2-Arylureidophenyl-4-(3-oxa-8-azabicyclo[3.2.1]octan-8-yl)triazines as highly potent and selective ATP competitive mTOR inhibitors: optimization of human microsomal stability

In-vitro Evaluation of Triazine Scaffold for Anticancer Drug Development: A Review

INTRODUCTION

The widespread importance of the synthesis and modification of anticancer agents has given rise to many numbers of medicinal chemistry programs. In this regard, triazine derivatives have attracted attention due to their remarkable activity against a wide range of cancer cells. This evaluation covers work reports to define the anticancer activity, the most active synthesized compound for the target, the SAR and, when described, the probable MOA besides similarly considered to deliver complete and target-pointed data for the development of types of anti-tumour medicines of triazine derivatives. Triazine scaffold for the development of anticancer analogues. Triazine can also relate to numerous beneficial targets, and their analogues have auspicious in-vitro and in-vivo anti-tumour activity. Fused molecules can improve efficacy, and drug resistance and diminish side effects, and numerous hybrid molecules are beneath diverse stages of clinical trials, so hybrid derivatives of triazine may offer valuable therapeutic involvement for the dealing of tumours.

OBJECTIVE

The objective of the recent review was to summarize the recent reports on triazine as well as its analogues with respect to its anticancer therapeutic potential.

CONCLUSION

The content of the review would be helpful to update the researchers working towards the synthesis and designing of new molecules for the treatment of various types of cancer disease with the recent molecules that have been produced from the triazine scaffold. Triazine scaffolds based on 1,3,5-triazine considerably boost molecular diversity levels and enable covering chemical space in key medicinal chemistry fields.

1,3,5-Triazine Analogs: A Potent Anticancer Scaffold

Background:

This review presents the exhaustive exploration of 1,3,5-triazine scaffold for development of analogs of anticancer drugs, over the last century. In the recent years, striazine moiety has been one of the most studied moiety, showing broad-spectrum pharmacological activities such as antibacterial, antifungal, analgesic, anti-HIV, antileishmanial, antitrypanosomal, antimalarial and antiviral. Nowadays, many boffins are have become interested in novel synthesis of s-triazine derivatives because of low cost and ease of availability.

Methods:

This scaffold has been extensively investigated mainly in the past decade. Many products have been synthesized from different starting materials and these synthetic products possess anticancer potential against various cell lines.

Results:

Many 1,3,5-triazine analogs exhibited significant anticancer activity in various models and cell lines exhibiting different mechanisms. Some analogs have also shown good pharmacokinetic parameters with less IC50 values.

Conclusion:

Various 1,3,5-triazine analogs have shown potent activities and may be regarded as clinical candidates for future anticancer formulations. This review may be helpful to those researchers seeking required information with regard to the drug design and medicinal properties of 1,3,5-triazine derivatives for selected targets. This review may also offer help to find and improve clinically viable anticancer molecules.

Recent development of ATP-competitive small molecule phosphatidylinostitol-3-kinase inhibitors as anticancer agents

Phosphatidylinostitol-3-kinase (PI3K) is the potential anticancer target in the PI3K/Akt/ mTOR pathway. Here we reviewed the ATP-competitive small molecule PI3K inhibitors in the past few years, including the pan Class I PI3K inhibitors, the isoform-specific PI3K inhibitors and/or the PI3K/mTOR dual inhibitors.

1,3,5-Triazines: A promising scaffold for anticancer drugs development

This review covering literature reports from the beginning of this century to 2016 describes the synthetic pathways, the antitumor activity, the structure-activity relationship and, whenever reported, the possible mechanism of action of 1,3,5-triazine derivatives as well as of their hetero-fused compounds. Many 1,3,5-triazine derivatives, both uncondensed and hetero-fused, have shown remarkable antitumor activities and some of them reached clinical development.

Privileged s-triazines: structure and pharmacological applications

This review summarizes recent reports on s-triazine and its respective analogs from the medicinal chemistry angle. Due to its high reactivity and binding characteristic towards various enzymes, s-triazine has attracted attention. This is combined with facile synthesis and interesting pharmacology. The triazine class demonstrates wide biological applications - including antimicrobial, antituberculosis, anticancer, antiviral and antimalarial. In this article the library of s-triazine-based molecular designs has been collated with respective bioactivity. Compounds are further compared with other heterocyclic/nontriazine moieties to correlate the efficiency of privileged s-triazine. We hope this article may assist chemists in their drug design and discovery efforts.

