Synthesis and biological evaluation of novel 3,4-diaryl-1,2,5-selenadiazol analogues of combretastatin A-4

Selenization of Small Molecule Drugs: A New Player on the Board

There is an urgent need to develop safer and more effective modalities for the treatment of a wide range of pathologies due to the increasing rates of drug resistance, undesired side effects, poor clinical outcomes, etc. Throughout the years, selenium (Se) has attracted a great deal of attention due to its important role in human health. Besides, a growing body of work has unveiled that the inclusion of Se motifs into a great number of molecules is a promising strategy for obtaining novel therapeutic agents. In the current Perspective, we have gathered the most recent literature related to the incorporation of different Se moieties into the scaffolds of a wide range of known drugs and their feasible pharmaceutical applications. In addition, we highlight different representative examples as well as provide our perspective on Se drugs and the possible future directions, promises, opportunities, and challenges of this ground-breaking area of research.

Incorporating Selenium into Heterocycles and Natural Products─From Chemical Properties to Pharmacological Activities

Selenium (Se)-containing compounds have emerged as potential therapeutic agents for the treatment of a range of diseases. Through tremendous effort, considerable knowledge has been acquired to understand the complex chemical properties and biological activities of selenium, especially after its incorporation into bioactive molecules. From this perspective, we compiled extensive literature evidence to summarize and critically discuss the relationship between the pharmacological activities and chemical properties of selenium compounds and the strategic incorporation of selenium into organic molecules, especially bioactive heterocycles and natural products. We also provide perspectives regarding the challenges in selenium-based medicinal chemistry and future research directions.

Recent Trends in Tubulin-Binding Combretastatin A-4 Analogs for Anticancer Drug Development

Although significant progress over several decades has been evidenced in cancer therapy, there still remains a need for the development of novel and effective therapeutic strategies to treat several relapsed and intractable cancers. In this regard, tubulin protein has become one of the efficient and major targets for anticancer drug discovery. Considering the antimitotic ability, several tubulin inhibitors have been developed to act against various cancers. Among various tubulin inhibitors available, combretastatin-A4 (CA-4), a naturally occurring lead molecule, offers exceptional cytotoxicity (including the drug-resistant cell lines) and antivascular effects. Although CA-4 offers exceptional therapeutic efficacy, several new advancements have been proposed, such as the structural modification via A and B rings, as well as cis-olefinic bridging, which provide highly efficient analogs with improved tubulin-binding efficiency to meet the anticancer drug development requirements. This review systematically emphasizes the recent trends and latest developments in the anticancer drug design & discovery, using CA-4 analogs as the tubulin inhibiting agents, highlighting their structure-activity relationships (SAR) and resultant pharmacological efficacies.

New Multi-Targeted Antiproliferative Agents: Design and Synthesis of IC261-Based Oxindoles as Potential Tubulin, CK1 and EGFR Inhibitors

A series of 3-benzylideneindolin-2-one compounds was designed and synthesized based on combretastatin A-4 and compound IC261, a dual casein kinase (CK1)/tubulin polymerization inhibitor, taking into consideration the pharmacophore required for EGFR-tyrosine kinase inhibition. The new molecular entities provoked significant growth inhibition against PC-3, MCF-7 and COLO-205 at a 10 μM dose. Compounds 6-chloro-3-(2,4,6-trimethoxybenzylidene) indolin-2-one, 4b, and 5-methoxy-3-(2,4,6-trimethoxybenzylidene)indolin-2-one, 4e, showed potent activity against the colon cancer COLO-205 cell line with an IC50 value of 0.2 and 0.3 μM. A mechanistic study demonstrated 4b's efficacy in inhibiting microtubule assembly (IC50 = 1.66 ± 0.08 μM) with potential binding to the colchicine binding site (docking study). With an IC50 of 1.92 ± 0.09 μg/mL, 4b inhibited CK1 almost as well as IC261. Additionally, 4b and 4e were effective inhibitors of EGFR-TK with IC50s of 0.19 μg/mL and 0.40 μg/mL compared to Gifitinib (IC50 = 0.05 μg/mL). Apoptosis was induced in COLO-205 cells treated with 4b, with apoptotic markers dysregulated. Caspase 3 levels were elevated to more than three-fold, while Cytochrome C levels were doubled. The cell cycle was arrested in the pre-G1 phase with extensive cellular accumulation in the pre-G1 phase, confirming apoptosis induction. Levels of cell cycle regulating proteins BAX and Bcl-2 were also defective. The binding interaction patterns of these compounds at the colchicine binding site of tubulin and the Gifitinib binding site of EGFR were verified by molecular docking, which adequately matched the reported experimental result. Hence, 4b and 4e are considered promising potent multitarget agents against colon cancer that require optimization.

