Discovery of novel pyrimidine-based benzothiazole derivatives as potent cyclin-dependent kinase 2 inhibitors with anticancer activity

Benzothiazole a privileged scaffold for Cutting-Edges anticancer agents: Exploring drug design, structure-activity relationship, and docking studies

Cancer is a major societal, public health, and economic burden in the 21st century, with 9.7 million deaths in 2022 (9.96 million in 2020) and 20 million new cancer cases (19.6 million in 2020). Considering the increasing number of cancer cases and deaths, heterocyclic compounds always paved the gold mine for the development of potential anticancer drugs as these compounds have unique flexibility and dynamic cores. Benzothiazoles and their derivatives have potential anticancer properties, making them a desirable scaffold among different heterocycles. Title structures are a class of chemicals that may bind to various receptors with high affinity, particularly those engaged in oncogenic processes. The use of these compounds allows medicinal chemists to rapidly produce anticancer treatments across a large range of targets over an extended length of time. The current study presents a thorough success story of benzothiazole derivatives as anticancer agents. It discusses the current state of cancer, the profile of benzothiazole-based derivatives synthetic pathways, and its relevance as an anticancer agent on several oncogenic pathways. The structure-activity relationship was also added to offer insight into the connection of biological data with structure and the rational design of more active drugs.

Annulative coupling of sulfoxonium ylides with 2-amino(thio)phenols: easy access to 2-acyl benzox(thio)azoles

A novel method for synthesizing 2-acyl benzothiazoles and benzoxazole derivatives has been developed via the annulative coupling of sulfoxonium ylides with 2-aminobenzenethiol and 2-aminophenol derivatives, respectively. This metal-free, one-pot protocol employs elemental sulfur as a mediator to efficiently construct C-N, C-S, or C-O bonds and demonstrates a broad range of functional group compatibility. The potential utility of this approach is further demonstrated through large-scale reactions and the synthesis of some bioactive compounds.

Benzimidazole-oxindole hybrids: A novel class of selective dual CDK2 and GSK-3β inhibitors of potent anticancer activity

A new series of benzimidazole-oxindole hybrids 8a-x was discovered as dual cyclin-dependent kinase (CDK2) and glycogen synthase kinase-3-beta (GSK-3β) inhibitors with potent anticancer activity. The synthesized hits displayed potent anticancer activity against national cancer institute cancer cell lines in single-dose and five-dose assays. Moreover, the derivatives 8k, 8l, 8n, 8o, and 8p demonstrated potent cytotoxic activity against PANC-1 cells with IC50 = 1.88-2.79 µM. In addition, the hybrids 8l, 8n, 8o, and 8p displayed potent antiproliferative activity on the MG-63 cell line (IC50 = 0.99-1.90 µM). Concurrently, the benzimidazole-oxindole hybrid 8v exhibited potent dual CDK2/GSK-3β inhibitory activity with IC50 values of 0.04 and 0.021 µM, respectively. In addition, 8v displayed more than 10-fold higher selectivity toward CDK2 and GSK-3 β over CDK1, CDK5, GSK-3α, vascular endothelial growth factor receptor-2, and B-rapidly accelerated fibrosarcoma. Screening of the effect of 8n and 8v on the cell cycle and apoptosis of PANC-1 and MG-63 cells displayed their ability to arrest their cell cycle at the G2-M phase and to potentiate the apoptosis of both cell lines. In silico docking of the benzimidazole-oxindole hybrid 8v into the catalytic pocket of both CDK2 and GSK-3β revealed its perfect fitting through the formation of hydrogen bonding and hydrophobic interactions with the key amino acids in the binding sites. In addition, in silico absorption, distribution, metabolism, excretion studies proved that 8a-x exhibit satisfactory drug-likeness properties for drug development.

Approaches for the discovery of cinnamic acid derivatives with anticancer potential

INTRODUCTION

Cinnamic acid is a privileged scaffold for the design of biologically active compounds with putative anticancer potential, following different synthetic methodologies and procedures. Since there is a need for the production of potent anticancer, cinnamate moiety can significantly contribute in the design of new and more active anticancer agents.

AREAS COVERED

In this review, the authors provide a review on the synthetic approaches for the discovery of cinnamic acid derivatives with anticancer potential. Results from molecular simulations, hybridization, and chemical derivatization along with biological experiments in vitro and structural activity relationships are given, described, and discussed by the authors. Information for the mechanism of action is taken from original literature sources.

EXPERT OPINION

The authors suggest that (i) numerous areas of biology-pharmacology need to be considered: selectivity, in vivo studies, toxicity and drug-likeness, the mechanism of action in animals and humans, development of more efficient assays for various cancer types; (ii) hybridization techniques outbalance in the discovery and production of compounds with higher activity and greater selectivity; (iii) repositioning offers new anticancer cinnamic agents.

Benzothiazole derivatives in the design of antitumor agents

Benzothiazoles are a class of heterocycles with multiple applications as anticancer, antibiotic, antiviral, and anti-inflammatory agents. Benzothiazole is a privileged scaffold in drug discovery programs for modulating a variety of biological functions. This review focuses on the design and synthesis of new benzothiazole derivatives targeting hypoxic tumors. Cancer is a major health problem, being among the leading causes of death. Tumor-hypoxic areas promote proliferation, malignancy, and resistance to drug treatment, leading to the dysregulation of key signaling pathways that involve drug targets such as vascular endothelial growth factor, epidermal growth factor receptor, hepatocyte growth factor receptor, dual-specificity protein kinase, cyclin-dependent protein kinases, casein kinase 2, Rho-related coil formation protein kinase, tunica interna endothelial cell kinase, cyclooxygenase-2, adenosine kinase, lysophosphatidic acid acyltransferases, stearoyl-CoA desaturase, peroxisome proliferator-activated receptors, thioredoxin, heat shock proteins, and carbonic anhydrase IX/XII. In turn, they regulate angiogenesis, proliferation, differentiation, and cell survival, controlling the cell cycle, inflammation, the immune system, and metabolic alterations. A wide diversity of benzothiazoles were reported over the last years to interfere with various proteins involved in tumorigenesis and, more specifically, in hypoxic tumors. Many hypoxic targets are overexpressed as a result of the hypoxia-inducible factor activation cascade and may not be present in normal tissues, providing a potential strategy for selectively targeting hypoxic cancers.

