The CDK inhibitor AT7519M in patients with relapsed or refractory chronic lymphocytic leukemia (CLL) and mantle cell lymphoma. A Phase II study of the Canadian Cancer Trials Group

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.

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.

Discovery of novel macrocyclic derivatives as potent and selective cyclin-dependent kinase 2 inhibitors

Cyclin-dependent kinase 2 (CDK2) is a member of CDK family of kinases (CDKs) that regulate the cell cycle. Its inopportune or over-activation leads to uncontrolled cell cycle progression and drives numerous types of cancers, especially ovarian, uterine, gastric cancer, as well as those associated with amplified CCNE1 gene. However, developing selective lead compound as CDK2 inhibitors remains challenging owing to similarities in the ATP pockets among different CDKs. Herein, we described the optimization of compound 1, a novel macrocyclic inhibitor targeting CDK2/5/7/9, aiming to discover more selective and metabolically stable lead compound as CDK2 inhibitor. Molecular dynamic (MD) simulations were performed for compound 1 and 9 to gain insights into the improved selectivity against CDK5. Further optimization efforts led to compound 22, exhibiting excellent CDK2 inhibitory activity, good selectivity over other CDKs and potent cellular effects. Based on these characterizations, we propose that compound 22 holds great promise as a potential lead candidate for drug development.

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.

Combating relapsed and refractory Mantle cell lymphoma with novel therapeutic armamentarium: Recent advances and clinical prospects

Mantle cell lymphoma (MCL) is a rare, aggressive subtype of non-Hodgkin's lymphoma (NHL), accounting for 5% of all cases. Due to its virulence factor, it is an incurable disease and keeps relapsing despite an intensive treatment regimen. Advancements in research and drug discovery have shifted the treatment strategy from conventional chemotherapy to targeted agents and immunotherapies. The establishment of the role of Bruton tyrosine kinase led to the development of ibrutinib, a first-generation BTK inhibitor, and its successors. A conditioning regimen based immunotherapeutic agent like ibritumumob, has also demonstrated a viable response with a favorable toxicity profile. Brexucabtagene Autoleucel, the only approved CAR T-cell therapy, has proven advantageous for relapsed/refractory MCL in both children and adults. This article reviews certain therapies that could help update the current approach and summarizes a few miscellaneous agents, which, seldom studied in trials, could alleviate the regression observed in traditional therapies. DATA AVAILABILITY: The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

Glycogen synthase kinase-3: A potential target for diabetes

Elevated circulating glucose level due to β-cell dysfunction has been a key marker of Type-II diabetes. Glycogen synthase kinase-3 (GSK-3) has been recognized as an enzyme involved in the control of glycogen metabolism. Consequently, inhibitors of GSK-3 have been explored for anti-diabetic effects in vitro and in animal models. Further, the mechanisms governing the regulation of this enzyme have been elucidated by means of a combination of structural and cellular biological investigations. This review article examines the structural analysis of GSK-3 as well as molecular modeling reports from numerous researchers in the context of the design and development of GSK-3 inhibitors. This article centers on the signaling pathway of GSK-3 relevant to its potential as a target for diabetes and discusses advancements till date on different molecular modification approaches used by researchers in the development of novel GSK-3 inhibitors as potential therapeutics for the treatment of Type II diabetes.

Anti-hepatocellular carcinoma activity of the cyclin-dependent kinase inhibitor AT7519

Hepatocellular carcinoma (HCC) is one of the most common cancerous tumors and one of the leading causes of death among cancer-related disorders. Chemotherapy is ineffective in HCC patients, and the number of drugs that are in use is limited. Thus, new molecules are needed that could increase the effectiveness of anti-HCC regimens. Here, we show that AT7519, a CDK inhibitor, exerts positive effects on HCC cells: it inhibits proliferation, migration and clonogenicity. Detailed analysis of the transcriptomes of cells treated with this compound indicated that AT7519 affects a substantial portion of genes that are associated with HCC development and progression. Moreover, we showed that the concomitant use of AT7519 with gefitinib or cabozantinib sensitized HCC cells to these drugs. Thus, our research indicates that AT7519 is worth considering in monotherapy for hepatocellular carcinoma patients or in combination with other drugs, e.g., gefitinib or cabozantinib.