Colchicine-Binding Site Inhibitors from Chemistry to Clinic: A Review

It is over 50 years since the discovery of microtubules, and they have become one of the most important drug targets for anti-cancer therapies. Microtubules are predominantly composed of the protein tubulin, which contains a number of different binding sites for small-molecule drugs. There is continued interest in drug development for compounds targeting the colchicine-binding site of tubulin, termed colchicine-binding site inhibitors (CBSIs). This review highlights CBSIs discovered through diverse sources: from natural compounds, rational design, serendipitously and via high-throughput screening. We provide an update on CBSIs reported in the past three years and discuss the clinical status of CBSIs. It is likely that efforts will continue to develop CBSIs for a diverse set of cancers, and this review provides a timely update on recent developments.

Combretastatin analogues in cancer biology: A prospective view

The stilbenoid combretastatin and its derivatives are potent inhibitors of angiogenesis and cell proliferation and induce apoptosis. They disrupt cytoskeletal dynamics and modulate cell morphology, motility, and invasion. Hence they have been viewed as potential as anticancer agents. The impediments of poor solubility and bioavailability and the spontaneous geometric isomerisation of combretastatin into an inactive form have led to intensive efforts towards evolving novel analogues to provide more efficacious biological outcome. Importantly, isomerically stable and biologically active cis-restricted analogues have been synthesised and tested. However, very few analogues have been tested in preclinical models to assess their effects on processes relevant to cancer development and progression. Hence the accent here is on the signalling systems operated by the new derivatives and their biological effects with reference to cancer progression. Combretastatins modulate an extensive network of signalling emphasising their varied versatility. Harnessing these systems and accentuating or counteracting aberrant signalling could open potential avenues of approach to the designing of novel derivatives with enhanced performance. The import of mammalian target of rapamycin pathway, which co-ordinates growth factor receptor signalling, epithelial-mesenchymal transition activation and angiogenic signalling, is emphasised. It may be viewed as a prime target for allosteric inhibition in combination with combretastatin analogues to ascertain their potential in cancer control.

Activated carbon/Brønsted acid-promoted aerobic benzylic oxidation under "on-water" condition: Green and efficient synthesis of 3-benzoylquinoxalinones as potent tubulin inhibitors

Green chemistry is becoming the favored approach to preparing drug molecules in pharmaceutical industry. Herein, we developed a clean and efficient method to synthesize 3-benzoylquinoxalines via activated carbon promoted aerobic benzylic oxidation under "on-water" condition. Moreover, biological studies with this class of compounds reveal an antiproliferative profile. Further structure modifications are performed and the investigations exhibited that the most active 12a could inhibit the microtubule polymerization by binding to tubulin and thus induce multipolar mitosis, G2/M phase arrest, and apoptosis of cancer cells. In addition, molecular docking studies allow the rationalization of the pharmacodynamic properties observed. Our systematic studies provide not only guidance for applications of O₂/AC/H₂O system, but also a new scaffold targeting tubulin for antitumor agent discovery.

