Potent Tubulin Polymerization Inhibitors Research Articles

Modular Access to Aryl Quinolinyl Ketones via Visible‐Light‐Induced Palladium‐Catalyzed Aldehyde C−H Bond Arylation of Quinoline‐8‐Carbaldehydes with Arylboronic Acid

AbstractThis article describes the development of a room‐temperature visible‐light‐induced palladium‐catalyzed directed aldehyde C−H bond arylation to access aryl quinolinyl ketones. In this pathway, the Pd catalyst plays a dual role by harvesting light as a photocatalyst and catalyzing the chemical transformation via C−H bond activation. This process is general to synthesize a range of aryl quinolinyl ketones and tolerates many common functional groups. Our methodology was successfully applied to synthesize highly potent tubulin polymerization inhibitors.

Application of Chlorosulfonyl Isocyanate (CSI) in the Synthesis of Fused Tetracyclic Ketone Ring Systems.

Chlorosulfonyl isocyanate (CSI) is a complex reagent capable of facilitating numerous synthetic transformations, including lactam/lactone formation, sulfonylation, Friedel-Crafts-type acylations, and cycloadditions. Annulation reactions to form nitrogen-, oxygen-, and sulfur-bearing heterocycles have been observed with CSI; however, the application of CSI toward the generation of fused cyclic ketone ring systems has not been previously reported. A serendipitous discovery of the pertinence of CSI occurred during a structure-activity relationship campaign around our established lead benzosuberene-based molecule that functions as a potent inhibitor of tubulin polymerization. The benzylic olefin within this molecule represents a promising moiety for further functionalization. CSI was initially investigated as a reagent to effect transformation of this olefin to its corresponding β-lactam functionality, but instead resulted in an unexpected tetracyclic fused ring system in high yield (88%). This finding led to an exploration of the reactivity of CSI with various arenes. Benzosuberene analogues with varying functionalizations were synthesized and treated with CSI, with all examples resulting in a fused ring system except those bearing electron-withdrawing groups. Notably, simplified arene structures with fewer substituents were also observed to undergo cyclization under these conditions. This strategy represents a promising approach for the synthesis of appropriately functionalized tetracyclic ring systems.

Synthesis of New Thiazole-Privileged Chalcones as Tubulin Polymerization Inhibitors with Potential Anticancer Activities.

A series of novel thiazole-based chalcones were evaluated for their anticancer activity as potential tubulin polymerization inhibitors. In vitro anticancer screening for the thiazole derivatives 2a-2p exhibited broad-spectrum antitumor activity against various cancer cell lines particularly Ovar-3 and MDA-MB-468 cells with a GI50 range from 1.55 to 2.95 μΜ, respectively. Compound 2e demonstrated significant inhibition of tubulin polymerization, with an IC50 value of 7.78 μM compared to Combretastatin-A4 (CA-4), with an IC50 value of 4.93 μM. Molecular docking studies of compounds 2e, 2g, and 2h into tubulin further supported these findings, revealing that they bind effectively to the colchicine binding site, mirroring key interactions exhibited by CA-4. Computational predictions suggested favorable oral bioavailability and drug-likeness for these compounds, highlighting their potential for further development as chemotherapeutic agents.

Synthesis and biological evaluation of 4-phenyl-5-quinolinyl substituted isoxazole analogues as potent cytotoxic and tubulin polymerization inhibitors against ESCC

