Development of 13H-benzo[f]chromeno[4,3-b][1,7]naphthyridines and their salts as potent cytotoxic agents and topoisomerase I/IIα inhibitors.

A novel series of 35 angularly fused pentacyclic 13H-benzo[f]chromeno[4,3-b][1,7]naphthyridines and 13H-benzo[f]chromeno[4,3-b][1,7]naphthyridin-5-ium chlorides were designed and synthesized. Their cytotoxic activities were investigated against six human cancer cell lines (NCIH23, HCT15, NUGC-3, ACHN, PC-3, and MDA-MB-231). Among all screened compounds; 28, 30, 34, 35, 46, 48, 52, and 53 compounds exhibited potent cytotoxic activities against all tested human cancer cell lines. Further, these potent lead cytotoxic agents were evaluated against human Topoisomerase I and IIα inhibition. Among them, the compound 48 exhibited dual Topoisomerase I and IIα inhibition especially at 20 µM concentrations the compound 48 exhibited 1.25 times more potent Topoisomerase IIα inhibitory activity (38.3%) than the reference drug etoposide (30.6%). The compound 52 also exhibited excellent (88.4%) topoisomerase I inhibition than the reference drug camptothecin (66.7%) at 100 µM concentrations. Molecular docking studies of the compounds 48 and 52 with topo I discovered that they both intercalated into the DNA single-strand cleavage site where the compound 48 have van der Waals interactions with residues Arg364, Pro431, and Asn722 whilst the compound 52 have with Arg364, Thr718, and Asn722 residues. Both the compounds 48 and 52 have π-π stacking interactions with the stacked DNA bases. The docking studies of the compound 48 with topo IIα explored that it was bound to the topo IIα DNA cleavage site where etoposide was situated. The benzo[f]chromeno[4,3-b][1,7]naphthyridine ring of the compound 48 was stacked between the DNA bases of the cleavage site with π-π stacking interactions and there were no hydrogen bond interactions with topo IIα.

Design, synthesis and biological evaluation of 1,3-diphenylbenzo[f][1,7]naphthyrdines.

A novel series of twenty 1,3-diphenylbenzo[f][1,7]benzonaphthyrdine derivatives were designed and synthesized through intermolecular imino Diels-Alder reaction. Their in vitro cytotoxic activities were evaluated against six human cancer cell lines (NCIH23, HCT15, NUGC-3, ACHN, PC-3, and MDA-MB-231). Majority of synthesized compounds exhibited significant cytotoxic activities against all tested human cancer cell lines. Among them 4l, 4m, and 4o derivatives exhibited most promising cytotoxic activities. Furthermore these compounds were evaluated against human Topoisomerase IIα inhibition. Interestingly, the compound 4l exhibited 1.3 and 1.2 times more potent human Topoisomerase IIα inhibition than the reference drug etoposide in both 100µM and 20µM concentrations respectively. Molecular docking studies for the compound 4l have also been executed by Sybyl X-2.1 in which it reveals the binding site of the compound 4l with topo IIα DNA cleavage site where etoposide was situated. The benzo[f][1,7]naphthyridine ring was stacked between the DNA bases of the cleavage site.

Effect of chlorine substituent on cytotoxic activities: Design and synthesis of systematically modified 2,4-diphenyl-5H-indeno[1,2-b]pyridines.

In continuation of our previous work, six hydroxylated 2,4-diphenyl-5H-indeno[1,2-b]pyridine analogs were modified by introducing one chlorine functionality at ortho, meta or para position of the 2- or 4-phenyl ring. Eighteen new chlorinated compounds were thus prepared and assessed for topoisomerase inhibitory activity and cytotoxicity against HCT15, T47D, and HeLa cancer cell lines. All of the chlorinated compounds displayed significant cytotoxic effect, revealing potent anticancer activity against T47D breast cancer cells. This functional group modification allowed us to explore the importance of chlorine group substitution for the cytotoxic properties. The information reported here provides valuable insight for further study to develop new anticancer agents using related scaffolds.

Design, synthesis, topoisomerase I & II inhibitory activity, antiproliferative activity, and structure-activity relationship study of pyrazoline derivatives: An ATP-competitive human topoisomerase IIα catalytic inhibitor.

