Serendipitous Identification of Azine Anticancer Agents Using a Privileged Scaffold Morphing Strategy

The use of privileged scaffolds as a starting point for the construction of libraries of bioactive compounds is a widely used strategy in drug discovery and development. Scaffold decoration, morphing and hopping are additional techniques that enable the modification of the chosen privileged framework and better explore the chemical space around it. In this study, two series of highly functionalized pyrimidine and pyridine derivatives were synthesized using a scaffold morphing approach consisting of triazine compounds obtained previously as antiviral agents. Newly synthesized azines were evaluated against lymphoma, hepatocarcinoma, and colon epithelial carcinoma cells, showing in five cases acceptable to good anticancer activity associated with low cytotoxicity on healthy fibroblasts. Finally, ADME in vitro studies were conducted on the best derivatives of the two series showing good passive permeability and resistance to metabolic degradation.

A Critical Review on Therapeutic Potential of Benzimidazole Derivatives: A Privileged Scaffold

Benzimidazole nucleus is a predominant heterocycle displaying a wide spectrum of pharmacological activities. The privileged nature of the benzimidazole scaffold has been revealed by its presence in most small molecule drugs and in its ability to bind multiple receptors with high affinity. A literature review of the scaffold reveals several instances where structural modifications of the benzimidazole core have resulted in high-affinity lead compounds against a variety of biological targets. Hence, this structural moiety offers opportunities to discover novel, better, safe and highly potent biological agents. The goal of the present review is to compile the medicinal properties of benzimidazole derivatives with a focus on SAR (Structure-Activity Relationships).

Brief insight into the in silico properties, structure-activity relationships and biotransformation of fruquintinib, an anticancer drug of a new generation containing a privileged benzofuran scaffold

Current trends in drug design notably consider so-called privileged scaffolds as the core structural fragments with decisive impact on affinity to properly chosen biological targets, potency, selectivity and toxicological characteristics of drugs and prospective drug candidates. Fruquintinib (1) is a novel synthetic selective inhibitor of vascular endothelial growth factor receptor (VEGFR) isoforms, i.e., VEGFR-1, VEGFR-2 and VEGFR-3. The therapeutic agent (1) consists of a flat bicyclic heteroaromatic ring, in which two nitrogens are suitablyincorporated, a core bicyclic heteroaromatic ring - privileged (substituted) benzofuran scaffold, and a pair of hydrogen bond (H-bond) donor and acceptor group, i.e., amide functional moiety. Fruquintinib (1) was first approved in China for the treatment of metastatic colorectal cancer, a severe malignant disease with a high mortality rate. The review article offered a brief insight into the topic of privileged structures, their drug- -like ranges of several parameters, pharmacodynamic characteristics of fruquintinib (1) and various in silico descriptors characterizing drug's structural and physicochemical properties (molecular weight, number of heavy atoms, number of aromatic heavy atoms, fraction of sp3 C-atoms, number of H-bond acceptors, number of H-bond donors, total polar surface area, molar refractivity, molecular volume as well as parameters of lipophilicity and solubility). Some of these descriptors were related to pharmacokinetics and distribution of fruquintinib (1), and, in addition, might help predict its ability to cross passively the blood-brain barrier (BBB). Moreover, a possible connection between the induction potential on cytochrome P450 isoenzymes (CYP1A2 and CYP3A4) and passive transport of a given drug into the central nervous system via BBB was investigated. Current clinical experience and future directions regarding of fruquintinib (1) were also briefly outlined.

Privileged Scaffold Decoration for the Identification of the First Trisubstituted Triazine with Anti-SARS-CoV-2 Activity

Current therapy against severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) are based on the use of Remdesivir 1, Molnupiravir 2, and the recently identified Nirmatrelvir 3. Unfortunately, these three drugs showed some limitations regarding potency and possible drug-drug interactions. A series of derivatives coming from a decoration approach of the privileged scaffold s-triazines were synthesized and evaluated against SAR-CoV-2. One derivative emerged as the hit of the series for its micromolar antiviral activity and low cytotoxicity. Mode of action and pharmacokinetic in vitro preliminary studies further confirm the role as candidates for a future optimization campaign of the most active derivative identified with this work.