Cyclins and cyclin-dependent kinases: from biology to tumorigenesis and therapeutic opportunities

The discussion on cell proliferation cannot be continued without taking a look at the cell cycle regulatory machinery. Cyclin-dependent kinases (CDKs), cyclins, and CDK inhibitors (CKIs) are valuable members of this system and their equilibrium guarantees the proper progression of the cell cycle. As expected, any dysregulation in the expression or function of these components can provide a platform for excessive cell proliferation leading to tumorigenesis. The high frequency of CDK abnormalities in human cancers, together with their druggable structure has raised the possibility that perhaps designing a series of inhibitors targeting CDKs might be advantageous for restricting the survival of tumor cells; however, their application has faced a serious concern, since these groups of serine-threonine kinases possess non-canonical functions as well. In the present review, we aimed to take a look at the biology of CDKs and then magnify their contribution to tumorigenesis. Then, by arguing the bright and dark aspects of CDK inhibition in the treatment of human cancers, we intend to reach a consensus on the application of these inhibitors in clinical settings.

p53 directly downregulates the expression of CDC20 to exert anti-tumor activity in mantle cell lymphoma

BACKGROUND

Cell cycle dysregulation characterized by cyclin D1 overexpression is common in mantle cell lymphoma (MCL), while mitotic disorder was less studied. Cell division cycle 20 homologue (CDC20), an essential mitotic regulator, was highly expressed in various tumors. Another common abnormality in MCL is p53 inactivation. Little was known about the role of CDC20 in MCL tumorigenesis and the regulatory relationship between p53 and CDC20 in MCL.

METHODS

CDC20 expression was detected in MCL patients and MCL cell lines harboring mutant p53 (Jeko and Mino cells) and wild-type p53 (Z138 and JVM2 cells). Z138 and JVM2 cells were treated with CDC20 inhibitor apcin, p53 agonist nutlin-3a, or in combination, and then cell proliferation, cell apoptosis, cell cycle, cell migration and invasion were determined by CCK-8, flow cytometry and Transwell assays. The regulatory mechanism between p53 and CDC20 was revealed by dual-luciferase reporter gene assay and CUT&Tag technology. The anti-tumor effect, safety and tolerability of nutlin-3a and apcin were investigated in vivo in the Z138-driven xenograft tumor model.

RESULTS

CDC20 was overexpressed in MCL patients and cell lines compared with their respective controls. The typical immunohistochemical marker of MCL patients, cyclin D1, was positively correlated with CDC20 expression. CDC20 high expression indicated unfavorable clinicopathological features and poor prognosis in MCL patients. In Z138 and JVM2 cells, either apcin or nutlin-3a treatment could inhibit cell proliferation, migration and invasion, and induce cell apoptosis and cell cycle arrest. GEO analysis, RT-qPCR and WB results showed that p53 expression was negatively correlated with CDC20 expression in MCL patients, Z138 and JVM2 cells, while this relationship was not observed in p53-mutant cells. Dual-luciferase reporter gene assay and CUT&Tag assay revealed mechanistically that CDC20 was transcriptionally repressed by p53 through directly binding p53 to CDC20 promoter from - 492 to + 101 bp. Moreover, combined treatment of nutlin-3a and apcin showed better anti-tumor effect than single treatment in Z138 and JVM2 cells. Administration of nutlin-3a/apcin alone or in combination confirmed their efficacy and safety in tumor-bearing mice.

CONCLUSIONS

Our study validates the essential role of p53 and CDC20 in MCL tumorigenesis, and provides a new insight for MCL therapeutics through dual-targeting p53 and CDC20.

The CDK inhibitor AT7519 inhibits human glioblastoma cell growth by inducing apoptosis, pyroptosis and cell cycle arrest

Glioblastoma multiforme (GBM) is the most lethal primary brain tumor with a poor median survival of less than 15 months. However, clinical strategies and effective therapies are limited. Here, we found that the second-generation small molecule multi-CDK inhibitor AT7519 is a potential drug for GBM treatment according to high-throughput screening via the Approved Drug Library and Clinical Compound Library (2718 compounds). We found that AT7519 significantly inhibited the cell viability and proliferation of U87MG, U251, and patient-derived primary GBM cells in a dose-dependent manner. Furthermore, AT7519 also inhibited the phosphorylation of CDK1/2 and arrested the cell cycle at the G1-S and G2-M phases. More importantly, AT7519 induced intrinsic apoptosis and pyroptosis via caspase-3-mediated cleavage of gasdermin E (GSDME). In the glioblastoma intracranial and subcutaneous xenograft assays, tumor volume was significantly reduced after treatment with AT7519. In summary, AT7519 induces cell death through multiple pathways and inhibits glioblastoma growth, indicating that AT7519 is a potential chemical available for GBM treatment.

