Modification of N-(6-(2-methoxy-3-(4-fluorophenylsulfonamido)pyridin-5-yl)-[1,2,4]triazolo[1,5-a]pyridin-2-yl)acetamide as PI3Ks inhibitor by replacement of the acetamide group with alkylurea

doi:10.1016/j.bmc.2015.07.017

Bioorganic & Medicinal Chemistry

Volume 23, Issue 17, 1 September 2015, Pages 5662-5671

https://doi.org/10.1016/j.bmc.2015.07.017 Get rights and content

Abstract

N-(6-(2-Methoxy-3-(4-fluorophenylsulfonamido)pyridin-5-yl)-[1,2,4]triazolo[1,5-a]pyridin-2-yl)acetamide exhibits remarkable anticancer effects and toxicity when orally administrated. In present study, alkylurea moiety replaced the acetamide group in the compound and a series of 1-alkyl-3-(6-(2-methoxy-3-sulfonylaminopyridin-5-yl)-[1,2,4]triazolo[1,5-a]pyridin-2-yl)urea derivatives were synthesized. The antiproliferative activities of the synthesized compounds in vitro were evaluated against four human cancer cell lines. Several compounds with potent antiproliferative activities were tested for their acute oral toxicity and their inhibitory activity against PI3Ks and mTOR. The results indicate that the compound attached a alkylurea or 2-(dialkylamino)ethylurea moiety at the 2-position of [1,2,4]triazolo[1,5-a]pyridine can retain the antiproliferative activity and the inhibitory activity against PI3Ks and mTOR. In addition, their acute oral toxicity reduced dramatically. Moreover, the results also indicate that compound 1e can efficaciously inhibit tumor growth in a mice S180 model. These findings suggest that title compounds can serve as potent PI3K inhibitors and effective anticancer agents with low toxicity.

Graphical abstract

A series of 1-alkyl-3-(6-(2-methoxy-3-sulfonylaminopyridin-5-yl)-[1,2,4]triazolo[1,5-a]pyridin-2-yl)urea derivatives were synthesized and evaluated to discover anticancer agents with low toxicity.

Introduction

The chemical and biological study of heterocyclic compounds has been an interesting field in medicinal chemistry for a long time. [1,2,4]triazolo[1,5-a]pyridine consists of a triazole ring fused with a pyridine ring. There are hydrogen bond acceptors and hydrogen bond donor in the structure of 2-acetylmino-[1,2,4]triazolo[1,5-a]pyridine. Thus, the structure is considered as an ideal fragment or a scaffold in drug design. The derivatives of [1,2,4]triazolo[1,5-a]pyridine exhibit a broad spectrum of biological activities such as anticancer, anti-inflammatory, antimicrobial and antidiabetic activity. CEP-33779, possessing the scaffold of 1,2,4-triazolo[1,5-a]pyridine, was discovered as a novel, selective, and orally bioavailable JAK2 inhibitor and can be used for cancer therapy or rheumatoid arthritis treatment.1, 2, 3 2-Acylamino-6-aryl-[1,2,4]triazolo[1,5-a]pyridines were identified as inhibitors of the leishmania cdc 2-related protein kinase CRK3 and may be used to treat tropical parasitic diseases such as leishmaniasis and human African trypanosomiasis (HAT).⁴ PI3Kγ plays a key role in innate immune responses such as immune cell migration.5, 6 CZC19945 and CZC24832, derived from 6-aryl-[1,2,4]triazolo[1,5-a]pyridine, were identified as PI3Kγ inhibitors with good in vivo PK profile and efficacy in vitro and in vivo models of inflammation.⁷ Further, CZC24832 was proved to be efficacious in regulate interleukin-17-producing T helper cell (T_H17) differentiation and may be of use for the treatment of autoimmune and inflammatory disorders.⁸ Recently, a series of 2-ureido-[1,2,4]triazolo[1,5-a]pyridine derivatives were synthesized and two compounds exhibited excellent PI3Kγ/δ potency with high selectivity over the other isoforms and the general kinome.⁹ In addition, multisubstituted [1,2,4]triazolo[1,5-a]pyridines were discovered as inhibitors of β-1,6-glucan synthesis with potent antifungal activity.¹⁰ 2-Ureido-5,7-disubstituted-[1,2,4]triazolo[1,5-a]pyridine was reported as good antibacterial agent with potent Gram-positive antibacterial activity.¹¹ Early, 6-substituted [1,2,4]triazolo[1,5-a] pyridine was reported as a potent DPP-4 inhibitor and may be used to treat type 2 diabetes.¹²