Development and Therapeutic Potential of Selenazo Compounds

Incorporation of selenium (Se) atom into small molecules can substantially enhance their antioxidant, anti-inflammatory, antimutagenic, antitumoral or chemopreventive, antiviral, antibacterial, antifungal, antiparasitic, and neuroprotective effects. Specifically, selenazo compounds have received great attention owing to their chemical properties, pharmaceutical applications, and low toxicity. In this Perspective, we compile extensive literature evidence with the description and discussion of the most recent advances in different selenazo and selenadiazo motifs as potential pharmacological candidates. We also provide some perspectives on the challenges and future directions in the advancement of these selenazo compounds, each of which could generate drug candidates for various diseases.

Design, synthesis and biological evaluation of 3,4-diaryl-1,2,5-oxadiazole-2/5-oxides as highly potent inhibitors of tubulin polymerization

Structure-activity relationships for rigid analogues of combretastatin A-4 (CA-4) were investigated, leading to the discovery of a series of 3,4-diaryl-1,2,5-oxadiazole-N-oxides. Among them, 7n' and 7n'' showed remarkable antiproliferative activities against three cancer cell lines in nanomolar concentrations. Interestingly, 7n' inhibited tubulin polymerization much more efficiently than CA-4. Cellular mechanism investigation elucidated 7n' disrupted the cellular microtubule structure, arrested cell cycle at G₂/M phase and induces apoptosis. Molecular modeling study revealed 1,2,5-oxadiazole-N-oxide ring could increase a hydrogen bond interaction with the binding site. These results provide impetus and further guidance for the development of new CA-4 analogues.

Synthesis and antiproliferative activity of 17-[1',2',3']-selenadiazolylpregnenolone compounds

Using pregnenolone as a starting material, some 3-substituted 17-[1',2',3']-selenadiazolylpregnenolone derivatives were synthesized, and their structures were characterized by IR, NMR and HRMS. The in vitro antitumor activity of the compounds was assayed against PC-3、SKOV3、T47D、MCF-7 and HEK293T cell lines. The results show that some compounds display selective antiproliferative activity against PC-3 and SKOV3 cells lines and are almost inactive to normal kidney epithelial cells (HEK293T). The IC₅₀ value are much better than that of abiraterone (positive control).

Medicinal chemistry of vicinal diaryl scaffold: A mini review

The privileged structures have been widely used as a valuable template in new drug discovery. 1,2-Diaryl or vicinal diaryl is a simple scaffold found in many drugs and naturally occurring compounds. From synthetic point of view, the vicinal diaryl derivatives are easily accessible due to their facile and expedient syntheses. These scaffolds have shown numerous interesting pharmacological activities against various diseases with lot of clinical potentials. This review aims to highlight the evidence of vicinal diaryl motif as a privileged scaffold in COX-2 inhibitors and CA-4 analogs.

Synthesis and Reactions of α-Hydroxyphosphonates

This review summarizes the main synthetic routes towards α-hydroxyphosphonates that are known as enzyme inhibitors, herbicides and antioxidants, moreover, a number of representatives express antibacterial or antifungal effect. Special attention is devoted to green chemical aspects. α-Hydroxyphosphonates are also versatile intermediates for other valuable derivatives. O-Alkylation and O-acylation are typical reactions to afford α-alkoxy-, or α-acyloxyphosphonates, respectively. The oxidation of hydroxyphosphonates leads to ketophosphonates. The hydroxy function at the α carbon atom of hydroxyphosphonates may be replaced by a halogen atom. α-Aminophosphonates formed in the nucleophilic substitution reaction of α-hydroxyphosphonates with primary or secondary amines are also potentially bioactive compounds. Another typical reaction is the base-catalyzed rearrangement of α-hydroxy-phosphonates to phosphates. Hydrolysis of the ester function of hydroxyphosphonates leads to the corresponding phosphonic acids.

