Third-generation CDK inhibitors: A review on the synthesis and binding modes of Palbociclib, Ribociclib and Abemaciclib

Targeting cyclin-dependent kinases: From pocket specificity to drug selectivity

The development of selective modulators of cyclin-dependent kinases (CDKs), a kinase family with numerous members and functional variations, is a significant preclinical challenge. Recent advancements in crystallography have revealed subtle differences in the highly conserved CDK pockets. Exploiting these differences has proven to be an effective strategy for achieving excellent drug selectivity. While previous reports briefly discussed the structural features that lead to selectivity in individual CDK members, attaining inhibitor selectivity requires consideration of not only the specific structures of the target CDK but also the features of off-target members. In this review, we summarize the structure-activity relationships (SARs) that influence selectivity in CDK drug development and analyze the pocket features that lead to selectivity using molecular-protein binding models. In addition, in recent years, novel CDK modulators have been developed, providing more avenues for achieving selectivity. These cases were also included. We hope that these efforts will assist in the development of novel CDK drugs.

Investigation of differentially expressed genes related to cellular senescence between high-risk and non-high-risk groups in neuroblastoma

Object

This study aims to identify differentially expressed genes (DEGs) between high-risk and non-high-risk groups in neuroblastoma (NB), construct a prognostic model, and establish a risk score formula.

Materials and methods

The NB dataset GSE49710 (n = 498) from the GEO database served as the training cohort to select DEGs between high-risk and non-high-risk NB groups. Cellular senescence-related genes were obtained from the Aging Atlas database. Intersection genes from both datasets were identified as key genes of cellular senescence-related genes (SRGs). A prognostic model was constructed using Univariate Cox regression analysis and the Lasso algorithm with SRGs. Validation was performed using the E-MTAB-8248 cohort (n = 223). The expression levels of AURKA and CENPA were evaluated via RT-qPCR in two clinical NB sample groups.

Results

Eight SRGs were identified, and a prognostic model comprising five genes related to cellular senescence was constructed. AURKA and CENPA showed significant expression in clinical samples and were closely associated with cellular senescence.

Conclusion

The prognostic model consisted with five cellular senescence related genes effectively predicts the prognosis of NB patients. AURKA and CENPA represent promising targets in NB for predicting cellular senescence, offering potential insights for NB therapy.

Exploring the binding characteristics of bovine serum albumin with CDK4/6 inhibitors Ribociclib: Multi-spectral analysis and molecular simulation studies

Ribociclib (RIB), a tyrosine kinase inhibitor, exhibits promising antitumor efficacy and controlled toxicity in HR+/HER2- breast cancer patients, which is closely related to the binding with plasma proteins. This study utilized a combination of spectroscopic techniques including UV spectroscopy, fluorescence spectroscopy, and circular dichroism (CD) as well as molecular docking and molecular dynamic simulation to clarify the binding mechanism between bovine serum albumin (BSA) and RIB. The findings demonstrated that RIB produced a 1:1 stoichiometric complex with BSA, which quenched BSA's fluorescence in the manner of the static quenching mechanism. Site labelling experiments pinpointed Site III on BSA as the primary binding site for RIB, a finding validated by molecular docking. Van der Waals forces and hydrogen bonding interactions as key drivers in the formation of RIB-BSA complexes, a conclusion supported by molecular docking. Molecular simulation studies suggested that the insertion of RIB into the hydrophobic cavity (Site III) of BSA induced subtle conformational changes in the BSA protein, and CD measurements confirmed alterations in BSA secondary structure content. Synchronous and three-dimensional fluorescence spectroscopy further demonstrated that RIB decreased the hydrophobicity of the microenvironment surrounding tyrosine and tryptophan residues. These findings offer valuable insights into the pharmacokinetics and structural modifications of RIB.

Novel indolyl 1,2,4-triazole derivatives as potential anti-proliferative agents: in silico studies, synthesis, and biological evaluation

A new series of indolyl 1,2,4-triazole scaffolds was designed, synthesised, and biologically evaluated for their inhibitory activity against both CDK4 and CDK6. The results ranged from 0.049 μM to 3.031 μM on CDK4 and from 0.075 μM to 1.11 μM on CDK6 when compared to staurosporine, with IC50 values of 1.027 and 0.402 μM, respectively. Moreover, all compounds were tested for their cytotoxicity against two breast cancer cell lines, MCF-7 and MDA-MB-231. All of the synthesised compounds showed promising anti-proliferative activity, with two compounds Vf (IC50 = 2.91 and 1.914 μM, respectively) and Vg (IC50 = 0.891 and 3.479 μM, respectively) having potent cytotoxic activity in comparison to the reference staurosporine (IC50 = 3.144 and 4.385 μM, respectively). Vf and Vg were also found to significantly induce apoptosis to 45.33% and 37.26% (control = 1.91%) where Vf arrested the cell cycle at the S phase while Vg arrested the cycle at the G0/G1 phase. The binding mode and interactions of all compounds were studied and found to mimic those of the FDA approved CDK4/6 inhibitor palbociclib that was used as a reference throughout the study.

Facilitating the development of molecular glues: Opportunities from serendipity and rational design

Molecular glues can specifically induce interactions between two or more proteins to modulate biological functions and have been proven to be a powerful therapeutic modality in drug discovery. It plays a variety of vital roles in several biological processes, such as complex stabilization, interactome modulation and transporter inhibition, thus enabling challenging therapeutic targets to be druggable. Most known molecular glues were identified serendipitously, such as IMiDs, auxin, and rapamycin. In recent years, more rational strategies were explored with the development of chemical biology and a deep understanding of the interaction between molecular glues and proteins, which led to the rational discovery of several molecular glues. Thus, in this review, we aim to highlight the discovery strategies of molecular glues from three aspects: serendipitous discovery, screening methods and rational design principles. We expect that this review will provide a reasonable reference and insights for the discovery of molecular glues.

Synthetic Approaches to Piperazine-Containing Drugs Approved by FDA in the Period of 2011-2023

The piperazine moiety is often found in drugs or in bioactive molecules. This widespread presence is due to different possible roles depending on the position in the molecule and on the therapeutic class, but it also depends on the chemical reactivity of piperazine-based synthons, which facilitate its insertion into the molecule. In this paper, we take into consideration the piperazine-containing drugs approved by the Food and Drug Administration between January 2011 and June 2023, and the synthetic methodologies used to prepare the compounds in the discovery and process chemistry are reviewed.

