating the safety and efficacy of fostamatinib (an oral prodrug SYK inhibitor) in the treatment of patients with IgA nephropathy is ongoing, which may provide important evidence of the safety and efficacy of targeting this pathway in clinical disease.

Fostamatinib for the treatment of chronic immune thrombocytopenia

Fostamatinib is a spleen tyrosine kinase inhibitor recently approved for the treatment of chronic immune thrombocytopenia (ITP) in patients without adequate response to at least 1 prior line of therapy. This article reviews fostmatinib's mechanism of action and its clinical safety and efficacy in 2 industry-sponsored multicenter phase 3 randomized controlled trials in North America, Australia, and Europe (FIT1 and FIT2). Cost comparisons are discussed as well as the role of fostamatinib in relation to other options for chronic ITP.

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.

Fostamatinib for the treatment of adult persistent and chronic immune thrombocytopenia: Results of two phase 3, randomized, placebo-controlled trials

Spleen tyrosine kinase (Syk) signaling is central to phagocytosis-based, antibody-mediated platelet destruction in adults with immune thrombocytopenia (ITP). Fostamatinib, an oral Syk inhibitor, produced sustained on-treatment responses in a phase 2 ITP study. In two parallel, phase 3, multicenter, randomized, double-blind, placebo-controlled trials (FIT1 and FIT2), patients with persistent/chronic ITP were randomized 2:1 to fostamatinib (n = 101) or placebo (n = 49) at 100 mg BID for 24 weeks with a dose increase in nonresponders to 150 mg BID after 4 weeks. The primary endpoint was stable response (platelets ≥50 000/μL at ≥4 of 6 biweekly visits, weeks 14-24, without rescue therapy). Baseline median platelet count was 16 000/μL; median duration of ITP was 8.5 years. Stable responses occurred in 18% of patients on fostamatinib vs. 2% on placebo (P = .0003). Overall responses (defined retrospectively as ≥1 platelet count ≥50 000/μL within the first 12 weeks on treatment) occurred in 43% of patients on fostamatinib vs. 14% on placebo (P = .0006). Median time to response was 15 days (on 100 mg bid), and 83% responded within 8 weeks. The most common adverse events were diarrhea (31% on fostamatinib vs. 15% on placebo), hypertension (28% vs. 13%), nausea (19% vs. 8%), dizziness (11% vs. 8%), and ALT increase (11% vs. 0%). Most events were mild or moderate and resolved spontaneously or with medical management (antihypertensive, anti-motility agents). Fostamatinib produced clinically-meaningful responses in ITP patients including those who failed splenectomy, thrombopoietic agents, and/or rituximab. Fostamatinib is a novel ITP treatment option that targets an important mechanism of ITP pathogenesis.

Targeting the B cell receptor pathway in non-Hodgkin lymphoma

INTRODUCTION

Dysregulated B cell receptor (BCR) signaling has been identified as a potent contributor to tumor survival in B cell non-Hodgkin lymphomas (NHLs). This pathway's emergence as a rational therapeutic target in NHL led to development of BCR-directed agents, including inhibitors of Bruton's tyrosine kinase (BTK), spleen tyrosine kinase (SYK), and phosphatidylinositol 3 kinase (PI3K). Several drugs have become valuable assets in the anti-lymphoma armamentarium.

AREAS COVERED

We provide an overview of the BCR pathway, its dysregulation in B cell NHL, and the drugs developed to target BCR signaling in lymphoma. Mechanisms, pharmacokinetics, pharmacodynamics, efficacy, and toxicity of currently available BTK, SYK, and PI3K inhibitors are described.

EXPERT OPINION

While the excellent response rates and favorable toxicity profile of the BTK inhibitor ibrutinib in certain NHL subtypes have propelled it to consideration as frontline therapy in selected populations, additional data and clinical studies are needed before other agents targeting BCR signaling influence clinical practice similarly. PI3K inhibitors remain an option for some relapsed indolent lymphomas and chronic lymphocytic leukemia, but their widespread use may be limited by adverse effects. Future research should include efforts to overcome resistance to BTK inhibitors, combination therapy using BCR-targeted agents, and exploration of novel agents.