Synthesis and biological evaluation of new 3-amino-2-azetidinone derivatives as anti-colorectal cancer agents

Several synthetic combretastatin A4 (CA-4) derivatives were recently prepared to increase the drug efficacy and stability of the natural product isolated from the South African tree Combretum caffrum. A group of ten 3-amino-2-azetidinone derivatives, as combretastatin A4 analogues, was selected through docking experiments, synthesized and tested for their anti-proliferative activity against the colon cancer SW48 cell line. These molecules, through the formation of amide bonds in position 3, allow the synthesis of various derivatives that can modulate the activity with great resistance to hydrolytic conditions. The cyclization to obtain the 3-aminoazetidinone ring is highly diastereoselective and provides a trans biologically active isomer under mild reaction conditions with better yields than the 3-hydroxy-2-azetidinone synthesis. All compounds showed IC₅₀ values ranging between 14.0 and 564.2 nM, and the most active compound showed inhibitory activity against tubulin polymerization in vitro, being a potential therapeutic agent against colon cancer.

Synthesis of 28a-homoselenolupanes and 28a-homoselenolupane saponins

A practical synthesis of 28a-homo-28a-selenolupane triterpenes and the corresponding selenosaponins containing d-mannose, l-arabinose, l-rhamnose, and d-idose moieties is described. Selenium containing triterpenes were obtained from the readily available 3-O-allyl-homobetulin mesylate by nucleophilic substitution with the selenocyanate ion which upon reduction of the -SeCN group afforded the free selenol. Glycosylation using classical Schmidt donors gave 1,2-trans selenosaponins as the main product as well as minute amounts of 1,2-cis isomers. This is one of the very few examples of the synthesis of selenoglycosides by direct glycosylation of free selenols. The studied selenol showed high resistance to air oxidation resulting in good stability during the synthesis of selenolupane derivatives. Cytotoxic activities of new homoselenolupane derivatives were also evaluated in vitro and revealed that some triterpenes exhibited an interesting profile against human cancer cell lines.

Nontoxic combretafuranone analogues with high in vitro antibacterial activity

A library of thirty two 3,4-diphenylfuranones related to both combretastatin A-4 and antifungal 5-(acyloxymethyl)-3-(halophenyl)-2,5-dihydrofuran-2-ones was prepared. Cytotoxic effects on a panel of cancer and normal cell lines and antiinfective activity were evaluated, and the data were complemented with tests for the activation of caspase 3 and 7. High cytotoxicity was observed in some of the halogenated analogues, eg. 3-(3,4-dichlorophenyl)-4-(4-methylphenyl)-2,5-dihydrofuran-2-one with IC₅₀ 0.12-0.23 μM, but the compounds were also highly toxic against non-malignant control cells. More importantly, notable antibacterial activity indicating G⁺ selectivity has been found in the 3,4-diarylfuranone class of compounds for the first time. Hydroxymethylation of furanone C5 knocked out cytotoxic effects (up to 40 μM) while maintaining significant activity against Staphylococcus strains in some derivatives. MIC₉₅ of the most promising compound, 3-(4-bromophenyl)-5,5-bis(hydroxymethyl)-4-(4-methylphenyl)-2,5-dihydrofuran-2-one against S. aureus strain ATCC 6538 was 0.98 μM (0.38 μg/mL) and 3.9 μM (1.52 μg/mL) after 24 and 48 h, respectively.

The design, synthesis and evaluation of selenium-containing 4-anilinoquinazoline hybrids as anticancer agents and a study of their mechanism

We report the design, synthesis and evaluation of 2-chloro-N-methyl-N-(4-selenocyanatophenyl)quinazolin-4-amine and its analogues as anticancer agents and the mechanism study.

