Discovery of novel anti-angiogenesis agents. Part 11: Development of PROTACs based on active molecules with potency of promoting vascular normalization

Clioquinol inhibits angiogenesis by promoting VEGFR2 degradation and synergizes with AKT inhibition to suppress triple-negative breast cancer vascularization

Inhibition of angiogenesis, either as monotherapy or in conjunction with other treatments, holds significant promise in cancer treatment. However, the limited efficacy of clinically approved anti-angiogenic agents underscores the urgent need for the development of novel drugs and therapeutic strategies. In this study, we demonstrate the highly selective inhibitory effects of clioquinol, a topical antifungal and antibiotic agent, on the angiogenic activity of endothelial cells (ECs) in a series of in vitro angiogenesis assays. Moreover, clioquinol effectively suppressed blood vessel formation in ex vivo aortic ring and in vivo Matrigel plug assays. Mechanistic studies revealed that clioquinol directly binds to the ATP-binding site of vascular endothelial growth factor receptor 2 (VEGFR2), promoting its degradation through both proteasome and lysosome pathways. This led to the down-regulation of the downstream extracellular signal-regulated kinase (ERK) pathway. In addition, the combination with the AKT inhibitor MK-2206 synergistically boosted the anti-angiogenic efficacy of clioquinol in vitro and in an in vivo dorsal skinfold chamber model of triple-negative breast cancer (TNBC), leading to the suppression of TNBC growth. Accordingly, clioquinol, either alone or in combination with AKT inhibitors, represents a promising therapeutic agent for future anti-angiogenic cancer treatment.

Navigating PROTACs in Cancer Therapy: Advancements, Challenges, and Future Horizons

Proteolysis Targeting Chimeras (PROTACs) have revolutionized cancer therapy by offering a selective and innovative approach to degrade key oncogenic proteins associated with various malignancies. These hybrid molecules exploit the ubiquitin-proteasome system, facilitating the degradation of target proteins through an event-driven mechanism, thereby overcoming drug resistance and enhancing selectivity. With diverse targets including androgen receptors, BTK, estrogen receptors, BET proteins, and BRAF, PROTACs offer a versatile strategy for personalized cancer treatment. Advantages of PROTACs over traditional small molecule inhibitors include their ability to operate at lower concentrations, catalyzing the degradation of multiple proteins of interest with reduced cytotoxicity. Notably, PROTACs address challenges associated with traditionally "undruggable" targets, expanding the therapeutic landscape of cancer therapy. Ongoing preclinical and clinical studies highlight the transformative potential of PROTACs, with promising results in prostate, breast, lung, melanoma, and colorectal cancers. Despite their potential, challenges persist in optimizing physicochemical properties and enhancing bioavailability. Further research is needed to refine PROTAC design and address complexities in molecule development. Nevertheless, the development of oral androgen receptor PROTACs represents a significant milestone, demonstrating the feasibility and efficacy of this innovative therapeutic approach. This review provides a comprehensive overview of PROTACs in cancer therapy, emphasizing their mechanism of action, advantages, and challenges. As PROTAC research progresses, continued exploration in both preclinical and clinical settings will be crucial to unlocking their full therapeutic potential and shaping the future of personalized cancer treatment.

New 6-nitro-4-substituted quinazoline derivatives targeting epidermal growth factor receptor: design, synthesis and in vitro anticancer studies

Aim: Twenty compounds of 6-nitro-4-substituted quinazolines were synthesized.Materials & methods: The new derivatives were evaluated for their epidermal growth factor receptor (EGFR) inhibitory activity. The most potent derivatives were assessed for their cytotoxicity against colon cancer and lung cancer cells, in addition to normal fibroblast cells.Results & discussion: compound 6c showed a superior to nearly equal cytotoxicity in comparison to gefitinib, it also revealed a good safety profile. Compound 6c caused a cell cycle arrest at G2/M phase in addition to induction of apoptosis. A molecular docking study was conducted on the most active compounds to gain insights of their binding mode in the active site of EGFR enzyme besides ADME prediction of their physicochemical properties and drug likeness profile.