Unveiling the promise of pyrimidine-modified CDK inhibitors in cancer treatment

Cyclin-dependent kinases (CDKs) constitute a vital family of protein-serine kinases, pivotal in regulating various cellular processes such as the cell cycle, metabolism, proteolysis, and neural functions. Dysregulation or overexpression of CDK kinases is directly linked to the development of cancer. However, the currently approved CDK inhibitors by the US FDA, such as palbociclib, ribociclib, Trilaciclib, Abemaciclib, etc., although effective, exhibit limited specificity and often lead to undesirable adverse effects. First and second-generation CDK inhibitors have not gained significant clinical interaction due to their high toxicity and lack of specificity. To address these challenges, a combined approach is being employed in the quest for newer CDK inhibitors aimed at mitigating toxicity and side effects associated with CDKIs. The discovery of therapeutic agents selectively targeting tumorous cells, such as CDK inhibitors, has demonstrated promise in treating various cancers, including breast cancer. Extensive literature reviews have facilitated the development of novel CDK inhibitors by combining medicinally preferred pyrimidine derivatives with other heterocyclic rings. Pyrimidine derivatives substituted with pyrazole, imidazole, benzamide, benzene sulfonamide, indole carbohydrazide, and other privileged heterocyclic rings have shown encouraging efficacy in inhibiting cyclin-dependent kinase activity. This review provides comprehensive data, including structure-activity relationship (SAR), anticancer activity, and kinetics studies of potent compounds. Additionally, molecular docking studies with compounds under clinical trial and patents filed on pyrimidine based CDK inhibitors in cancer treatment are included. This review serves as a valuable resource for further development of CDK kinase inhibitors for cancer treatment, offering insights into their efficacy, specificity, and potential clinical applications.

In the pursuit of novel therapeutic agents: synthesis, anticancer evaluation, and physicochemical insights of novel pyrimidine-based 2-aminobenzothiazole derivatives

Cancer remains a worldwide healthcare undertaking, demanding continual innovation in anticancer drug development due to frequent drug resistance and adverse effects associated with existing therapies. The benzothiazole compounds, particularly 2-aminobenzothiazole derivatives, have attracted interest for their versatility in generating novel anticancer agents. This study explores the synthesis, and anticancer evaluation of new pyrimidine-based 2-aminobenzothiazole derivatives. A range of synthetic methods have been developed based on the reaction of 2-benzothaizolyl guanidine with various reagents such as α,β-unsaturated carbonyl, 2-cyano-three-(dimethylamino)-N-acrylamide, β-diketones, β-keto esters, and S,S ketene dithioacetals. Human tumour cell lines such as HepG2, HCT116, and MCF7 were used in in vitro cytotoxicity studies, and the results showed that several of the synthesized compounds were more potent than the standard drug, 5-fluorouracil, in terms of cell viability% with low IC50. Furthermore, the computed drug likeness and ADMET properties of the most potent synthesized compounds suggest their potential as promising candidates for further development, with favorable bioavailability and pharmacokinetic profiles.

Synthesis and SAR investigation of biphenylaminoquinoline derivatives with benzyloxy substituents as promising anticancer agents

The biphenyl scaffold represents a prominent privileged structure within the realms of organic chemistry and drug development. Biphenyl derivatives have demonstrated notable biological activities, including antimicrobial, anti-inflammatory, anti-HIV, and the treatment of neuropathic pain. Importantly, their anticancer abilities should not be underestimated. In this context, the present study involves the design and synthesis of a series of biphenyl derivatives featuring an additional privileged structure, namely the quinoline core. We have also diversified the substituents attached to the benzyloxy group at either the meta or para position of the biphenyl ring categorized into two distinct groups: [4,3']biphenylaminoquinoline-substituted and [3,3']biphenylaminoquinoline-substituted compounds. We embarked on an assessment of the cytotoxic activities of these derivatives in colorectal cancer cell line SW480 and prostate cancer cell line DU145 for exploring the structure-activity relationship. Furthermore, we determined the IC50 values of selected compounds that exhibited superior inhibitory effects on cell viability against SW480, DU145 cells, as well as MDA-MB-231 and MiaPaCa-2 cells. Notably, [3,3']biphenylaminoquinoline derivative 7j displayed the most potent cytotoxicity against these four cancer cell lines, SW480, DU145, MDA-MB-231, and MiaPaCa-2, with IC50 values of 1.05 μM, 0.98 μM, 0.38 μM, and 0.17 μM, respectively. This highly promising outcome underscores the potential of [3,3']biphenylaminoquinoline 7j for further investigation as a prospective anticancer agent in future research endeavors.

Deciphering the Lexicon of Protein Targets: A Review on Multifaceted Drug Discovery in the Era of Artificial Intelligence

Understanding protein sequence and structure is essential for understanding protein-protein interactions (PPIs), which are essential for many biological processes and diseases. Targeting protein binding hot spots, which regulate signaling and growth, with rational drug design is promising. Rational drug design uses structural data and computational tools to study protein binding sites and protein interfaces to design inhibitors that can change these interactions, thereby potentially leading to therapeutic approaches. Artificial intelligence (AI), such as machine learning (ML) and deep learning (DL), has advanced drug discovery and design by providing computational resources and methods. Quantum chemistry is essential for drug reactivity, toxicology, drug screening, and quantitative structure-activity relationship (QSAR) properties. This review discusses the methodologies and challenges of identifying and characterizing hot spots and binding sites. It also explores the strategies and applications of artificial-intelligence-based rational drug design technologies that target proteins and protein-protein interaction (PPI) binding hot spots. It provides valuable insights for drug design with therapeutic implications. We have also demonstrated the pathological conditions of heat shock protein 27 (HSP27) and matrix metallopoproteinases (MMP2 and MMP9) and designed inhibitors of these proteins using the drug discovery paradigm in a case study on the discovery of drug molecules for cancer treatment. Additionally, the implications of benzothiazole derivatives for anticancer drug design and discovery are deliberated.