Insights into the selectivity of a brain-penetrant CDK4/6 vs CDK1/2 inhibitor for glioblastoma used in multiple replica molecular dynamics simulations

Cyclin dependent kinases (CDKs) play an important role in cell cycle regulation and their dysfunction is associated with many cancers. That is why CDKs have been attractive targets for the treatment of cancer. Glioblastoma is a cancer caused by the aberrant expression of CDK4/6, so exploring the mechanism of the selection of CDK4/6 toward inhibitors relative to the other family members CDK1/2 is essential. In this work, multiple replica molecular dynamics (MRMD) simulations, principal component analysis (PCA), free energy landscapes (FELs), molecular mechanics Poisson-Boltzmann/Generalized Born surface area (MM-PB/GBSA) and other methods were integrated to decipher the selectively binding mechanism of the inhibitor N1J to CDK4/6 and CDK1/2. Molecular electrostatic potential (MESP) analysis provides an explanation for the N1J selectivity. Residue-based free energy decomposition reveals that most of the hot residues are located at the same location of CDKs proteins, but the different types of residues in different proteins cause changes in binding energy, which is considered as a potential developmental direction to improve the selectivity of inhibitors to CDK4/6. These results provide insights into the source of inhibitor and CDK4/6 selectivity for the future development of more selective inhibitors.Communicated by Ramaswamy H. Sarma.

Repurposing of approved drugs for targeting CDK4/6 and aromatase protein using molecular docking and molecular dynamics studies

Breast cancer is a leading cause of cancer-related morbidity and mortality worldwide, with the highest incidence among women. Among the various subtypes of breast cancer, estrogen-receptor positive (ER+) is the most diagnosed. Estrogen upregulates cyclin D1, which in turn promotes the activity of CDK4/6 and facilitates cell cycle progression. To address this, the first-line treatment for ER+ breast cancer focuses on inhibiting estrogen production by targeting aromatase, the enzyme responsible for the rate-limiting step in estrogen synthesis. Thus, combining CDK4/6 inhibitors with aromatase inhibitors has emerged as a crucial treatment strategy for this type of breast cancer. This approach effectively suppresses estrogen biosynthesis and controls uncontrolled cell proliferation, significantly improving overall survival rates and delayed disease progression. This study aimed to identify compounds that are likely to inhibit CDK4/6 and aromatase simultaneously by using a structure-based drug design strategy. 12,432 approved and investigational drugs were prepared and docked into the active site of CDK6 using HTVS and XP docking modes of Glide resulting in 277 compounds with docking scores ≤ -7 kcal/mol. These compounds were docked into aromatase enzyme using XP mode to give seven drugs with docking scores≤ -6.001 kcal/mol. Furthermore, the shortlisted drugs were docked against CDK4 showing docking scores ranging from -3.254 to -8.254 kcal/mol. Moreover, MM-GBSA for the top seven drugs was calculated. Four drugs, namely ellagic acid, carazolol, dantron, and apomorphine, demonstrated good binding affinity to all three protein targets CDK4/6 and aromatase. Specifically, they exhibited favourable binding free energy with CDK6, with values of -51.92, -53.90, -50.22, and -60.97 kcal/mol, respectively. Among these drugs, apomorphine displayed the most favourable binding free energy with all three protein targets. To further evaluate the stability of the interaction, apomorphine was subjected to a 100 ns molecular dynamics simulation with CDK6. The results indicated the formation of a stable ligand-protein complex. While the results obtained from the MM-GBSA calculation of the binding free energies of the MD conformations of apomorphine showed less favourable binding free energy compared to that obtained post-docking. All these computational findings will provide better structural insight for the development of CDK4/6 and aromatase multi-target inhibitors.

The Therapeutic Potential of CDK4/6 Inhibitors, Novel Cancer Drugs, in Kidney Diseases

Inflammation is a crucial pathological feature in cancers and kidney diseases, playing a significant role in disease progression. Cyclin-dependent kinases CDK4 and CDK6 not only contribute to cell cycle progression but also participate in cell metabolism, immunogenicity and anti-tumor immune responses. Recently, CDK4/6 inhibitors have gained approval for investigational treatment of breast cancer and various other tumors. Kidney diseases and cancers commonly exhibit characteristic pathological features, such as the involvement of inflammatory cells and persistent chronic inflammation. Remarkably, CDK4/6 inhibitors have demonstrated impressive efficacy in treating non-cancerous conditions, including certain kidney diseases. Current studies have identified the renoprotective effect of CDK4/6 inhibitors, presenting a novel idea and potential direction for treating kidney diseases in the future. In this review, we briefly reviewed the cell cycle in mammals and the role of CDK4/6 in regulating it. We then provided an introduction to CDK4/6 inhibitors and their use in cancer treatment. Additionally, we emphasized the importance of these inhibitors in the treatment of kidney diseases. Collectively, growing evidence demonstrates that targeting CDK4 and CDK6 through CDK4/6 inhibitors might have therapeutic benefits in various cancers and kidney diseases and should be further explored in the future.

Quinazolinone derivatives as new potential CDK4/6 inhibitors, apoptosis inducers and radiosensitizers for breast cancer

Background: Targeting CDK4/6 has advanced breast cancer treatment. Herein, new quinazolinones were synthesized with acetamide linkers as potential anti-breast cancer agents. Methods & results: In vitro cytotoxic evaluation on human breast cancer cell lines (MCF7 and MDA-MB-231) identified 1,3-benzodioxole (5d) to be of the highest potency. It showed good inhibitory activity on CDK4/6. Compound 5d arrested the cell cycle at the G1-phase, caused induction of early and late apoptosis in an Annexin V-FITC assay, led to an increase in the level of caspase-3 and upregulated Bax expression and downregulated Bcl-2 in MCF7 cells. Compound 5d showed good radiosensitizing activity when combined with a single dose of 8-Gy γ-radiation. Conclusion: This study introduces quinazolinone scaffolds as new CDK4/6 inhibitors for breast cancer.

Applications of palladium-catalyzed C-N cross-coupling reactions in pharmaceutical compounds

C-N cross-coupling bond formation reactions have become valuable approaches to synthesizing anilines and their derivatives, known as important chemical compounds. Recent developments in this field have focused on versatile catalysts, simple operation methods, and green reaction conditions. This review article presents an overview of C-N cross-coupling reactions in pharmaceutical compound synthesis reports. Selected examples of N-arylation reactions of various nitrogen-based compounds and aryl halides are defined for preparing pharmaceutical molecules.

Rational Chemical Design of Molecular Glue Degraders

Targeted protein degradation with molecular glue degraders has arisen as a powerful therapeutic modality for eliminating classically undruggable disease-causing proteins through proteasome-mediated degradation. However, we currently lack rational chemical design principles for converting protein-targeting ligands into molecular glue degraders. To overcome this challenge, we sought to identify a transposable chemical handle that would convert protein-targeting ligands into molecular degraders of their corresponding targets. Using the CDK4/6 inhibitor ribociclib as a prototype, we identified a covalent handle that, when appended to the exit vector of ribociclib, induced the proteasome-mediated degradation of CDK4 in cancer cells. Further modification of our initial covalent scaffold led to an improved CDK4 degrader with the development of a but-2-ene-1,4-dione ("fumarate") handle that showed improved interactions with RNF126. Subsequent chemoproteomic profiling revealed interactions of the CDK4 degrader and the optimized fumarate handle with RNF126 as well as additional RING-family E3 ligases. We then transplanted this covalent handle onto a diverse set of protein-targeting ligands to induce the degradation of BRD4, BCR-ABL and c-ABL, PDE5, AR and AR-V7, BTK, LRRK2, HDAC1/3, and SMARCA2/4. Our study undercovers a design strategy for converting protein-targeting ligands into covalent molecular glue degraders.