Natural Compound-Rhein and PROTACs Unleash Potent VEGFR-2 Degraders

VEGFR-2 is a prominent therapeutic target in antitumor drug research to block tumor angiogenesis. This study focused on the synthesis and optimization of PROTACs based on the natural product rhein, resulting in the successful synthesis of 15 distinct molecules. In A549 cells, D9 exhibited remarkable antitumor efficacy with an IC50 of 5.88±0.50 μM, which was 15-fold higher compared to rhein (IC50=88.45±2.77 μM). An in-depth study of the effect of D9 on the degradation of VEGFR-2 revealed that D9 was able to induce the degradation of VEGFR-2 in A549 cells in a time-dependent manner. The observed effect was reversible, contingent upon the proteasome and ubiquitination system, and demonstrably linked to CRBN. Further experiments revealed that D9 induced apoptosis in A549 cells and led to cell cycle arrest in the G1 phase. Molecular docking simulations validated the binding mode of D9 to VEGFR, establishing the potential of D9 to bind to VEGFR-2 in its natural state. In summary, this study confirms the feasibility of natural product-bound PROTAC technology for the development of a new generation of VEGFR-2 degraders, offering a novel trajectory for the future development of pharmacological agents targeting VEGFR-2.

Novel angiogenesis inhibitors with superoxide anion radical amplification effect: Surmounting the Achilles' heels of angiogenesis inhibitors and photosensitizers

Angiogenesis inhibitors and photosensitizers are pivotal in tumor clinical treatment, yet their utilization is constrained. Herein, eleven novel angiogenesis inhibitors were developed through hybridization strategy to overcome their clinical limitations. These title compounds boast excitation wavelengths within the "therapeutic window", enabling deep tissue penetration. Notably, they could generate superoxide anion radicals via the Type I mechanism, with compound 36 showed the strongest superoxide anion radical generating capacity. Biological evaluation demonstrated remarkable cellular activity of all the title compounds, even under hypoxic conditions. Among them, compound 36 stood out for its superior anti-proliferative activity in both normoxic and hypoxic environments, surpassing individual angiogenesis inhibitors and photosensitizers. Compound 36 induced cell apoptosis via superoxide anion radical generation, devoid of dark toxicity. Molecular docking revealed that the target-recognizing portion of compound 36 was able to insert into the ATP binding pocket of the target protein similar to sorafenib. Collectively, our results suggested that hybridization of angiogenesis inhibitors and photosensitizers was a potential strategy to address the limitations of their clinical use.

Recent advances and future directions on small molecule VEGFR inhibitors in oncological conditions

"A journey of mixed emotions" is a quote that best describes the progress chart of vascular endothelial growth factor receptor (VEGFR) inhibitors as cancer therapeutics in the last decade. Exhilarated with the Food and Drug Administration (FDA) approvals of numerous VEGFR inhibitors coupled with the annoyance of encountering the complications associated with their use, drug discovery enthusiasts are on their toes with an unswerving determination to enhance the rate of translation of VEGFR inhibitors from preclinical to clinical stage. The recently crafted armory of VEGFR inhibitors is a testament to their growing dominance over other antiangiogenic therapies for cancer treatment. This review perspicuously underscores the earnest attempts of the researchers to extract the antiproliferative potential of VEGFR inhibitors through the design of mechanistically diverse structural assemblages. Moreover, this review encompasses sections on structural/molecular properties and physiological functions of VEGFR, FDA-approved VEGFR inhibitors, and hurdles restricting the activity range/clinical applicability of VEGFR targeting antitumor agents. In addition, tactics to overcome the limitations of VEGFR inhibitors are discussed. A clear-cut viewpoint transmitted through this compilation can provide practical directions to push the cart of VEGFR inhibitors to advanced-stage clinical investigations in diverse malignancies.

