Structure-based optimization of a potent class of arylamide FMS inhibitors

Direct C-H aminocarbonylation of N-heteroarenes with isocyanides under transition metal-free conditions

A C-C bond forming amide synthesis through direct C-H aminocarbonylation of N-heteroarenes with isocyanides was developed. The reaction was mediated by an inorganic persulfate salt under transition metal-free conditions. Mechanistic studies suggested a radical pathway for this reaction without the participation of H₂O and O₂. This method also showed merits of substrate availability, easy operation and atom economy. It provided an efficient route for straightforward synthesis of N-heteroaryl amides.

Oxidative cross-dehydrogenative coupling between iodoarenes and acylanilides for C–N bond formation under metal-free conditions

A metal-free oxidative cross-dehydrogenative coupling between iodoarenes and acylanilides was developed. It gave highly para-selectivie C–N coupling products with the retention of iodine atom which enables further transformations.

Clinically Precedented Protein Kinases: Rationale for Their Use in Neurodegenerative Disease

Kinases are an intensively studied drug target class in current pharmacological research as evidenced by the large number of kinase inhibitors being assessed in clinical trials. Kinase-targeted therapies have potential for treatment of a broad array of indications including central nervous system (CNS) disorders. In addition to the many variables which contribute to identification of a successful therapeutic molecule, drug discovery for CNS-related disorders also requires significant consideration of access to the target organ and specifically crossing the blood-brain barrier (BBB). To date, only a small number of kinase inhibitors have been reported that are specifically designed to be BBB permeable, which nonetheless demonstrates the potential for success. This review considers the potential for kinase inhibitors in the context of unmet medical need for neurodegenerative disease. A subset of kinases that have been the focus of clinical investigations over a 10-year period have been identified and discussed individually. For each kinase target, the data underpinning the validity of each in the context of neurodegenerative disease is critically evaluated. Selected molecules for each kinase are identified with information on modality, binding site and CNS penetrance, if known. Current clinical development in neurodegenerative disease are summarized. Collectively, the review indicates that kinase targets with sufficient rationale warrant careful design approaches with an emphasis on improving brain penetrance and selectivity.

Small-Molecule CSF1R Inhibitors as Anticancer Agents

Persuasive evidence has been presented linking the infiltration of Tumor-Associated Macrophages (TAMs) with the driving force of tumorigenesis and in the suppression of antitumor immunity. In this context CSF1R, the cellular receptor for Colony Stimulating Factor-1 (CSF1) and Interleukin 34 (IL-34), occupies a central role in manipulating the behavior of TAMs and the dysregulation of CSF1R signaling has been implicated in cancer progression and immunosuppression in many specific cancers. Consequently, CSF1R kinase has been a target of great interest in cancer treatment and significant research efforts have focused on the development of smallmolecule CSF1R inhibitors. In this review, we highlight current progress on the development of these small molecule CSF1R inhibitors as anticancer agents. Special attention is paid to the compounds available in advanced clinical trials.

An Efficient Greener Approach for N-Acylation of Amines in Water Using Benzotriazole Chemistry

A straightforward, mild and cost-efficient synthesis of various arylamides in water was accomplished using versatile benzotriazole chemistry. Acylation of various amines was achieved in water at room temperature as well as under microwave irradiation. The developed protocol unfolds the synthesis of amino acid aryl amides, drug conjugates and benzimidazoles. The environmentally friendly synthesis, short reaction time, simple workup, high yields, mild conditions and free of racemization are the key advantages of this protocol.

Pyrrolo[3,2-c]pyridine derivatives with potential inhibitory effect against FMS kinase: in vitro biological studies

A series of eighteen pyrrolo[3,2-c]pyridine derivatives were tested for inhibitory effect against FMS kinase. Compounds 1e and 1r were the most potent among all the other tested analogues (IC₅₀ = 60 nM and 30 nM, respectively). They were 1.6 and 3.2 times, respectively, more potent than our lead compound, KIST101029 (IC₅₀ = 96 nM). Compound 1r was tested over a panel of 40 kinases including FMS, and exerted selectivity against FMS kinase. It was further tested against bone marrow-derived macrophages (BMDM) and its IC₅₀ was 84 nM (2.32-fold more potent than KIST101029 (IC₅₀ = 195 nM)). Compound 1r was also tested for antiproliferative activity against a panel of six ovarian, two prostate, and five breast cancer cell lines, and its IC₅₀ values ranged from 0.15–1.78 µM. It possesses also the merit of selectivity towards cancer cells than normal fibroblasts.