The identification of chemically different inhibitors that target the colchicine site of tubulin is still of great value for cancer treatment. Combretastatin A-4(CA-4), a naturally occurring colchicine-site binder characterized by its structural simplicity and biological activity, has served as a structural blueprint for the development of novel analogues with improved safety and therapeutic efficacy. In this study, a library of forty-eight 4-phenyl-5-quinolinyl substituted triazole, pyrazole or isoxazole analouges of CA-4, were synthesized and evaluated for their cytotoxicity against Esophageal Squamous Cell Carcinoma (ESCC) cell lines. Compound C11, which features a 2-methyl substitution at the quinoline and carries an isoxazole ring, emerged as the most promising, with 48 h IC50s of less than 20 nmol/L against two ESCC cell lines. The findings from EBI competitive assay, CETA, and in vitro tubulin polymerization assay of C11 are consistent with those of the positive control colchicine, demonstrating the clear affinity of compound C11 to the colchicine binding site. The subsequent cellular-based mechanism studies revealed that C11 significantly inhibited ESCC cell proliferation, arrested cell cycle at the M phase, induced apoptosis, and impeded migration. Experiments conducted in vivo further confirmed that C11 effectively suppressed the growth of ESCC without showing any toxicity towards the selected animal species. Overall, our research suggests that the tubulin polymerization inhibitor incorporating quinoline and the isoxazole ring may deserve consideration for cancer therapy.

Aluminum-Catalyzed Intramolecular Vinylation of Arenes by Vinyl Cations.

This study addresses the challenges associated with vinyl cation generation, a process that traditionally requires quite specific counterions. Described herein is a novel intramolecular vinylation of arenes catalyzed by aluminum(III) chloride, utilizing practical conditions and readily available vinyl triflates derived from 2-aceto-3-arylpropionates. Comprehensive experimental data support diverse carbocycle synthesis, exemplified by indenes and higher analogues. Control experiments verify the applicability of the vinylation protocol, and synthetic applications showcase a potent tubulin polymerization inhibitor with anticancer properties. Density functional theory computations reveal a Lewis-acid-driven mechanism involving triflate moiety abstraction to generate a reactive vinyl cation.

Structure-based approaches for the design of 6-aryl-1-(3,4,5-trimethoxyphenyl)-1H-benzo[d][1,2,3]triazoles as tubulin polymerization inhibitors

The colchicine binding site on tubulin has been widely acknowledged as an attractive target for anticancer drug exploitation. Here, we reported the structural optimization of the lead compound 4, which was proved in our previous work as a colchicine binding site inhibitor (CBSI). Based on docking researches for the active binding conformation of compound 4, a series of novel 6-aryl-1-(3,4,5-trimethoxyphenyl)-1H-benzo[d][1,2,3]triazole derivatives (9a–9x) were developed by replacing a CH group in the 1H-benzo[d]imidazole skeleton of compound 4 with a nitrogen atom as a hydrogen bond acceptor. Among them, compound 9a showed the strongest antiproliferative activity with IC50 values ranging from 14 to 45 nM against three human cancer cell lines (MCF-7, SGC-7901 and A549), lower than that of compound 4. Mechanistic studies indicated that compound 9a could inhibit tubulin polymerization, destroy the microtubule skeleton, block the cell cycle in G2/M phase, induce cancer cell apoptosis, prevent cancer cell migration and colony formation. Moreover, compound 9a significantly inhibited tumor growth in vivo without observable toxicity in the mice 4T1 xenograft tumor model. In conclusion, this report shows a successful case of the structure-based design approach of a potent tubulin polymerization inhibitor for cancer treatment.

Novel tubulin polymerization inhibitors based on the hybridization of coumarin and indole ring: Design, synthesis and bioactivities evaluation

In order to find the potent tubulin polymerization inhibitors as anticancer drugs, a series of novel coumarin-indole derivatives were synthesized, and the bioactivity of these synthetic compounds was performed to elucidate the mechanism of anticancer activity. In vitro cell experiments indicated that among these compounds, 7a exhibited excellent inhibitory activities on MCF-7, A549 and HepG2 cells, having IC50 values ranging from 1.79 to 40.55 nanomolar, which was better than the positives cisplatin and colchicine. Tubulin polymerization inhibition assay found 7a could inhibit the polymerization of tubulin. Meanwhile, immunofluorescence staining of A549 cells showed that 7a targeted the tubulin to exert its anticancer activity. Additionally, compound 7a displayed significant inhibition of the wound-healing activity of A549 cells. The outcomes of flow cytometry demonstrated 7a could significantly halt the progression of the cell cycle during the G2/M phase and induce the apoptosis of A549 cells by reducing the mitochondrial membrane potential and increasing the level of ROS. Finally, molecular docking further demonstrated 7a could interact with tubulin.Collectively, the promising biological activity of 7a makes it valuable as further development of antitumor drugs.

