Characterization of the mechanism of action of lanraplenib, a novel spleen tyrosine kinase inhibitor, in models of lupus nephritis

Pyrazine-based small molecule kinase inhibitors: clinical applications and patent review (2019-2023)

Protein kinases play a key role in cellular signaling pathways including proliferation, apoptosis, inflammation and immune regulation. Therefore, targeting kinases with small molecules has emerged as a therapeutic potential in cancers and other diseases including inflammatory and autoimmune disorders. The main chemical motifs of the available small molecule kinase inhibitors are heterocyclic, nitrogen-containing and six-membered rings including pyrazine. Several potent and selective pyrazine-based kinase inhibitors have been developed and progressed into clinical trials. The data of clinical application of kinase inhibitors demonstrate good clinical activity with manageable toxicity in several relapse-resistant malignancies and severe to moderate immunological disorders. All pyrazine-based kinase inhibitors are orally active. This paper reviews the most recent kinase literature (2019-2023) related to pyrazine-based small molecule inhibitors. This review includes the FDA (Food and Drug Administration)-approved and patent agents along with their targeted kinase, scaffold, potency, selectivity profile, assignee and biological results in clinical and preclinical studies.

Podocyte SIRPα reduction aggravates lupus nephritis via promoting T cell inflammatory responses

Signal-regulatory protein alpha (SIRPα) has recently been found to be highly expressed in podocytes and is essential for maintaining podocyte function. However, its immunoregulatory function in podocytes remains elusive. Here, we report that SIRPα controls podocyte antigen presentation in specific T cell activation via inhibiting spleen tyrosine kinase (Syk) phosphorylation. First, podocyte SIRPα under lupus nephritis (LN) conditions is strongly downregulated. Second, podocyte-specific deletion of SIRPα exacerbates renal disease progression in lupus-prone mice, as evidenced by an increase in T cell infiltration. Third, SIRPα deletion or knockdown enhances podocyte antigen presentation, which activates specific T cells, via enhancing Syk phosphorylation. Supporting this, Syk inhibitor GS-9973 prevents podocyte antigen presentation, resulting in a decrease of T cell activation and mitigation of renal disease caused by SIRPα knockdown or deletion. Our findings reveal an immunoregulatory role of SIRPα loss in promoting podocyte antigen presentation to activate specific T cell immune responses in LN.

The ABCB1 and ABCG2 efflux transporters limit brain disposition of the SYK inhibitors entospletinib and lanraplenib

The highly selective Spleen Tyrosine Kinase (SYK) inhibitors entospletinib and lanraplenib disrupt kinase activity and inhibit immune cell functions. They are developed for treatment of B-cell malignancies and autoimmunity diseases. The impact of P-gp/ABCB1 and BCRP/ABCG2 efflux transporters, OATP1a/1b uptake transporters and CYP3A drug-metabolizing enzymes on the oral pharmacokinetics of these drugs was assessed using mouse models. Entospletinib and lanraplenib were orally administered simultaneously at moderate dosages (10 mg/kg each) to female mice to assess the possibility of examining two structurally and mechanistically similar drugs at the same time, while reducing the number of experimental animals and sample-processing workload. The plasma pharmacokinetics of both drugs were not substantially restricted by Abcb1 or Abcg2. The brain-to-plasma ratios of entospletinib in Abcb1a/b-/-, Abcg2-/- and Abcb1a/b;Abcg2-/- mice were 1.7-, 1.8- and 2.9-fold higher, respectively, compared to those in wild-type mice. For lanraplenib these brain-to-plasma ratios were 3.0-, 1.3- and 10.4-fold higher, respectively. This transporter-mediated restriction of brain penetration for both drugs could be almost fully inhibited by coadministration of the dual ABCB1/ABCG2 inhibitor elacridar, without signs of acute toxicity. Oatp1a/b and human CYP3A4 did not seem to affect the pharmacokinetics of entospletinib and lanraplenib, but mouse Cyp3a may limit lanraplenib plasma exposure. Unexpectedly, entospletinib and lanraplenib increased each other's plasma exposure by 2.6- to 2.9-fold, indicating a significant drug-drug interaction. This interaction was, however, unlikely to be mediated through any of the studied transporters or CYP3A. The obtained insights may perhaps help to further improve the safety and efficacy of entospletinib and lanraplenib.