Elaborate ligand-based modeling coupled with multiple linear regression and k nearest neighbor QSAR analyses unveiled new nanomolar mTOR inhibitors

The mammalian target of rapamycin (mTOR) has an important role in cell growth, proliferation, and survival. mTOR is frequently hyperactivated in cancer, and therefore, it is a clinically validated target for cancer therapy. In this study, we combined exhaustive pharmacophore modeling and quantitative structure-activity relationship (QSAR) analysis to explore the structural requirements for potent mTOR inhibitors employing 210 known mTOR ligands. Genetic function algorithm (GFA) coupled with k nearest neighbor (kNN) and multiple linear regression (MLR) analyses were employed to build self-consistent and predictive QSAR models based on optimal combinations of pharmacophores and physicochemical descriptors. Successful pharmacophores were complemented with exclusion spheres to optimize their receiver operating characteristic curve (ROC) profiles. Optimal QSAR models and their associated pharmacophore hypotheses were validated by identification and experimental evaluation of several new promising mTOR inhibitory leads retrieved from the National Cancer Institute (NCI) structural database. The most potent hit illustrated an IC50 value of 48 nM.

Furthering the design and the discovery of small molecule ATP-competitive mTOR inhibitors as an effective cancer treatment

INTRODUCTION

The mammalian target of rapamycin (mTOR) is a serine/threonine kinase, which is the key component of two distinct signaling complexes in cells; these complexes are the mTOR complex 1 (mTORC1) and the mTOR complex 2 (mTORC2). Given the importance of these complexes in cellular growth, survival, motility, proliferation, protein synthesis and transcription, it is not surprising that they are impacted in multiple types of cancer. Studies on a number of ATP-competitive mTOR inhibitors have suggested that these inhibitors have a therapeutic superiority to rapalogs (rapamycin analogs) in a number of cancers.

AREAS COVERED

This review provides insight into the binding of mTOR inhibitors with the ATP-binding site, for the benefit of future mTOR inhibitor design and discovery. The authors, furthermore, deduce that a hypothetical binding mode is from docking studies, co-crystal structures and the structure-activity relationships (SARs). The authors also highlight the preclinical and clinical development of hit/lead compounds, and the selectivity for representative mTOR inhibitors.

EXPERT OPINION

The structural analysis of mTOR is hampered by its large size and complexity. Further exploration of mTOR inhibitors may therefore require the combination of structure-based drug design (SBDD, based on the mTOR homology models), fragment-based drug design (FBDD) and analog synthesis. Recent studies suggested that the global inhibition of PI3Ks may be harmful to organisms. Therefore, the future discovery of dual mTOR/PI3K inhibitors needs to ensure that inhibitors are both efficacious and have reduced adverse effects.

Synthesis and cytotoxicity studies of bifunctional hybrids of nitrogen mustards with potential enzymes inhibitors based on melamine framework

The new class of hybrid anticancer drugs were obtained by selective functionalization of the triazine scaffold. These were prepared by rearrangement of mono-, bis- and/or tris-(1,3,5-triazin-2-yl)-1,4-diazabicyclo[2.2.2]octanium chlorides leading to formation of 2-chloroethylamino fragments attached to 1,3,5-triazine via one, two or three piperazine rings respectively. Their inhibitory effect was found strongly dependent on the structure of substituents in triazine ring. The anti-proliferative activity of the hybrids evaluated in vitro by using mammalian tumour cells estimated as IC(50) was in the range 0.62-139,78 µM. Both cytotoxicity and alkylating activity depended on the substituents of triazine ring, however, also the mono-functional analogues of nitrogen mustards, which are unable to form liaisons between two DNA strands, induced apoptosis and necrosis in the tested cells.

Recent advances in the discovery of small-molecule ATP competitive mTOR inhibitors: a patent review

INTRODUCTION

The mammalian target of rapamycin (mTOR) is a protein kinase and a key component of the PI3K/Akt/mTOR signaling pathway, and is deregulated in half of all human cancers. Rapamycin and its analogs (rapalogs) are allosteric inhibitors of one functional mTOR complex, mTORC1, and are clinically proven therapeutic agents for the treatment of certain cancers. However, rapalogs mainly partially inhibit mTORC1, while ATP competitive inhibitors suppress both mTORC1 and mTORC2, and therefore may offer advantages in the clinic. Recently, small-molecule inhibitors have entered clinical trials that are mTOR-selective or dual mTOR/PI3K inhibitors.