1,3,4-thiadiazole: a privileged scaffold for drug design and development

1,3,4-thiadiazole is a five-membered aromatic heterocycle containing two nitrogen atoms and one sulfur atom. As a privileged scaffold, it has its unique chemical properties and biological characteristics. In the design of drugs, they are widely and flexibly applied by medicinal chemists, and many candidates with therapeutic prospects have been developed. In this review, we focus on 1,3,4-thiadiazole derivatives and their various biological activities reported in the past five years (from 2015 to early 2020), such as anticancer, antibacterial, antifungal, anti-tuberculosis, anti-inflammatory, antivirus, anti-leishmania and other functions. It is believed that this review can provide some new ideas for seeking rational design to develop 1,3,4-thiadiazole based medicinal agents with better activity and lower toxicity.

Cyclic Dipeptides: The Biological and Structural Landscape with Special Focus on the Anti-Cancer Proline-Based Scaffold

Cyclic dipeptides, also know as diketopiperazines (DKP), the simplest cyclic forms of peptides widespread in nature, are unsurpassed in their structural and bio-functional diversity. DKPs, especially those containing proline, due to their unique features such as, inter alia, extra-rigid conformation, high resistance to enzyme degradation, increased cell permeability, and expandable ability to bind a diverse of targets with better affinity, have emerged in the last years as biologically pre-validated platforms for the drug discovery. Recent advances have revealed their enormous potential in the development of next-generation theranostics, smart delivery systems, and biomaterials. Here, we present an updated review on the biological and structural profile of these appealing biomolecules, with a particular emphasis on those with anticancer properties, since cancers are the main cause of death all over the world. Additionally, we provide a consideration on supramolecular structuring and synthons, based on the proline-based DKP privileged scaffold, for inspiration in the design of compound libraries in search of ideal ligands, innovative self-assembled nanomaterials, and bio-functional architectures.

Design and Synthesis of Quinolizidine Derivatives as Influenza Virus and HIV-1 Inhibitors

BACKGROUND

We have previously reported that a quinolizidine natural product, aloperine, and its analogs can inhibit influenza virus and/or HIV-1 at low μM concentrations.

OBJECTIVE

The main goal of this study was to further optimize aloperine for improved anti-influenza virus activity.

METHODS

Structural modifications have been focused on the N12 position of aloperine scaffold. Conventional chemical synthesis was used to obtain derivatives with improved antiviral activities. The anti-HIV and anti-influenza virus activities of the synthesized compounds were determined using an MT4 cell-based HIV-1 replication assay and an anti- influenza virus infection of MDCK cell assay, respectively.

RESULTS

Aloperine derivatives can be classified into three activity groups: those that exhibit anti-HIV activity only, anti-influenza virus only, or activity against both viruses. Aloperine optimized for potent anti-influenza activity often lost anti-HIV-1 activity, and vice versa. Compound 19 inhibited influenza virus PR8 replication with an IC50 of 0.091 μM, which is approximately 160- and 60-fold more potent than aloperine and the previously reported aloperine derivative compound 3, respectively.

CONCLUSION

The data suggest that aloperine is a privileged scaffold that can be modified to become a selective antiviral compound with markedly improved potency against influenza virus or HIV-1.

Recent Applications of Benzimidazole as a Privileged Scaffold in Drug Discovery

Benzimidazole is an aromatic bicyclic heterocycle that is regarded as a valuable privileged scaffold in medicinal chemistry. Many marketed drugs and natural products containing benzimidazole scaffolds exert great influence in fighting various diseases, such as hypertension, peptic ulcers, parasitic infections, and cancer. In this review, we introduce the pharmacological applications of some marketed drugs and lead compounds with a focus on anticancer agents, reporting the corresponding data to show the biological activities at their targets. The publications in this review encompass those from 2014 to 2019.

