Pyrrolopyrazines as Selective Spleen Tyrosine Kinase Inhibitors

Recent progress in therapeutic applications of fluorinated five-membered heterocycles and their benzo-fused systems

Heterocyclic derivatives grafted with fluorine atom(s) have attracted the attention of scientists due to the unique physicochemical properties of the C-F bond. The inclusion of fluorine atom(s) into organic compounds often increases their lipophilicity and metabolic stability, enhancing their bioavailability and affinity for target proteins. Therefore, it is not surprising to find that more than 20% of the medications on the market contain fluorine, and nearly 300 fluorine-containing drugs have been officially approved for use as medicines. In this review article, we are interested in classifying and describing the reports comprising varied therapeutic activities of the directly fluorinated five-membered heterocycles and their fused systems during the last two decades. These therapeutic activities included antiviral, anti-inflammatory, enzymatic inhibitory, antimalarial, anticoagulant, antipsychotic, antioxidant, antiprotozoal, histamine-H3 receptor, serotonin receptor, chemokine receptor, prostaglandin-D2 receptor, and PBR inhibition activities. In many cases, the activities of fluorinated azoles were almost equal to or exceeded the potency of reference drugs.

Discovery of 3-(1H-benzo[d]imidazole-2-yl)-1H-pyrazol-4 -amine derivatives as novel and potent syk inhibitors for the treatment of hematological malignancies

Spleen tyrosine kinase (Syk) is an important oncogene and signal transduction mediator that is mainly expressed in hematopoietic cells. Syk plays a key role in the B cell receptor (BCR) signaling pathway. Abnormal activation of Syk is closely related to the occurrence and development of hematological malignancies. Therefore, Syk is a potential target for the treatment of various hematologic cancers. Starting from compound 6(Syk, IC₅₀ = 15.8 μM), we performed fragment-based rational drug design for structural optimization based on the specific solvent-accessible region, hydrophobic region, and ribose region of Syk. This resulted in the discovery of a series of novel 3-(1H-benzo [d]imidazole-2-yl)-1H-pyrazol-4-amine Syk inhibitors, which led to the identification of 19q, a highly potent Syk inhibitor that exhibited excellent inhibitory activity on Syk enzyme (IC₅₀ = 0.52 nM) and showed potency against several other kinases. In addition, compound 19q effectively reduced phosphorylation of downstream PLCγ2 level in Romos cells. And it also exhibited antiproliferative activity in multiple hematological tumour cells. More gratifyingly, 19q showed impressive efficacy at a low dosage (1 mg/kg/day) in the MV4-11 mouse xenograft model without affecting the body weight of the mice. These findings suggest that 19q is a promising new Syk inhibitor for treating blood cancers.

Combination of bendamustine-azacitidine against Syk target of breast cancer: an in silico study

Breast cancer (BC) is the most serious and second leading cause of death in women worldwide. When breast cancer is diagnosed and treated early, the chance of long-term survival is up to 90%. On the other hand, 90% of BC patient deaths are due to metastasis and a lack of effective early diagnosis. The existing conventional chemotherapy provides negative feedback due to transportation barriers towards the action sites, multidrug resistance, poor bio-availability, non-specific delivery and systemic side effects on the healthy tissue. Syk protein Kinase has been reported in BC, as a tumor modulator, providing a pro-survival signal and also by restricting epithelial-mesenchymal transition, enhancing cell-cell interactions and inhibiting migration. In the present study, we explored the possibility of targeting BC by attenuating Syk protein Kinase. Hence, we have conjugated the hydrophobic Bendamustine (BEN) and hydrophilic Azacitidine (AZA) anticancer drugs to evaluate their efficacy against BC. The native drugs (BEN and AZA) and designed drug-drug conjugate (BEN-AZA) were docked with Syk protein. Then, the docked complex was performed for Binding Free Energy and Molecular Dynamics Simulations. Furthermore, DFT and ADME properties were carried out. The results revealed that the designed drug-drug conjugate has a better docking score, ΔGbind and admirable stability throughout the simulation when compared with native drugs. In DFT and ADME analyses, the designed drug-drug conjugate has shown good stereo electronic features and pharmaceutical relevant parameters than that of native drugs. The overall results suggested that the designed drug-drug conjugate may be a suitable candidate for BC treatment.Communicated by Ramaswamy H. Sarma.