Super-Enhancer–Associated nine-gene prognostic score model for prediction of survival in chronic lymphocytic leukemia patients

Chronic lymphocytic leukemia (CLL) is a type of highly heterogeneous mature B-cell malignancy with various disease courses. Although a multitude of prognostic markers in CLL have been reported, insights into the role of super-enhancer (SE)–related risk indicators in the occurrence and development of CLL are still lacking. A super-enhancer (SE) is a cluster of enhancers involved in cell differentiation and tumorigenesis, and is one of the promising therapeutic targets for cancer therapy in recent years. In our study, the CLL-related super-enhancers in the training database were processed by LASSO-penalized Cox regression analysis to screen a nine-gene prognostic model including TCF7, VEGFA, MNT, GMIP, SLAMF1, TNFRSF25, GRWD1, SLC6AC, and LAG3. The SE-related risk score was further constructed and it was found that the predictive performance with overall survival and time-to-treatment (TTT) was satisfactory. Moreover, a high correlation was found between the risk score and already known prognostic markers of CLL. In the meantime, we noticed that the expressions of TCF7, GMIP, SLAMF1, TNFRSF25, and LAG3 in CLL were different from those of healthy donors (p < 0.01). Moreover, the risk score and LAG3 level of matched pairs before and after treatment samples varied significantly. Finally, an interactive nomogram consisting of the nine-gene risk group and four clinical traits was established. The inhibitors of mTOR and cyclin-dependent kinases (CDKs) were considered effective in patients in the high-risk group according to the pRRophetic algorithm. Collectively, the SE-associated nine-gene prognostic model developed here may be used to predict the prognosis and assist in the risk stratification and treatment of CLL patients in the future.

Advances in Pyrazole Based Scaffold as Cyclin-Dependent Kinase 2 Inhibitors for the Treatment of Cancer

The transformation of a normal cell into a tumor cell is one of the initial steps in cell cycle deregulation. The cell cycle is regulated by cyclin-dependent kinases (CDKs) that belong to the protein kinase family. CDK2 is an enchanting target for specific genotypes tumors since cyclin E is selective for CDK2 and the deregulation of specific cancer forms. Thus, CDKs inhibitor specifically CDK2/cyclin A-E has the potential to be a valid cancer target as per the currently undergoing clinical trials. Mostly pyrazole scaffolds have shown selectivity and potency for CDK2 inhibitors. This review demonstrates pyrazole and pyrazole fused with other heterocyclic rings for anti-proliferative activity. Based on the in vitro and molecular docking studies, the IC50 value of various hybrids is revealed to display the most potent analogs for CDK2 inhibition. Thus, the review emphasizes various lead analogs of pyrazole hybrids which can be found to be very potent and selective for anti-cancer drugs.

Analyzing the scaffold diversity of cyclin-dependent kinase inhibitors and revisiting the clinical and preclinical pipeline

Kinases have gained an important place in the list of vital therapeutic targets because of their overwhelming clinical success in the last two decades. Among various clinically validated kinases, the cyclin-dependent kinases (CDK) are one of the extensively studied drug targets for clinical development. Food and Drug Administration has approved three CDK inhibitors for therapeutic use, and at least 27 inhibitors are under active clinical development. In the last decade, research and development in this area took a rapid pace, and thus the analysis of scaffold diversity is essential for future drug design. Available reviews lack the systematic study and discussion on the scaffold diversity of CDK inhibitors. Herein we have reviewed and critically analyzed the chemical diversity present in the preclinical and clinical pipeline of CDK inhibitors. Our analysis has shown that although several scaffolds represent CDK inhibitors, only the amino-pyrimidine is a well-represented scaffold. The three-nitrogen framework of amino-pyrimidine is a fundamental hinge-binding unit. Further, we have discussed the selectivity aspects among CDKs, the clinical trial dose-limiting toxicities, and highlighted the most advanced clinical candidates. We also discuss the changing paradigm towards selective inhibitors and an overview of ATP-binding pockets of all druggable CDKs. We carefully analyzed the clinical pipeline to unravel the candidates that are currently under active clinical development. In addition to the plenty of dual CDK4/6 inhibitors, there are many selective CDK7, CDK9, and CDK8/19 inhibitors in the clinical pipeline.