Novel 2-Aminobenzothiazole Derivatives: Docking, Synthesis, and Biological Evaluation as Anticancer Agents

Sixteen novel 2-aminobenzothiazole compounds with different amines or substituted piperazine moieties were designed, synthesized, and tested using various methods. Potential interactions were assessed by docking new compounds in the adenosine triphosphate (ATP) binding domain of the PI3Kγ enzyme (PDB code: 7JWE) by nucleophilic substitution or solvent-free/neat fusion for docked compound synthesis. Final 2-aminobenzothiazole compounds were characterized by direct probe gas chromatography-mass spectrometry (GC-MS), proton (1H-NMR), carbon-13 (13C-NMR), and attenuated total reflectance-infrared Fourier transform infrared (ATR FT-IR). The synthesized compounds were investigated for anticancer activities on lung cancer (A549) and breast cancer (MCF-7) cell lines. The compounds' PI3Kγ inhibition was evaluated at a 100 μM concentration. 4-Nitroaniline and piperazine-4-nitroaniline combination in OMS5 and OMS14 reduced lung and breast cancer cell line growth. IC50 values for OMS5 and OMS14, the strongest compounds, ranged from 22.13 to 61.03 μM. OMS1 and OMS2 inhibited PI3Kγ at the highest rates (47 and 48%, respectively) at a 100 μM concentration. Results show that the PI3Kγ enzyme suppression is not the main mechanism behind these OMS5 and OMS14 anticancer effects. CDK2, Akt, mTOR, and p42/44 MAPK are affected. EGF receptor suppression matters. AKT1, AKT3, CDK1/cyclin B, PDK1 direct, PIK3CA E542 K/PIK3R1 (p110 α/p85 α), PIK3CD/PIK3R1 (p110 δ/p85 α), and PKN inhibition were measured to evaluate the possible mechanism of compound OMS14. PIK3CD/PIK3R1 (p110 δ/p85 α) is the most, with 65% inhibition, suggesting a possible mechanism of anticancer properties. Furthermore, the NCI 60-cell line inhibition demonstrates promising broad anticancer inhibition against numerous cancer cell lines of OMS5 and OMS14, which could be good lead compounds for future development.

Design, synthesis and biological evaluation of rhein-piperazine-furanone hybrids as potential anticancer agents

Novel rhein-piperazine-furanone hybrids, 5, were designed and synthesized efficiently from rhein. Cytotoxicity of all hybrids 5a-j against A549 human lung cancer cells was superior to the parent rhein and the reference cytarabine (CAR). Hybrid 5e (IC50 = 5.74 μM), the most potent compound, was 46- and 35-fold more toxic against A549 cells than rhein (IC50 = 265.59 μM) and CAR (IC50 = 202.57 μM), respectively. Moreover, hybrid 5e (IC50 = 69.28 μM) was less toxic to normal WI-38 human lung fibroblast cells with good selectivity (WI-38/A549, SI ≈ 12), being much higher than rhein (SI ≈ 1) and CAR (SI ≈ 2). Structure-activity relationship (SAR) analysis showed that cytotoxicity and selectivity against A549 lung cancer cells were greatly enhanced when methoxy-containing furanone was introduced to the hybrids (5e and 5h). Further, hybrid 5e showed better cytotoxicity against four types of human lung cancer cells (H460, A549, PC-9, and Calu-1; IC50 = 4.35-15.39 μM) than six other types of human cancer cells (SK-BR-3, SK-OV-3, 786-O, Huh-7, HCT116, and HeLa; IC50 = 13.77-60.45 μM), showing specificity. In particular, hybrid 5e showed the highest cytotoxicity (IC50 = 4.35 μM) and the highest selectivity (WI-38/H460, SI ≈ 16) against H460 human lung cancer cells. Flow cytometric analysis showed that hybrid 5e induced apoptosis in a concentration-dependent manner in H460 cells. The results show that the cytotoxicity and selectivity of rhein can be greatly enhanced by hybridization with furanone. Hybrid 5e is expected to be a leading candidate for anti-lung cancer drugs.

Design, synthesis, and biological evaluation of N-(pyridin-3-yl)pyrimidin-4-amine analogues as novel cyclin-dependent kinase 2 inhibitors for cancer therapy

The discovery and development of CDK2 inhibitors has currently been validated as a hot topic in cancer therapy. Herein, a series of novel N-(pyridin-3-yl)pyrimidin-4-amine derivatives were designed and synthesized as potent CDK2 inhibitors. Among them, the most promising compound 7l presented a broad antiproliferative efficacy toward diverse cancer cells MV4-11, HT-29, MCF-7, and HeLa with IC50 values of 0.83, 2.12, 3.12, and 8.61 μM, respectively, which were comparable to that of Palbociclib and AZD5438. Interestingly, these compounds were less toxic on normal embryonic kidney cells HEK293 with high selectivity index. Further mechanistic studies indicated 7l caused cell cycle arrest and apoptosis on HeLa cells in a concentration-dependent manner. Moreover, 7l manifested potent and similar CDK2/cyclin A2 nhibitory activity to AZD5438 with an IC50 of 64.42 nM. These findings revealed that 7l could serve as ahighly promisingscaffoldfor CDK2 inhibitors as potential anticancer agents and functional probes.