AREAS COVERED

This review focuses on ATP-competitive mTOR inhibitors that have appeared in the patent literature in 2010. Many inhibitors with new structural motifs have been discovered as well as inhibitors that are related to previously disclosed structures. This review endeavors to put into perspective the diverse structural elements that make up these compounds. Patent applications are covered that include either selective mTOR inhibitors or dual mTOR/PI3K inhibitors.

EXPERT OPINION

The PI3K/mTOR signaling pathway is an exciting target for the development of pharmaceuticals to treat cancer and other diseases, due to the unique combination of a clinically and commercially validated pathway approach (i.e., rapalogs), combined with a biological rationale for further increased efficacy (i.e., ATP-competitive inhibitors). With the number of candidate drugs currently in development or at earlier stages of the drug discovery pipeline, we are bound to see small-molecule inhibitors reach pivotal trials, and hopefully the market, in the near future.

A selectivity study on mTOR/PI3Kα inhibitors by homology modeling and 3D-QSAR

The phosphatidylinositol-3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling pathway plays a critical role in the regulation of cellular growth, survival and proliferation. mTOR and PI3K have attracted particular attention as cancer targets. These kinases belong to the phosphatidylinositol-3-kinase-related kinase (PIKK) family and therefore have considerable homology in their active sites. To accelerate the discovery of inhibitors with selective activity against mTOR and PI3K as cancer targets, in this work, a homology model of mTOR was developed to identify the structural divergence in the active sites between mTOR and PI3Kα. Furthermore, two highly predictive comparative molecular similarity index analyses (CoMSIA) models were built based on 304 selective inhibitors docked into mTOR and PI3Kα, respectively (mTOR: q(2) = 0.658, r(pre)(2) = 0.839; PI3Kα: q(2) = 0.540, r(pre)(2) = 0.719). The results showed that steric and electrostatic fields have an important influence on selectivity towards mTOR and PI3Kα-a finding consistent with the structural divergence between the active sites. The findings may be helpful in investigating selective mTOR/PI3Kα inhibitors.

Recent advances in the discovery of small molecule mTOR inhibitors

Mammalian target of rapamycin (mTOR) belongs to the atypical kinase family of phosphatidylinositol-3-kinase-related kinase and function as a master regulators of the switch between catabolic and anabolic metabolism. In the last decade mTOR has emerged as a therapeutic target for various diseases such as cancer, inflammation and metabolic disorders. mTOR plays a crucial role in the PI3K/AKT/PDK1 pathway. In this review we will provide an overview of both selective and nonselective mTOR inhibitors. Since rapamycin and rapalogs have been reviewed before, more emphasis has been placed on nonrapamycin-based small-molecule inhibitors and their modulation of mTOR selectivity. Recent efforts in obtaining mTOR-selective inhibitors have produced a range of compounds with more than 1000-fold selectivity over PI3K, but it is still a matter of debate whether an mTOR-selective inhibitor will be of more clinical significance over a PI3K/AKT/mTOR inhibitor.

Discovery of 2-ureidophenyltriazines bearing bridged morpholines as potent and selective ATP-competitive mTOR inhibitors

Incorporation of bridged morpholines in monocyclic triazine PI3K/mTOR inhibitors gave compounds with increased mTOR selectivity relative to the corresponding morpholine analogs. Compounds with ureidophenyl groups gave highly potent and selective mTOR inhibitors. Potency and selectivity was demonstrated both in vitro and in vivo through biomarker suppression studies. Select compounds exhibited potent inhibition of tumor growth in nude mouse xenograft assays upon PO and IV administration.

Triazines incorporating (R)-3-methylmorpholine are potent inhibitors of the mammalian target of rapamycin (mTOR) with selectivity over PI3Kalpha

Potent inhibitors of the mammalian target of rapamycin (mTOR) which contain the triazine scaffold and the (R)-3-methyl morpholine moiety have been identified. Such compounds also demonstrated good selectivity over the related lipid kinase PI3Kalpha. Incorporation of additional functionality at the 4-position of the arylureidophenyl ring resulted in compounds with enhanced cellular activity.