Novel multi-target angiogenesis inhibitors as potential anticancer agents: Design, synthesis and preliminary activity evaluation

Based on the crucial role of histone deacetylase (HDAC) and receptor tyrosine kinase in angiogenesis, in situ assembly, skeletal transition, molecular hybridization, and pharmacophore fusion were employed to yield seventy-six multi-target angiogenesis inhibitors. Biological evaluation indicated that most of the compounds exhibited potent proliferation inhibitory activity on MCF-7 cells, with the TH series having the highest inhibitory activity on MCF-7 cells. In addition, the IC50 values of TA11 and TH3 against HT-29 cellswere 0.078 μmol/L and 0.068 μmol/L, respectively. The cytotoxicity evaluation indicated that TC9, TA11, TM4, and TH3 displayed good safety against HEK293T cells. TH2 and TH3 could induce apoptosis of MCF-7 cells. Molecular modeling and ADMET prediction results indicated that most of target compounds showed promising medicinal properties, which was consistent with the experimental results. Our findings provided new lead compounds for the structural optimization of multi-target angiogenesis inhibitors.

Novel quinazolines bearing 1,3,4-thiadiazole-aryl urea derivative as anticancer agents: design, synthesis, molecular docking, DFT and bioactivity evaluations

A novel series of 1-(5-((6-nitroquinazoline-4-yl)thio)-1,3,4-thiadiazol-2-yl)-3-phenylurea derivatives 8 were designed and synthesized to evaluate their cytotoxic potencies. The structures of these obtained compounds were thoroughly characterized by IR, 1H, and 13C NMR, MASS spectroscopy and elemental analysis methods. Additionally, their in vitro anticancer activities were investigated using the MTT assay against A549 (human lung cancer), MDA-MB231 (human triple-negative breast cancer), and MCF7 (human hormone-dependent breast cancer). Etoposide was used as a reference marketed drug for comparison. Among the compounds tested, compounds 8b and 8c demonstrated acceptable antiproliferative activity, particularly against MCF7 cells. Considering the potential VEGFR-2 inhibitor potency of these compounds, a molecular docking study was performed for the most potent compound, 8c, to determine its probable interactions. Furthermore, computational investigations, including molecular dynamics, frontier molecular orbital analysis, Fukui reactivity descriptor, electrostatic potential surface, and in silico ADME evaluation for all compounds were performed to illustrate the structure-activity relationship (SAR).

Proteolysis-targeting chimeras in biotherapeutics: Current trends and future applications

The success of inhibitor-based therapeutics is largely constrained by the acquisition of therapeutic resistance, which is partially driven by the undruggable proteome. The emergence of proteolysis targeting chimera (PROTAC) technology, designed for degrading proteins involved in specific biological processes, might provide a novel framework for solving the above constraint. A heterobifunctional PROTAC molecule could structurally connect an E3 ubiquitin ligase ligand with a protein of interest (POI)-binding ligand by chemical linkers. Such technology would result in the degradation of the targeted protein via the ubiquitin-proteasome system (UPS), opening up a novel way of selectively inhibiting undruggable proteins. Herein, we will highlight the advantages of PROTAC technology and summarize the current understanding of the potential mechanisms involved in biotherapeutics, with a particular focus on its application and development where therapeutic benefits over classical small-molecule inhibitors have been achieved. Finally, we discuss how this technology can contribute to developing biotherapeutic drugs, such as antivirals against infectious diseases, for use in clinical practices.