Some important inhibitors and mechanisms of rheumatoid arthritis

Rheumatoid arthritis is a chronic disease that seriously affects human health and quality of life, and it is one of the main causes of labor loss and disability. Many countries have listed rheumatoid arthritis as one of the national a key diseases to tackle. The pathogenesis of RA in humans is still unknown, and medical researchers believe that the pathogenesis of RA may be the result of a combination of genetic and environmental factors. RA is an incurable condition that can only be controlled and treated with conventional drugs. In this paper, the pathologic features and pathogenesis of RA were introduced, and the research progress of new anti-rheumatoid arthritis chemical drugs in recent years was reviewed.

Cyclic cis-1,3-Diamines Derived from Bicyclic Hydrazines: Synthesis and Applications

Cyclic cis-1,3-diamines are versatile building blocks frequently found in natural molecules or biologically active compounds. In comparison with widely studied 1,2-diamines, and despite their chemical similarity, 1,3-diamines have been investigated less intensively probably because of a lack of general synthetic procedures giving access to these compounds with good levels of chemo-, regio-, and stereocontrol. In this Account we will give a general overview of the biological interest of cyclic cis-1,3-diamines. We will then describe the synthesis and potential applications of these compounds with a particular focus on the work realized in our laboratory.

1 Introduction

2 Biological Relevance of the cis-1,3-Diamine Motif

3 Classical Synthetic Strategies towards cis-1,3-Diamines

4 N–N Bond Cleavage of Bicyclic Hydrazines: A Versatile Method to Access cis-1,3-Diamines

4.1 Preparation of Five-Membered Cyclic cis-1,3-Diamino Alcohols

4.2 Access to Fluorinated 1,3-cis-Diaminocyclopentanes

4.3 Synthesis of cis-1,3-Diaminocyclohexitols

4.4 Formation of Cyclic cis-3,5-Diaminopiperidines

5 Applications of Cyclic cis-1,3-Diamines

5.1 Small-Molecular RNA Binders

5.2 Fluorinated 1,3-Diamino Cyclopentanes as NMR Probes

6 Concluding Remarks

Characterizing the structure-activity relationships of natural products, tanshinones, reveals their mode of action in inhibiting spleen tyrosine kinase

The cytosolic non-receptor protein kinase, spleen tyrosine kinase (SYK), is an attractive drug target in autoimmune, inflammatory disorder, and cancers indications. Here, we employed pharmacophore-based drug screening combined with biochemical assay and molecular dynamics (MD) simulations to identify and characterize inhibitors targeting SYK. The built pharmacophore model, phar-TanI, successfully identified tanshinone (TanI (IC50 = 1.72 μM)) and its analogs (TanIIA (IC50 = 3.2 μM), ST32da (IC50 = 46 μM), and ST32db (IC50 = 51 μM)) which apparently attenuated the activities of SYK in vitro. Additionally, the MD simulations followed by Ligplot analyses revealed that TanI and TanIIA interfered SYK activity through binding deeply into the active site. Besides, TanI and TanIIA mainly interact with residues L377, A400, V433, M448, M450, A451, E452, L453, G454, P455, and L501, which are functional hotspots for structure-based inhibitor optimization against SYK. The structure-activity relationships (SAR) study of the identified SYK inhibitors demonstrated that the pharmacophore model, phar-TanI is reliable and precise in screening inhibitors against SYK. This study disclosed the structure-function relationships of tanshinones from Traditional Chinese Medicine (Danshen), revealing their binding site and mode of action in inhibiting SYK and provides applicability in developing new therapeutic agents.

Syk Inhibitors: New Computational Insights into Their Intraerythrocytic Action in Plasmodium falciparum Malaria