Design of balanced dual-target inhibitors of EGFR and microtubule

Motivated by the clinical success of combining tyrosine kinase inhibitors with microtubule-targeted drugs in antitumor treatment, this paper presents a novel combi-targeting design for dual-target inhibitors, featuring arylformylurea-coupled quinazoline backbones. A series of target compounds (10a-10r) were designed, synthesized, and characterized. Biological assessments demonstrated that 10c notably potentiated ten tumor cell lines in vitro, with IC50 values ranging from 1.04 µM to 7.66 µM. Importantly, 10c (IC50 = 10.66 nM) exhibited superior inhibitory activity against EGFR kinases compared to the reference drug Gefitinib (25.42 nM) and reduced phosphorylated levels of EGFR, AKT, and ERK. Moreover, 10c significantly impeded tubulin polymerization, disrupted the intracellular microtubule network in A549 cells, induced apoptosis, led to S-phase cell cycle arrest, and hindered cell migration. In anticancer evaluation tests using A549 cancer-bearing nude mice models, 10c showed a therapeutic effect similar to Gefitinib, but required only half the dosage (15 mg/kg). These findings indicate that compound 10c is a promising dual-target candidate for anticancer therapy.

Advances in synthesis and biological evaluation of CDK2 inhibitors for cancer therapy

One of the leading causes of mortality in the world is cancer. This disease occurs when responsible genes that regulate the cell cycle become inactive due to internal or external factors. Specifically, the G1/S and S/G2 transitions in the cell cycle are controlled by a protein called cyclin-dependent kinase 2 (CDK2). CDKs, which play a crucial role in managing the cell cycle, have been a wide area of research in cancer treatment. Over the past 11 years, significant research has been made in identifying potent, targeted, and efficient inhibitors of CDK2. In this summary, we have summarized recent developments in the synthesis and biological evaluation of CDK2 inhibitors.

Discovery of pyrimidine-tethered benzothiazole derivatives as novel anti-tubercular agents towards multi- and extensively drug resistant Mycobacterium tuberculosis

In this study, new benzothiazole-pyrimidine hybrids (5a-c, 6, 7a-f, and 8-15) were designed and synthesised. Two different functionalities on the pyrimidine moiety of lead compound 4 were subjected to a variety of chemical changes with the goal of creating various functionalities and cyclisation to further elucidate the target structures. The potency of the new molecules was tested against different tuberculosis (TB) strains. The results indicated that compounds 5c, 5b, 12, and 15 (MIC = 0.24-0.98 µg/mL) are highly active against the first-line drug-sensitive strain of Mycobacterium tuberculosis (ATCC 25177). Thereafter, the anti-tubercular activity was evaluated against the two drug-resistant TB strains; ATCC 35822 and RCMB 2674, where, many compounds exhibited good activity with MIC = 0.98-62.5 3 µg/mL and 3.9-62.5 µg/mL, respectively. Compounds 5c and 15 having the highest anti-tubercular efficiency towards sensitive strain, displayed the best activity for the resistant strains by showing the MIC = 0.98 and 1.95 µg/mL for MDR TB, and showing the MIC = 3.9 and 7.81 µg/mL for XDR TB, consecutively. Finally, molecular docking studies were performed for the two most active compounds 5c and 15 to explore their enzymatic inhibitory activities.

Identification of aneuploidy-related gene signature to predict survival in head and neck squamous cell carcinomas

BACKGROUND

To parse the characteristics of aneuploidy related riskscore (ARS) model in head and neck squamous cell carcinomas (HNSC) and their predictive ability on patient prognosis.

METHODS

Molecular subtyping of HNSC specimens was clustered by Copy Number Variation (CNV) data from The Cancer Genome Atlas (TCGA) dataset applying consistent clustering, followed by immune condition evaluation, differentially expressed genes (DEGs) analysis and DEGs function annotation. Weighted gene co-expression network analysis (WGCNA), protein-protein interaction, Univariate Cox regression analysis, least absolute shrinkage and selection operator (LASSO) and stepwise multivariate Cox regression analysis were implemented to construct an ARS model. A nomogram for clinic practice was designed by rms package. Immunotherapy evaluation and drug sensitivity prediction were also carried out.

RESULTS

We stratified HNSC patients into three different molecular subgroups, with the best prognosis in C1 cluster among 3 clusters. C1 cluster displayed greatest immune infiltration status. The most DEGs between C1 and C2 groups, mainly enriched in cell cycle and immune function. We constructed a nine-gene ARS model (ICOS, IL21R, CCR7, SELL, CYTIP, ZAP70, CCR4, S1PR4 and CD79A) that effectively differentiates between high- and low-risk patients. Patients in low ARS group showed a higher sensitivity to immunotherapy. A nomogram built by integrating ARS and clinic-pathological characteristics helped predict clinic survival benefit. Drug sensitivity evaluation found that 4/9 inhibitor drugs (MK-8776, AZD5438, PD-0332991, PHA-665752) acted on the cell cycle.

CONCLUSIONS

We classified 3 molecular subtypes for HNSC patients and established an ARS prognostic model, which offered a prospective direction for prognosis in HNSC.

Design, synthesis and biological evaluation of 4-arylamino-pyrimidine derivatives as focal adhesion kinase inhibitors

A novel series of 4-arylamino-pyrimidine derivatives were designed and synthesized as focal adhesion kinase (FAK) inhibitors under the strategy of structure-based drug design. Most compounds performed excellent anti-proliferative activity against U87-MG cells. Especially, compounds 8d and 9b revealed the highest activity with IC50 values of 0.975 μM and 1.033 μM, which was much potent than the positive control TAE-226 (IC50 = 2.659 μM). On the other hand, the total 27 compounds exhibited low inhibition against human normal 2BS cells. Moreover, compounds 8d and 9b showed outstanding activity against FAK with IC50 values of 0.2438 nM and 0.2691 nM, which was very close to TAE-226 (IC50 = 0.1390 nM). Further studies proved that compounds 8d and 9b could induce U87-MG cell early apoptosis and arrest the cell at G2/M phase. The action mechanism indicated that they could significantly inhibit U87-MG cell clone formation, cell migration, and FAK phosphorylation. Molecular docking and molecular dynamics simulation investigations suggested that compounds 8d and 9b could firmly occupy the ATP binding site of FAK. These findings supported the further researches of compounds 8d and 9b as FAK inhibitors for antitumor drug discovery.

