Design, Synthesis, and Structure–Activity Relationship Study of 2-Oxo-3,4-dihydropyrimido[4,5-d]pyrimidines as New Colony Stimulating Factor 1 Receptor (CSF1R) Kinase Inhibitors

Insights into fourth generation selective inhibitors of (C797S) EGFR mutation combating non-small cell lung cancer resistance: a critical review

Lung cancer is the second most common cause of morbidity and mortality among cancer types worldwide, with non-small cell lung cancer (NSCLC) representing the majority of most cases. Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR TKIs) are among the most commonly used targeted therapy to treat NSCLC. Recent years have seen the evaluation of many synthetic EGFR TKIs, most of which showed therapeutic activity in pertinent models and were classified as first, second, and third-generation. The latest studies have concluded that their efficacy was also compromised by additional acquired mutations, including C797S. Because second- and third-generation EGFR TKIs are irreversible inhibitors, they are ineffective against C797S containing EGFR triple mutations (Del19/T790M/C797S and L858R/T790M/C797S). Therefore, there is an urgent unmet medical need to develop next-generation EGFR TKIs that selectively inhibit EGFR triple mutations via a non-irreversible mechanism. This review covers the fourth-generation EGFR-TKIs' most recent design with their essential binding interactions, the clinical difficulties, and the potential outcomes of treating patients with EGFR mutation C797S resistant to third-generation EGFR-TKIs was also discussed. Moreover, the utilization of various therapeutic strategies, including multi-targeting drugs and combination therapies, has also been reviewed.

Synthesis and Evaluation of 2-Amine-4-oxyphosaniline Pyrimidine Derivatives as EGFR L858R/T790M/C797S Mutant Inhibitors

Epidermal growth factor receptor (EGFR) C797S mutation leads to Osimertinib drug resistance by disturbing the covalent biding of Michael acceptor group to the Cys797 residue in the ATP biding cleft. In this manuscript, a class of 2-amine-4-oxyphosaniline pyrimidine derivatives were designed, synthesized and evaluated as new noncovalent reversible EGFR inhibitors against L858R/T790M/C797S (CTL) triple mutant. The kinases inhibitiory activity evaluation showed that four compounds exhibited significant inhibitory activities against CTL (IC₅₀ < 30 nM). In particularly, the most promising compound 7a showed excellent enzymatic inhibitory activity against CTL with IC₅₀ value of 9.9 nM, which was more potent than control compound Osimertinib. Moreover, cell proliferation assays indicated that 7a effectively inhibited H1975-EGFR L858R/T790M/C797S with IC₅₀ value of 0.33 µM. Furthermore, compound 7a displayed good metabolic stabilities in human, rat and mouse liver microsomes, and the putative biding mode of compound 7a with ATP was revealed by molecular docking study. These findings strongly indicated that compound 7a was a promising L858R/T790M/C797S mutant EGFR inhibitor.

Targeting CSF-1R represents an effective strategy in modulating inflammatory diseases

Colony-stimulating factor-1 receptor (CSF-1R), also known as FMS kinase, is a type I single transmembrane protein mainly expressed in myeloid cells, such as monocytes, macrophages, glial cells, and osteoclasts. The endogenous ligands, colony-stimulating factor-1 (CSF-1) and Interleukin-34 (IL-34), activate CSF-1R and downstream signaling pathways including PI3K-AKT, JAK-STATs, and MAPKs, and modulate the proliferation, differentiation, migration, and activation of target immune cells. Over the past decades, the promising therapeutic potential of CSF-1R signaling inhibition has been widely studied for decreasing immune suppression and escape in tumors, owing to depletion and reprogramming of tumor-associated macrophages. In addition, the excessive activation of CSF-1R in inflammatory diseases is consecutively uncovered in recent years, which may result in inflammation in bone, kidney, lung, liver and central nervous system. Agents against CSF-1R signaling have been increasingly investigated in preclinical or clinical studies for inflammatory diseases treatment. However, the pathological mechanism of CSF-1R in inflammation is indistinct and whether CSF-1R signaling can be identified as biomarkers remains controversial. With the background information aforementioned, this review focus on the dialectical roles of CSF-1R and its ligands in regulating innate immune cells and highlights various therapeutic implications of blocking CSF-1R signaling in inflammatory diseases.