Quantifying the relationship between inhibition of VEGF receptor 2, drug-induced blood pressure elevation and hypertension

BACKGROUND AND PURPOSE

Several anti-angiogenic cancer drugs that inhibit VEGF receptor (VEGFR) signalling for efficacy are associated with a 15-60% incidence of hypertension. Tyrosine kinase inhibitors (TKIs) that have off-target activity at VEGFR-2 may also cause blood pressure elevation as an undesirable side effect. Therefore, the ability to translate VEGFR-2 off-target potency into blood pressure elevation would be useful in development of novel TKIs. Here, we have sought to quantify the relationship between VEGFR-2 inhibition and blood pressure elevation for a range of kinase inhibitors.

EXPERIMENTAL APPROACH

Porcine aortic endothelial cells overexpressing VEGFR-2 (PAE) were used to determine IC₅₀ for VEGFR-2 phosphorylation. These IC₅₀ values were compared with published reports of exposure attained during clinical use and the corresponding incidence of all-grade hypertension. Unbound average plasma concentration (C_av,u ) was selected to be the most appropriate pharmacokinetic parameter. The pharmacokinetic-pharmacodynamic (PKPD) relationship for blood pressure elevation was investigated for selected kinase inhibitors, using data derived either from clinical papers or from rat telemetry experiments.

KEY RESULTS

All-grade hypertension was predominantly observed when the C_av,u was >0.1-fold of the VEGFR-2 (PAE) IC₅₀ . Furthermore, based on the PKPD analysis, an exposure-dependent blood pressure elevation >1 mmHg was observed only when the C_av,u was >0.1-fold of the VEGFR-2 (PAE) IC₅₀ .

CONCLUSIONS AND IMPLICATIONS

Taken together, these data show that the risk of blood pressure elevation is proportional to the amount of VEGFR-2 inhibition, and a margin of >10-fold between VEGFR-2 IC₅₀ and C_av,u appears to confer a minimal risk of hypertension.

Fostamatinib for persistent/chronic adult immune thrombocytopenia

Immune thrombocytopenia (ITP) is an acquired autoimmune disorder characterized by phagocytosis and destruction of autoantibody-coated platelets via spleen tyrosine kinase (Syk)-mediated signal transduction in macrophages. Effectiveness of existing therapies varies, and even leading treatments (e.g., IVIg, splenectomy, rituximab, thrombopoietic agents) do not provide optimal management for a substantial number of patients with chronic ITP. Fostamatinib disodium is an orally-bioavailable investigational agent being developed for treatment of primary persistent/chronic adult ITP. Fostamatinib inhibits FcR-triggered, Syk-dependent cytoskeletal rearrangement during phagocytosis. Promising findings have been described in several autoimmune diseases, including rheumatoid arthritis, and sustained responses with manageable adverse events observed with ongoing treatment in patients with heavily treated chronic ITP. Fostamatinib represents an active therapy targeting a previously unexplored mechanism of ITP pathogenesis.

Targeting the tyrosine kinase signalling pathways for treatment of immune-mediated glomerulonephritis: from bench to bedside and beyond

Glomerulonephritis (GN) affects patients of all ages and is an important cause of morbidity and mortality. Non-selective immunosuppressive drugs have been used in immune-mediated GN but often result in systemic side effects and occasionally fatal infective complications. There is increasing evidence from both preclinical and clinical studies that abnormal activation of receptor and non-receptor tyrosine kinase signalling pathways are implicated in the pathogenesis of immune-mediated GN. Activation of spleen tyrosine kinase (SYK), Bruton's tyrosine kinase (BTK), platelet-derived growth factor receptor (PDGFR), epidermal growth factor receptor (EGFR) and discoidin domain receptor 1 (DDR1) have been demonstrated in anti-GBM disease. SYK is implicated in the pathogenesis of ANCA-associated GN. SYK, BTK, PDGFR, EFGR, DDR1 and Janus kinase are implicated in the pathogenesis of lupus nephritis. A representative animal model of IgA nephropathy (IgAN) is lacking. Based on the results from in vitro and human renal biopsy study results, a phase II clinical trial is ongoing to evaluate the efficacy and safety of fostamatinib (an oral SYK inhibitor) in high-risk IgAN patient. Various tyrosine kinase inhibitors (TKIs) have been approved for cancer treatment. Clinical trials of TKIs in GN may be justified given their long-term safety data. In this review we will discuss the current unmet medical needs in GN treatment and research as well as the current stage of development of TKIs in GN treatment and propose an accelerated translational research approach to investigate whether selective inhibition of tyrosine kinase provides a safer and more efficacious option for GN treatment.