N-Benzyl arylamide derivatives as novel and potent tubulin polymerization inhibitors against gastric cancers: Design, structure–activity relationships and biological evaluations

N-Benzyl arylamide derivatives as novel and potent tubulin polymerization inhibitors against gastric cancers: Design, structure–activity relationships and biological evaluations

Synthesis, biological evaluation and molecular docking of thiazole hydrazone derivatives grafted with indole as novel tubulin polymerization inhibitors

Tubulin-targeting drugs have increasingly become the focus of anticancer drugs research. Twenty-six novel thiazole hydrazone derivatives grafted with indole were synthesized and estimated for bioactivity as potential tubulin polymerization inhibitors. Among them, compound D11 showed the most excellent inhibition against tubulin assembly (IC50 = 1.68 μM) and in vitro growth inhibitory activity against three human cancer cell lines (IC50 = 0.46, 0.21 and 0.32 μM, respectively for MCF-7, A549 and Hela). Moreover, it can effectively induce apoptosis, block cell cycle in G2/M phase and disrupt the cellular microtubule network. These results, along with molecular docking data, provided an important basis for further optimization of compound D11 as a potential anticancer agent.

Natural-Product-Inspired Discovery of Trimethoxyphenyl-1,2,4-triazolosulfonamides as Potent Tubulin Polymerization Inhibitors.

An approach of natural product-inspired strategy and incorporation of an NP-privileged motif has been investigated for the discovery of new tubulin polymerization inhibitors. Two series, N-Arylsulfonyl-3-arylamino-5-amino-1,2,4-triazole derivatives, and their isomers were considered. The compounds were synthesized by construction of the N-aryl-1,2,4-triazole-3,5-diamine motif and sulfonylation. Although the chemo- and regioselectivity in sulfonylation were challenging due to multiple ring-tautomerizable-NH and exocyclic NH2 functionalities present in the molecular motifs, the developed synthetic method enabled the preparation of designed molecular skeletons with biologically important motifs. The approach also led to explore interesting molecular regio- and stereochemical aspects valuable for activity. The X-ray crystallography study indicated that the hydrogen bonding between the arylamine-NH and the arylsulfonyl-"O" unit and appropriate molecular-functionality topology allowed the cis-locking of two aryls, which is important for tubulin-binding and antiproliferative properties. All synthesized compounds majorly showed characteristic antiproliferative effects in breast cancer cells (MCF-7), and four compounds exhibited potent antiproliferative activity. One compound potently bound to tubulin at the colchicine site and inhibited tubulin polymerization in vitro. The compound significantly depolymerized microtubules in MCF-7 cells, arrested the cells at the G2/M phase, and induced cell death. This study represents the importance of the design strategy in medicinal chemistry and the molecular structural features relevant to anticancer anti-tubulin properties. The explored molecules have the potential for further development.

Verubulin (Azixa) Analogues with Increased Saturation: Synthesis, SAR and Encapsulation in Biocompatible Nanocontainers Based on Ca2+ or Mg2+ Cross-Linked Alginate.

Tubulin-targeting agents attract undiminished attention as promising compounds for the design of anti-cancer drugs. Verubulin is a potent tubulin polymerization inhibitor, binding to colchicine-binding sites. In the present work, a series of verubulin analogues containing a cyclohexane or cycloheptane ring 1,2-annulated with pyrimidine moiety and various substituents in positions 2 and 4 of pyrimidine were obtained and their cytotoxicity towards cancer and non-cancerous cell lines was estimated. The investigated compounds revealed activity against various cancer cell lines with IC50 down to 1-4 nM. According to fluorescent microscopy data, compounds that showed cytotoxicity in the MTT test disrupt the normal cytoskeleton of the cell in a pattern similar to that for combretastatin A-4. The hit compound (N-(4-methoxyphenyl)-N,2-dimethyl-5,6,7,8-tetrahydroquinazolin-4-amine) was encapsulated in biocompatible nanocontainers based on Ca2+ or Mg2+ cross-linked alginate and it was demonstrated that its cytotoxic activity was preserved after encapsulation.