A series of pyrazoline derivatives (5) were synthesized in 92-96% yields from chalcones (3) and hydrazides (4). Subsequently, topo-I and IIα-mediated relaxation and antiproliferative activity assays were evaluated for 5. Among the tested compounds, 5h had a very strong topo-I activity of 97% (Camptothecin, 74%) at concentration of 100 µM. Nevertheless, all the compounds 5a-5i showed significant topo II inhibitory activity in the range of 90-94% (Etoposide, 96%) at the same concentration. Cytotoxic potential of these compounds was tested in a panel of three human tumor cell lines, HCT15, BT474 and T47D. All the compounds showed strong activity against HCT15 cell line with IC50 at the range of 1.9-10.4 µM (Adriamycin, 23.0; Etoposide, 6.9; and Camptothecin, 7.1 µM). Moreover, compounds 5c, 5f and 5i were observed to have strong antiproliferative activity against BT474 cell lines. Since, compound 5d showed antiproliferative activity at a very low IC50 thus 5d was then selected to study on their mode of action with diverse methods of ATP competition assay, ATPase assay and DNA-topo IIα cleavable complex assay and the results revealed that it functioned as a ATP-competitive human topoisomerase IIα catalytic inhibitor. Further evaluation of endogenous topo-mediated DNA relaxation in cells has been conducted to find that, 5d inhibited endogenous topo-mediated pBR322 plasmid relaxation is more efficient (78.0 ± 4.7% at 50 µM) than Etoposide (36.0 ± 1.7% at 50 µM).

Design and synthesis of novel 2,4-diaryl-5H-indeno[1,2-b]pyridine derivatives, and their evaluation of topoisomerase inhibitory activity and cytotoxicity.

For the development of potential anticancer agents, we designed and synthesized 30 new 2,4-diaryl-5H-indeno[1,2-b]pyridine derivatives containing aryl moiety such as furyl, thienyl, pyridyl, and phenyl at 2- and 4-position of 5H-indeno[1,2-b]pyridine. They were evaluated for topoisomerase I and II inhibitory activity, and cytotoxicity against several human cancer cell lines. Among prepared 30 compounds, 7, 8, 9, 10, 12, 14, 16, 19, 20, 22, and 23 with 2- or 3-furyl and/or 2- or 3-thienyl either at 2- or 4-position of central pyridine showed the significant or moderate topoisomerase II inhibitory activity. Compounds 7, 8, 11, 12, 13, and 22 with 2-furyl, 2-thienyl or 3-thienyl at 2-position of central pyridine showed the significant or moderate topoisomerase I inhibitory activity. Especially, compound 12 with strong topoisomerase II inhibitory activity at 100 µM and 20 µM, and moderate topoisomerase I inhibitory activity displayed strong cytotoxicity against several human cancer cell lines.

Design and synthesis of conformationally constrained hydroxylated 4-phenyl-2-aryl chromenopyridines as novel and selective topoisomerase II-targeted antiproliferative agents.

To develop novel selective topoisomerase II inhibitors, we designed and synthesized a series of conformationally constrained hydroxylated 4-phenyl-2-aryl chromenopyridines and evaluated their topoisomerase inhibitory activity and cytotoxicity against three human cancer cell lines (DU145, HCT15, and T47D) and a normal cell line (MCF10A). All of the prepared compounds displayed stronger or similar topoisomerase II inhibitory activity as well as cytotoxicity against three human cancer cell lines compared to etoposide. Compounds 10a, 10g, 11a, 11f, 11g, 12a, 12f, and 12g especially showed stronger topoisomerase II inhibitory activity as compared to etoposide at both 100 µM and 20 µM. A structure-activity relationship study revealed that hydroxyphenyl moiety at 4-position of pyridine and ortho-hydroxyphenyl or thienyl moiety at 2-position of pyridine has an important role in displaying selective topoisomerase II inhibition. The compound 12b with para-hydroxyphenyl and meta-hydroxyphenyl at 4- and 2-position of pyridine, respectively, showed the most significant cytotoxicity against all three cancer cell lines, whereas less cytotoxicity to a normal cell line as compared to adriamycin.

Effect of conjugated linoleic acid, µ-calpain inhibitor, on pathogenesis of Alzheimer's disease.

µ-Calpain is a calcium-dependent cysteine protease, which is activated by µM concentration of calcium in vitro. Disrupted intracellular calcium homeostasis leads to hyper-activation of µ-calpain. Hyper-activated µ-calpain enhances the accumulation of ß-amyloid peptide by increasing the expression level of ß-secretase (BACE1) and induces hyper-phosphorylation of tau along with the formation of neurofibrillary tangle by mediating p35 cleavage into p25, both of which are the major mechanisms of neurodegeneration in Alzheimer's disease (AD). Hence, inhibition of µ-calpain activity is very important in the treatment and prevention of AD. In this study, conjugated linoleic acid (CLA), an eighteen-carbon unsaturated fatty acid, was discovered as a µ-calpain-specific inhibitor. CLA showed neuroprotective effects against neurotoxins such as H2O2 and Aß1-42 in SH-SY5Y cells, and inhibited Aß oligomerization/fibrillation and Aß-induced Zona Occludens-1 degradation. In addition, CLA decreased the levels of proapoptotic proteins, p35 conversion to p25 and tau phosphorylation. These findings implicate CLA as a new core structure for selective µ-calpain inhibitors with neuroprotective effects. CLA should be further evaluated for its potential use as an AD therapeutic agent.