Resistance to antimalarial drugs has spread rapidly over the past few decades. The WHO recommends artemisinin-based combination therapies for the treatment of uncomplicated malaria, but unfortunately these approaches are losing their efficacy in large areas of Southeast Asia. In 2016, artemisinin resistance was confirmed in 5 countries of the Greater Mekong subregion. We focused our study on Syk inhibitors as antimalarial drugs. The Syk protein is present in human erythrocytes, and the membrane of protein band 3 is its major target following activation by oxidant stress. Tyr phosphorylation of band 3 occurs during P. falciparum growth, leading to the release of microparticles containing hemicromes and structural weakening of the host cell membrane, simplifying merozoite reinfection. Syk inhibitors block these events by interacting with the Syk protein’s catalytic site. We performed in vitro proteomics and in silico studies and compared the results. In vitro studies were based on treatment of the parasite’s cellular cultures with different concentrations of Syk inhibitors, while proteomics studies were focused on the Tyr phosphorylation of band 3 by Syk protein with the same concentrations of drugs. In silico studies were based on different molecular modeling approaches in order to analyze and optimize the ligand–protein interactions and obtain the highest efficacy in vitro. In the presence of Syk inhibitors, we observed a marked decrease of band 3 Tyr phosphorylation according to the increase of the drug’s concentration. Our studies could be useful for the structural optimization of these compounds and for the design of novel Syk inhibitors in the future.

Discovery of Lanraplenib (GS-9876): A Once-Daily Spleen Tyrosine Kinase Inhibitor for Autoimmune Diseases

Spleen tyrosine kinase (SYK) is a critical regulator of signaling in a variety of immune cell types such as B-cells, monocytes, and macrophages. Accordingly, there have been numerous efforts to identify compounds that selectively inhibit SYK as a means to treat autoimmune and inflammatory diseases. We previously disclosed GS-9973 (entospletinib) as a selective SYK inhibitor that is under clinical evaluation in hematological malignancies. However, a BID dosing regimen and drug interaction with proton pump inhibitors (PPI) prevented development of entospletinib in inflammatory diseases. Herein, we report the discovery of a second-generation SYK inhibitor, GS-9876 (lanraplenib), which has human pharmacokinetic properties suitable for once-daily administration and is devoid of any interactions with PPI. Lanraplenib is currently under clinical evaluation in multiple autoimmune indications.

Silver-promoted selective fluorination of 2-aminopyrimidines: synthesis of 5-fluoro-2-aminopyrimidine derivatives

Ag-Promoted selective fluorination of 2-aminopyrimidine derivatives with Selectfluor is presented, giving 4-substituted 5-fluoro-2-aminopyrimidines in fair to high yields with excellent regioselectivities.

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.

Synthesis, biological evaluation and mechanism studies of matrine derivatives as anticancer agents

A total of five matrine derivatives were synthesized and evaluated for their anti-proliferation activity using a panel of four human cancer cell lines, including A549 lung, BT20 breast, MCF-7 breast and U2OS osteosarcoma cells. The YF3-5, YF3-7 and YF3-9, three novel compounds, demonstrated increased anti-proliferation activity compared with matrine, of which YF3-5 revealed the strongest anti-proliferation activity with a half-maximal inhibitory concentration value of 15.49-16.67 µM against the four human cancer cell lines. The anti-proliferation mechanism underlying YF3-5 was investigated in the A549 human lung cancer cell line and the results demonstrated that YF3-5 exerted its anti-proliferation activity through the induction of apoptosis and oxidative stress, in addition to arresting the cell cycle at the G₁ phase in a dose-dependent manner.

Targeted inhibition of Polo-like kinase 1 by a novel small-molecule inhibitor induces mitotic catastrophe and apoptosis in human bladder cancer cells

Bladder cancer is a common cancer with particularly high recurrence after transurethral resection. Despite improvements in neoadjuvant chemotherapy, the outcome of patients with advanced bladder cancer has changed very little. In this study, the anti-tumour activities of a novel Polo-like kinase 1 (PLK1) inhibitor (RO3280) was evaluated in vitro and in vivo in the bladder carcinoma cell lines 5637 and T24. MTT assays, colony-formation assays, flow cytometry, cell morphological analysis and trypan blue exclusion assays were used to examine the proliferation, cell cycle distribution and apoptosis of bladder carcinoma cells with or without RO3280 treatment. Moreover, real-time RT-PCR and Western blotting were used to detect the expressions of genes that are related to these cellular processes. Our results showed that RO3280 inhibited cell growth and cell cycle progression, increased Wee1 expression and cell division cycle protein 2 phosphorylation. In addition, RO3280 induced mitotic catastrophe and apoptosis, increased cleaved PARP (poly ADP-ribose polymerase) and caspase-3, and decreased BubR1 expression. The in vivo assay revealed that RO3280 retarded bladder cancer xenograft growth in a nude mouse model. Although further laboratory and pre-clinical investigations are needed to corroborate these data, our demonstration of bladder cancer growth inhibition and dissemination using a pharmacological inhibitor of PLK1 provides new opportunities for future therapeutic intervention.