Approaches Towards Better Immunosuppressive Agents

Several classes of compounds are applied in clinics due to their immunosuppressive properties in transplantology and the treatment of autoimmune diseases. Derivatives of mycophenolic acid, corticosteroids and chemotherapeutics bearing heterocyclic moieties like methotrexate, azathioprine, mizoribine, and ruxolitinib are active substances with investigated mechanisms of action. However, improved synthetic approaches of known drugs and novel derivatives are still being reported to attempt better accessibility and therapeutic properties. In this review article, we present the synthesis of the designed chemical structures based on recent literature reports concerning novel compounds as promising immunosuppressive drugs. Moreover, some of the discussed derivers revealed also other types of activities with prospective medicinal potential.

Biomarkers Associated with Drugs for the Treatment of Lupus Nephritis

The constant updating of lupus drug treatment guidelines has led to a question. How can the efficacy of treatment be more effectively monitored? Systemic lupus erythematosus (SLE) is a complex autoimmune disease that often presents clinically with multi-organ involvement, and approximately 30% of patients with SLE develop lupus nephritis (LN). Therefore, it is important to better track disease progression and drug efficacy. Now, kidney biopsy is still the gold standard for diagnosing and guiding the treatment of LN, but it is invasive and expensive. If simple, non-invasive and effective biomarkers can be found, drug intervention and prognosis can be better monitored and targeted. In this review, we focus on LN and explore biomarkers related to LN therapeutics, providing clinicians with more possibilities to track the therapeutic effect of drugs, improve treatment options and assess patient outcomes.

Immunomodulatory role of spleen tyrosine kinase in chronic inflammatory and autoimmune diseases

BACKGROUND

The high prevalence of chronic inflammatory diseases or autoimmune reactions is a major source of concern and affects the quality of life of patients. Chronic inflammatory or autoimmune diseases are associated with many diseases in humans, including asthma, rheumatoid arthritis, systemic lupus erythematosus, inflammatory bowel disease and cancer. Splenic tyrosine kinase (SYK) is a non-receptor tyrosine kinase that plays an important role in immune receptor signalling in immune and inflammatory responses.

METHODS

This is a review article in which we searched for keywords "splenic tyrosine kinase", "inflammation" and "autoimmune diseases" in published literature such as Pubmed and Web of Science to collect relevant information and then conducted a study focusing on the latest findings on the involvement of SYK in chronic inflammatory or autoimmune diseases.

RESULTS

This paper reviews the regulation of Fcγ, NF-κB, B cell and T cell-related signalling pathways by SYK, which contributes to disease progression in chronic inflammatory and autoimmune diseases such as airway fibrosis, inflammatory skin disease and inflammatory bowel disease.

CONCLUSION

This paper shows that SYK plays an important role in chronic inflammatory and autoimmune diseases. syk targets hematological, autoimmune and other inflammatory diseases and therefore, inhibition of SYK expression or blocking its related pathways may provide new ideas for clinical prevention and treatment of inflammatory or autoimmune diseases.

Restoration of aberrant gene expression of monocytes in systemic lupus erythematosus via a combined transcriptome-reversal and network-based drug repurposing strategy

BACKGROUND

Monocytes -key regulators of the innate immune response- are actively involved in the pathogenesis of systemic lupus erythematosus (SLE). We sought to identify novel compounds that might serve as monocyte-directed targeted therapies in SLE.