Review of rationale and progress toward targeting cyclin-dependent kinase 2 (CDK2) for male contraception†

Cyclin-dependent kinase 2 (CDK2) is a member of the larger cell cycle regulating CDK family of kinases, activated by binding partner cyclins as its name suggests. Despite its canonical role in mitosis, CDK2 knockout mice are viable but sterile, suggesting compensatory mechanisms for loss of CDK2 in mitosis but not meiosis. Here, we review the literature surrounding the role of CDK2 in meiosis, particularly a cyclin-independent role in complex with another activator, Speedy 1 (SPY1). From this evidence, we suggest that CDK2 could be a viable nonhormonal male contraceptive target. Finally, we review the literature of pertinent CDK2 inhibitors from the preclinical to clinical stages, mostly developed to treat various cancers. To date, there is no potent yet selective CDK2 inhibitor that could be repurposed as a contraceptive without appreciable off-target toxicity. To achieve selectivity for CDK2 over closely related kinases, developing compounds that bind outside the conserved adenosine triphosphate-binding site may be necessary.

The cyclin-dependent kinase inhibitor AT7519 augments cisplatin's efficacy in ovarian cancer via multiple oncogenic signaling pathways

Although cisplatin is the most active drug for the treatment of ovarian cancer, majority of patients develop resistance and ultimately relapse. Enhancing the efficacy of cisplatin could represent a promising strategy to improve the clinical outcome of patients with ovarian cancer. AT7519 is a multitargeted cyclin-dependent kinase (CDK) inhibitor and displays potent anticancer activities. In this work, we show that the combination of AT7519 with cisplatin is much more superior to cisplatin alone in inhibiting ovarian cancer. AT7519 at nanomolar concentrations inhibits proliferation and migration and induces apoptosis of multiple ovarian cancer cell lines. In contrast, AT7519 at the same concentrations either does not affect survival or is significantly less effective in inhibiting proliferation and migration in normal ovarian cells and fibroblast cells. AT7519 significantly augments the inhibitory effects of cisplatin in ovarian cancer cells in a dose-dependent manner. Mechanistic studies suggest that AT7519 (i) inhibits proliferation via decreasing activities of CDK1 and 2, and via inhibiting RNA transcription; (ii) inhibits migration via suppressing epithelial-mesenchymal transition (EMT); and (iii) induces apoptosis via decreasing Mcl-1 and increasing Bim in ovarian cancer cells. Using a human ovarian cancer xenograft mouse model, we confirm the in vivo efficacy of AT7519 alone, and the synergistic effects of AT7519 and cisplatin in combination, at doses that cause minimal toxicity in mice. Our findings provide systematic preclinical evidence to support the initialization of clinical trials of the AT7519 and cisplatin combination for the treatment of ovarian cancer.

Cyclin-Dependent Kinase Inhibitors in Hematological Malignancies-Current Understanding, (Pre-)Clinical Application and Promising Approaches

Simple Summary

Cyclin-dependent kinases are involved in the regulation of cancer-initiating processes like cell cycle progression, transcription, and DNA repair. In hematological neoplasms, these enzymes are often overexpressed, resulting in increased cell proliferation and cancer progression. Early (pre-)clinical data using cyclin-dependent kinase inhibitors are promising but identifying the right drug for each subgroup and patient is challenging. Certain chromosomal abnormalities and signaling molecule activities are considered as potential biomarkers. We therefore summarized relevant studies investigating cyclin-dependent kinase inhibitors in hematological malignancies and further discuss molecular mechanisms of resistance and other open questions.

Abstract

Genetically altered stem or progenitor cells feature gross chromosomal abnormalities, inducing modified ability of self-renewal and abnormal hematopoiesis. Cyclin-dependent kinases (CDK) regulate cell cycle progression, transcription, DNA repair and are aberrantly expressed in hematopoietic malignancies. Incorporation of CDK inhibitors (CDKIs) into the existing therapeutic regimens therefore constitutes a promising strategy. However, the complex molecular heterogeneity and different clinical presentation is challenging for selecting the right target and defining the ideal combination to mediate long-term disease control. Preclinical and early clinical data suggest that specific CDKIs have activity in selected patients, dependent on the existing rearrangements and mutations, potentially acting as biomarkers. Indeed, CDK6, expressed in hematopoietic cells, is a direct target of MLL fusion proteins often observed in acute leukemia and thus contributes to leukemogenesis. The high frequency of aberrancies in the retinoblastoma pathway additionally warrants application of CDKIs in hematopoietic neoplasms. In this review, we describe the preclinical and clinical advances recently made in the use of CDKIs. These include the FDA-approved CDK4/6 inhibitors, traditional and novel pan-CDKIs, as well as dual kinase inhibitors. We additionally provide an overview on molecular mechanisms of response vs. resistance and discuss open questions.