Design, synthesis and structure-activity relationship of 3,6-diaryl-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazines as novel tubulin inhibitors

A novel series of 3,6-diaryl-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazines were designed, synthesized and biologically evaluated as vinylogous CA-4 analogues, which involved a rigid [1,2,4]triazolo[3,4-b][1,3,4]thiadiazine scaffold to fix the configuration of (Z,E)-butadiene linker of A-ring and B-ring. Among these rigidly vinylogous CA-4 analogues, compounds 4d, 5b, 5i, 6c, 6e, 6g, 6i and 6k showed excellent antiproliferative activities against SGC-7901, A549 and HT-1080 cell lines with IC₅₀ values at the nanomolar level. Compound 6i showed the most highly active antiproliferative activity against the three human cancer cell lines with an IC₅₀ values of 0.011-0.015 µM, which are comparable to those of CA-4 (IC₅₀ = 0.009-0.013 µM). Interestingly, SAR studies revealed that 3,4-methylenedioxyphenyl, 3,4-dimethoxyphenyl, 3-methoxyphenyl and 4-methoxyphenyl could replace the classic 3,4,5-trimethoxyphenyl in CA-4 structure and keep antiproliferative activity in this series of designed compounds. Tubulin polymerization experiments showed that 6i could effectively inhibit tubulin polymerization, which was corresponded with CA-4, and immunostaining experiments suggested that 6i significantly disrupted microtubule/tubulin dynamics. Furthermore, 6i potently induced cell cycle arrest at G₂/M phase in SGC-7901 cells. Competitive binding assays and docking studies suggested that compound 6i binds to the tubulin perfectly at the colchicine binding site. Taken together, these results revealed that 6i may become a promising lead compound for new anticancer drugs discovery.

Recent advances in combretastatin based derivatives and prodrugs as antimitotic agents

The dynamic and crucial role of tubulin in different cellular functions rendered it a promising target in anticancer drug development. Combretastatin A-4 (CA-4), an inhibitor of tubulin polymerization isolated from natural sources, is a lead molecule with significant cytotoxicity against tumour cells. Owing to its non polar nature it exhibits low solubility in natural biological fluids, thereby prompting the development of new CA-4 based derivatives. The modification of this lead molecule was mostly carried out by keeping the crucial cis-orientation of the double bond intact, along with a trimethoxyphenyl aromatic ring, by employing different approaches. The issue of solubility was also addressed by the development of water soluble prodrugs of CA-4. The present review highlights the investigations into the parallel development of both new CA-4 based derivatives and prodrugs in the past few years.

Synthesis and bioevaluation of N,4-diaryl-1,3-thiazole-2-amines as tubulin inhibitors with potent antiproliferative activity

A series of N,4-diaryl-1,3-thiazole-2-amines containing three aromatic rings with an amino linker were designed and synthesized as tubulin inhibitors and evaluated for their antiproliferative activity in three human cancer cell lines. Most of the target compounds displayed moderate antiproliferative activity, and N-(2,4-dimethoxyphenyl)-4-(4-methoxyphenyl)-1,3-thiazol-2-amine (10s) was determined to be the most potent compound. Tubulin polymerization and immunostaining experiments revealed that 10s potently inhibited tubulin polymerization and disrupted tubulin microtubule dynamics in a manner similar to CA-4. Moreover, 10s effectively induced SGC-7901 cell cycle arrest at the G₂/M phase in both concentration- and time-dependent manners. The molecular docking results revealed that 10s could bind to the colchicine binding site of tubulin.

Discovery and Optimization of Novel 5-Indolyl-7-arylimidazo[1,2-a]pyridine-8-carbonitrile Derivatives as Potent Antitubulin Agents Targeting Colchicine-binding Site