Targeting Breast Cancer: An Overlook on Current Strategies

Breast cancer (BC) is one of the most widely diagnosed cancers and a leading cause of cancer death among women worldwide. Globally, BC is the second most frequent cancer and first most frequent gynecological one, affecting women with a relatively low case-mortality rate. Surgery, radiotherapy, and chemotherapy are the main treatments for BC, even though the latter are often not aways successful because of the common side effects and the damage caused to healthy tissues and organs. Aggressive and metastatic BCs are difficult to treat, thus new studies are needed in order to find new therapies and strategies for managing these diseases. In this review, we intend to give an overview of studies in this field, presenting the data from the literature concerning the classification of BCs and the drugs used in therapy for the treatment of BCs, along with drugs in clinical studies.

Comparative docking studies of drugs and phytocompounds for emerging variants of SARS-CoV-2

In the last three years, COVID-19 has impacted the world with back-to-back waves leading to devastating consequences. SARS-CoV-2, the causative agent of COVID-19, was first detected in 2019 and since then has spread to 228 countries. Even though the primary focus of research groups was diverted to fight against COVID-19, yet no dedicated drug has been developed to combat the emergent life-threatening medical conditions. In this study, 35 phytocompounds and 43 drugs were investigated for comparative docking analysis. Molecular docking and virtual screening were performed against SARS-CoV-2 spike glycoprotein of 13 variants using AutoDock Vina tool 1.5.6 and Discovery Studio, respectively, to identify the most efficient drugs. Selection of the most suitable compounds with the best binding affinity was done after screening for toxicity, ADME (absorption, distribution, metabolism and excretion) properties and drug-likeliness. The potential candidates were discovered to be Liquiritin (binding affinities ranging between -7.0 and -8.1 kcal/mol for the 13 variants) and Apigenin (binding affinities ranging between -6.8 and -7.3 kcal/mol for the 13 variants) based on their toxicity and consistent binding affinity with the Spike protein of all variants. The stability of the protein-ligand complex was determined using Molecular dynamics (MD) simulation of Apigenin with the Delta plus variant of SARS-CoV-2. Furthermore, Liquiritin and Apigenin were also found to be less toxic than the presently used drugs and showed promising results based on in silico studies, though, confirmation using in vitro studies is required. This in-depth comparative investigation suggests potential drug candidates to fight against SARS-CoV-2 variants.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03450-6.

NOTCH Signaling Limits the Response of Low-Grade Serous Ovarian Cancers to MEK Inhibition

Low-grade serous ovarian cancer (LGSOC) is a rare subtype of epithelial ovarian cancer with high fatality rates in advanced stages due to its chemoresistant properties. LGSOC is characterized by activation of MAPK signaling, and recent clinical trials indicate that the MEK inhibitor (MEKi) trametinib may be a good treatment option for a subset of patients. Understanding MEKi-resistance mechanisms and subsequent identification of rational drug combinations to suppress resistance may greatly improve LGSOC treatment strategies. Both gain-of-function and loss-of-function CRISPR-Cas9 genome-wide libraries were used to screen LGSOC cell lines to identify genes that modulate the response to MEKi. Overexpression of MAML2 and loss of MAP3K1 were identified, both leading to overexpression of the NOTCH target HES1, which has a causal role in this process as its knockdown reversed MEKi resistance. Interestingly, increased HES1 expression was also observed in selected spontaneous trametinib-resistant clones, next to activating MAP2K1 (MEK1) mutations. Subsequent trametinib synthetic lethality screens identified SHOC2 downregulation as being synthetic lethal with MEKis. Targeting SHOC2 with pan-RAF inhibitors (pan-RAFis) in combination with MEKi was effective in parental LGSOC cell lines, in MEKi-resistant derivatives, in primary ascites cultures from patients with LGSOC, and in LGSOC (cell line-derived and patient-derived) xenograft mouse models. We found that the combination of pan-RAFi with MEKi downregulated HES1 levels in trametinib-resistant cells, providing an explanation for the synergy that was observed. Combining MEKis with pan-RAFis may provide a promising treatment strategy for patients with LGSOC, which warrants further clinical validation.

Design, synthesis and biological evaluation of pteridine-7(8H)-one derivatives as potent and selective CDK4/6 inhibitors

Cyclin-dependent kinases play an important role in the regulation of cell cycle and transcription. Selective CDK4/6 inhibitors have been demonstrated to be effective in the treatment of cancer. In this article, we described the design and synthesis of a series of pteridine-7(8H)-one derivatives as dual CDK4/6 inhibitors. Among them, the most promising compound L2 exhibited significant inhibitory activity against CDK4 and CDK6 with IC₅₀ values of 16.7 nM and 30.5 nM respectively and showed excellent selectivity to CDK1/2/7/9. Moreover, compound L2 displayed potent antiproliferative activities at low digital micromolar range via inducing apoptosis in breast and colon cancer cells. In all, we developed a new series of pteridine-7(8H)-one derivatives which exhibited promising antitumor activities as selective CDK4/6 inhibitors.

Human hair rich in pyridinic nitrogen-base DNA biosensor for direct electrochemical monitoring of palbociclib-DNA interaction

Carbon material derived from the waste-based biomass human hair (H), which is naturally rich in pyridinic nitrogen, provides a significant benefit in biosensor applications with its dominant conductivity character. The carbon material was synthesized from human hair waste by the hydrothermal carbonization (HTC) method, which is a promising green synthesis. A morphological characterization of the carbon materials was performed. In this study, H and amine-functionalized multi-walled carbon nanotubes (NH₂-MWCNT) were combined for the first time as a modifier, which enhanced the glassy carbon electrode (GCE) surface area for deoxyribonucleic acid (DNA) biosensor studies. Palbociclib (PLB) is clinically used in the treatment of breast cancer. The novel electrochemical nanobiosensor was used to investigate the dsDNA-PLB interaction to evaluate the possibility that PLB causes conformational changes in DNA structure and/or oxidative damage. The interaction was conducted based on the voltammetric signals of deoxyguanosine (dGuo) and deoxyadenosine (dAdo) by differential pulse voltammetry (DPV) on a bare and H + NH₂-MWCNT modified GCE. The proposed analytical method was applied to a pharmaceutical dosage form with a satisfactory recovery of 98.25 %. The nanobiosensor was tested in the presence of some interfering agents. The binding mechanism of dsDNA-PLB was also evaluated by spectroscopic and theoretical calculations.