Pharmacophore-based virtual screening, synthesis, biological evaluation, and molecular docking study of novel pyrrolizines bearing urea/thiourea moieties with potential cytotoxicity and CDK inhibitory activities

In the current study, virtual screening of a small library of 1302 pyrrolizines bearing urea/thiourea moieties was performed. The top-scoring hits were synthesised and evaluated for their cytotoxicity against three cancer (MCF-7, A2780, and HT29) and one normal (MRC-5) cell lines. The results of the MTT assay revealed potent cytotoxic activities for most of the new compounds (IC₅₀ = 0.16–34.13 μM). The drug-likeness study revealed that all the new compounds conform to Lipinski’s rule. Mechanistic studies of compounds 18 b, 19a, and 20a revealed the induction of apoptosis and cell cycle arrest at the G₁ phase in MCF-7 cells. The three compounds also displayed potent inhibitory activity against CDK-2 (IC₅₀ = 25.53–115.30 nM). Moreover, the docking study revealed a nice fitting of compound 19a into the active sites of CDK-2/6/9. These preliminary results suggested that compound 19a could serve as a promising scaffold in the discovery of new potent anticancer agents.

Small Molecule CDK Inhibitors for the Therapeutic Management of Cancer

Cyclin-dependent kinases (CDKs) are a group of multifunctional enzymes consisting of catalytic and regulatory subunits. The regulatory subunit, cyclin, remains dissociated under normal circumstances, and complexation of cyclin with the catalytic subunit of CDK leads to its activation for phosphorylation of protein substrates. The primary role of CDKs is in the regulation of the cell cycle. Retinoblastoma protein (Rb) is one of the widely investigated tumor suppressor protein substrates of CDK, which prevents cells from entering into cell-cycle under normal conditions. Phosphorylation of Rb by CDKs causes its inactivation and ultimately allows cells to enter a new cell cycle. Many cancers are associated with hyperactivation of CDKs as a result of mutation of the CDK genes or CDK inhibitor genes. Therefore, CDK modulators are of great interest to explore as novel therapeutic agents against cancer and led to the discovery of several CDK inhibitors to clinics. This review focuses on the current progress and development of anti-cancer CDK inhibitors from preclinical to clinical and synthetic to natural small molecules.

Targeting CDK9 for Anti-Cancer Therapeutics

Cyclin Dependent Kinase 9 (CDK9) is one of the most important transcription regulatory members of the CDK family. In conjunction with its main cyclin partner-Cyclin T1, it forms the Positive Transcription Elongation Factor b (P-TEFb) whose primary function in eukaryotic cells is to mediate the positive transcription elongation of nascent mRNA strands, by phosphorylating the S2 residues of the YSPTSPS tandem repeats at the C-terminus domain (CTD) of RNA Polymerase II (RNAP II). To aid in this process, P-TEFb also simultaneously phosphorylates and inactivates a number of negative transcription regulators like 5,6-dichloro-1-β-D-ribofuranosylbenzimidazole (DRB) Sensitivity-Inducing Factor (DSIF) and Negative Elongation Factor (NELF). Significantly enhanced activity of CDK9 is observed in multiple cancer types, which is universally associated with significantly shortened Overall Survival (OS) of the patients. In these cancer types, CDK9 regulates a plethora of cellular functions including proliferation, survival, cell cycle regulation, DNA damage repair and metastasis. Due to the extremely critical role of CDK9 in cancer cells, inhibiting its functions has been the subject of intense research, resulting the development of multiple, increasingly specific small-molecule inhibitors, some of which are presently in clinical trials. The search for newer generation CDK9 inhibitors with higher specificity and lower potential toxicities and suitable combination therapies continues. In fact, the Phase I clinical trials of the latest, highly specific CDK9 inhibitor BAY1251152, against different solid tumors have shown good anti-tumor and on-target activities and pharmacokinetics, combined with manageable safety profile while the phase I and II clinical trials of another inhibitor AT-7519 have been undertaken or are undergoing. To enhance the effectiveness and target diversity and reduce potential drug-resistance, the future of CDK9 inhibition would likely involve combining CDK9 inhibitors with inhibitors like those against BRD4, SEC, MYC, MCL-1 and HSP90.

Global Phosphoproteomics Reveal CDK Suppression as a Vulnerability to KRas Addiction in Pancreatic Cancer

PURPOSE

Among human cancers that harbor mutant (mt) KRas, some, but not all, are dependent on mt KRas. However, little is known about what drives KRas dependency.