Ethyl 2-(benzylidene)-7-methyl-3-oxo-2,3-dihydro-5H-thiazolo[3,2-a]pyrimidine-6-carboxylate analogues as a new scaffold for protein kinase casein kinase 2 inhibitor.

Protein kinase casein kinase 2 (PKCK2) is a constitutively active, growth factor-independent serine/threonine kinase, and changes in PKCK2 expression or its activity are reported in many cancer cells. To develop a novel PKCK2 inhibitor(s), we first performed cell-based phenotypic screening using 4000 chemicals purchased from ChemDiv chemical libraries (2000: randomly selected; 2000: kinase-biased) and performed in vitro kinase assay-based screening using hits found from the first screening. We identified compound 24 (C24)[(Z)-ethyl 5-(4-chlorophenyl)-2-(3,4-dihydroxybenzylidene)-7-methyl-3-oxo-3,5-dihydro-2H-thiazolo[3,2-a] pyrimidine-6-carboxylate] as a novel inhibitor of PKCK2 that is more potent and selective than 4,5,6,7-tetrabromobenzotriazole (TBB). In particular, compound 24 [half maximal inhibitory concentration (IC50)=0.56µM] inhibited PKCK2 2.2-fold more efficiently than did TBB (IC50=1.24µM), which is quite specific toward PKCK2 with respect to ATP binding, in a panel of 31 human protein kinases. The Ki values of compound 24 and TBB for PKCK2 were 0.78µM and 2.70µM, respectively. Treatment of cells with compound 24 inhibited endogenous PKCK2 activity and showed anti-proliferative and pro-apoptotic effects against stomach and hepatocellular cancer cell lines more efficiently than did TBB. As expected, compound 24 also enabled tumor necrosis factor-related apoptosis inducing ligand (TRAIL)-resistant cancer cells to be sensitive toward TRAIL. In comparing the molecular docking of compound 24 bound to PKCK2α versus previously reported complexes of PKCK2 with other inhibitors, our findings suggest a new scaffold for specific PKCK2α inhibitors. Thus, compound 24 appears to be a selective, cell-permeable, potent, and novel PKCK2 inhibitor worthy of further characterization.

Expression and purification of a soluble ESX-binding core domain of SUR2.

For HER2 overexpression, the ESX transcription factor must interact with both the HER2 promoter and Sur2, a subunit of human mediator complex, using its Ets domain and transactivation domain, respectively. HER2 overexpression is a marker of poor prognosis in various types of cancers. Thus, interfering with the ESX-Sur2 interaction has been suggested as a novel strategy for the treatment of HER2 positive cancers. To design small molecule inhibitors against the ESX-Sur2 interaction, it is necessary to identify the structure of the interface of ESX-Sur2 binding. Therefore, in this study, we determined the optimal conditions for the overexpression and purification of a new version of Sur2, Sur2391-582, which was able to bind to ESX. To stabilize (His)6-Sur2391-582, various different buffered conditions over a wide range of pH and ionic strengths were examined. The molecular mass of (His)6-Sur2391-582 was determined using mass spectroscopy and size exclusion chromatography. The purified (His)6-Sur2391-582 protein displayed the same biological properties as that of the Sur2 full-length protein.

Mutations in SOHLH1 gene associate with nonobstructive azoospermia.

In a previous study, we found SOHLH1 (spermatogenesis and oogenesis-specific basic helix-loop-helix 1) as the first testis-specific basic helix-loop-helix transcription factor essential for spermatogonial differentiation. SOHLH1 therefore represents an excellent candidate gene for testicular failure such as nonobstructive azoospermia (NOA). We analyzed whether there were mutations in the SOHLH1 gene in 96 Korean patients with NOA. The sequence analysis discovered three novel variations: one intronic variant (c.346-1G>A), and two nonsynonymous exonic variants (c.91T>C and c.529C>A) with known single nucleotide polymorphisms (SNPs), which included six intronic variants, two synonymous, and two nonsynonymous variants. We examined the consequences of mutations in SOHLH1 using in vivo and in vitro assays. Analysis of transcripts from minigenes carrying the c.346-1G>A revealed that splicing site variation leads to the partial deletion at a cryptic splicing site within exon 4. This deletion results in SOHLH1 with a truncated bHLH domain. Transient transfection assay showed that the SOHLH1 mutant with the truncated domain disrupted the transcriptional activity of KIT promoter, whereas two missense mutations harboring either p.Arg37Gln or p.Pro269Ser did not have a significant effect on its transactivation. Our findings indicate that a splice-acceptor site mutation that probably causes a nonfunctional SOHLH1 protein results in nonobstructive azoospermia by the lack of normal spermatogenesis.