Off the Clock: the Non-canonical Roles of Cyclin-Dependent Kinases in Neural and Glioma Stem Cell Self-Renewal

Glioma stem cells (GSCs) are thought to drive growth and therapy resistance in glioblastoma (GBM) by "hijacking" at least a subset of signaling pathways active in normal neural stem cells (NSCs). Though the origins of GSCs still remain elusive, uncovering the mechanisms of self-renewing division and cell differentiation in normal NSCs has shed light on their dysfunction in GSCs. However, the distinction between self-renewing division pathways utilized by NSC and GSC becomes critical when considering options for therapeutically targeting signaling pathways that are specifically active or altered in GSCs. It is well-established that cyclin-dependent kinases (CDKs) regulate the cell cycle, yet more recent studies have shown that CDKs also play important roles in the regulation of neuronal survival, metabolism, differentiation, and self-renewal. The intimate relationship between cell cycle regulation and the cellular programs that determine self-renewing division versus cell differentiation is only beginning to be understood, yet seems to suggest potential differential vulnerabilities in GSCs. In this timely review, we focus on the role of CDKs in regulating the self-renewal properties of normal NSCs and GSCs, highlighting novel opportunities to therapeutically target self-renewing signaling pathways specifically in GBM.

One-step synthesis of PdCu@Ti3C2 with high catalytic activity in the Suzuki-Miyaura coupling reaction

Owing to their enhanced catalytic stability and cyclability, two-dimensional (2D) material-supported Pd-based bimetallic alloys have promising applications for catalytic reactions. Furthermore, the alloying strategy can effectively reduce costs and improve catalytic performance. In this paper, we report a one-step reduction method to synthesize a novel heterogeneous catalyst, PdCu@Ti₃C₂, with good catalytic performance. The composition and structure of the as-prepared catalyst were characterized by inductively coupled plasma-mass spectrometry (ICP-MS), scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). The catalyst particles, which were identified as a PdCu bimetallic alloy, exhibited good dispersion on the substrate. The performance of the catalyst in the Suzuki-Miyaura coupling reaction was studied, and the results showed that PdCu@Ti₃C₂ had excellent catalytic activity, similar to that of homogeneous Pd catalysts such as Pd(PPh₃)₄. Moreover, the prepared catalyst could be reused at least 10 times in the Suzuki-Miyaura coupling reaction with high yield.

Precision Medicine Highlights Dysregulation of the CDK4/6 Cell Cycle Regulatory Pathway in Pediatric, Adolescents and Young Adult Sarcomas

Simple Summary

This review provides an overview of clinical features and current therapies in children, adolescents, and young adults (AYA) with sarcoma. It highlights the basic and clinical findings on the cyclin-dependent kinases 4 and 6 (CDK4/6) cell cycle regulatory pathway in the context of the precision medicine-based molecular profiles of the three most common types of pediatric and AYA sarcomas—osteosarcoma (OS), rhabdomyosarcoma (RMS), and Ewing sarcoma (EWS).

Abstract

Despite improved therapeutic and clinical outcomes for patients with localized diseases, outcomes for pediatric and AYA sarcoma patients with high-grade or aggressive disease are still relatively poor. With advancements in next generation sequencing (NGS), precision medicine now provides a strategy to improve outcomes in patients with aggressive disease by identifying biomarkers of therapeutic sensitivity or resistance. The integration of NGS into clinical decision making not only increases the accuracy of diagnosis and prognosis, but also has the potential to identify effective and less toxic therapies for pediatric and AYA sarcomas. Genome and transcriptome profiling have detected dysregulation of the CDK4/6 cell cycle regulatory pathway in subpopulations of pediatric and AYA OS, RMS, and EWS. In these patients, the inhibition of CDK4/6 represents a promising precision medicine-guided therapy. There is a critical need, however, to identify novel and promising combination therapies to fight the development of resistance to CDK4/6 inhibition. In this review, we offer rationale and perspective on the promise and challenges of this therapeutic approach.

The piperazine scaffold for novel drug discovery efforts: the evidence to date

INTRODUCTION

. Piperazine is a structural element present in drugs belonging to various chemical classes and used for numerous different therapeutic applications; it has been considered a privileged scaffold for drug design.

AREAS COVERED

The authors have searched examples of piperazine-containing compounds among drugs recently approved by the FDA, and in some research fields (nicotinic receptor modulators, compounds acting against cancer and bacterial multi-drug resistance), looking in particular to the design behind the insertion of this moiety.

EXPERT OPINION

Piperazine is widely used due to its peculiar characteristics, such as solubility, basicity, chemical reactivity, and conformational properties. This moiety has represented an important tool to modulate pharmacokinetic and pharmacodynamic properties of drugs.

Cellular senescence in neuroblastoma

Neuroblastoma is a tumour that arises from the sympathoadrenal lineage occurring predominantly in children younger than five years. About half of the patients are diagnosed with high-risk tumours and undergo intensive multi-modal therapy. The success rate of current treatments for high-risk neuroblastoma is disappointingly low and survivors suffer from multiple therapy-related long-term side effects. Most chemotherapeutics drive cancer cells towards cell death or senescence. Senescence has long been considered to represent a terminal non-proliferative state and therefore an effective barrier against tumorigenesis. This dogma, however, has been challenged by recent observations that infer a much more dynamic and reversible nature for this process, which may have implications for the efficacy of therapy-induced senescence-oriented treatment strategies. Neuroblastoma cells in a dormant, senescent-like state may escape therapy, whilst their senescence-associated secretome may promote inflammation and invasiveness, potentially fostering relapse. Conversely, due to its distinct molecular identity, senescence may also represent an opportunity for the development of novel (combination) therapies. However, the limited knowledge on the molecular dynamics and diversity of senescence signatures demands appropriate models to study this process in detail. This review summarises the molecular knowledge about cellular senescence in neuroblastoma and investigates current and future options towards therapeutic exploration.

Preclinical Head and Neck Squamous Cell Carcinoma Models for Combined Targeted Therapy Approaches

This study aimed to refine combined targeted approaches on well-characterized, low-passage tumor models. Upon in vivo xenografting in immunodeficient mice, three cell lines from locally advanced or metastatic HNSCC were established. Following quality control and basic characterization, drug response was examined after therapy with 5-FU, Cisplatin, and cyclin-dependent kinase inhibitors (abemaciclib, THZ1). Our cell lines showed different in vitro growth kinetics, morphology, invasive potential, and radiosensitivity. All cell lines were sensitive to 5-FU, Cisplatin, and THZ1. One cell line (HNSCC48 P0 M1) was sensitive to abemaciclib. Here, Cyto-FISH revealed a partial CDKN2a deletion, which resulted from a R58* mutation. Moreover, this cell line demonstrated chromosome 12 polysomy, accompanied by an increase in CDK4-specific copy numbers. In HNSCC16 P1 M1, we likewise identified polysomy-associated CDK4-gains. Although not sensitive to abemaciclib per se, the cell line showed a G1-arrest, an increased number of acidic organelles, and a swollen structure. Notably, intrinsic resistance was conquered by Cisplatin because of cMYC and IDO-1 downregulation. Additionally, this Cisplatin-CDKI combination induced HLA-ABC and PD-L1 upregulation, which may enhance immunogenicity. Performing functional and molecular analysis on patient-individual HNSCC-models, we identified CDK4-gains as a biomarker for abemaciclib response prediction and describe an approach to conquer intrinsic CDKI resistance.