Design, synthesis, docking studies and biological screening of 2-pyrimidinyl-2, 3-dihydro-1H-naphtho [1, 2-e][1, 3] oxazines as potent tubulin polymerization inhibitors

A series of novel substituted 2-pyrimidinyl-2,3-dihydro-1H-naphtho[1,2-e][1, 3]oxazine analogs have been designed and synthesized based on structure-activity relationships from 2-naphthol, substituted pyrimidinyl amines and formalin through ring closure by one-pot three component reaction. These derivatives were evaluated for their in vitro cytotoxicity, cell cycle assay and their inhibitory effect on tubulin polymerization. From the MTT assay, it is clear that most of the synthesized compounds displayed potent cytotoxic activities on HeLa (cervical cancer) and B16F10 (melanoma) cancerous cell lines. The compounds 6b and 6k were found to be more effective against HeLa cell lines and exhibited significant cytotoxicity (with IC50 values 1.26 ± 0.12 µM and 1.16 ± 0.27 µM respectively), accumulation of HeLa cells in G2/M phase and exhibiting induced apoptosis. The immunohistochemistry and fluorescence assays showed that these compounds 6b and 6k inhibited the microtubule assembly in human cervical cancer cells (HeLa) at 2 µM concentration. Furthermore, molecular docking studies of these molecules revealed their better-fit potential as anticancer molecules and have a high affinity for colchicine binding site, indicating more inhibitory potential at the cellular level. Our studies suggest that the newly synthesized compounds may become promising leads for the development of new anti-cancer agents. Communicated by Ramaswamy H. Sarma

Design, synthesis, and biological evaluation of 4-aryl-9H-carbazoles as tubulin polymerization inhibitors with potent anticancer activities

Some novel 4-aryl-9H-carbazoles were designed as potential tubulin polymerization inhibitors through structural optimization and bioisosteric strategy. These compounds showed effective antiproliferative activities against a diverse set of cancer cell lines, including HeLa, HepG2, and SGC-7901 cells. Among them, compound 13k exerted the strongest inhibitory effect on HeLa cells with an IC50 of 1.2 ± 0.09 μM. Mechanism studies indicated that 13k significantly inhibited tubulin polymerization in vitro and disrupted the dynamic homeostasis of microtubules in HeLa cells. Furthermore, 13k concentration-dependently caused G2/M phase cell cycle arrest and apoptosis in HeLa cells. Molecular docking analysis demonstrated the interaction of 13k at the colchicine binding site of tubulin. In addition, the prediction of physicochemical properties studies shows that 13k has good pharmacokinetic properties. These preliminary results suggested that 13k is a new tubulin polymerization inhibitor and worthy of further investigation.

Discovery of 6-aryl-2-(3,4,5-trimethoxyphenyl)thiazole[3,2-b][1,2,4]triazoles as potent tubulin polymerization inhibitors

Tubulin/colchicine-binding site inhibitors (CBSIs) co-crystal structures play an important role in the exploration of novel small molecules for oncotherapy. Based on the analysis of the binding models of tubulin and reported CBSIs, a series of 6-aryl-2-(3,4,5-trimethoxyphenyl)thiazole[3,2-b][1,2,4]triazoles were designed as potential tubulin polymerization inhibitors by binding to distinct colchicine domain of tubulin. Among the compounds synthesized, 7w not only shown noteworthy potency against SGC-7901 cancer cell line (IC50 = 0.21 μM) but also exhibited lower cytotoxicity than colchicine in normal cell line (HUVEC). The mechanism studies elucidated that 7w could cause the apoptosis of cancer cells by inhibiting tubulin polymerization to trigger G2/M arrest. In 4T1-xenograft mice model, 7w significantly inhibited tumor growth without losing weight, demonstrating a promising potential for further development with a unique binding mode at the colchicine-binding site.