Development of pyrolo[2,3-c]pyrazole, pyrolo[2,3-d]pyrimidine and their bioisosteres as novel CDK2 inhibitors with potent in vitro apoptotic anti-proliferative activity: Synthesis, biological evaluation and molecular dynamics investigations

Inhibiting the CDK2/cyclin A2 enzyme has been validated in multiple clinical manifestations related to multiple types of cancer. Herein, novel series of pyrolo[2,3-c]pyrazole, pyrolo[2,3-c]isoaxazole and pyrolo[2,3-d]pyrimidine, pyrolo[3,2-c]pyridine & indole based analogs were designed, synthesized and biologically evaluated for their in vitro antiproliferative activity where the obtained results revealed that most of the newly synthesized compounds showed significant cytotoxic activity towards MCF-7 (breast cancer cell lines) and HepG-2 (hepatocellular carcinoma) with IC50 ranging from 3.20 µM to 10.05 µM & from 2.18 µM to 13.49 µM, respectively, compared to that of Sorafenib (IC50 9.76 & 13.19 µM, respectively). The in vitro inhibitory profile of the most promising compounds (9, 11, 14, 15, 16, 17 and 20) towards CDK2/CyclinA2 was evaluated. Compounds 14 & 15 exhibited potent inhibitory profile against CDK2 with (IC50 0.11 and 0.262 µM, respectively comparable to Sorafenib IC50 0.184 µM. Western blotting of 14 & 15 at MCF-7 cell line confirmed the diminishing activity on CDK2. Furthermore, both compounds exserted a significant cell cycle arrest and apoptosis. Moreover, the normal cell line cytotoxicity for both compounds revealed low cytotoxic results in normal cells rather than cancer cells. Molecular docking and dynamic simulation validated the potentiality of the newly synthesized compounds to have high binding affinity within CDK2 binding pocket. 3DQSAR pharmacophore, in-silico ADME/TOPKAT studies and drug-likeness showed proper pharmacokinetic properties and helped in structure requirements prediction. The obtained model and pattern of substitution could be used for further development of CDK2 inhibitors.

Design, synthesis, and biological evaluation of novel pyrimidin-2-amine derivatives as potent PLK4 inhibitors

Serine/threonine protein kinase PLK4 is a master regulator of centriole duplication, which is significant for maintaining genome integrity. Accordingly, due to the detection of PLK4 overexpression in a variety of cancers, PLK4 has been identified as a candidate anticancer target. Thus, it is a very meaningful to find effective and safe PLK4 inhibitors for the treatment of cancer. However, the reported PLK4 inhibitors are scarce and have potential safety issues. In this study, a series of novel and potent PLK4 inhibitors with an aminopyrimidine core was obtained utilizing the scaffold hopping strategy. The in vitro enzyme activity results showed that compound 8h (PLK4 IC50 = 0.0067 μM) displayed high PLK4 inhibitory activity. In addition, compound 8h exhibited a good plasma stability (t1/2 > 289.1 min), liver microsomal stability (t1/2 > 145 min), and low risk of DDIs. At the cellular level, it presented excellent antiproliferative activity against breast cancer cells. Taken together, these results suggest that compound 8h has potential value in the further research of PLK4-targeted anticancer drugs.

2-Aminobenzothiazoles in anticancer drug design and discovery

Cancer is one of the major causes of mortality and morbidity worldwide. Substantial research efforts have been made to develop new chemical entities with improved anticancer efficacy. 2-Aminobenzothiazole is an important class of heterocycles containing one sulfur and two nitrogen atoms, which is associated with a broad spectrum of medical and pharmacological activities, including antitumor, antibacterial, antimalarial, anti-inflammatory, and antiviral activities. In recent years, an extraordinary collection of potent and low-toxicity 2-aminobenzothiazole compounds have been discovered as new anticancer agents. Herein, we provide a comprehensive review of this class of compounds based on their activities against tumor-related proteins, including tyrosine kinases (CSF1R, EGFR, VEGFR-2, FAK, and MET), serine/threonine kinases (Aurora, CDK, CK, RAF, and DYRK2), PI3K kinase, BCL-XL, HSP90, mutant p53 protein, DNA topoisomerase, HDAC, NSD1, LSD1, FTO, mPGES-1, SCD, hCA IX/XII, and CXCR. In addition, the anticancer potentials of 2-aminobenzothiazole-derived chelators and metal complexes are also described here. Moreover, the design strategies, mechanism of actions, structure-activity relationships (SAR) and more advanced stages of pre-clinical development of 2-aminobenzothiazoles as new anticancer agents are extensively reviewed in this article. Finally, the examples that 2-aminobenzothiazoles showcase an advantage over other heterocyclic systems are also highlighted.