From Structure Modification to Drug Launch: A Systematic Review of the Ongoing Development of Cyclin-Dependent Kinase Inhibitors for Multiple Cancer Therapy

Herein, we discuss more than 50 cyclin-dependent kinase (CDK) inhibitors that have been approved or have undergone clinical trials and their therapeutic application in multiple cancers. This review discusses the design strategies, structure-activity relationships, and efficacy performances of these selective or nonselective CDK inhibitors. The theoretical basis of early broad-spectrum CDK inhibitors is similar to the scope of chemotherapy, but because their toxicity is greater than the benefit, there is no clinical therapeutic window. The notion that selective CDK inhibitors have a safer therapeutic potential than pan-CDK inhibitors has been widely recognized during the research process. Four CDK4/6 inhibitors have been approved for the treatment of breast cancer or for prophylactic administration during chemotherapy to protect bone marrow and immune system function. Furthermore, the emerging strategies in the field of CDK inhibitors are summarized briefly, and CDKs continue to be widely pursued as emerging anticancer drug targets for drug discovery.

Ribociclib-Loaded Ethylcellulose-Based Nanosponges: Formulation, Physicochemical Characterization, and Cytotoxic Potential against Breast Cancer

In the present study, ribociclib-loaded nanosponges (RCNs) composed of ethylcellulose and polyvinyl alcohol were developed using an emulsion-solvent evaporation method. Preliminary evaluations of the developed RCNs (RCN1 to RCN7) were performed in terms of size, polydispersity index (PDI), zeta potential (ZP), entrapment efficiency (EE), and drug loading (DL), which allowed us to select the optimized formulation. RCN3 was selected as the optimized carrier system with particle size ( $363.5\pm 4.8\text{nm}$ ), PDI ( $0.292\pm 0.012$ ), zeta potential ( $-18.5\pm 0.05\text{mV}$ ), EE ( $81.35\pm 1.64\%$ ), and DL ( $21.96\pm 0.28\%$ ). Further, the optimized nanosponges (RCN3) were subjected to FTIR, XRD, DSC, and SEM studies, and results confirmed the proper encapsulation of the drug within the porous polymeric matrix. In vitro drug release studies showed that the drug release was significantly enhanced with a maximum drug release through RCN3 formulation ( $81.85\pm 0.37\%$ ) and followed the Higuchi model. Moreover, the RCN3 system showed greater cytotoxicity than free ribociclib (RC) against MDA-MB-231 and MCF-7 breast cancer cell lines. The percentage of apoptosis induced by RCN3 was found significantly higher than that of free RC ( $p<0.05$ ). Overall, ribociclib-loaded ethylcellulose nanosponges could be a potential nanocarrier to enhance the effectiveness of ribociclib in breast cancer treatment.

Cyclin-dependent Kinases 4/6 Inhibitors in Neuroendocrine Neoplasms: from Bench to Bedside

PURPOSE OF REVIEW

Cyclin-dependent kinases (CDKs) are key regulators that play an important role in cell division. Palbociclib, ribociclib and abemaciclib showed significant antitumor activity in several malignancies and, recently, also a myeloprotective effect for trilaciclib when added to chemotherapy. The purpose of this review is to highlight the current evidence for CDK4/6 inhibitors in neuroendocrine neoplasms (NENs).

RECENT FINDINGS

Preclinical results showed a promising antitumor activity of CDK4/6 inhibitors in neuroendocrine tumors (NETs), but so far, the very few small clinical trials did not show a strong impact on progression free survival (PFS) and objective response in NETs. Meanwhile, the CDK4/6 inhibitor trilaciclib revealed significant effects in reducing chemotherapy-induced myelosuppression in small cell lung cancer (SCLC). Up to date, CDK4/6 inhibitors are still considered investigational in NETs as antitumor agents, whereas trilaciclib can be used in the routine clinical practice in extensive stage SCLC patients for reducing myelotoxicity of standard chemotherapy.

Kinases as Potential Therapeutic Targets for Anti-coronaviral Therapy

The global coronavirus disease-19 (COVID-19) has affected more than 140 million and killed more than 3 million people worldwide as of April 20, 2021. The novel human severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has been identified as an etiological agent for COVID-19. Several kinases have been proposed as possible mediators of multiple viral infections, including life-threatening coronaviruses like SARS-CoV-1, Middle East syndrome coronavirus (MERS-CoV), and SARS-CoV-2. Viral infections hijack abundant cell signaling pathways, resulting in drastic phosphorylation rewiring in the host and viral proteins. Some kinases play a significant role throughout the viral infection cycle (entry, replication, assembly, and egress), and several of them are involved in the virus-induced hyperinflammatory response that leads to cytokine storm, acute respiratory distress syndrome (ARDS), organ injury, and death. Here, we highlight kinases that are associated with coronavirus infections and their inhibitors with antiviral and potentially anti-inflammatory, cytokine-suppressive, or antifibrotic activity.

Discovery of novel and orally bioavailable CDK 4/6 inhibitors with high kinome selectivity, low toxicity and long-acting stability for the treatment of multiple myeloma

Multiple myeloma (MM) ranks second in malignant hematopoietic cancers, and the most common anti-MM drugs easily generate resistance. CDK4/6 have been validated to play determinant roles in MM, but no remarkable progress has been obtained from clinical trials of CDK4/6 inhibitors for MM. To discover novel CDK6 inhibitors with better potency and high druggability, structure-based virtual screening was conducted to identify compound 10. Further chemical optimization afforded a better derivative, compound 32, which exhibited strong inhibition of CDK4/6 and showed high selectivity over 360+ kinases, including homologous CDKs. The in vivo evaluation demonstrated that compound 32 possessed low toxicity (LD₅₀ > 10,000 mg/kg), favorable bioavailability (F% = 51%), high metabolic stability (t_1/2 > 24 h) and strong anti-MM potency. In summary, we discovered a novel CDK4/6 inhibitor bearing favorable drug-like properties and offered a great candidate for MM preclinical studies.

Pyrrolo[2,1-f][1,2,4]triazine: a promising fused heterocycle to target kinases in cancer therapy

Cancer is the second leading cause of death worldwide responsible for about 10 million deaths per year. To date several approaches have been developed to treat this deadly disease including surgery, chemotherapy, radiation therapy, hormonal therapy, targeted therapy, and synthetic lethality. The targeted therapy refers to targeting only specific proteins or enzymes that are dysregulated in cancer rather than killing all rapidly dividing cells, has gained much attention in the recent past. Kinase inhibition is one of the most successful approaches in targeted therapy. As of 30 March 2021, FDA has approved 65 small molecule protein kinase inhibitors and most of them are for cancer therapy. Interestingly, several kinase inhibitors contain one or more fused heterocycles as part of their structures. Pyrrolo[2,1-f][1,2,4]triazine is one the most interesting fused heterocycle that is an integral part of several kinase inhibitors and nucleoside drugs viz. avapritinib and remdesivir. This review articles focus on the recent advances made in the development of kinase inhibitors containing pyrrolo[2,1-f][1,2,4]triazine scaffold.