Clean STD-NMR spectrum for improved detection of ligand-protein interactions at low concentration of protein.

Saturation transfer difference (STD)-NMR has been widely used to screen ligand compound libraries for their binding activities to proteins and to determine the binding epitopes of the ligands. We report herein, a Clean STD-NMR method developed to overcome false positives (artifacts) observed in the STD-NMR spectrum due to the power spillover of RF irradiation. The method achieved higher degree of resonance saturation through digital editing of two STD-NMR spectra to generate a concatenated difference spectrum and three times of sensitivity enhancement for a loose binding complex involving DNA oligonucleotide and an RNA-binding protein, CUGBP-1ab (25.2 kDa). The interesting binding characteristics of the complex dCTGTCT-CUGBP1ab were obtained. The method was applied to a mixture of small ligand and bovine serum albumin protein (BSA, 66.3 kDa), and detected the intermolecular contacts at a BSA concentration as low as 0.1 µM, a working concentration useful for the detection of proteins of low solubility at biologically relevant conditions.

Bacterial Nucleoside Catabolism Controls Quorum Sensing and Commensal-to-Pathogen Transition in the Drosophila Gut.

Although the gut microbiome is generally symbiotic or commensal, some microbiome members become pathogenic under certain circumstances. However, the factors driving this pathogenic switch are largely unknown. Pathogenic bacteria can generate uracil that triggers host dual oxidase (DUOX) to produce antimicrobial reactive oxygen species (ROS). We show that pathogens generate uracil and ribose upon nucleoside catabolism of gut luminal uridine, which triggers not only host defenses but also inter-bacterial communication and pathogenesis in Drosophila. Uridine-derived uracil triggers DUOX-dependent ROS generation, whereas ribose induces bacterial quorum sensing (QS) and virulence gene expression. Genes implicated in nucleotide metabolism are found in pathogens but not commensal bacteria, and their genetic ablation blocks QS and the commensal-to-pathogen transition in vivo. Furthermore, commensal bacteria lack functional nucleoside catabolism, which is required to achieve gut-microbe symbiosis, but can become pathogenic by enabling nucleotide catabolism. These findings reveal molecular mechanisms governing the commensal-to-pathogen transition in different contexts of host-microbe interactions.

A rapid and sensitive screening system for human type I collagen with the aim of discovering potent anti-aging or anti-fibrotic compounds.

This study was undertaken with the aim of developing an easy and quick means of analyzing the effect of various compounds on the synthesis and secretion of human type I collagen at the protein level. A modification of the ELISA method was used on HFF-1 cells. For the proof of concept, we used thirteen compounds most of which are known to be antioxidants. Each compound was tested at concentrations of 0, 10 and 100 microM on HFF-1 cells for 24 h. Thirteen sets of experiments for each compound were performed in ANOVA with three replicates. Duncan multiple range test (DMRT) was used to compare the mean values obtained from the treatment groups. From the results it was concluded that Vitamin C, undecylenic acid, conjugated linoleic acid, glycolic acid, and citric acid at 100 microM concentration could be used for anti-wrinkling or protection from premature aging, which requires enhancement of collagen synthesis. Lactic acid, EGCG, resveratrol, and retinol that can inhibit collagen synthesis effectively in a dose-dependent manner may be used for anti-fibrosis treatment purposes.

Modification of translationally controlled tumor protein-derived protein transduction domain for improved intranasal delivery of insulin.