Discovery of a CSF-1R inhibitor and PET tracer for imaging of microglia and macrophages in the brain

Colony stimulating factor 1 receptor (CSF-1R) is a kinase expressed on macrophages and microglia in the brain. It has been recognized as a potential drug and imaging target in treatment of neuroinflammatory diseases and glioblastoma. Despite several attempts, no validated CSF-1R PET tracer is currently available. The aim of this work was to develop a brain permeable CSF-1R PET tracer for non-invasive imaging of CSF-1R in vivo. Based on fragments of two potent and selective CSF-1R inhibitors, novel hybrid molecules were designed and synthesized. Affinity for human recombinant CSF-1R and selectivity over c-KIT and PDGFR-β was determined using a FRET based in vitro assay. Radiosynthesis was performed by fully automated [11C]CH3I methylation of the corresponding des-methyl precursor. PET imaging was performed at baseline, efflux transporter blocking and CSF-1R blocking conditions. Moreover, tracer distribution and blood and plasma radiometabolites were determined following injection in healthy mice. The most promising CSF-1R inhibitor, compound 4, showed high selectivity and high affinity for CSF-1R (IC50: 12 ± 3 nM) and no affinity for kinase family members c-KIT and PDGFR-beta. [11C]4 was obtained in good yield (15 ± 0.2 % decay corrected yield, (2.0 ± 0.26 GBq at end of synthesis) and excellent purity. The compound demonstrated high brain penetration and good metabolic stability (>2 %ID/g at 60 min post injection and 79 ± 8 % intact [11C]4 in brain at 60 min post injection) and no strong efflux transporter substrate behavior. Blocking CSF-1R prior to imaging with [11C]4 resulted in significant decrease in brain uptake. In conclusion, [11C]4 shows good potential as a novel PET tracer for imaging of CSF-1R in the CNS and future experiments in relevant animal models are warranted.

Discovery of Pyrrolo[2,3-d]pyrimidine derivatives as potent and selective colony stimulating factor 1 receptor kinase inhibitors

Colony stimulating factor 1 receptor kinase (CSF1R) plays an integral role in tumor-associated macrophage repolarization and has emerged as a novel therapeutic target for cancer immunotherapy. Most of the current CSF1R kinase inhibitors lack selectivity between CSF1R kinase and other type III growth factor receptor members. Herein, we report a potent and selective CSF1R inhibitor 18h, which displays an IC₅₀ value of 5.14 nM against CSF1R and achieves selectivity over other type III receptor tyrosine kinases (>38-fold). 18h inhibits the phosphorylation of CSF1R and its downstream signaling pathway in RAW264.7, THP-1, and M-NFS-60 cells. Treatment with this compound leads to alteration of the macrophage polarization in RAW264.7 macrophages in a dose-dependent manner. In vivo, 18h demonstrates acceptable pharmacokinetic profiles and suppresses the tumor growth in a mouse xenograft model inoculated with M-NFS-60 cells.

Discovery of Hexahydrofuro[3,2-b]furans as New Kinase-Selective and Orally Bioavailable JAK3 Inhibitors for the Treatment of Leukemia Harboring a JAK3 Activating Mutant

Janus kinase 3 (JAK3) is a potential target for the treatment of hematological malignancies. Herein, we report the discovery of a series of new orally bioavailable irreversible JAK3 kinase inhibitors. The representative compound 12n potently inhibited JAK3 kinase activity with an IC₅₀ value of 1.2 nM and was more than 900-fold selective over JAK1, JAK2, and Tyk2. Cell-based assays revealed that 12n significantly suppressed phosphorylation of JAK3 and the downstream effectors STAT3/5 and also robustly restrained proliferation of BaF3 cells transfected with JAK3^M511I activating mutation and human leukemia U937 cells harboring JAK3^M511I with IC₅₀ values of 22.9 and 20.2 nM, respectively. More importantly, 12n showed reasonable pharmacokinetic (PK) properties, and oral administration of 12n at a dose of 50 mg/kg twice daily led to tumor regression in a U937 cell inoculated xenograft mouse model. Thus, 12n represents a promising lead compound for further optimization to discover new therapeutic agents for hematological malignancies.

Anti-depressive effects of Jiao-Tai-Wan on CORT-induced depression in mice by inhibiting inflammation and microglia activation

ETHNOPHARMACOLOGICAL RELEVANCE

Jiao-Tai-Wan (JTW) is a very famous traditional Chinese medicine formula for the treatment of psychiatric disorders, especially in anxiety, insomnia and depression. However, its molecular mechanism of treatment remains indistinct.

AIM OF THE STUDY

We aimed to reveal the action mechanism of JTW on anti-depression via inhibiting microglia activation and pro-inflammatory response both in vivo and in vitro.

MATERIAL AND METHODS

The corticosterone (CORT)-induced depression mouse model was used to evaluate the therapeutic efficacy of JTW. Behavioral tests (open field, elevated plus maze, tail suspension and forced swim test) were conducted to evaluate the effect of JTW on depressive-like behaviors. The levels of inflammatory factors and the concentration of neurotransmitters were detected by RT-qPCR or ELISA assays. Then three hippocampal tissue samples per group (Control, CORT, and JTW group) were sent for RNA sequencing (RNA-seq). Transcriptomics data analysis was used to screen the key potential therapeutic targets and signaling pathways of JTW. Based on 8 bioactive species of JTW by our previous study using High-performance liquid chromatography (HPLC) analysis, molecular docking analyses were used to predict the interaction of JTW-derived compounds and depression targets. Finally, the results of transcriptome and molecular docking analyses were combined to verify the targets, key pathways, and efficacy of JTW treatment in vivo and vitro.