Identification of 3, 4-disubstituted pyridine derivatives as novel CDK8 inhibitors

Selective inhibition of cyclin-dependent kinase 8 (CDK8) has been recently regarded as a potential approach for cancer therapy. A series of novel CDK8 inhibitors with the pyridine core was identified via scaffold hopping from the known CDK8 inhibitor A-7. The new inhibitors were designed to improve the ligand efficiency so as to enhance drug-likeness. Most of the compounds showed significant inhibition against CDK8/cyclin C, and the most active compounds (5d, 5e and 7') displayed IC50 values of 2.4 nM, 5.0 nM and 7.7 nM, respectively. Preliminary kinase profiling of selected compounds against a panel of kinases from different families indicated that this compound class might selectively inhibit CDK8 as well as its paralog CDK19. Some compounds exhibited cellular activity in both MTT and SRB assays against a variety of tumor cells, including HCT-116, A549, MDA-MB-231, KB, KB-VIN and MCF-7. Further flow cytometry analysis revealed a dose-dependent G2/M phase arrest in MDA-MB-231 cells treated with compounds 6'a, 6'b, 6'j and 6'k. In addition, compound 6'k demonstrated moderate antitumor efficacy in HCT-116 mouse models, although unfavorable pharmacokinetic profiles were suggested by preliminary study in mice. The results provided a new structural prototype for the search of selective CDK8 inhibitors as antitumor agents.

Small Molecule Kinase Inhibitor Drugs (1995-2021): Medical Indication, Pharmacology, and Synthesis

The central role of dysregulated kinase activity in the etiology of progressive disorders, including cancer, has fostered incremental efforts on drug discovery programs over the past 40 years. As a result, kinase inhibitors are today one of the most important classes of drugs. The FDA approved 73 small molecule kinase inhibitor drugs until September 2021, and additional inhibitors were approved by other regulatory agencies during that time. To complement the published literature on clinical kinase inhibitors, we have prepared a review that recaps this large data set into an accessible format for the medicinal chemistry community. Along with the therapeutic and pharmacological properties of each kinase inhibitor approved across the world until 2020, we provide the synthesis routes originally used during the discovery phase, many of which were only available in patent applications. In the last section, we also provide an update on kinase inhibitor drugs approved in 2021.

Synthesis and cytotoxic evaluation of some novel 3-[2-(2-phenyl-thiazol-4-yl)-ethyl]-3H-pyrido[2,3-d]pyrimidin-4-one derivatives

Background and purpose

Pyridopyrimidine and its derivatives have a variety of chemical and biological significances. Thiazole-containing compounds have also been reported to have a wide range of biological activities. Due to the valuable cytotoxic effects of both thiazole and pyridopyrimidinone derivatives, a series of pyridopyrimidinone-thiazole hybrids were synthesized in the present study.

Experimental approach

Briefly, different acyl chlorides were reacted with 2-amino nicotinic acid followed by anhydride acetic to give the corresponding pyridobenzoxazinones. The aminothiazole derivative G was also prepared via a multistep procedure and incorporated into the benzoxazinones to furnish the target pyridopyrimidinone, K1-K5. Furthermore, the cytotoxic activity of the final compounds was determined against MCF-7 and HeLa cell lines using MTT assay.

Findings/Results

The results indicated that aromatic substitution on C2 of pyridopyrimidine nucleus was in favor of cytotoxic activity on both cell lines, of which, compound K5 bearing a chlorophenyl group showed the highest cytotoxicity.

Conclusion and implications

The results of the present study are valuable in terms of synthesis of hybrid molecules and also cytotoxic evaluations which can be useful for future investigations about the design of novel pyridopyrimidinone-thiazole hybrids possessing better cytotoxic activities.

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.

CDK4/6 inhibitors: a brief overview and prospective research directions

The discovery of cyclin-dependent kinases (CDK) and their mechanism in regulating the cell cycle process was considered a game-changer in cancer therapy. Cell cycle arrest and apoptosis were both triggered by their inhibition. The CDK4/6 complex acts as a checkpoint during the cell cycle transition from cell growth (G1) to DNA synthesis (S) phase and its deregulation or overexpression induces abnormal cell proliferation and cancer development. Consequently, targeting CDK4/6 has been proposed as a paradigm shift in the anticancer approach. The design and development of effective CDK4/6 inhibitors are increasingly becoming a promising cancer therapy evident with approved drugs such as palbociclib, ribociclib, and abemaciclib, etc. In this article, we explore the biological importance of CDK4/6 in cancer therapy, the development of resistance to monotherapy, and a short overview of PROTAC (Proteolysis Targeting Chimera), a unique and pioneering technique for degrading CDK4/6 enzymes. Overall, our prime focus is to discuss novel CDK4/6 inhibitors with diverse chemical classes and their correlation with computational studies.

The discovery of cyclin-dependent kinases (CDK) and their mechanism in regulating the cell cycle process was considered a game-changer in cancer therapy.

Cyclin-dependent kinase (CDK) inhibitors in solid tumors: a review of clinical trials

Cyclin-dependent kinases (CDKs) play a key regulating role in the cell cycle, which is almost universally altered in cancer, leading to sustained proliferation. Early pan-CDK inhibitors showed poor results in clinical trials for solid malignancies, as the lack of selectivity produced significant toxicity. The production of more selective inhibitors led to significant developments in cancer therapy, as CDK4/6 inhibitors in combination with endocrine therapy changed the landscape of the treatment of hormone-receptor positive (HR +) metastatic breast cancer. Recently, Trilaciclib demonstrated benefits regarding hematological toxicity compared to placebo when administered in combination with chemotherapy in small cell lung cancer. Newer agents, such as SY-5609, a selective CDK7 inhibitor, have also shown promising results in early clinical trials. In this paper, we review the data from clinical trials of CDK inhibitors in solid tumors, either as a monotherapy or in combination with other agents, with an emphasis on novel agents and potential new indications for this drug class.

In vitro therapeutic effects of abemaciclib on triple-negative breast cancer cells

The cyclin-dependent kinases 4 and 6 have led to a significant improvement in the treatment of hormone-receptor-positive breast cancer. However, the therapeutic potential of abemaciclib in triple-negative breast cancer (TNBC) has not been definitively elucidated. Therefore, the objective of this study was to investigate abemaciclib mediated antiproliferative effects on MDA-MB-231 and MDA-MB-468 TNBC and MCF-10A cell line through annexin V, cell cycle, caspase-3, reverse transcription-polymerase chain reaction analysis, acridine orange, and DAPI staining, for the first time. In addition, the autophagy-related cell death was assessed by autophagy-LC3 assay and acidic vesicular organelles staining. Our findings demonstrated that abemaciclib treatment resulted in significant apoptotic cell death in TNBC cells via G0/G1 arrest, chromatin condensation, the upregulation of caspase-3 and Bax levels, and the downregulation of Bcl-2. However, the formation of a large number of cytoplasmic vacuoles was not associated with autophagy. Therefore, abemaciclib treatment could be an effective treatment for TNBC. However, further studies are needed to elucidate the molecular mechanism of abemaciclib-induced apoptotic as well as atypical cell death derived from lysosomes in TNBC.