Syk inhibitors in clinical development for hematological malignancies

Spleen tyrosine kinase (Syk) is a cytosolic non-receptor protein tyrosine kinase (PTK) and is mainly expressed in hematopoietic cells. Syk was recognized as a critical element in the B-cell receptor signaling pathway. Syk is also a key component in signal transduction from other immune receptors like Fc receptors and adhesion receptors. Several oral Syk inhibitors including fostamatinib (R788), entospletinib (GS-9973), cerdulatinib (PRT062070), and TAK-659 are being assessed in clinical trials. The second generation compound, entospletinib, showed promising results in clinical trials against B-cell malignancies, mainly chronic lymphoid leukemia. Syk inhibitors are being evaluated in combination regimens in multiple malignancies.

Endothelial dysfunction and vascular disease - a 30th anniversary update

The endothelium can evoke relaxations of the underlying vascular smooth muscle, by releasing vasodilator substances. The best-characterized endothelium-derived relaxing factor (EDRF) is nitric oxide (NO) which activates soluble guanylyl cyclase in the vascular smooth muscle cells, with the production of cyclic guanosine monophosphate (cGMP) initiating relaxation. The endothelial cells also evoke hyperpolarization of the cell membrane of vascular smooth muscle (endothelium-dependent hyperpolarizations, EDH-mediated responses). As regards the latter, hydrogen peroxide (H₂ O₂ ) now appears to play a dominant role. Endothelium-dependent relaxations involve both pertussis toxin-sensitive G_i (e.g. responses to α₂ -adrenergic agonists, serotonin, and thrombin) and pertussis toxin-insensitive G_q (e.g. adenosine diphosphate and bradykinin) coupling proteins. New stimulators (e.g. insulin, adiponectin) of the release of EDRFs have emerged. In recent years, evidence has also accumulated, confirming that the release of NO by the endothelial cell can chronically be upregulated (e.g. by oestrogens, exercise and dietary factors) and downregulated (e.g. oxidative stress, smoking, pollution and oxidized low-density lipoproteins) and that it is reduced with ageing and in the course of vascular disease (e.g. diabetes and hypertension). Arteries covered with regenerated endothelium (e.g. following angioplasty) selectively lose the pertussis toxin-sensitive pathway for NO release which favours vasospasm, thrombosis, penetration of macrophages, cellular growth and the inflammatory reaction leading to atherosclerosis. In addition to the release of NO (and EDH, in particular those due to H₂ O₂ ), endothelial cells also can evoke contraction of the underlying vascular smooth muscle cells by releasing endothelium-derived contracting factors. Recent evidence confirms that most endothelium-dependent acute increases in contractile force are due to the formation of vasoconstrictor prostanoids (endoperoxides and prostacyclin) which activate TP receptors of the vascular smooth muscle cells and that prostacyclin plays a key role in such responses. Endothelium-dependent contractions are exacerbated when the production of nitric oxide is impaired (e.g. by oxidative stress, ageing, spontaneous hypertension and diabetes). They contribute to the blunting of endothelium-dependent vasodilatations in aged subjects and essential hypertensive and diabetic patients. In addition, recent data confirm that the release of endothelin-1 can contribute to endothelial dysfunction and that the peptide appears to be an important contributor to vascular dysfunction. Finally, it has become clear that nitric oxide itself, under certain conditions (e.g. hypoxia), can cause biased activation of soluble guanylyl cyclase leading to the production of cyclic inosine monophosphate (cIMP) rather than cGMP and hence causes contraction rather than relaxation of the underlying vascular smooth muscle.

Drug-induced blood pressure increase - recommendations for assessment in clinical and non-clinical studies

INTRODUCTION

Changes in blood pressure (BP) are now proactively examined throughout the drug development process as an integral aspect of safety monitoring. This is because hypertension is a very strong risk factor for cardiovascular events and drug-induced increases in BP have attracted increased regulatory attention. However, there is currently no guidance from regulatory agencies on the minimum BP data required for submissions, and there are no specific criteria for what constitutes a safety signal for increased BP in non clinical studies. Areas covered: Evaluation of BP increases through the drug discovery and development process. Expert opinion: Research into the effects of drugs should begin before clinical development is initiated and continue throughout the clinical trial program. Non clinical studies should inform a benefit-risk analysis that will aid decision-making of whether to enter the drug into Phase I development. The degree of acceptable risk will vary according to the therapy area, treatment indication and intended population for the new drug, and the approach to BP assessment and risk mitigation should be tailored accordingly. However, BP monitoring should always be included in clinical trials, and data collected from multiple studies, to convincingly prove or refute a suspicion of BP effects.