RESULTS

JTW ameliorated CORT-induced depressive-like behaviors, neuronal damage and enhanced the levels of monoamine neurotransmitters in the serum of mice. JTW also inhibited CORT-induced inflammatory activation of microglia and decreased the serum levels of interleukin- 6(IL-6) and interleukin- 1β (IL-1β) in vivo. Transcriptomic data analysis showed there were 10 key driver analysis (KDA) genes with the strongest correlation which JTW regulated in depression mice. Molecular docking analysis displayed bioactive compound Magnoflorine had the strongest binding force to the key gene colony-stimulating factor 1 receptor (CSF1R), which is the signaling microglia dependent upon for their survival. Meanwhile, CSF1R staining showed it was consistent with inflammatory activation of microglia. Our vitro experiment also showed JTW and CSF1R inhibitor significantly reduced lipopolysaccharide (LPS)/interferon-gamma (IFNɣ)-induced inflammatory activation response in macrophage cells.

CONCLUSIONS

Our study suggests that JTW might ameliorate CORT-induced neuronal damage in depression mice by inhibiting CSF1R mediated microglia activation and pro-inflammatory response.

Discovery of BPR1R024, an Orally Active and Selective CSF1R Inhibitor that Exhibits Antitumor and Immunomodulatory Activity in a Murine Colon Tumor Model

Colony-stimulating factor-1 receptor (CSF1R) is implicated in tumor-associated macrophage (TAM) repolarization and has emerged as a promising target for cancer immunotherapy. Herein, we describe the discovery of orally active and selective CSF1R inhibitors by property-driven optimization of BPR1K871 (9), our clinical multitargeting kinase inhibitor. Molecular docking revealed an additional nonclassical hydrogen-bonding (NCHB) interaction between the unique 7-aminoquinazoline scaffold and the CSF1R hinge region, contributing to CSF1R potency enhancement. Structural studies of CSF1R and Aurora kinase B (AURB) demonstrated the differences in their back pockets, which inspired the use of a chain extension strategy to diminish the AURA/B activities. A lead compound BPR1R024 (12) exhibited potent CSF1R activity (IC50 = 0.53 nM) and specifically inhibited protumor M2-like macrophage survival with a minimal effect on antitumor M1-like macrophage growth. In vivo, oral administration of 12 mesylate delayed the MC38 murine colon tumor growth and reversed the immunosuppressive tumor microenvironment with the increased M1/M2 ratio.

Design, Synthesis, and Activity Evaluation of Novel Acyclic Nucleosides as Potential Anticancer Agents In Vitro and In Vivo

In the present work, 103 novel acyclic nucleosides were designed, synthesized, and evaluated for their anticancer activities in vitro and in vivo. The structure-activity relationship (SAR) studies revealed that most target compounds inhibited the growth of colon cancer cells in vitro, of which 3-(6-chloro-9H-purin-9-yl)dodecan-1-ol (9b) exhibited the most potent effect against the HCT-116 and SW480 cells with IC50 values of 0.89 and 1.15 μM, respectively. Furthermore, all of the (R)-configured acyclic nucleoside derivatives displayed more potent anticancer activity compared to their (S)-counterparts. Mechanistic studies revealed that compound 9b triggered apoptosis in the cancer cell lines via depolarization of the mitochondrial membrane and effectively inhibited colony formation. Importantly, compound 9b inhibited the growth of the SW480 xenograft in a mouse model with low systemic toxicity. These results indicated that acyclic nucleoside compounds are viable as potent and effective anticancer agents, and compound 9b may serve as a promising lead compound that merits further attention in future anticancer drug discovery.

The new opportunities in medicinal chemistry of fourth-generation EGFR inhibitors to overcome C797S mutation

Epidermal growth factor receptor (EGFR) is a receptor for epithelial growth factor (EGF) cell proliferation and signaling, which is related to the inhibition of tumor cell proliferation, angiogenesis, tumor invasion, metastasis, and apoptosis. Thus, it has become an important target for the treatment of non-small cell lung cancer (NSCLC). The first to the third-generation EGFR inhibitors have demonstrated powerful efficacy and brought a prospect to patients. Unfortunately, after 9-15 months of treatment, they all developed resistance without exception. As for the resistance of third-generation inhibitors, no major breakthrough has been made in this field. In this review, we discussed the recent advances in medicinal chemistry of fourth-generation EGFR-TKIs, as well as further discussed the clinical challenges and future prospects of treating patients with EGFR mutations resistant to third-generation EGFR-TKIs.