Targeted Therapies in Lung Cancers: Current Landscape and Future Prospects

BACKGROUND

Lung cancer is the most common and malignant cancer worldwide. Targeted therapies have emerged as a promising treatment strategy for lung cancers.

OBJECTIVE

The objective of this study is to evaluate the current landscape of targets and finding promising targets for future new drug discovery for lung cancers by identifying the science-technology-clinical development pattern and mapping the interaction network of targets.

METHODS

Targets for cancers were classified into 3 groups based on a paper published in Nature. We search for scientific literature, patent documents and clinical trials of targets in Group 1 and Group 2 for lung cancers. Then, a target-target interaction network of Group 1 was constructed, and the science-technology-clinical(S-T-C) development patterns of targets in Group 1 were identified. Finally, based on the cluster distribution and the development pattern of targets in Group 1, interactions between the targets were employed to predict potential targets in Group 2 on drug development.

RESULTS

The target-target interaction(TTI)network of group 1 resulted in 3 clusters with different developmental stages. The potential targets in Group 2 are divided into 3 ranks. Level-1 is the first priority and level-3 is the last. Level-1 includes 16 targets, such as STAT3, CRKL, and PTPN11, that are mostly involved in signaling transduction pathways. Level-2 and level-3 contain 8 and 6 targets related to various biological functions.

CONCLUSION

This study will provide references for drug development in lung cancers, emphasizing that priorities should be given to targets in Level-1, whose mechanisms are worth further exploration.

Anti-cancer therapy with cyclin-dependent kinase inhibitors: impact and challenges

The introduction of cyclin-dependent kinase 4/6 inhibitors (CKIs) has marked a major development in the standard treatment of advanced breast cancer. Extensive preclinical, translational and clinical research efforts into CKI agents are ongoing, and clinical application of this class of systemic anti-cancer therapy is anticipated to expand beyond metastatic breast cancer treatment. Emerging evidence indicates that mechanisms by which CKI agents exert their therapeutic effect transcend their initially expected impacts on cell cycle control into the realms of cancer immunology and metabolism. The recent expansion in our understanding of the multifaceted impact of CKIs on tumour biology has the potential to improve clinical study design, therapeutic strategies and ultimately patient outcomes. This review contextualises the current status of CKI therapy by providing an overview of the original and emerging insights into mechanisms of action and the evidence behind their current routine use in breast cancer management. Recent preclinical and clinical studies into CKIs across tumour types are discussed, including a synthesis of the more than 300 clinical trials of CKI-combination treatments registered as of November 2020. Key challenges and opportunities anticipated in the 2020s are explored, including treatment resistance, combination therapy strategies and potential biomarker development.

CDK4/6 Inhibitors in Melanoma: A Comprehensive Review

Historically, metastatic melanoma was considered a highly lethal disease. However, recent advances in drug development have allowed a significative improvement in prognosis. In particular, BRAF/MEK inhibitors and anti-PD1 antibodies have completely revolutionized the management of this disease. Nonetheless, not all patients derive a benefit or a durable benefit from these therapies. To overtake this challenges, new clinically active compounds are being tested in the context of clinical trials. CDK4/6 inhibitors are drugs already available in clinical practice and preliminary evidence showed a promising activity also in melanoma. Herein we review the available literature to depict a comprehensive landscape about CDK4/6 inhibitors in melanoma. We present the molecular and genetic background that might justify the usage of these drugs, the preclinical evidence, the clinical available data, and the most promising ongoing clinical trials.

Preclinical Evaluation of the Association of the Cyclin-Dependent Kinase 4/6 Inhibitor, Ribociclib, and Cetuximab in Squamous Cell Carcinoma of the Head and Neck

Simple Summary

We previously showed that ribociclib induces cell cycle arrest in some human papillomavirus (HPV)-negative squamous cell carcinomas of the head and neck (SCCHN) models. However, in vivo, ribociclib has only a cytostatic effect, suggesting that its activity needs to be optimized in combination with other treatments. We investigated the activity of ribociclib in combination with cetuximab in several HPV-negative SCCHN patient-derived tumor xenograft (PDTX) models. We found that the combination of cetuximab and ribociclib was not significantly more active than cetuximab monotherapy. In addition, our observations also suggest that the combination of cetuximab with a cyclin-dependent kinase (CDK) 4/6 inhibitor may reduce the activity of the CDK4/6 inhibitor in some cetuximab-resistant models. Our work has significant clinical implications since combinations of anti-epidermal growth factor receptor (EGFR) therapy and CDK4/6 inhibitors are currently being investigated in clinical trials.

Abstract

Epidermal growth factor receptor (EGFR) overexpression is observed in 90% of human papillomavirus (HPV)-negative squamous cell carcinomas of the head and neck (SCCHN). Cell cycle pathway impairments resulting in cyclin-dependent kinase (CDK) 4 and 6 activation, are frequently observed in SCCHN. We investigated the efficacy of ribociclib, a CDK4/6 inhibitor, in combination with cetuximab, a monoclonal antibody targeting the EGFR, in HPV-negative SCCHN patient-derived tumor xenograft (PDTX) models. The combination of cetuximab and ribociclib was not significantly more active than cetuximab monotherapy in all models investigated. In addition, the combination of cetuximab and ribociclib was less active than ribociclib monotherapy in the cetuximab-resistant PDTX models. In these models, a significant downregulation of the retinoblastoma (Rb) protein was observed in cetuximab-treated mice. We also observed Rb downregulation in the SCCHN cell lines chronically exposed and resistant to cetuximab. In addition, Rb downregulation induced interleukin 6 (Il-6) secretion and the Janus kinase family member/signal transducer and activator of transcription (JAK/STAT) pathway activation that might be implicated in the cetuximab resistance of these cell lines. To conclude, cetuximab is not an appropriate partner for ribociclib in cetuximab-resistant SCCHN models. Our work has significant clinical implications since the combination of anti-EGFR therapy with CDK4/6 inhibitors is currently being investigated in clinical trials.

Development of CDK4/6 Inhibitors: A Five Years Update

The inhibition of cyclin dependent kinases 4 and 6 plays a role in aromatase inhibitor resistant metastatic breast cancer. Three dual CDK4/6 inhibitors have been approved for the breast cancer treatment that, in combination with the endocrine therapy, dramatically improved the survival outcomes both in first and later line settings. The developments of the last five years in the search for new selective CDK4/6 inhibitors with increased selectivity, treatment efficacy, and reduced adverse effects are reviewed, considering the small-molecule inhibitors and proteolysis-targeting chimeras (PROTACs) approaches, mainly pointing at structure-activity relationships, selectivity against different kinases and antiproliferative activity.

Cyclin-dependent kinase inhibitors in head and neck cancer and glioblastoma-backbone or add-on in immune-oncology?