Spleen Tyrosine Kinase: A Crucial Player and Potential Therapeutic Target in Renal Disease

Spleen tyrosine kinase (Syk), a 72 kDa cytoplasmic non-receptor protein-tyrosine kinase, plays an important role in signal transduction in a variety of cell types. Ever since its discovery in the early 1990s, there has been accumulating evidence to suggest a pathogenic role of Syk in various allergic disorders, autoimmune diseases and malignancies. Additionally, there is emerging data from both pre-clinical and clinical studies that Syk is implicated in the pathogenesis of proliferative glomerulonephritis (GN), including anti-glomerular basement membrane disease, anti-neutrophil cytoplasmic antibody-associated GN, lupus nephritis and immunoglobulin A nephropathy (IgAN). Moreover, recent animal studies have shed light on the importance of Syk in mediating acute renal allograft rejection, Epstein Barr virus-associated post-transplant lymphoproliferative disease and kidney fibrosis. Fostamatinib, an oral Syk inhibitor, has undergone clinical testing in rheumatoid arthritis, refractory immune thrombocytopenic purpura, leukemia and lymphoma. The recent STOP-IgAN trial showed that the addition of non-selective immunosuppressive therapy to intensive supportive care did not improve clinical outcomes in high-risk IgAN patients. A Syk-targeted approach may be beneficial and is currently being evaluated in a phase II randomized controlled trial. In this review, we will discuss the pathogenic role of Syk and potential use of Syk inhibitor in a variety of renal diseases.

A Novel Triazolopyridine-Based Spleen Tyrosine Kinase Inhibitor That Arrests Joint Inflammation

Autoantibodies and the immunoreceptors to which they bind can contribute to the pathogenesis of autoimmune diseases such as rheumatoid arthritis (RA). Spleen Tyrosine Kinase (Syk) is a non-receptor tyrosine kinase with a central role in immunoreceptor (FcR) signaling and immune cell functionality. Syk kinase inhibitors have activity in antibody-dependent immune cell activation assays, in preclinical models of arthritis, and have progressed into clinical trials for RA and other autoimmune diseases. Here we describe the characterization of a novel triazolopyridine-based Syk kinase inhibitor, CC-509. This compound is a potent inhibitor of purified Syk enzyme, FcR-dependent and FcR-independent signaling in primary immune cells, and basophil activation in human whole blood. CC-509 is moderately selective across the kinome and against other non-kinase enzymes or receptors. Importantly, CC-509 was optimized away from and has modest activity against cellular KDR and Jak2, kinases that when inhibited in a preclinical and clinical setting may promote hypertension and neutropenia, respectively. In addition, CC-509 is orally bioavailable and displays dose-dependent efficacy in two rodent models of immune-inflammatory disease. In passive cutaneous anaphylaxis (PCA), CC-509 significantly inhibited skin edema. Moreover, CC-509 significantly reduced paw swelling and the tissue levels of pro-inflammatory cytokines RANTES and MIP-1α in the collagen-induced arthritis (CIA) model. In summary, CC-509 is a potent, moderately selective, and efficacious inhibitor of Syk that has a differentiated profile when compared to other Syk compounds that have progressed into the clinic for RA.

In vitro pharmacological profiling of R406 identifies molecular targets underlying the clinical effects of fostamatinib

Off-target pharmacology may contribute to both adverse and beneficial effects of a new drug. In vitro pharmacological profiling is often applied early in drug discovery; there are fewer reports addressing the relevance of broad profiles to clinical adverse effects. Here, we have characterized the pharmacological profile of the active metabolite of fostamatinib, R406, linking an understanding of drug selectivity to the increase in blood pressure observed in clinical studies. R406 was profiled in a broad range of in vitro assays to generate a comprehensive pharmacological profile and key targets were further investigated using functional and cellular assay systems. A combination of traditional literature searches and text-mining approaches established potential mechanistic links between the profile of R406 and clinical side effects. R406 was selective outside the kinase domain, with only antagonist activity at the adenosine A3 receptor in the range relevant to clinical effects. R406 was less selective in the kinase domain, having activity at many protein kinases at therapeutically relevant concentrations when tested in multiple in vitro systems. Systematic literature analyses identified KDR as the probable target underlying the blood pressure increase observed in patients. While the in vitro pharmacological profile of R406 suggests a lack of selectivity among kinases, a combination of classical searching and text-mining approaches rationalized the complex profile establishing linkage between off-target pharmacology and clinically observed effects. These results demonstrate the utility of in vitro pharmacological profiling for a compound in late-stage clinical development.