Design, Synthesis, and Biological Evaluation of Pyrimidine Dihydroquinoxalinone Derivatives as Tubulin Colchicine Site-Binding Agents That Displayed Potent Anticancer Activity Both In Vitro and In Vivo.

Polymerization of tubulin dimers to form microtubules is one of the key events in cell proliferation. The inhibition of this event has long been recognized as a potential treatment option for various types of cancer. Compound 1e was previously developed by our team as a potent inhibitor of tubulin polymerization that binds to the colchicine site. To further improve the potency and therapeutic properties of compound 1e, we hypothesized based on the X-ray crystal structure that modification of the pyrimidine dihydroquinoxalinone scaffold with additional hetero-atom (N, O, and S) substituents could allow the resulting new compounds to bind more tightly to the colchicine site and display greater efficacy in cancer therapy. We therefore synthesized a series of new pyrimidine dihydroquinoxalinone derivatives, compounds 10, 12b-c, 12e, 12h, and 12j-l, and evaluated their cytotoxicity and relative ability to inhibit proliferation, resulting in the discovery of new tubulin-polymerization inhibitors. Among these, the most potent new inhibitor was compound 12k, which exhibited high cytotoxic activity in vitro, a longer half-life than the parental compound in liver microsomes (IC50 = 0.2 nM, t 1/2 = >300 min), and significant potency against a wide range of cancer cell lines including those from melanoma and breast, pancreatic, and prostate cancers. High-resolution X-ray crystal structures of the best compounds in this scaffold series, 12e, 12j, and 12k, confirmed their direct binding to the colchicine site of tubulin and revealed their detailed molecular interactions. Further evaluation of 12k in vivo using a highly taxane-resistant prostate cancer xenograft model, PC-3/TxR, demonstrated the strong tumor growth inhibition at the low dose of 2.5 mg/kg (i.v., twice per week). Collectively, these results strongly support further preclinical evaluations of 12k as a potential candidate for development.

Structural Perspective of Benzophenones Targeting Tubulin as Anticancer Agents.

Cancer is the leading cause of death and the most significant determinant of life expectancy in almost every country in this twenty-first century. According to the World Health Organization (WHO), cancer is responsible for the leading cause of death globally. Benzophenone derivatives are found in a variety of naturally occurring compounds which are known to be pharmacologically efficacious against a variety of diseases, including cancer. Microtubules are thought to be a good target for cancer chemotherapies. Microtubule polymerization and depolymerization are induced by a variety of natural, synthetic, and semisynthetic chemicals having a benzophenone nucleus, affecting tubulin dynamics. Several medications that affect microtubule dynamics are in various stages of clinical trials, including Combretastatins (phase II), Vincristine (clinically approved), Paclitaxel (in clinical usage), and epothilone (phase III), and only a few have been patented. Benzophenone derivatives target the colchicine binding site of microtubules, damage them and cause cell cycle arrest in the G2-M phase. Belonging to this class of molecules, phenstatin, a potent inhibitor of tubulin polymerization, has shown strongly inhibit cancer cell growth and arrest the G2/M phase of the cell cycle by targeting the colchicine binding site of microtubules. In the present manuscript, we described the benzophenone as tubulin polymerization inhibitors, their Structure-Activity Relationships (SARs) and molecular docking studies that reveal its binding affinity with the colchicine binding site.

Palladium-Catalyzed Directed Aldehyde C-H Arylation of Quinoline-8-carbaldehydes: Exploring the Reactivity Differences between Aryl (Pseudo) Halides.