Cyclin-dependent kinases (CDK) control the cell cycle and play a crucial role in oncogenesis. Pharmacologic inhibition of CDK has contributed to the recent clinical approval of dual CDK4/6 inhibitors for the treatment of breast and small cell lung cancer. While the anticancer cell effects of CDK inhibitors are well-established, preclinical and early clinical studies describe additional mechanisms of action such as chemo- and radiosensitization or immune stimulation. The latter offers great potential to incorporate CDK inhibitors in immune-based treatments. However, dosing schedules and accurate timing of each combination partner need to be respected to prevent immune escape and resistance. In this review, we provide a detailed summary of CDK inhibitors in the two solid cancer types head and neck cancer and glioblastoma multiforme; it describes the molecular mechanisms of response vs. resistance and covers strategies to avoid resistance by the combination of immunotherapy or targeted therapy.

Pyrazole[3,4-d]pyrimidine derivatives loaded into halloysite as potential CDK inhibitors

Uncontrolled cell proliferation is a hallmark of cancer as a result of rapid and deregulated progression through the cell cycle. The inhibition of cyclin-dependent kinases (CDKs) activities is a promising therapeutic strategy to block cell cycle of tumor cells. In this work we reported a new example of nanocomposites based on halloysite nanotubes (HNTs)/pyrazolo[3,4-d]pyrimidine derivatives (Si306 and Si113) as anticancer agents and CDK inhibitors. HNTs/Si306 and HNTs/Si113 nanocomposites were synthesized and characterized. The release kinetics were also investigated. Antitumoral activity was evaluated on three cancer cell lines (HeLa, MDA-MB-231 and HCT116) and the effects on cell cycle arrest in HCT116 cells were evaluated. Finally, molecular dynamics simulations were performed of the complexes between Si113 or Si306 and the active site of both CDK 1 and 2.

Palladium catalyzed C–C and C–N bond forming reactions: an update on the synthesis of pharmaceuticals from 2015–2020

Some of the most prominent and promising catalysts in organic synthesis for the requisite construction of C–C and C–N bonds are palladium (Pd) catalysts, which play a pivotal role in pharmaceutical and medicinal chemistry.

Identifying SARS-CoV-2 Entry Inhibitors through Drug Repurposing Screens of SARS-S and MERS-S Pseudotyped Particles

While vaccine development will hopefully quell the global pandemic of COVID-19 caused by SARS-CoV-2, small molecule drugs that can effectively control SARS-CoV-2 infection are urgently needed. Here, inhibitors of spike (S) mediated cell entry were identified in a high throughput screen of an approved drugs library with SARS-S and MERS-S pseudotyped particle entry assays. We discovered six compounds (cepharanthine, abemaciclib, osimertinib, trimipramine, colforsin, and ingenol) to be broad spectrum inhibitors for spike-mediated entry. This work could contribute to the development of effective treatments against the initial stage of viral infection and provide mechanistic information that might aid the design of new drug combinations for clinical trials for COVID-19 patients.

Synthesis and Clinical Development of Palbociclib: An overview

Breast cancer is the second most commonly identified cancer in women in the United States after skin cancer. The past few years have seen a substantial increase in breast cancer awareness campaigns and active research in fields of diagnosis and targeted therapy. These factors have led to a better mechanistic understanding of the disease, detection at earlier stages and more personalized approach to treatment, ultimately causing a crucial increase in the survival rates after detection. However, with the advances in treatment, cases of patients developing primary resistance and acquired resistance are increasing. Most of the breast cancers which develop resistance to therapy are ER+ and are typically treated with tamoxifen and fulvestrant. These drugs either lower the levels of estrogen or inhibit the receptors for estrogen and prevent the tumor from spreading. Around one third of women treated with these drugs develop resistance to them, lowering their chances of survival. This has directed to the search of newer drug therapies to target advanced breast cancer and resistance. One of these efforts has resulted in the development of Palbociclib, a first in class inhibitor of cyclin dependent kinases 4 and 6 (CDK4 and CDK6), which was granted accelerated approval from FDA for combination therapy in postmenopausal women with ER+, HER2- metastatic breast cancer. This review is focused on the various aspects of "Palbociclib" including its synthesis, molecular modeling studies and efficacy and safety profile with clinical trials data.

Identification of novel CDK 9 inhibitors based on virtual screening, molecular dynamics simulation, and biological evaluation

AIMS

Cyclin-dependent kinase 9 (CDK9) is a member of the CDK subfamily and plays a major role in the regulation of transcriptional elongation. It has attracted widespread attention as a therapeutic target for cancer. Here, we aimed to explore novel CDK 9 inhibitors by using a hybrid virtual screening strategy.

MAIN METHODS

A hybrid virtual screening strategy was constructed with computer-aided drug design (CADD). First, compounds were filtered in accordance with Lipinski's rule of five and adsorption, distribution, metabolism, excretion, and toxicity (ADMET) properties. Second, a 3D-QSAR pharmacophore model was built and used as a 3D query to screen the obtained hit compounds. Third, the hit compounds were subjected to molecular docking studies. Fourth, molecular dynamics (MD) simulations were performed on CDK9 in complex with the final hits to examine the structural stability. Finally, CDK9 kinase biochemical assay was performed to identify the biological activity of the hit compounds.

KEY FINDINGS

Seven hit compounds were screened out. These hit compounds showed drug-like properties in accordance with Lipinski's rule of five and ADMET. Complexes involving the six hit compounds bound to CDK9 exhibited good structural stability in the MD simulation. Furthermore, these six hit compounds had strong inhibitory activity against CDK9 kinase. In particular, hit 3 showed the most promising activity with the percentage of 71%.

SIGNIFICANCE

The six hit compounds may be promising novel CDK9 inhibitors, and the hybrid virtual screening strategy designed in this study provides an important reference for the design and synthesis of novel CDK9 inhibitors.

CDK4/6 Inhibitors in Breast Cancer Treatment: Potential Interactions with Drug, Gene, and Pathophysiological Conditions

Palbociclib, ribociclib, and abemaciclib belong to the third generation of cyclin-dependent kinases inhibitors (CDKis), an established therapeutic class for advanced and metastatic breast cancer. Interindividual variability in the therapeutic response of CDKis has been reported and some individuals may experience increased and unexpected toxicity. This narrative review aims at identifying the factors potentially concurring at this variability for driving the most appropriate and tailored use of CDKis in the clinic. Specifically, concomitant medications, pharmacogenetic profile, and pathophysiological conditions could influence absorption, distribution, metabolism, and elimination pharmacokinetics. A personalized therapeutic approach taking into consideration all factors potentially contributing to an altered pharmacokinetic/pharmacodynamic profile could better drive safe and effective clinical use.

Identifying SARS-CoV-2 entry inhibitors through drug repurposing screens of SARS-S and MERS-S pseudotyped particles

While vaccine development will hopefully quell the global pandemic of COVID-19 caused by SARS-CoV-2, small molecule drugs that can effectively control SARS-CoV-2 infection are urgently needed. Here, inhibitors of spike (S) mediated cell entry were identified in a high throughput screen of an approved drugs library with SARS-S and MERS-S pseudotyped particle entry assays. We discovered six compounds (cepharanthine, abemaciclib, osimertinib, trimipramine, colforsin, and ingenol) to be broad spectrum inhibitors for spike-mediated entry. This work should contribute to the development of effective treatments against the initial stage of viral infection, thus reducing viral burden in COVID-19 patients.

Abstract Figure