Thienopyrimidine-based agents bearing diphenylurea: Design, synthesis, and evaluation of antiproliferative and antiangiogenic activity

An important role has been considered for the vascular endothelial growth factor receptor 2 (VEGFR-2) in the angiogenesis process, so that its inhibition is an important scientific way for cancer treatment. In this work, new thienopyrimidine derivatives were synthesized and evaluated. Compared with sorafenib, the majority of the target compounds had antiproliferative activity against the PC3, HepG2, MCF7, SW480, and HUVEC cell lines, especially 9h with IC₅₀ values of 4.5-15.1 μM, confirming the noticeable cytotoxic effects on the listed cell lines (PC3, HepG2, SW480, and HUVEC). Analyses by flow cytometry on SW480 and HUVEC cells revealed that 9n, 9k, 9h, and 9q led to apoptotic cell death. The result of the chick chorioallantoic membrane assay showed that 9h effectively reduced the number of corresponding blood vessels. Finally, the inhibitory effect on VEGFR-2 phosphorylation was considered as the outcome of Western blot analysis of compound 9h.

Targeting micro-environmental pathways by PROTACs as a therapeutic strategy

Tumor microenvironment (TME) composes of multiple cell types and non-cellular components, which supports the proliferation, metastasis and immune surveillance evasion of tumor cells, as well as accounts for the resistance to therapies. Therefore, therapeutic strategies using small molecule inhibitors (SMIs) and antibodies to block potential targets in TME are practical for cancer treatment. Targeted protein degradation using PROteolysis-TArgeting Chimera (PROTAC) technic has several advantages over traditional SMIs and antibodies, including overcoming drug resistance. Thus many PROTACs are currently under development for cancer treatment. In this review, we summarize the recent progress of PROTAC development that target TME pathways and propose the potential direction of future PROTAC technique to advance as novel cancer treatment options.

PROTACs: great opportunities for academia and industry (an update from 2020 to 2021)

PROteolysis TArgeting Chimeras (PROTACs) technology is a new protein-degradation strategy that has emerged in recent years. It uses bifunctional small molecules to induce the ubiquitination and degradation of target proteins through the ubiquitin-proteasome system. PROTACs can not only be used as potential clinical treatments for diseases such as cancer, immune disorders, viral infections, and neurodegenerative diseases, but also provide unique chemical knockdown tools for biological research in a catalytic, reversible, and rapid manner. In 2019, our group published a review article "PROTACs: great opportunities for academia and industry" in the journal, summarizing the representative compounds of PROTACs reported before the end of 2019. In the past 2 years, the entire field of protein degradation has experienced rapid development, including not only a large increase in the number of research papers on protein-degradation technology but also a rapid increase in the number of small-molecule degraders that have entered the clinical and will enter the clinical stage. In addition to PROTAC and molecular glue technology, other new degradation technologies are also developing rapidly. In this article, we mainly summarize and review the representative PROTACs of related targets published in 2020-2021 to present to researchers the exciting developments in the field of protein degradation. The problems that need to be solved in this field will also be briefly introduced.

Proteolysis-targeting chimeras (PROTACs) in cancer therapy

Proteolysis-targeting chimeras (PROTACs) are engineered techniques for targeted protein degradation. A bifunctional PROTAC molecule with two covalently-linked ligands recruits target protein and E3 ubiquitin ligase together to trigger proteasomal degradation of target protein by the ubiquitin-proteasome system. PROTAC has emerged as a promising approach for targeted therapy in various diseases, particularly in cancers. In this review, we introduce the principle and development of PROTAC technology, as well as the advantages of PROTACs over traditional anti-cancer therapies. Moreover, we summarize the application of PROTACs in targeting critical oncoproteins, provide the guidelines for the molecular design of PROTACs and discuss the challenges in the targeted degradation by PROTACs.

VHL-based PROTACs as potential therapeutic agents: Recent progress and perspectives

Proteolysis targeting chimeras (PROTACs), which hijack proteins of interest (POIs) and recruit E3 ligases for target degradation via the ubiquitin-proteasome pathway, are a novel drug discovery paradigm that has been widely used as biological tools and medicinal molecules with the potential of clinical application value. To date, a wide variety of small molecule PROTACs have been developed. Importantly, VHL-based PROTACs have emerged to be a promising approach for proteins, including those non-druggable ones, such as transcriptional factors and scaffold proteins. VHL-based PRTOACs have been developed for the treatment of diseases that are difficult to be dealt with by conventional methods, such as radiotherapy, chemotherapy, and small molecule inhibitors. In this review, the recent advances of VHL-based PRTOACs were summarized, and the chances and challenges associated with this area were also highlighted.

