Structure-activity relationship of 7-aryl-2-anilino-pyrrolopyrimidines as Mer and Axl tyrosine kinase inhibitors.

The TAM (Axl, Mer, and Tyro3) family is implicated in the survival and chemoresistance of tumours and has emerged as a potential therapeutic target. A novel series of 7-aryl-2-anilino-pyrrolopyrimidines were identified as potent Axl/Mer tyrosine kinase inhibitors without significant inhibition of Tyro3. A representative compound 27 exhibited IC50 values of 2 nM and 16 nM for Mer and Axl, respectively, and considerable inhibition for Mer phosphorylation in cells. Docking studies suggested that the formation of a salt bridge between the nitrogen of the aniline moiety with ASP678 of the Mer kinase domain as well as an interaction with the hinge region that most kinase inhibitors have in common would be essential to retain activity. These results could provide useful information for finding promising inhibitors of Axl/Mer for the treatment of cancer.

Synthesis and biological activity of 2-cyanoacrylamide derivatives tethered to imidazopyridine as TAK1 inhibitors.

The importance of transforming growth factor beta-activated kinase 1 (TAK1) to cell survival has been demonstrated in many studies. TAK1 regulates signalling cascades, the NF-κB pathway and the mitogen-activated protein kinase (MAPK) pathway. TAK1 inhibitors can induce the apoptosis of cancerous cells, and irreversible inhibitors such as (5Z)-7-oxozeaenol are highly potent. However, they can react non-specifically with cysteine residues in proteins, which may have serious adverse effects. Reversible covalent inhibitors have been suggested as alternatives. We synthesised imidazopyridine derivatives as novel TAK1 inhibitors, which have 2-cyanoacrylamide moiety that can form reversible covalent bonding. A derivative with 2-cyano-3-(6-methylpyridin-2-yl)acrylamide (13h) exhibited potent TAK1 inhibitory activity with an IC50 of 27 nM. It showed a reversible reaction with ß-mercaptoethanol, which supports its potential as a reversible covalent inhibitor.

Click chemistry for improvement in selectivity of quinazoline-based kinase inhibitors for mutant epidermal growth factor receptors.

Discovery of mutant-selective kinase inhibitors is one of the challenges in medicinal chemistry and is a main issue for epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors. We tried to improve the selectivity of pan-HER inhibitors for mutant EGFRs. Utilizing click chemistry, triazole-tethered quinazoline derivatives were synthesized, based on a quinazoline scaffold showing pan-HER inhibition. The representative compound 5j exhibited 17- and 52-fold improved selectivity for EGFR L858R/T790M over wild-type EGFR and HER2, respectively, and demonstrated 6.7-fold more potent antiproliferative activity against PC9 cells harboring EGFR-activating mutation than gefitinib. Although the described quinazolines did not surpass pyrimidines as 3rd generation EGFR inhibitors in terms of selectivity for mutant EGFRs, our approach might provide information that would help in the identification of mutant-selective compounds among pan-HER inhibitors using the quinazoline scaffold.

Structure-activity relationships of novel quinazoline derivatives with high selectivity for HER2 over EGFR.

The gene amplification of human epidermal growth factor receptor 2 (HER2) plays an essential role in the proliferation and progression of several cancers. However, HER2 inhibitors such as lapatinib strongly suppress wild-type EGFR, resulting in severe adverse effects. Therefore, there is an unmet need for highly selective HER2 inhibitors. In this study, we describe the design and synthesis of novel quinazoline derivatives that exhibit enhanced selectivity for HER2 over wild-type EGFR. Structure-activity relationship analysis indicated that the selectivity for HER2 over EGFR depends on the aniline moiety at C-4 and the substituents at C-6 in the quinazoline derivatives. Compound 7c with an IC50 of 8 nM for HER2 exhibited significantly higher selectivity for HER2 over EGFR, with a 240-fold improvement over lapatinib. In addition, the synthesized compounds exhibited anti-proliferative activity in the nanomolar range against SKBR3, a human breast cancer cell line that overexpresses HER2.

Discovery of potent colony-stimulating factor 1 receptor inhibitors by replacement of hinge-binder moieties.

Tumor-associated macrophages (TAMs) are predominantly associated with tumor growth. Colony-stimulating factor 1 receptor (CSF1R) acts as a key regulator of TAM survival and differentiation and is a molecular target for cancer therapies. Herein, novel CSF1R inhibitors were identified through a replacement strategy for the hinge-binding moiety. The introduction of imidazo[1,2-a]pyridine (49) or pyrazolo[1,5-a]pyridine (50) as hinge binders led to 87% and 82% inhibition at 10 nM for CSF1R in the enzymatic assay, with IC50 values of 25 nM and 27 nM in MNFS60 cells, respectively. These derivatives significantly inhibited CSF1R phosphorylation in cells. Our approach could be utilized as a strategy to discover novel kinase inhibitors.

Exogenous Addition of 25-Hydroxycholesterol Reduces Level of Very Long-Chain Fatty Acids in X-Linked Adrenoleukodystrophy.

X-Linked adrenoleukodystrophy (X-ALD) is a severe metabolic disorder characterized by the accumulation of very long-chain fatty acids (VLCFAs). Recently, we demonstrated that levels of 25-hydroxycholesterol (25-HC) and cholesterol 25-hydroxylase (CH25H) were found to be elevated in X-ALD. Herein, we report that the exogenous addition of 25-HC significantly reduces C26:0 levels in X-ALD patient-derived fibroblasts and oligodendrocytes differentiated from induced pluripotent stem cells (iPSCs) derived from X-ALD patients. Moreover, 25-HC treatment was found to down-regulate the expression of ELOVL1, a key enzyme for the synthesis of C26. In addition, activation of liver X receptor (LXR), a molecular target of endogenous 25-HC, also reduced C26:0 level. The reduction of C26:0 levels by 25-HC treatment might result, at least partially, from the decrease of ELOVL1 expression as well as the activation of LXR. Our findings could provide a better understanding of the role of 25-HC in X-ALD and useful information to find therapeutic agents to treat X-ALD.

Synthesis and anti-tumor activity of imidazopyrazines as TAK1 inhibitors.

Transforming growth factor-ß activated kinase-1 (TAK1) is a potential therapeutic target for cancers and inflammatory diseases. We synthesized a series of novel imidazopyrazine derivatives, which were found to exhibit potent inhibitory effect against TAK1. Compound 22a, which possesses a good pharmacokinetic profile, showed excellent in vitro kinase activity and significant in vivo efficacy in mice xenografted with SW620, a KRAS-dependent colon cancer cell line.

Transetherification of 2,4-dimethoxynitrobenzene by aromatic nucleophilic substitution.

In view of the few reports concerning aromatic nucleophilic substitution reactions featuring an alkoxy group as a leaving group, the aromatic nucleophilic substitution of 2,4-dimethoxynitrobenzene was investigated with a bulky t-butoxide nucleophile under microwave irradiation. The transetherification of 2,4-dimethoxynitrobenezene with sodium t-butoxide under specific conditions, namely for 20 min at 110°C in 10% dimethoxyethane in toluene, afforded the desired product in 87% yield with exclusive ortho-selectivity. A variety of reaction conditions were screened to obtain the maximum yield. The aromatic nucleophilic substitution of 2,4-dimethoxynitrobenzene with t-butoxide should be carried out under controlled conditions in order to avoid the formation of byproducts, unlike that of dihalogenated activated benzenes. Among the formed byproducts, a major compound was elucidated as 2,4-dimethoxy-N-(5-methoxy-2-nitrophenyl)aniline by X-ray crystallography.