Recent advances in colony stimulating factor-1 receptor/c-FMS as an emerging target for various therapeutic implications

Colony stimulating factor-1 (CSF-1) is one of the most common proinflammatory cytokine responsible for various inflammatory disorders. It has a remarkable role in the development and progression of osteoarthritis, cancer and other autoimmune disease conditions. The CSF-1 acts by binding to the receptor, called colony stimulating factor-1 receptor (CSF-1R) also known as c-FMS resulting in the cascade of signalling pathway causing cell proliferation and differentiation. Interleukin-34 (IL-34), recently identified as another ligand for CSF-IR, is a cytokine protein. Both, CSF-1 and IL-34, although two distinct cytokines, follow the similar signalling pathway on binding to the same receptor, CSF-1R. Like CSF-1, IL-34 promotes the differentiation and survival of monocyte, macrophages and osteoclasts. This CSF-1R/c-FMS is over expressed in many cancers and on tumour associated macrophages, consequently, have been exploited as a drug target for promising treatment for cancer and inflammatory diseases. Some CSF-1R/c-FMS inhibitors such as ABT-869, Imatinib, AG013736, JNJ-40346527, PLX3397, DCC-3014 and Ki20227 have been successfully used in these disease conditions. Many c-FMS inhibitors have been the candidates of clinical trials, but suffer from some side effects like cardiotoxicity, vomiting, swollen eyes, diarrhoea, etc. If selectivity of cFMS inhibition is achieved successfully, side effects can be overruled and this approach may become a novel therapy for treatment of various therapeutic interventions. Thus, successful targeting of c-FMS may result in multifunctional therapy. With this background of information, the present review focuses on the recent developments in the area of CSF-1R/c-FMS inhibitors with emphasis on crystal structure, mechanism of action and various therapeutic implications in which c-FMS plays a pivotal role. The review on structure activity relationship of various compounds acting as the inhibitors of c-FMS which gives the selection criteria for the development of novel molecules is also being presented.

Recent Advances of Colony-Stimulating Factor-1 Receptor (CSF-1R) Kinase and Its Inhibitors

Colony stimulation factor-1 receptor (CSF-1R), which is also known as FMS kinase, plays an important role in initiating inflammatory, cancer, and bone disorders when it is overstimulated by its ligand, CSF-1. Innate immunity, as well as macrophage differentiation and survival, are regulated by the stimulation of the CSF-1R. Another ligand, interlukin-34 (IL-34), was recently reported to activate the CSF-1R receptor in a different manner. The relationship between CSF-1R and microglia has been reviewed. Both CSF-1 antibodies and small molecule CSF-1R kinase inhibitors have now been tested in animal models and in humans. In this Perspective, we discuss the role of CSF-1 and IL-34 in producing cancer, bone disorders, and inflammation. We also review the newly discovered and improved small molecule kinase inhibitors and monoclonal antibodies that have shown potent activity toward CSF-1R, reported from 2012 until 2017.

Copper(ii) incorporated functionalized polystyrene catalyzed N-arylation of amides under solvent free condition with broad substrate scope

A new polymer supported Cu(ii) catalyst has been reported for N-arylation of various amides with aryl halides under neat reaction conditions.

Metal-free N-arylation of secondary amides at room temperature

The arylation of secondary acyclic amides has been achieved with diaryliodonium salts under mild and metal-free conditions. The methodology has a wide scope, allows synthesis of tertiary amides with highly congested aryl moieties, and avoids the regioselectivity problems observed in reactions with (diacetoxyiodo)benzene.

Novel pyridazinone inhibitors for vascular adhesion protein-1 (VAP-1): old target-new inhibition mode

Vascular adhesion protein-1 (VAP-1) is a primary amine oxidase and a drug target for inflammatory and vascular diseases. Despite extensive attempts to develop potent, specific, and reversible inhibitors of its enzyme activity, the task has proven challenging. Here we report the synthesis, inhibitory activity, and molecular binding mode of novel pyridazinone inhibitors, which show specificity for VAP-1 over monoamine and diamine oxidases. The crystal structures of three inhibitor-VAP-1 complexes show that these compounds bind reversibly into a unique binding site in the active site channel. Although they are good inhibitors of human VAP-1, they do not inhibit rodent VAP-1 well. To investigate this further, we used homology modeling and structural comparison to identify amino acid differences, which explain the species-specific binding properties. Our results prove the potency and specificity of these new inhibitors, and the detailed characterization of their binding mode is of importance for further development of VAP-1 inhibitors.

Enhancement of kinase selectivity in a potent class of arylamide FMS inhibitors

Structure-activity relationship (SAR) studies on a highly potent series of arylamide FMS inhibitors were carried out with the aim of improving FMS kinase selectivity, particularly over KIT. Potent compound 17r (FMS IC50 0.7 nM, FMS cell IC50 6.1 nM) was discovered that had good PK properties and a greater than fivefold improvement in selectivity for FMS over KIT kinase in a cellular assay relative to the previously reported clinical candidate 4. This improved selectivity was manifested in vivo by no observed decrease in circulating reticulocytes, a measure of bone safety, at the highest studied dose. Compound 17r was highly active in a mouse pharmacodynamic model and demonstrated disease-modifying effects in a dose-dependent manner in a strep cell wall-induced arthritis model of rheumatoid arthritis in rats.