Research Progress and Application of Bioorthogonal Reactions in Biomolecular Analysis and Disease Diagnosis

Bioorthogonal reactions are rapid, specific and high yield reactions that can be performed in in vivo microenvironments or simulated microenvironments. At present, the main biorthogonal reactions include Staudinger ligation, copper-catalyzed azide alkyne cycloaddition, strain-promoted [3 + 2] reaction, tetrazine ligation, metal-catalyzed coupling reaction and photo-induced biorthogonal reactions. To date, many reviews have reported that bioorthogonal reactions have been used widely as a powerful tool in the field of life sciences, such as in target recognition, drug discovery, drug activation, omics research, visualization of life processes or exogenous bacterial infection processes, signal transduction pathway research, chemical reaction dynamics analysis, disease diagnosis and treatment. In contrast, to date, few studies have investigated the application of bioorthogonal reactions in the analysis of biomacromolecules in vivo. Therefore, the application of bioorthogonal reactions in the analysis of proteins, nucleic acids, metabolites, enzyme activities and other endogenous molecules, and the determination of disease-related targets is reviewed. In addition, this review discusses the future development opportunities and challenges of biorthogonal reactions. This review presents an overview of recent advances for application in biomolecular analysis and disease diagnosis, with a focus on proteins, metabolites and RNA detection.

Effective and transient mapping of protein-protein interactions: Application of novel releasable photoaffinity linkers

Herein, two novel multifunctional releasable photoaffinity linkers were developed for effective and transient tracking interacting proteins with the overall objective of understanding their in vivo biological functions in real-time. These linkers could be used for the chemical modification of protein under moderate experimental conditions to form protein photoaffinity probes. These probes incorporated with both photoaffinity labels and tag-transfer, enable photo-crosslinking of bait proteins along with the release of unrelated groups. These photoaffinity linkers can be utilized to construct probes for disease markers, which could enable rapid diagnosis in a clinical setting at minimal interference with normal physiology.

PROTACs technology for targeting non-oncoproteins: Advances and perspectives

Proteolysis targeting chimeras (PROTACs) have been developed to be an effective technology for targeted protein degradation. Each PROTAC contains three key components: a protein-of-interest (POI) ligand, an E3 ligase ligand, and a linker. These bifunctional molecules can hijack the intracellular inherent ubiquitin-proteasome system to degrade different POIs. With several advantages over other therapeutic strategies, PROTACs have set off a new upsurge of drug discovery in recent years. PRTOACs have been extensively explored worldwide and have excelled not only in cancer diseases but also in cardiovascular diseases, fatty liver disease, immune diseases, neurodegenerative diseases, and viral infections. In this review, we aim to summarize the rapid progress from 2010 to 2021 in PROTACs targeting various non-oncoproteins and elucidate the advantages of PROTACs technology. Finally, the potential challenges of this dynamic field are also discussed.

Design, synthesis and evaluation of novel thienopyrimidine-based agents bearing diaryl urea functionality as potential inhibitors of angiogenesis

Inhibition of angiogenesis is a promising strategy for the treatment of cancer. Herein, we describe the design and synthesis of thieno[2,3-d]pyrimidine-1,3,4-thiadiazole-aryl urea derivatives 11a-m to evaluate their efficacy in the chick chorioallantoic membrane (CAM) assay. Among target agents, 11i had a considerable activity against prostate cancer cell line, PC3 (IC₅₀ = 3.6 μM). Moreover, induction of apoptosis, good inhibitory activity against the growth of capillary blood vessels, and inhibition of VEGFR-2 phosphorylation were noticeable parameters which convinced us that 11i could be considered as a promising candidate for the discovery of novel drugs to treat tumors, particularly prostate cancer.