Both PI3K (a family of lipid kinase) and mTOR (mammalian target of rapamycin) have been found to play key regulatory roles in many cellular processes, including cell growth, proliferation, differentiation, motility and survival.¹³ Accumulation evidence supports the notion that The PI3K/AKT/mTOR signal transduction pathway is dysregulated expression in many cancers, contributing to cellular transformation and tumor growth.¹⁴ Therefore, PI3Kα and mTOR, as key nodes of the PI3K/AKT/mTOR pathway, have been identified as promising kinase targets for cancer therapy.15, 16 Recently, several PI3K inhibitors and PI3K/mTOR dual inhibitors have been in clinical development.17, 18 Among the reported PI3K/mTOR dual inhibitors, N-(5-(quinilin-6-yl)-pyridin-3-yl)phenylsulfonamide derivatives are a class of PI3K/mTOR dual inhibitors with potent anticancer activity in vitro and in vivo. Two ring nitrogen atoms in pyridine and quinoline are the main components of pharmacophore. GlaxoSmithKline discovered GSK2126458¹⁹ (Fig. 1) as a potent, orally bioavailable PI3Kα and mTOR dual inhibitor. Amgen Inc. designed, synthesized and evaluated several classes of N-(2,5-disubstituted-pyridin-3-yl)phenylsulfonamides, and discovered that N-(2-chloro-5-(4-morpholinoquinilin-6-yl)pyridin-3-yl)-4-fluorophenylsulfonamide,²⁰ N-(2-chloro-5-(2-acetylaminobenzo[d]thiazol-6-yl)pyridin-3-yl)-4-fluorophenylsulfonamide²¹ (compound A, Fig. 1) and N-(2-chloro-5-(2-acetylamonoimidazo[1,2-b]pyridazin-6-yl)pyridin-3-yl)-4-fluoro phenylsulfonamide²² are excellent PI3K/mTOR dual inhibitors and anticancer agents. According to the X-ray cocrystal structure of PI3Kγ with GSK2126458,¹⁹ we proposed that the structure of an amide group may take the place of the water molecule bridge. Thereupon, we synthesized a series of 2-substituted-3-phenylsulfonylamino-5-(quinazolin-6-yl or quinolin-6-yl)benzamides and discovered that the designed compounds are novel PI3K inhibitors and anticancer agents.²³ Thereafter, we combined the benzamide moiety with 2-aminobenzothiazole to discover novel anticancer agents.²⁴ Recently, it has been reported that PI3K/mTOR dual inhibitor VS-5584 can preferentially targets cancer stem cells.²⁵ This discovery may potentially bring a breakthrough to the treatment of cancer. Thus, developing new PI3K/mTOR dual inhibitors is still needed.

In an attempt to develop novel anticancer agents, we combined 2-acetylamino-[1,2,4]triazolo[1,5-a]pyridine with N-pyridin-3-ylphenylsulfonamide to synthesize a series of [1,2,4]triazolo[1,5-a]pyridinylpyridines and the anticancer effects of the synthesized compounds were evaluated in vitro and in vivo. Therefore we discovered that compound B (Fig. 1) displayed potent antiproliferative activities in vitro and remarkable anticancer effects in vivo.²⁶ However, the body weight of mice dropped below 90% of the starting body weight over the course of oral administration at 5 mg/kg, which indicated that compound B displayed some toxicity. Therefore, the toxicity of compound B caught our attention.

To reduce the toxicity and retain the anticancer effect of compound B, we intend to replace the 2-acetylamide in compound B with chain-extended urea to search for the novel anticancer agents with low toxicity (Fig. 2). In this paper, we reported our studies on the synthesis, biological activities evaluation of a series of 1-alkyl-3-(6-(2-methoxy-3-sulfonylaminopyridin-5-yl)-[1,2,4]triazolo[1,5-a]pyridin-2-yl)urea derivatives.

Section snippets

Chemistry

The synthetic route of compounds 1a–1q is outlined in Scheme 1. 6-Bromo-[1,2,4]triazolo[1,5-a]pyridine-2-ylamine was reacted successively with CDI (N,N’-carbonyldiimidazole) and amine to yield intermediates 2a–2l. In the case of preparing 2l, glycine ethyl ester was used as an amine. The ester group in intermediate 2l was hydrolyzed to afford the carboxylic acid 2m, which was subsequently condensed with pyrrolidine, piperidine or morpholine to produce intermediates 2n–2p. The phenylsulfonamides

Antiproliferative activities in vitro

We first evaluated the antiproliferative activities of the synthesized compounds against human colon carcinoma cell line (HCT-116, PI3CA, mutant: H1047R), human breast adenocarcinoma carcinoma cell line (MCF-7, PI3CA, mutant: E545K), glioma cell line (U87 MG, PTEN null) and lung adenocarcinoma epithelial cell line (A549, KRAS mutant) by applying the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) colorimetric assay. The PI3K and mTOR dual inhibitor BEZ235 was used as the

Conclusions

In present study, a series of 1-alkyl-3-(6-(5,6-disubstitutedpyridin-3-yl)-[1,2,4]triazolo[1,5-a]pyridin-2-yl)urea derivatives were synthesized and characterized. Their antiproliferative activities in vitro were evaluated via MTT assay against four cancer cell lines including HCT-116, MCF-7, U87 MG and A549. The SAR of the title compounds was discussed. Compounds 1c and 1e were tested for their inhibitory activity against PI3Ks and mTOR. Meanwhile, the acute oral toxicity of four compounds was

Chemistry

Unless specified otherwise, all the starting materials, reagents and solvents were commercially available. All the reactions were monitored by thin-layer chromatography on silica gel plates (GF-254) and visualized with UV light. All the melting points were determined on a Beijing micro melting-point apparatus and thermometer was uncorrected. NMR spectra were recorded on a 400 Bruker NMR spectrometer with tetramethylsilane (TMS) as an internal reference. All chemical shifts are reported in parts

Acknowledgment

Financial support from National Natural Science Foundation of China (Grant Nos. 21072156 and 81272448) is gratefully acknowledged.

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Modification of N-(6-(2-methoxy-3-(4-fluorophenylsulfonamido)pyridin-5-yl)-[1,2,4]triazolo[1,5-a]pyridin-2-yl)acetamide as PI3Ks inhibitor by replacement of the acetamide group with alkylurea

Abstract

Graphical abstract

Introduction

Section snippets

Chemistry

Antiproliferative activities in vitro

Conclusions

Chemistry

Acknowledgment

J. Med. Chem.

Mol. Cancer. Ther.

Arthritis Res. Ther.

ChemMedChem

Biochem. Soc. Trans.

J. Med. Chem.

Bioorg. Med. Chem. Lett.

Nat. Chem. Biol.

Bioorg. Med. Chem. Lett.

Bioorg. Med. Chem.

Bioorg. Med. Chem. Lett.

J. Med. Chem.

Nat. Rev. Genet.

Cell

Nat. Rev. Drug Disc.