EXPERIMENTAL DESIGN

Global phosphoproteomics, screening of a chemical library of FDA drugs, and genome-wide CRISPR/Cas9 viability database analysis were used to identify vulnerabilities of KRas dependency.

RESULTS

Global phosphoproteomics revealed that KRas dependency is driven by a cyclin-dependent kinase (CDK) network. CRISPR/Cas9 viability database analysis revealed that, in mt KRas-driven pancreatic cancer cells, knocking out the cell-cycle regulators CDK1 or CDK2 or the transcriptional regulators CDK7 or CDK9 was as effective as knocking out KRas. Furthermore, screening of a library of FDA drugs identified AT7519, a CDK1, 2, 7, and 9 inhibitor, as a potent inducer of apoptosis in mt KRas-dependent, but not in mt KRas-independent, human cancer cells. In vivo AT7519 inhibited the phosphorylation of CDK1, 2, 7, and 9 substrates and suppressed growth of xenografts from 5 patients with pancreatic cancer. AT7519 also abrogated mt KRas and mt p53 primary and metastatic pancreatic cancer in three-dimensional (3D) organoids from 2 patients, 3D cocultures from 8 patients, and mouse 3D organoids from pancreatic intraepithelial neoplasia, primary, and metastatic tumors.

CONCLUSIONS

A link between CDK hyperactivation and mt KRas dependency was uncovered and pharmacologically exploited to abrogate mt KRas-driven pancreatic cancer in highly relevant models, warranting clinical investigations of AT7519 in patients with pancreatic cancer.

Design, synthesis, and biological evaluation of 4-benzoylamino-1H-pyrazole-3-carboxamide derivatives as potent CDK2 inhibitors

Cyclin-dependent kinases play significant roles in cell cycle progression and are promising targets for cancer therapy. However, most potent CDK inhibitors lack the balance between efficacy and safety because of poor selectivity. Given the roles of CDK2 in tumorigenesis, selective CDK2 inhibition may provide therapeutic benefits against certain cancer. In this study, a series of 4-benzoylamino-1H-pyrazole-3-carboxamide derivatives were designed, synthesized, and evaluated. The most selective compound DC-K2in212 in this series exhibited high potency towards CDK2 and had effective anti-proliferative activity against A2058 melanoma cell line and MV4-11 leukemia cell line while exhibiting low toxic effect on human normal cell lines MRC5 and LX2. The molecular modeling illustrated that compound DC-K2in212 had the similar binding mode with CDK2 as C-73, the most selective CDK2 inhibitor reported so far, which might account for selectivity against CDK2 over CDK1. Further biological studies revealed that compound DC-K2in212 suppressed CDK2-associated downstream signaling pathway, blocked cell cycle progression, and induced cellular apoptosis. Therefore, compound DC-K2in212 could serve as a potential CDK2 inhibitor for further development.

Phase 1 study of the HSP90 inhibitor onalespib in combination with AT7519, a pan-CDK inhibitor, in patients with advanced solid tumors

PURPOSE

We conducted a phase 1 trial of the HSP90 inhibitor onalespib in combination with the CDK inhibitor AT7519, in patients with advanced solid tumors to determine the safety profile and maximally tolerated dose, pharmacokinetics, preliminary antitumor activity, and to assess the pharmacodynamic (PD) effects on HSP70 expression in patient-derived PBMCs and plasma.

METHODS

This study followed a 3 + 3 trial design with 1 week of intravenous (IV) onalespib alone, followed by onalespib/AT7519 (IV) on days 1, 4, 8, and 11 of a 21-days cycle. PK and PD samples were collected at baseline, after onalespib alone, and following combination therapy.

RESULTS

Twenty-eight patients were treated with the demonstration of downstream target engagement of HSP70 expression in plasma and PBMCs. The maximally tolerated dose was onalespib 80 mg/m² IV + AT7519 21 mg/m² IV. Most common drug-related adverse events included Grade 1/2 diarrhea (79%), fatigue (54%), mucositis (57%), nausea (46%), and vomiting (50%). Partial responses were seen in a palate adenocarcinoma and Sertoli-Leydig tumor; a colorectal and an endometrial cancer patient both remained on study for ten cycles with stable disease as the best response. There were no clinically relevant PK interactions for either drug.

CONCLUSIONS

Combined onalespib and AT7519 is tolerable, though below monotherapy RP2D. Promising preliminary clinical activity was seen. Further benefit may be seen with the incorporation of molecular signature pre-selection. Further biomarker development will require the assessment of the on-target impact on relevant client proteins in tumor tissue.