Aiming at development of potent antitubulin agents targeting colchicine-binding site, a series of novel 5-indolyl-7-arylimidazo[1,2-a]pyridine-8-carbonitrilederivatives (5a–5v and 7a–7h) were designed based on bioisosterism and hybridization strategies. All these compounds were concisely synthesized via a three-step process and examined against five human cancer cell lines (HT-29, A549, MKN-45, MDA-MB-231 and SMMC-7721) along with a normal human cell (L02) in vitro. A structure-activity relationships (SARs) study was carried out and optimization towards this series of compounds in cellular assay resulted in the discovery of 5k, which displayed similar or better antitumor potency against the tested cancer cells with IC₅₀ value ranging from 0.02 to 1.22 μM superior to CA-4 and Crolibulin. Significantly, a cell cycle study disclosed the ability of 5k to arrest cell cycle at the G2/M phase, and immunofluorescence assay as well as a colchicine competition assay revealed that tubulin polymerization was disturbed by 5k by binding to the colchicine site. Moreover, the molecular modeling mode showed the posture of 5k and Crolibulin was similar in the colchcine-binding pocket of tubulin as identified with the SARs and pharmacological results. Together, all these results rationalized 5k might serve as a promising lead for a novel class of antitubulin agents for cancer treatments.

Synthesis and Bioevaluation of 3,6-Diaryl-[1,2,4]triazolo[4,3-b] Pyridazines as Antitubulin Agents

A series of 3,6-diaryl-[1,2,4]triazolo[4,3-b]pyridazines were designed as a class of vinylogous CA-4 analogues. The easily isomerized (Z,E)-butadiene linker of vinylogous CA-4 was replaced by a rigid [1,2,4]triazolo[4,3-b]pyridazine scaffold. Twenty-one target compounds were synthesized and exhibited moderate to potent antiproliferative activity. The compound 4q with a 3-amino-4-methoxyphenyl moiety as the B-ring, comparable to CA-4 (IC₅₀ = 0.009-0.012 μM), displayed the highly active antiproliferative activity against SGC-7901, A549, and HT-1080 cell lines with IC₅₀ values of 0.014, 0.008, and 0.012 μM, respectively. Tubulin polymerization experiments indicated that 4q effectively inhibited tubulin polymerization, and immunostaining assay revealed that 4q significantly disrupted tubulin microtubule dynamics. Moreover, cell cycle studies revealed that compound 4q dramatically arrested cell cycle progression at G2/M phase in A549 cells. Molecular modeling studies showed that 4q could bind to the colchicine binding site on microtubules.

Novel Natural Product- and Privileged Scaffold-Based Tubulin Inhibitors Targeting the Colchicine Binding Site

Tubulin inhibitors are effective anticancer agents, however, there are many limitations to the use of available tubulin inhibitors in the clinic, such as multidrug resistance, severe side-effects, and generally poor bioavailability. Thus, there is a constant need to search for novel tubulin inhibitors that can overcome these limitations. Natural product and privileged structures targeting tubulin have promoted the discovery and optimization of tubulin inhibitors. This review will focus on novel tubulin inhibitors derived from natural products and privileged structures targeting the colchicine binding site on tubulin.

Combretastatin A-4 analogues with benzoxazolone scaffold: Synthesis, structure and biological activity

In order to design and synthesize a new class of heterocyclic analogues of natural combretastatin A-4 and its synthetic derivative AVE8062, the benzoxazolone ring was selected as a scaffold for a bioisosteric replacement of the ring B of both molecules. A library of 28 cis- and trans-styrylbenzoxazolones was obtained by a modified Wittig reaction under Boden's conditions. Structures of the newly synthesized compounds bearing the 3,4,5-trimethoxy-, 3,4-dimethoxy-, 3,5-dimethoxy-, and 4-methoxystyryl fragment at position 4, 5, 6 or 7 of benzoxazolone core were determined on the basis of spectral and X ray data. The in vitro cytotoxicity of styrylbenzoxazolones against different cell lines was examined. Stilbene derivative 16Z, (Z)-3-methyl-6-(3,4,5-trimethoxystyryl)-2(3H)-benzoxazolone, showed highest antiproliferative potential of the series, with IC50 of 0.25 μM against combretastatin resistant cell line HT-29, 0.19 μM against HepG2, 0.28 μM against EA.hy926 and 0.73 μM against K562 cells. Furthermore, the results of flow cytometric analysis confirmed that 16Z induced cell cycle arrest in G2/M phase in the cell lines like combretastatin A-4. This arrest is followed by an abnormal exit of cells from mitosis without cytokinesis into a pseudo G1-like multinucleate state leading to late apoptosis and cell death. Accordingly, synthetic analogue 16Z was identified as the most promising potential anticancer agent in present study, and was selected as lead compound for further detailed investigations.