We have developed a method for Pd-catalyzed direct C-H arylation of quinoline-8-carbaldehydes with either aryl iodides or aryl diazonium salts for the synthesis of aryl quinolinyl ketones. Aryl iodide substituted with an electron-donating group favors the reaction, whereas aryl diazonium salt substituted with an electron-withdrawing group showed excellent reactivity. A range of aryl quinolinyl ketones were synthesized in good-to-excellent yields, with very good functional group tolerance. Our methodology was successfully applied to synthesize highly potent tubulin polymerization inhibitors and can be easily scaled up to a gram scale.

Advances in antitumor research of CA-4 analogs carrying quinoline scaffold

Combretastatin A-4 (CA-4) is a potent inhibitor of tubulin polymerization and a colchicine binding site inhibitor (CBSI). The structure-activity relationship study of CA-4 showed that the cis double bond configuration and the 3,4,5-trimethoxy group on the A ring were important factors to maintain the activity of CA-4. Therefore, starting from this condition, chemists modified the double bond and also substituted 3,4,5-trimethoxyphenyl with various heterocycles, resulting in a new generation of CA-4 analogs such as chalcone, Flavonoid derivatives, indole, imidazole, etc. Quinoline derivatives have strong biological activity and have been sought after by major researchers for their antitumor activity in recent years. This article reviews the research progress of novel CA-4 containing quinoline analogs in anti-tumor from 1992 to 2022 and expounds on the pharmacological mechanisms of these effective compounds, including but not limited to apoptosis, cell cycle, tubulin polymerization inhibition, immune Fluorescence experiments, etc., which lay the foundation for the subsequent development of CA-4 containing quinoline analogs for clinical use.

Rational design, synthesis and biological evaluation of novel 2-(substituted amino)-[1,2,4]triazolo[1,5-a]pyrimidines as novel tubulin polymerization inhibitors

Following our previously reported compound 3, we designed and synthesized a series of new 2-(substituted amino)- [1,2,4]triazolo[1,5-a]pyrimidines as potential tubulin polymerization inhibitors. Among them, analogue 4k, having a 3-hydroxy-4-methoxyphenylamino group, was observed to display excellent antiproliferative activity toward HeLa, HCT116, A549, and T47D with the IC50 values of 0.31, 1.28, 3.99 and 10.32 μM, respectively, which were approximately 32, 48, 4, and 5-fold improvement compared with 3. Importantly, 4k possessed significant selectivity in inhibiting cancer cell lines over the normal HEK293 cells. Moreover, futher mechanism analysis demonstrated that 4k caused G2/M arrest, induced cells apoptosis in HeLa cells, and manifested significant tubulin polymerization inhibitory activity with the IC50 value of 4.9 μM, which is comparable to CA-4 (IC50 = 4.2 μM). The observations performed in this study reveal that 2-arylamino- [1,2,4]triazolo[1,5-a]pyrimidines represent a novel class of tubulin polymerization inhibitors with potent antiproliferative efficacy.

Design, synthesis and biological evaluation of 9-aryl-5H-pyrido[4,3-b]indole derivatives as potential tubulin polymerization inhibitors.

A series of new 9-aryl-5H-pyrido[4,3-b]indole derivatives as tubulin polymerization inhibitors were designed, synthesized, and evaluated for antitumor activity. All newly prepared compounds were tested for their anti-proliferative activity in vitro against three different cancer cells (SGC-7901, HeLa, and MCF-7). Among the designed compounds, compound 7k displayed the strongest anti-proliferative activity against HeLa cells with IC50 values of 8.7 ± 1.3 μM. In addition, 7k could inhibit the polymerization of tubulin and disrupt the microtubule network of cells. Further mechanism studies revealed that 7k arrested cell cycle at the G2/M phase and induced apoptosis in a dose-dependent manner. Molecular docking analysis confirmed that 7k may bind to colchicine binding sites on microtubules. Our study aims to provide a new strategy for the development of antitumor drugs targeting tubulin.