Anti-tumor Drug Targets Analysis: Current Insight and Future Prospect

The incidence and mortality of malignant tumors are on the rise, which has become the second leading cause of death in the world. At present, anti-tumor drugs are one of the most common methods for treating cancer. In recent years, with the in-depth study of tumor biology and related disciplines, it has been gradually discovered that the essence of cell carcinogenesis is the infinite proliferation of cells caused by the disorder of cell signal transduction pathways, followed by a major shift in the concept of anti-tumor drugs research and development. The focus of research and development is shifting from traditional cytotoxic drugs to a new generation of anti-tumor drugs targeted at abnormal signaling system targets in tumor cells. In this review, we summarize the targets of anti-tumor drugs and analyse the molecular mechanisms of their effects, which lay a foundation for subsequent treatment, research and development.

Cell Cycle Dysregulation in Mantle Cell Lymphoma: Genomics and Therapy

Cell cycle dysregulation caused by aberrant cyclin D1 and CDK4 expression is a major determinant for proliferation of cancer cells in mantle cell lymphoma (MCL). Inhibition of CDK4/6 induces G1 arrest of MCL cells in patients, appearing to deepen and prolong the clinical response to partner agents. This article reviews aberrations of cell cycle genes in MCL cells and clinical trials of CDK4/6 inhibitors for MCL. Integrative longitudinal functional genomics is discussed as a strategy to discover genomic drivers for resistance in cancer cells and cancer-immune interactions that potentially contribute to the clinical response to palbociclib combination therapy in MCL.

Novel agents for mantle cell lymphoma: molecular rational and clinical data

INTRODUCTION

Mantle cell lymphoma (MCL) is an aggressive B cell non-Hodgkin lymphoma (NHL) that is characterized by the translocation t(11;14)(q13;q32) and a poor response to rituximab-anthracycline-based chemotherapy. Intensive regimens offer durable response, but a subgroup of MCL patients will not be eligible for those regimens and hence are candidates for less toxic, novel therapies based on a more tailored personalized approach.

AREAS COVERED

This article examines the molecular landscape of MCL, drug resistance mechanisms, and the data on emerging targeted therapies.

EXPERT OPINION

DNA damage pathway, ATM mutation, TP53, and epigenetic abnormalities are key drivers of MCL. sBCL2, PARP, ATR, CDK inhibitors or epigenetic modifiers are among the most promising drugs under investigation in clinical trials. The genomic landscape of MCL suggests two types of disease based on the presence of ATM or TP53 alterations which should be the framework of future molecular driven strategies. Among novel drugs, those interacting with the DNA damage response pathway offer the most effective rational for their use in MCL.

Targeting CDK4/6 in mantle cell lymphoma

Targeting the cell cycle represents a rational approach to mantle cell lymphoma (MCL) therapy, as aberrant expression of cyclin D1 and dysregulation of CDK4 underlie cell cycle progression and proliferation of MCL cells. Although cell cycle cancer therapy was historically ineffective due to a lack of selective and effective drugs, this landscape changed with the advent of selective and potent small-molecule oral CDK4/6 inhibitors. Here, we review the anti-tumor activities and clinical data of selective CDK4/6 inhibitors in MCL. We summarize the known mechanism of action of palbociclib, the most specific CDK4/6 inhibitor to date, and the strategy to leverage this specificity to reprogram MCL for a deeper and more durable clinical response to partner drugs. We also discuss integrative longitudinal functional genomics as a strategy to discover tumor-intrinsic genomic biomarkers and tumor-immune interactions that potentially contribute to the clinical response to palbociclib in combination therapy for MCL. Understanding the genomic basis for targeting CDK4/6 and the mechanisms of action and resistance in MCL may advance personalized therapy for MCL and shed light on drug resistance in other cancers.

Clinical management of mantle cell lymphoma in the elderly

Introduction: Mantle cell lymphoma (MCL) is a disease with an indolent histology, but mostly aggressive clinical course. While treatment can yield more promising results in younger patients, the disease is most diagnosed at a median age of approximately 70 years, and treatment in this group still presents a major challenge for oncohematologists. Unfortunately, due to comorbidities and poorer general status, the implementation of intensive treatment approaches with the cytarabine-based regimens and autologous stem cell transplantation is generally not possible, and the disease remains incurable, especially in elderly patients. Areas covered: In this paper, the authors discuss the therapeutic options available for older patients with MCL in the first line and relapsed/refractory settings, indicating new therapeutic options, which may achieve longer remissions and overall survival. Expert opinion: Although great progress has been made in the treatment of MCL in recent years, there remains a need for new treatment lines which can allow improved patient outcomes. Novel agents targeting altered the signal transduction pathways in MCL cells may offer more promise than traditional chemotherapy or immunochemotherapy and are currently being tested in clinical trials.