Prevention of fostamatinib-induced blood pressure elevation by antihypertensive agents

Fostamatinib is a tyrosine kinase inhibitor with activity against spleen tyrosine kinase which has completed clinical trials for patients with rheumatoid arthritis. In clinical studies fostamatinib treatment was associated with a small elevation of systemic arterial blood pressure (BP), a similar finding to that seen with other kinase inhibitors, especially those that inhibit VEGFR2 signaling. We have investigated the link between fostamatinib-induced blood pressure elevation and plasma levels of the fostamatinib-active metabolite R940406 in conscious rats and found the time course of the BP effect correlated closely with changes in R940406 plasma concentration, indicating a direct pharmacological relationship. Free plasma levels of R940406 produced in these studies (up to 346 nmol/L) span the clinically observed mean peak free plasma concentration of 49 nmol/L. We have demonstrated that the blood pressure elevation induced by fostamatinib dosing can be successfully controlled by a variety of methods, notably simple drug withdrawal or codosing with a range of standard antihypertensive agents such as atenolol, captopril, and nifedipine. These findings support potential methods of maintaining patient safety while on fostamatinib therapy. Furthermore, we have demonstrated, using nifedipine as an example agent, that this blood pressure control was not achieved by reduction in plasma exposure of R940406, suggesting that potential benefits from the pharmacology of the investigational drug can be maintained while blood pressure control is managed by use of standard comedications.

Etiology of angiogenesis inhibition-related hypertension

Angiogenesis inhibition, targeting vascular endothelial growth factor (VEGF) or its receptors, is an established treatment for solid tumors. A common side effect of this treatment is the development of sometimes severe hypertension. This hypertension is associated with a decrease in nitric oxide production, activation of the endothelin-signaling pathway and renin suppression. The mechanism underlying activation of the endothelin-signaling pathway is not fully understood. Both activation of endothelial cells and disinhibition of the VEGF-induced suppression of endothelin production by endothelial cells may be involved. The development of hypertension can be a reason to discontinue the angiogenesis inhibitor, thereby compromising anticancer treatment, but possibly is also a biomarker for a favorable antitumor response.

Small-molecule inhibitors of spleen tyrosine kinase as therapeutic agents for immune disorders: will promise meet expectations?

Following on the heels of the US FDA approval of tofacitinib (Xeljanz, Pfizer, USA), an inhibitor of the JAK family members, and ibrutinib (Imbruvica, Janssen, Belgium), an inhibitor of BTK, for the treatment of rheumatoid arthritis and chronic lymphocytic leukemia, respectively, there is now renewed interest in the biopharmaceutical industry in the development of orally active small-molecule agents targeting key protein kinases implicated in immune regulation. One such ‘immunokinase’ target is SYK, a non-receptor tyrosine protein kinase critical for transducing intracellular signaling cascades for various immune recognition receptors, such as the B-cell receptor and the Fc receptor. Here, we review and discuss the progress and challenges in the development of small-molecule inhibitors of SYK and their potential as a new class of disease-modifying immunosuppressive agents for certain inflammatory and autoimmune disorders.

Exposure vs. response of blood pressure in patients with rheumatoid arthritis following treatment with fostamatinib

Fostamatinib is an oral spleen tyrosine kinase (SYK) inhibitor which has been evaluated as a potential treatment for rheumatoid arthritis (RA). Treatment with fostamatinib has been associated with an increase in blood pressure (BP). In this work, we present a pooled analysis of the pharmacokinetic-pharmacodynamic (PKPD) relationship for BP, based on 3 Phase III studies, aiming to increase the knowledge about fostamatinib's effect on BP in the RA population. Fostamatinib is rapidly and extensively converted to R406 after oral administration of fostamatinib, and the PK of R406 could be described by a two-compartment population PK model with first order absorption, with an estimated CL/F of 18.7 L/h. Average steady-state concentrations, predicted based on the individual CL/F estimates, were subsequently used in the PKPD analysis. The population PKPD analysis revealed a concentration dependent increase of BP with increasing R406 concentrations, where a power model and an Emax model best described the increase in SBP and DBP, respectively. The predicted increases were +5.2 mmHg for SBP and +4.2 mmHg for DBP, for a 100 mg bid dose. The impact of covariates on the PKPD relationship was investigated but covariates did only explain a minor part of the overall high variability in BP.