FMS Kinase Inhibitors: Current Status and Future Prospects

FMS, first discovered as the oncogene responsible for Feline McDonough Sarcoma, is a type III receptor tyrosine kinase that binds to the macrophage or monocyte colony-stimulating factor (M-CSF or CSF-1). Signal transduction through that binding results in survival, proliferation, and differentiation of monocyte/macrophage lineage. Overexpression of CSF-1 and/or FMS has been implicated in a number of disease states such as the growth of metastasis of certain types of cancer, in promoting osteoclast proliferation in bone osteolysis, and many inflammatory disorders. Inhibition of CSF-1 and/or FMS may help treat these pathological conditions. This article reviews FMS gene, FMS kinase, CSF-1, IL-34, and their roles in bone osteolysis, cancer biology, and inflammation. Monoclonal antibodies, FMS crystal structure, and small molecule FMS kinase inhibitors of different chemical scaffolds are also reviewed.

The colony-stimulating factor-1 (CSF-1) receptor sustains ERK1/2 activation and proliferation in breast cancer cell lines

Breast cancer is the second leading cause of cancer-related deaths in western countries. Colony-Stimulating Factor-1 (CSF-1) and its receptor (CSF-1R) regulate macrophage and osteoclast production, trophoblast implantation and mammary gland development. The expression of CSF-1R and/or CSF-1 strongly correlates with poor prognosis in several human epithelial tumors, including breast carcinomas. We demonstrate that CSF-1 and CSF-1R are expressed, although at different levels, in 16/17 breast cancer cell lines tested with no differences among molecular subtypes. The role of CSF-1/CSF-1R in the proliferation of breast cancer cells was then studied in MDAMB468 and SKBR3 cells belonging to different subtypes. CSF-1 administration induced ERK1/2 phosphorylation and enhanced cell proliferation in both cell lines. Furthermore, the inhibition of CSF-1/CSF-1R signaling, by CSF-1R siRNA or imatinib treatment, impaired CSF-1 induced ERK1/2 activation and cell proliferation. We also demonstrate that c-Jun, cyclin D1 and c-Myc, known for their involvement in cell proliferation, are downstream CSF-1R in breast cancer cells. The presence of a proliferative CSF-1/CSF-1R autocrine loop involving ERK1/2 was also found. The wide expression of the CSF-1/CSF-1R pair across breast cancer cell subtypes supports CSF-1/CSF-1R targeting in breast cancer therapy.

c-FMS inhibitors: a patent review

INTRODUCTION

Macrophages are key drivers of both the innate and adaptive immune systems. The cellular receptor for CSF-1 and IL-34, c-FMS, is a key component of the mechanism(s) by which macrophages are regulated. Several drug discovery programs aimed at uncovering inhibitors of the tyrosine kinase activity of this receptor are now entering clinical phase, and the prospect of readjusting the behavior of macrophages in a number of pathological situations, such as inflammation and cancer, is now on us.

AREAS COVERED

In this review, we evaluate the available patent literature on the topic of small molecule inhibitors of c-FMS. By way of background, we review the biology of c-FMS and make an analysis of the therapeutic opportunities that a small molecule c-FMS inhibitor might present. In order to place the pharmacology in perspective, we examine the literature concerning the role of the CSF-1-IL-34-c-FMS axis in macrophage function as well as cell types related to macrophages, such as the osteoclast, the dendritic cell and microglia, and provide a background to the understanding of the therapeutic opportunities for c-FMS inhibitors as well as potential obstacles that could limit their use.

EXPERT OPINION

The c-FMS receptor is a hot target for the development of novel regulators of macrophage behavior. Some nice candidates have been developed by a number of groups, and their recent entry into clinical phase testing means that we are now on the cusp of a fuller understanding of the role of these important regulators of the innate and adaptive immune systems in the development of cancer and inflammatory diseases.

Handling reactive metabolite positives in drug discovery: What has retrospective structure-toxicity analyses taught us?

Because of the inability to predict and quantify the risk of idiosyncratic adverse drug reactions (IADRs) and because reactive metabolites (RMs) as opposed to the parent molecules from which they are derived are thought to be responsible for the pathogenesis of some IADRs, procedures (RM trapping/covalent binding) are being incorporated into the discovery screening funnel early-on to assess the risk of RM formation. Utility of the methodology in structure-toxicity relationships and scope in abrogating RM formation at the lead optimization stage are discussed in this article. Interpretation of the output from RM assessment assays, however, is confounded by the fact that many successfully marketed drugs are false positives. Therefore, caution must be exercised in deprioritizing a compound based on a positive result, so that the development of a useful and potentially profitable compound won't be unnecessarily halted. Risk mitigation strategies (e.g., competing detoxication pathways, low daily dose, etc.) when selecting RM positives for clinical development are also reviewed.