Design, synthesis and biological evaluation of novel 2,3-indolinedione derivatives against mantle cell lymphoma

2,3-Indolinedione derivatives have been identified as a novel class of promising agents for cancer treatment. In this study, eighteen 2,3-indolinedione derivatives were designed and synthesized, and their anticancer activities against mantle cell lymphoma (MCL) cells were evaluated. Most of them exhibited significant antiproliferative activity against the tested cell lines, and compound K5 was the most potent (MCL cellular IC₅₀ = 0.4-0.7 μM). Further, compound K5 could induce cell apoptosis and cell cycle arrest in G2/M phase. Additionally, the results of drug-likeness analysis demonstrated that these novel 2,3-indolinedione derivatives could have potential as novel treatment strategies for MCL.

Cyclin-Dependent Kinase 2 Inhibitors in Cancer Therapy: An Update

Cyclin-dependent kinase 2 (CDK2) drives the progression of cells into the S- and M-phases of the cell cycle. CDK2 activity is largely dispensable for normal development, but it is critically associated with tumor growth in multiple cancer types. Although the role of CDK2 in tumorigenesis has been controversial, emerging evidence proposes that selective CDK2 inhibition may provide a therapeutic benefit against certain tumors, and it continues to appeal as a strategy to exploit in anticancer drug development. Several small-molecule CDK2 inhibitors have progressed to the clinical trials. However, a CDK2-selective inhibitor is yet to be discovered. Here, we discuss the latest understandings of the role of CDK2 in normal and cancer cells, review the core pharmacophores used to target CDK2, and outline strategies for the rational design of CDK2 inhibitors. We attempt to provide an outlook on how CDK2-selective inhibitors may open new avenues for cancer therapy.

Development of Second-Generation CDK2 Inhibitors for the Prevention of Cisplatin-Induced Hearing Loss

There are currently no FDA-approved therapies to prevent the hearing loss associated with the usage of cisplatin in chemotherapeutic regimens. We recently demonstrated that the pharmacologic inhibition with kenpaullone or genetic deletion of CDK2 preserved hearing function in animal models treated with cisplatin, which suggests that CDK2 is a promising therapeutic target to prevent cisplatin-induced ototoxicity. In this study, we identified two lead compounds, AT7519 and AZD5438, from a focused library screen of 187 CDK2 inhibitors, performed in an immortalized cell line derived from neonatal mouse cochleae treated with cisplatin. Moreover, we screened 36 analogues of AT7519 and identified analogue 7, which exhibited an improved therapeutic index. When delivered locally, analogue 7 and AZD5438 both provided significant protection against cisplatin-induced ototoxicity in mice. Thus, we have identified two additional compounds that prevent cisplatin-induced ototoxicity in vivo and provided further evidence that CDK2 is a druggable target for treating cisplatin-induced ototoxicity.

In Vitro and In Vivo Antitumor and Anti-Inflammatory Capabilities of the Novel GSK3 and CDK9 Inhibitor ABC1183

Glycogen synthase kinase-3s (GSK3α and GSK3β) are constitutively active protein kinases that target over 100 substrates, incorporate into numerous protein complexes, and regulate such vital cellular functions as proliferation, apoptosis, and inflammation. Cyclin-dependent kinase 9 (CDK9) regulates RNA production as a component of positive transcription elongation factor b and promotes expression of oncogenic and inflammatory genes. Simultaneous inhibition of these signaling nodes is a promising approach for drug discovery, although previous compounds exhibit limited selectivity and clinical efficacy. The novel diaminothiazole ABC1183 is a selective GSK3α/β and CDK9 inhibitor and is growth-inhibitory against a broad panel of cancer cell lines. ABC1183 treatment decreases cell survival through G2/M arrest and modulates oncogenic signaling through changes in GSK3, glycogen synthase, and β-catenin phosphorylation and MCL1 expression. Oral administration, which demonstrates no organ or hematologic toxicity, suppresses tumor growth and inflammation-driven gastrointestinal disease symptoms, owing in part to downregulation of tumor necrosis factor α and interleukin-6 proinflammatory cytokines. Therefore, ABC1183 is strategically poised to effectively mitigate multiple clinically relevant diseases.