Combretastatins: more than just vascular targeting agents?

Several prodrugs of the naturally occurring combretastatins have undergone extensive clinical evaluation as vascular targeting agents (VTAs). Their increased selectivity toward endothelial cells together with their innate ability to rapidly induce vascular shutdown and inhibit tumor growth at doses up to 10-fold less than the maximum tolerated dose led to the clinical evaluation of combretastatins as VTAs. Tubulin is well established as the molecular target of the combretastatins and the vast majority of its synthetic derivatives. Furthermore, tubulin is a highly validated molecular target of many direct anticancer agents routinely used as front-line chemotherapeutics. The unique vascular targeting properties of the combretastatins have somewhat overshadowed their development as direct anticancer agents and the delineation of the various cell death pathways and anticancer properties associated with such chemotherapeutics. Moreover, the ongoing clinical trial of OXi4503 (combretastatin-A1 diphosphate) together with preliminary preclinical evaluation for the treatment of refractory acute myelogenous leukemia has successfully highlighted both the indirect and direct anticancer properties of combretastatins. In this review, we discuss the development of the combretastatins from nature to the clinic. The various mechanisms underlying combretastatin-induced cell cycle arrest, mitotic catastrophe, cell death, and survival are also reviewed in an attempt to further enhance the clinical prospects of this unique class of VTAs.

Microwave-assisted synthesis, molecular docking and antiproliferative activity of (3/5-aryl-1,2,4-oxadiazole-5/3-yl)(3,4,5-trimethoxyphenyl)methanone oxime derivatives

A microwave-assisted synthesis method of building a 1,2,4-oxadiazole skeleton was developed.

Synthesis, anticancer activity and molecular docking studies on a series of heterocyclic trans-cyanocombretastatin analogues as antitubulin agents

A series of heterocyclic combretastatin analogues have been synthesized and evaluated for their anticancer activity against a panel of 60 human cancer cell lines. The most potent compounds were two 3,4,5-trimethoxy phenyl analogues containing either an (Z)-indol-2-yl (8) or (Z)-benzo[b]furan-2-yl (12) moiety; these compounds exhibited GI50 values of <10 nM against 74% and 70%, respectively, of the human cancer cell lines in the 60-cell panel. Compounds 8, and 12 and two previously reported compounds in the same structural class, i.e. 29 and 31, also showed potent anti-leukemic activity against leukemia MV4-11 cell lines with LD50 values = 44 nM, 47 nM, 18 nM, and 180 nM, respectively. From the NCI anti-cancer screening results and the data from the in vitro toxicity screening on cultured AML cells, seven compounds: 8, 12, 21, 23, 25, 29 and 31 were screened for their in vitro inhibitory activity on tubulin polymerization in MV4-11 AML cells; at 50 nM, 8 and 29 inhibited polymerization of tubulin by >50%. The binding modes of the three most active compounds (8, 12 and 29) to tubulin were also investigated utilizing molecular docking studies. All three molecules were observed to bind in the same hydrophobic pocket at the interface of α- and β-tubulin that is occupied by colchicine, and were stabilized by van der Waals' interactions with surrounding tubulin residues. The results from the tubulin polymerization and molecular docking studies indicate that compounds 8 and 29 are the most potent anti-leukemic compounds in this structural class, and are considered lead compounds for further development as anti-leukemic drugs.