A review on the design, synthesis, and structure-activity relationships of benzothiazole derivatives against hypoxic tumors

There has been a growing body of studies on benzothiazoles and benzothiazole derivatives as strong and effective antitumor agents against lung, liver, pancreas, breast, and brain tumors. Due to highly proliferative nature of the tumor cells, the oxygen levels get lower than that of a normal tissue in the tumor microenvironment. This situation is called as hypoxia and has been associated with increased ability for carcinogenesis. For the drug design and development strategies, hypoxic nature of the tumor tissues has been exploited more aggressively. Hypoxia itself acts as a signal initiating system to activate the pathways that eventually lead to the spread of the tumor cells into the different tissues, increases the rate of DNA damage and eventually ends up with more mutation levels that may increase the drug resistance. As one of the major mediators of hypoxic response, hypoxia inducible factors (HIFs) has been shown to activate to angiogenesis, metastasis, apoptosis resistance, and many other protumorigenic responses in cancer development. In the current review, we will be discussing the design, synthesis and structure-activity relationships of benzothiazole derivatives against hypoxic tumors such lung, liver, pancreas, breast and brain as potential anticancer drug candidates. The focus points of the study will be the biology behind carcinogenesis and how hypoxia contributes to the process, recent studies on benzothiazole and its derivatives as anti-cancer agents against hypoxic cancers, conclusions and future perspectives. We believe that this review will be useful for the researchers in the field of drug design during their studies to generate novel benzothiazole-containing hybrids against hypoxic tumors with higher efficacies.

Novel 1,3,5-triazine-nicotinohydrazide derivatives induce cell arrest and apoptosis in osteosarcoma cancer cells and inhibit osteosarcoma in a patient-derived orthotopic xenograft mouse model

The present study deals with developing novel 1,3,5-triazine-nicotinohydrazide derivatives as potent CDK9 inhibitors in a straightforward synthetic route with potent anti-osteosarcoma activity. The most potent CDK9 inhibitor compound 5k inhibits proliferation of MG-63 cells via induction of apoptosis and G2/M cell cycle arrest. It reduces tumor progression in the patient-derived orthotopic xenograft (PDOX) mouse model with significant antioxidant and anti-inflammatory activity. In tumor tissue homogenates, it caused significant inhibition of CDK9 and inhibited the phosphorylation of RNAPII ser2 and reduced MCL-1 expression in Western blot analysis. Compound 5k also showed considerable bioavailability in SD mice. Our results demonstrated that compound 5k inhibits growth of OS in vitro and in vivo via inhibition of CDK9 which attenuated the downstream phosphorylation of RNAPII ser2 and represses expression of the anti-apoptotic protein, MCL-1 for the induction of apoptosis in OS.

Exploring biological efficacy of novel benzothiazole linked 2,5-disubstituted-1,3,4-oxadiazole hybrids as efficient α-amylase inhibitors: Synthesis, characterization, inhibition, molecular docking, molecular dynamics and Monte Carlo based QSAR studies

In an effort to explore a class of novel antidiabetic agents, we have made an effort to synergize the α-amylase inhibitory potential of 1,3-benzothiazole and 1,3,4-oxadiazole scaffolds by combining the two into a single structure via an ether linkage. The structure of synthesized benzothiazole clubbed oxadiazole derivatives are established by different spectral techniques. The synthesized hybrids are evaluated for their in vitro inhibitory potential against α-amylase. Compound 8f is found to be the most potent with a significant inhibition (87.5 ± 0.74% at 50 μg/mL, 82.27 ± 1.85% at 25 μg/mL and 79.94 ± 1.88% at 12.5 μg/mL) when compared to positive control acarbose (77.96 ± 2.06%, 71.17 ± 0.60%, 67.24 ± 1.16% at 50 μg/mL, 25 μg/mL and 12.5 μg/mL concentration). Molecular docking of the most potent enzyme inhibitor, 8f, shows promising interaction with the binding site of biological macromolecule Aspergillus oryzae α-amylase (PDB ID: 7TAA) and human pancreatic α-amylase (PDB ID: 3BAJ). To a step further, in-depth QSAR studies show a significant correlation between the experimental and the predicted inhibitory activities with the best R_validation²= 0.8701. The developed QSAR model can provide ample information about the structural features responsible for the increase and decrease of inhibitory activity. The mechanistic interpretation of the structure-activity relationship (SAR) is done with the help of combined computational calculations i.e. molecular docking and QSAR. Finally, molecular dynamic simulations are performed to get an insight into the binding mode of the most potent derivative with α-amylase from A. oryzae (PDB ID: 7TAA) and human pancreas (PDB ID: 3BAJ).

Development of pteridin-7(8H)-one analogues as highly potent cyclin-dependent kinase 4/6 inhibitors: Synthesis, structure-activity relationship, and biological activity

CDK4/6 have been validated as the cancer therapeutic targets. Here, we describe a series of pteridin-7(8H)-one analogues as potent CDK4/6 inhibitors. Among them, the most promising compound 7s demonstrated remarkable and broad-spectrum antiproliferative activities toward HCT116, HeLa, MDA-MB-231, and HT-29 cells with IC₅₀ values of 0.65, 0.70, 0.39, and 2.53 μM, respectively, which were more potent than that of the anticancer drug Palbociclib. Interestingly, 7s also manifested the greatest inhibitory activities toward both CDK4/cyclin D3 and CDK6/cyclin D3 (IC₅₀ = 34.0 and 65.1 nM, respectively), which was comparable with Palbociclib. Additionally, molecular simulation indicated that 7s bound efficiently at the ATPbindingsitesofCDK4 and CDK6. Further mechanistic studies revealed that compound 7s could concentration-dependently induce cell cycle arrest and apoptosis in HeLa cells. Takentogether, 7s represents a promising novel CDK4/6 inhibitor for the potential treatment of cancer.

Advances in 2-substituted benzothiazole scaffold-based chemotherapeutic agents

Targeted therapy plays a pivotal role in cancer therapeutics by countering the drawbacks of conventional treatment like adverse events and drug resistance. Over the last decade, heterocyclic derivatives have received considerable attention as cytotoxic agents by modulating various signaling pathways. Benzothiazole is an important heterocyclic scaffold that has been explored for its therapeutic potential. Benzothiazole-based derivatives have emerged as potent inhibitors of enzymes such as EGFR, VEGFR, PI3K, topoisomerases, and thymidylate kinases. Several researchers have designed, synthesized, and evaluated benzothiazole scaffold-based enzyme inhibitors. Of these, several inhibitors have entered various phases of clinical trials. This review describes the recent advances and developments of benzothiazole architecture-based derivatives as potent anticancer agents.