Pyrido[2, 3-d]pyrimidin-7(8H)-ones as new selective orally bioavailable Threonine Tyrosine Kinase (TTK) inhibitors

A series of pyrido [2, 3-d]pyrimidin-7(8H)-ones were designed and synthesized as new selective orally bioavailable Threonine Tyrosine Kinase (TTK) inhibitors. One of the representative compounds, 5o, exhibited strong binding affinity with a K_d value of 0.15 nM, but was significantly less potent against a panel of 402 wild-type kinases at 100 nM. The compound also potently inhibited the kinase activity of TTK with an IC₅₀ value of 23 nM, induced chromosome missegregation and aneuploidy, and suppressed proliferation of a panel of human cancer cell lines with low μM IC₅₀ values. Compound 5o demonstrated good oral pharmacokinetic properties with a bioavailability value of 45.3% when administered at a dose of 25 mg/kg in rats. Moreover, a combination therapy of 5o with paclitaxel displayed promising in vivo efficacy against the HCT-116 human colon cancer xenograft model in nude mice with a Tumor Growth Inhibition (TGI) value of 78%. Inhibitor 5o may provide a new research tool for further validating therapeutic potential of TTK inhibition.

Small-molecule CSF1R kinase inhibitors; review of patents 2015-present

INTRODUCTION

Colony stimulating factor 1 receptor (CSF-1R, also known as c-FMS kinase) is in the class III receptor tyrosine kinase family, along with c-Kit, Flt3 and PDGFRα. CSF-1/CSF-1R signaling promotes the differentiation and survival of myeloid progenitors into populations of monocytes, macrophages, dendritic cells and osteoclasts, as well as microglial cells and also recruits host macrophages to develop into tumor-associated macrophages (TAMs), which promote tumor progression and metastasis.

AREAS COVERED

In the last 5 years, and recently stimulated by the approval of pexidartinib (Turalio™, Daiichi Sankyo) in 2019 for the treatment of tenosynovial giant cell tumors, there has been a large increase in activity (both journal articles and patent applications) around small molecule inhibitors of CSF1R. Features of this work have been the surprising diversity of chemical classes shown to be potent and selective inhibitors, and the breadth of disease states (cancer, arthritis, and 'cytokine storm' syndromes) covered by CSF1R inhibitors. All these aspects are covered in the following sections.

EXPERT OPINION

The field has developed rapidly from 2014 to the present, with many different chemotypes proving to be potent inhibitors. The range of potential utilities of CSF1R inhibitors has also expanded to include dementia, ulcerative colitis/Crohn's disease, rheumatoid arthritis inflammation, and fibrosis.

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.

3D-QSAR and Docking Studies on Pyrimidine Derivatives as CSF-1R Inhibitors

Background:

Colony Stimulating Factor-1 Receptor (CSF-1R) is associated with malignancy, invasiveness and poor prognosis of tumors, and pyrimidine derivatives are considered as a novel class of CSF-1R inhibitor.

Methods:

To explore the relationship between the structures of substituted pyrimidine derivatives and their inhibitory activities against CSF-1R, CoMFA and CoMSIA analyses, and molecular docking studies were performed on a dataset of forty-four compounds.

Results:

We found in CoMFA model including steric and electrostatic fields for the training set, the cross-validated q2 value was 0.617 and the non-cross-validated r2 value was 0.983. While, the crossvalidated q2 value was 0.637 and the non-cross-validated r2 value was 0.984 in CoMSIA Model which include steric, electrostatic and hydrophobic fields. 3D equipotential maps generated from CoMFA and CoMSIA along with the docking binding structures provided enough information about the structural requirements for better activity.

Conclusion:

The data generated from the present study helped us to predict the activity of new inhibitors and further design some novel and potent CSF-1R inhibitors.

Discovery of JND3229 as a New EGFRC797S Mutant Inhibitor with In Vivo Monodrug Efficacy

EGFR^C797S mutation inducing resistance against third generation EGFR inhibitor drugs is an emerging "unmet clinical need" for nonsmall cell lung cancer patients. The pyrimidopyrimidinone derivative JND3229 was identified as a new highly potent EGFR^C797S inhibitor with single digit nM potency. It also exhibited good in vitro and in vivo monodrug anticancer efficacy in a xenograft mouse model of BaF3/EGFR^{19D/T790M/C797S} cells. A high-resolution X-ray crystallographic structure was also determined to elucidate the interactions between JND3229 and EGFR^T790M/C797S. Our study provides an important structural and chemical basis for future development of new generation EGFR^C797S inhibitors as anticancer drugs.