Inhibitors of JAK-family kinases: an update on the patent literature 2013-2015, part 2

INTRODUCTION

Janus kinases (JAKs) are a family of four enzymes; JAK1, JAK2, JAK3 and tyrosine kinase 2 (TYK2) that are critical in cytokine signalling and are strongly linked to both cancer and inflammatory diseases. There are currently two launched JAK inhibitors for the treatment of human conditions: tofacitinib for Rheumatoid arthritis (RA) and ruxolitinib for myeloproliferative neoplasms including intermediate or high risk myelofibrosis and polycythemia vera. Areas covered: This review covers patents claiming activity against one or more JAK family members in the period 2013-2015 inclusive, and covers 95 patents from 42 applicants, split over two parts. The authors have ordered recent patents according to the primary applicant's name, with part 2 covering J through Z. Expert opinion: Inhibition of JAK-family kinases is an area of growing interest, catalysed by the maturity of data on marketed inhibitors ruxolitinib and tofacitinib in late stage clinical trials. Many applicants are pursuing traditional fast-follower strategies around these inhibitors, with a range of chemical strategies adopted. The challenge will be to show sufficient differentiation to the originator compounds, since dose limiting toxicities with such agents appear to be on target and mechanism-related and also considering that such agents may be available as generic compounds by the time follower agents reach market.

Orally bioavailable Syk inhibitors with activity in a rat PK/PD model

Design and optimization of benzo- and pyrido-thiazoles/isothiazoles are reported leading to the discovery of the potent, orally bioavailable Syk inhibitor 5, which was found to be active in a rat PK/PD model. Compound 5 showed acceptable overall kinase selectivity. However, in addition to Syk it also inhibited Aurora kinase in enzymatic and cellular settings leading to findings in the micronucleus assay. As a consequence, compound 5 was not further pursued.

New spleen tyrosine kinase inhibitors: patent applications published during 2011-2013

Spleen tyrosine kinase (SYK) is one of the more advanced small-molecule targets with regard to clinical development for treatment of inflammatory diseases. In this review we continue our analysis of the patent literature covering the time period 2011-2013. The analysis relates to any organization that has filed applications that explicitly discloses SYK as the intended target. In the last 2 years there has been a surge of application with a few new entries in a crowded field with the structural theme of compounds in these applications being a traditional type I ATP competitive inhibitor [ 1 ]. This overview of the SYK patent literature and the learning's of the inhibitors substitution patterns would be an important reading for anyone working in the area of SYK inhibitors.

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.

A combined experimental and computational study of Vam3, a derivative of resveratrol, and Syk interaction

Spleen tyrosine kinase (Syk) plays an indispensable role through preliminary extracellular antigen-induced crosslinking of Fc receptor (FcR) in the pathogenesis of autoimmune disorders, such as rheumatoid arthritis. In this study, we identify Vam3, a dimeric derivative of resveratrol isolated from grapes, as an ATP-competitive inhibitor of Syk with an IC₅₀ of 62.95 nM in an in vitro kinase assay. Moreover, docking and molecular dynamics simulation approaches were performed to get more detailed information about the binding mode of Vam3 and Syk. The results show that 11b-OH on ring-C and 4b-OH on ring-D could form two hydrogen bonds with Glu449 and Phe382 of Syk, respectively. In addition, arene-cation interaction between ring-D of Vam3 and Lys402 of Syk was also observed. These results indicate that ring-C and D play an essential role in Vam3–Syk interaction. Our studies may be helpful in the structural optimization of Vam3, and also aid the design of novel Syk inhibitors in the future.

Using ovality to predict nonmutagenic, orally efficacious pyridazine amides as cell specific spleen tyrosine kinase inhibitors

Inhibition of spleen tyrosine kinase has attracted much attention as a mechanism for the treatment of cancers and autoimmune diseases such as asthma, rheumatoid arthritis, and systemic lupus erythematous. We report the structure-guided optimization of pyridazine amide spleen tyrosine kinase inhibitors. Early representatives of this scaffold were highly potent and selective but mutagenic in an Ames assay. An approach that led to the successful identification of nonmutagenic examples, as well as further optimization to compounds with reduced cardiovascular liabilities is described. Select pharmacokinetic and in vivo efficacy data are presented.