Pharmacologic activities of 5, 6-Diaryl/heteroaryl-3-substituted-1, 2, 4-triazines as a privileged scaffold in drug development

1, 2, 4-Triazine derivatives have received much attention due to their multifunctional nature, especially in diverse pharmacological properties as well as a key fragment in many drug candidates. Introduction of a vicinal 5, 6-diaryl/heteroaryl moiety on the 1, 2, 4-triazine ring has attracted plentiful attention in the field of medicinal chemistry. 5, 6-Diaryl/heteroaryl-3-substituted-1, 2, 4-triazine is as a prominent scaffold in many drug candidates which has shown a wide range of pharmacological activities such as anti-diabetic, antifungal, anti-inflammatory, anticancer, anti-HIV, neuroprotective, anticonvulsant, anti- Alzheimer, anti-Parkinson and antioxidant. In this review, we have discussed synthesis, various pharmacological activities of 5, 6-diaryl/heteroaryl-3-substituted-1, 2, 4-triazines, their structure-activity relationship (SAR), pharmacophoric elements and their mechanism of action reported in the published articles during 2000-2019. Evaluation of compounds by PAINS filtering tool was accomplished and showed that this versatile structure could be considered as a privileged structure. Compilation of the biological data confirmed that the position 3 of the 1,2,4-triazine is a key location to determine the affinity and selectivity of the 5,6-diaryl/heteroaryl-3-substituted-1, 2, 4-triazines towards different biologic targets. Specific geometrical and thermodynamic characters of this motif have prompted it as a frequent hitter.

Triazolopyrimidinium salts: discovery of a new class of agents for cancer therapy

Aim: The [1,2,4]triazolo[1,5-a]pyrimidine core is highly privileged in medicinal chemistry due to its versatile pharmacological activity profile. Recently, the search for novel anticancer agents has focused on [1,2,4]triazolo[1,5-a]pyrimidine derivatives. Results: Our hit functionalization has led to the discovery of new [1,2,4]triazolo[1,5-a]pyrimidinium salts with potential anticancer activity. Among a small library of molecules, compound 9 significantly inhibits cancer cell growth in a panel of in vitro models. Molecular docking studies and preliminary binding assay have displayed that 9 could directly bind the Src homology 2 (SH2) domain of STAT3 protein. Conclusion: Compound 9 is a novel promising lead compound that motivates additional evaluation of [1,2,4]triazolo[1,5-a]pyrimidinium salts as novel potential chemotherapeutics.

Lessons from black pepper: piperine and derivatives thereof

INTRODUCTION

Piperine is a simple and pungent alkaloid found in the seeds of black pepper (Piper nigrum). Following its isolation and full characterization, the biological properties of piperine have been extensively studied, and piperine-like derivatives have shown an interesting range of pharmacological activities. In this context, significant advances have been made in the discovery of new chemical entities based on the piperine scaffold endowed with therapeutic potential.

AREAS COVERED

The aim of this review is to provide a thorough inquiry on the therapeutic potential of piperine and related derivatives. It provides an overview of recent developments in patented processes and applications thereof between 2000 and 2015.

EXPERT OPINION

Cumulative evidence shows that piperine is currently paving its way to become a privileged scaffold for the development of bioactive compounds with therapeutic application in multiple human diseases. In particular, piperine derivatives were shown to modulate the activity of several targets related to neurological disorders, including epilepsy, Parkinson's disease, depression and pain related disorders. Moreover, the efflux pump inhibitory ability of piperine and its analogues tackles important drug resistance mechanisms and may improve the clinical efficacy of antibiotic and anticancer drugs. Although the use of piperine as a scaffold for bioactive compounds is still in its early stages, the continuous exploration of this structure may lead to remarkable advances in drug discovery programs.