Novel N-bridged pyrazole-1-carbothioamides with potential antiproliferative activity: design, synthesis, in vitro and in silico studies

Thiazole-substituted pyrazole is an important structural feature of many bioactive compounds, including antiviral, antitubercular, analgesic and anticancer agents. Herein we describe an efficient and facile approach for the synthesis of two series of 36 novel N-bridged pyrazole-1-phenylthiazoles. The antiproliferative activity of a set of representative compounds was evaluated in vitro against different human cancer cell lines. Among the identified compounds, compound 18 showed potent anticancer activity against the examined cancer cell lines. The in silico molecular docking study revealed that compound 18 possesses high binding affinity toward both SK1 and CDK2. Overall, these results indicate that compound 18 is a promising lead anticancer compound which may be exploited for development of antiproliferative drugs.

Quantitative Structure-Activity Relationship Evaluation of MDA-MB-231 Cell Anti-Proliferative Leads

In the present endeavor, for the dataset of 219 in vitro MDA-MB-231 TNBC cell antagonists, a (QSAR) quantitative structure–activity relationships model has been carried out. The quantitative and explicative assessments were performed to identify inconspicuous yet pre-eminent structural features that govern the anti-tumor activity of these compounds. GA-MLR (genetic algorithm multi-linear regression) methodology was employed to build statistically robust and highly predictive multiple QSAR models, abiding by the OECD guidelines. Thoroughly validated QSAR models attained values for various statistical parameters well above the threshold values (i.e., R² = 0.79, Q²_LOO = 0.77, Q²_LMO = 0.76–0.77, Q²-Fⁿ = 0.72–0.76). Both de novo QSAR models have a sound balance of descriptive and statistical approaches. Decidedly, these QSAR models are serviceable in the development of MDA-MB-231 TNBC cell antagonists.

Design of ferrocenylseleno-dopamine derivatives to optimize the Fenton-like reaction efficiency and antitumor efficacy

In the current study, six ferrocenylseleno-dopamine derivatives with different structural parameters were designed. Among these derivatives, F4b, containing two ferrocene units and a tertiary amine, showed in vitro anticancer activity with IC50 = 2.4 ± 0.4 μM for MGC-803 cells, and its in vivo studies suggested effective antitumor activity in mice bearing an MGC-803 tumor xenograft. Mechanistic study revealed that the cytotoxicity of these ferrocenylseleno-dopamine derivatives is mainly related to the Fenton-like reaction under physiological conditions, and the tertiary amine in F4b can facilitate the H2O2 decomposition to generate toxic ˙OH which induces apoptosis through CDK-2 inactivation.

High activity, high selectivity and high biocompatibility BODIPY-pyrimidine derivatives for fluorescence target recognition and evaluation of inhibitory activity

BODIPY-Pyrimidine (BP) is a highly selective, highly active, and highly biocompatible fluorescent drug, which is characterized by its own activity combined with a fluorophore. The combination of pyrimidines with good biological activity and fluorophores to obtain new compounds with both anti-tumor activity and fluorescent targeting probe functions is the focus of this research. In terms of biological activity, in vitro cytotoxicity of the compounds on four human cancer cells (HepG2, HeLa, A-459, and HCT-116) and the human normal cell line L-02 was studied. BP-4 has good antiproliferative activity, and its IC₅₀ values are 19.12 ± 2.29, 13.47 ± 3.80, 18.59 ± 7.42, 14.57 ± 2.44 and 92.48 ± 6.03 μM, respectively. Good biocompatibility with tumor cells can be observed in cell imaging. The anti-tumor mechanism of the compound was further studied by flow cytometry. After BP-2, BP-3 and BP-4 treated HeLa cells, the percentage of apoptotic cells was 19.07%, 22.09% and 27.3%, respectively. The cell cycle study found that, compared with the positive control 5-FU (48.05%), the compounds BP-2, BP-3 and BP-4 all increased the proportion of HeLa cells in the G1 phase, reaching 57.65%, 55.46% and 53.58%, respectively. In vivo bioimaging results show that all three compounds can be targeted and accurately expressed in tumor tissues. In addition, molecular docking analyzes the possible interaction between the compound and the active site of thymidylate synthase.

Facile One-Pot Multicomponent Synthesis of Pyrazolo-Thiazole Substituted Pyridines with Potential Anti-Proliferative Activity: Synthesis, In Vitro and In Silico Studies

Pyrazolothiazole-substituted pyridine conjugates are an important class of heterocyclic compounds with an extensive variety of potential applications in the medicinal and pharmacological arenas. Therefore, herein, we describe an efficient and facile approach for the synthesis of novel pyrazolo-thiazolo-pyridine conjugate 4, via multicomponent condensation. The latter compound was utilized as a base for the synthesis of two series of 15 novel pyrazolothiazole-based pyridine conjugates (5-16). The newly synthesized compounds were fully characterized using several spectroscopic methods (IR, NMR and MS) and elemental analyses. The anti-proliferative impact of the new synthesized compounds 5-13 and 16 was in vitro appraised towards three human cancer cell lines: human cervix (HeLa), human lung (NCI-H460) and human prostate (PC-3). Our outcomes regarding the anti-proliferative activities disclosed that all the tested compounds exhibited cytotoxic potential towards all the tested cell lines with IC₅₀ = 17.50-61.05 µM, especially the naphthyridine derivative 7, which exhibited the most cytotoxic potential towards the tested cell lines (IC₅₀ = 14.62-17.50 µM) compared with the etoposide (IC50 = 13.34-17.15 µM). Moreover, an in silico docking simulation study was performed on the newly prepared compounds within topoisomerase II (3QX3), to suggest the binding mode of these compounds as anticancer candidates. The in silico docking results indicate that compound 7 was a promising lead anticancer compound which possesses high binding affinity toward topoisomerase II (3QX3) protein.