RESULTS

We performed mRNA sequencing in monocytes from 15 patients with active SLE and 10 healthy individuals. Disease activity was assessed with the Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2 K). Leveraging the drug repurposing platforms iLINCS, CLUE and L1000CDS², we identified perturbagens capable of reversing the SLE monocyte signature. We identified transcription factors and microRNAs (miRNAs) that regulate the transcriptome of SLE monocytes, using the TRRUST and miRWalk databases, respectively. A gene regulatory network, integrating implicated transcription factors and miRNAs was constructed, and drugs targeting central components of the network were retrieved from the DGIDb database. Inhibitors of the NF-κB pathway, compounds targeting the heat shock protein 90 (HSP90), as well as a small molecule disrupting the Pim-1/NFATc1/NLRP3 signaling axis were predicted to efficiently counteract the aberrant monocyte gene signature in SLE. An additional analysis was conducted, to enhance the specificity of our drug repurposing approach on monocytes, using the iLINCS, CLUE and L1000CDS² platforms on publicly available datasets from circulating B-lymphocytes, CD4⁺ and CD8⁺ T-cells, derived from SLE patients. Through this approach we identified, small molecule compounds, that could potentially affect more selectively the transcriptome of SLE monocytes, such as, certain NF-κB pathway inhibitors, Pim-1 and SYK kinase inhibitors. Furthermore, according to our network-based drug repurposing approach, an IL-12/23 inhibitor and an EGFR inhibitor may represent potential drug candidates in SLE.

CONCLUSIONS

Application of two independent - a transcriptome-reversal and a network-based -drug repurposing strategies uncovered novel agents that might remedy transcriptional disturbances of monocytes in SLE.

Targeted Small Molecules for Systemic Lupus Erythematosus: Drugs in the Pipeline

Despite the uncertainty of the pathogenesis of systemic lupus erythematosus, novel small molecules targeting specific intracellular mechanisms of immune cells are being developed to reverse the pathophysiological processes. These targeted molecules have the advantages of convenient administration, lower production costs, and the lack of immunogenicity. The Janus kinases, Bruton's tyrosine kinases, and spleen tyrosine kinases are important enzymes for activating downstream signals from various receptors on immune cells that include cytokines, growth factor, hormones, Fc, CD40, and B-cell receptors. Suppression of these kinases impairs cellular activation, differentiation, and survival, leading to diminished cytokine actions and autoantibody secretion. Intracellular protein degradation by immunoproteasomes, levered by the cereblon E3 ubiquitin ligase complex, is an essential process for the regulation of cellular functions and survival. Modulation of the immunoproteasomes and cereblon leads to depletion of long-lived plasma cells, reduced plasmablast differentiation, and production of autoantibodies and interferon-α. The sphingosine 1-phosphate/sphingosine 1-phosphate receptor-1 pathway is responsible for lymphocyte trafficking, regulatory T-cell/Th17 cell homeostasis, and vascular permeability. Sphingosine 1-phosphate receptor-1 modulators limit the trafficking of autoreactive lymphocytes across the blood-brain barrier, increase regulatory T-cell function, and decrease production of autoantibodies and type I interferons. This article summarizes the development of these targeted small molecules in the treatment of systemic lupus erythematosus, and the future prospect for precision medicine.

Investigational spleen tyrosine kinase (SYK) inhibitors for the treatment of autoimmune diseases

INTRODUCTION

Autoimmune diseases (ADs) are disorders induced by multiple inflammatory mediators, in which immune system attacks healthy tissues and triggers tissue injury. Targeted regulation of the activity of kinases that influence inflammation is one of the major therapies for ADs. Recently, investigational spleen tyrosine kinase (SYK) inhibitors have shown encouraging results in the ADs therapy.

AREAS COVERED

This article provides a background on autoimmune diseases and provides an update on investigational SYK inhibitors. This literature review was conducted by searching publications about investigational Spleen tyrosine kinase inhibitors in the treatment of ADs from experimental to clinical studies. The search terms used were SYK inhibitors, R406, fostamatinib (R788), P505-15 (PRT062607), entospletinib (GS-9973), R112, lanraplenib (GS-9876), cerdulatinib, R343, BAY-61-3606, GSK compound 143 (GSK143), R211, SKI-G-618, SKI-O-85, ER-27319, YM193306, RO9021 in conjunction with autoimmune disease using electronic databases including PubMed, EMBASE, MEDLINE and Google Scholar.

EXPERT OPINION

SYK inhibitors are promising drugs with unique advantages and acceptable tolerability and safety for the treatment of ADs. However, the difficulties in developing highly selective SYK inhibitors and the unknown effects are challenges. Long term and real-world data are essential to determine the risk-benefit ratio and true role of SYK inhibitors in the therapy of ADs.