Cinnamide derived pyrimidine-benzimidazole hybrids as tubulin inhibitors: Synthesis, in silico and cell growth inhibition studies

An approach in modern medicinal chemistry to discover novel bioactive compounds is by mimicking diverse complementary pharmacophores. In extension of this strategy, a new class of piperazine-linked cinnamide derivatives of benzimidazole-pyrimidine hybrids have been designed and synthesized. Their in vitro cytotoxicity profiles were explored on selected human cancer cell lines. Specifically, structural comparison of target hybrids with tubulin-DAMA-colchicine and tubulin-nocodazole complexes has exposed a deep position of benzimidazole ring into the αT5 loop. All the synthesized compounds were demonstrated modest to interesting cytotoxicity against different cancer cell lines. The utmost cytotoxicity has shown with an amine linker of benzimidazole-pyrimidine series, with specificity toward A549 (lung cancer) cell line. The most potent compound in this series was 18i, which inhibited cancer cell growth at micromolar concentrations ranging 2.21-7.29 µM. Flow cytometry studies disclosed that 18i inhibited the cells in G2/M phase of cell cycle. The potent antitumor activity of 18i resulted from enhanced microtubule disruption at a similar level as nocodazole on β-tubulin antibody, explored using immunofluorescence staining. The most active compound 18i also inhibited tubulin polymerization with an IC₅₀ of 5.72 ± 0.51 µM. In vitro biological analysis of 18i presented apoptosis induction on A549 cells with triggering of ROS generation and loss of mitochondrial membrane potential, resulting in DNA injury. In addition, 18i displayed impairment in cellular migration and inhibited the colony formation. Notably, the safety profile of most potent compound 18i was revealed by screening against normal human pulmonary epithelial cells (L132: IC₅₀: 69.25 ± 5.95 μM). The detailed binding interactions of 18i with tubulin was investigated by employing molecular docking, superimposition and free energy analyses. Thus remarks made in this study established that pyrimidine-benzimidazole hybrids as a new class of tubulin polymerization inhibitors with significant anticancer activity.

Design, synthesis, and cytotoxic activity of novel 2H-imidazo[1,2-c]pyrazolo[3,4-e]pyrimidine derivatives

In this study, a series of novel 2H-imidazo [1, 2-c] pyrazolo [3, 4-e] pyrimidine derivatives were designed, synthesized, and evaluated for their cytotoxic activities. The in vitro cell growth inhibition assay of the target compounds indicated their selectivity in inhibiting the proliferation of blood tumor cells (K562, U937) and solid tumor cells (HCT116, HT-29). Compound 9b exhibited the highest antiproliferative activities against K562 (IC₅₀ = 5.597 µM) and U937 (IC₅₀ = 3.512 µM). Based on the flow cytometry assays, compound 9b caused obvious induction of cell apoptosis and cell arrest at the S phase. Furthermore, western blot analysis revealed that compound 9b upregulated the expression of Bax, downregulated the levels of Bcl-2, and further activated caspase-3 in K562 cells. Therefore, compound 9b may be a potential anticancer agent that deserves further investigation.

Insight on [1,3]thiazolo[4,5-e]isoindoles as tubulin polymerization inhibitors

A series of [1,3]thiazolo[4,5-e]isoindoles has been synthesized through a versatile and high yielding multistep sequence. Evaluation of the antiproliferative activity of the new compounds on the full NCI human tumor cell line panel highlighted several compounds that are able to inhibit tumor cell proliferation at micromolar-submicromolar concentrations. The most active derivative 11g was found to cause cell cycle arrest at the G2/M phase and induce apoptosis in HeLa cells, following the mitochondrial pathway, making it a lead compound for the discovery of new antimitotic drugs.

Antiproliferative benzothiazoles incorporating a trimethoxyphenyl scaffold as novel colchicine site tubulin polymerisation inhibitors

Tubulin polymerisation inhibitors exhibited an important role in the treatment of patients with prostate cancer. Herein, we reported the medicinal chemistry efforts leading to a new series of benzothiazoles by a bioisosterism approach. Biological testing revealed that compound 12a could significantly inhibit in vitro tubulin polymerisation of a concentration dependent manner, with an IC₅₀ value of 2.87 μM. Immunofluorescence and EBI competition assay investigated that compound 12a effectively inhibited tubulin polymerisation and directly bound to the colchicine-binding site of β-tubulin in PC3 cells. Docking analysis showed that 12a formed hydrogen bonds with residues Tyr357, Ala247 and Val353 of tubulin. Importantly, it displayed the promising antiproliferative ability against C42B, LNCAP, 22RV1 and PC3 cells with IC₅₀ values of 2.81 μM, 4.31 μM, 2.13 μM and 2.04 μM, respectively. In summary, compound 12a was a novel colchicine site tubulin polymerisation inhibitor with potential to treat prostate cancer.

Oxidant/Solvent-Controlled I2-Catalyzed Domino Annulation for Selective Synthesis of 2-Aroylbenzothiazoles and 2-Arylbenzothiazoles under Metal-Free Conditions

A simple and practical domino protocol for the selective synthesis of 2-aroylbenzothiazoles and 2-aryl benzothiazoles catalyzed by I₂ is developed under metal-free conditions. The reaction outcomes are exclusively controlled by the reaction oxidant/medium. With DMSO employed as both the solvent and the oxidant, an oxidation of aromatic methyl ketones takes precedence over the condensation with 2-aminobenzenethiols. On the other hand, when the reaction was carried out in PhNO₂ or in 1,4-dioxane containing PhNO₂, the condensation of aromatic methyl ketones with 2-aminobenzenethiols has priority to form imines which is followed by an oxidation of the methyl group from ketones to afford 2-arylbenzothiazoles as a sole product. The PhNO₂/I₂ co-catalytic system is proposed first time.