Carrier peptides, termed protein transduction domains (PTDs), serve as provide promising vehicles for intranasal delivery of macromolecular drugs. A mutant PTD derived from human translationally controlled tumor protein (TCTP-PTD 13, MIIFRALISHKK) was reported to provide enhanced intranasal delivery of insulin. In this study, we tested whether its efficiency could be further improved by replacing amino acids in TCTP-PTD 13 or changing the amino acids in the carrier peptides from the l- to the d-form. We assessed the pharmacokinetics of PTD-mediated transmucosal delivery of insulin in normal rats and the activity of insulin in alloxan-induced diabetic rats. The safety/toxicity profile of the carrier peptides was evaluated based on the release of lactate dehydrogenase (LDH) in nasal wash fluid, body weight changes, and several biochemical parameters. Pharmacokinetic and pharmacodynamic studies showed that the l-form of a double substitution A6L, I8A (MIIFRLLASHKK), designated as l-TCTP-PTD 13M2 was the most effective carrier for intranasal insulin delivery. The relative bioavailability of insulin co-administered intranasally with l-TCTP-PTD 13M2 was 37.1% of the value obtained by the subcutaneous route, which was 1.68-fold higher than for insulin co-administered with l-TCTP-PTD 13. Moreover, co-administration of insulin plus l-TCTP-PTD 13M2 reduced blood glucose levels compared to levels in diabetic rats treated with insulin plus l-TCTP-PTD 13. There was no evidence of toxicity. These results suggest that the newly designed PTD is a useful carrier peptide for the intranasal delivery of drugs or biomolecules.

microParaflo biochip for nucleic acid and protein analysis.

We describe in this chapter the use of oligonucleotide or peptide microarrays (arrays) based on microfluidic chips. Specifically, three major applications are presented: (1) microRNA/small RNA detection using a microRNA detection chip, (2) protein binding and function analysis using epitope, kinase substrate, or phosphopeptide chips, and (3) protein-binding analysis using oligonucleotide chips. These diverse categories of customizable arrays are based on the same biochip platform featuring a significant amount of flexibility in the sequence design to suit a wide range of research needs. The protocols of the array applications play a critical role in obtaining high quality and reliable results. Given the comprehensive and complex nature of the array experiments, the details presented in this chapter is intended merely as a useful information source of reference or a starting point for many researchers who are interested in genome- or proteome-scale studies of proteins and nucleic acids and their interactions.

Novel 2-aryl-4-(4'-hydroxyphenyl)-5H-indeno[1,2-b]pyridines as potent DNA non-intercalative topoisomerase catalytic inhibitors.

On the basis of previous reports on the importance of thienyl, furyl or phenol group substitution on 5H-indeno[1,2-b]pyridine skeleton, a new series of rigid 2-aryl-4-(4'-hydroxyphenyl)-5H-indeno[1,2-b]pyridine derivatives were systematically designed and synthesized. Topoisomerase inhibitory activity and antiproliferative activity of all the synthesized compounds were determined using human colorectal (HCT15), breast (T47D), prostate (DU145) and cervix (HeLa) cancer cells. Compounds 9, 10, 12, 13, 15, 16, 18 and 19 with thienyl or furyl moiety at the 2-position and hydroxyl group at the meta or para positions of 4-phenyl ring displayed strong to moderate topoisomerase IIα (topo IIα) inhibitory activity and significant antiproliferative activity. The evaluation of compound 16 to determine its mechanism of action was performed with topo IIα-DNA cleavable complex, topo IIα-mediated ATPase assay, DNA unwinding and in vitro and ex vivo topo IIα relaxation assay. Compound 16 functioned as a DNA non-intercalative topo IIα catalytic inhibitor with better potency than etoposide in T47D breast cancer cells. Molecular docking study revealed that compound 16 cannot intercalate into regularly stacked base-pairs of DNA duplex but can interact or intercalate to topo IIα-bound DNA.

Proposal of Dual Inhibitor Targeting ATPase Domains of Topoisomerase II and Heat Shock Protein 90.

There is a conserved ATPase domain in topoisomerase II (topo II) and heat shock protein 90 (Hsp90) which belong to the GHKL (gyrase, Hsp90, histidine kinase, and MutL) family. The inhibitors that target each of topo II and Hsp90 are intensively studied as anti-cancer drugs since they play very important roles in cell proliferation and survival. Therefore the development of dual targeting anti-cancer drugs for topo II and Hsp90 is suggested to be a promising area. The topo II and Hsp90 inhibitors, known to bind to their ATP binding site, were searched. All the inhibitors investigated were docked to both topo II and Hsp90. Four candidate compounds as possible dual inhibitors were selected by analyzing the molecular docking study. The pharmacophore model of dual inhibitors for topo II and Hsp90 were generated and the design of novel dual inhibitor was proposed.

Synthesis and biological evaluation of C1-O-substituted-3-(3-butylamino-2-hydroxy-propoxy)-xanthen-9-one as topoisomerase IIα catalytic inhibitors.

Topoisomerase II poison blocks the transitorily generated DNA double-strand breaks (DSBs) from religation, thereby causes severe DNA damage and gene toxicity. While topoisomerase II catalytic inhibitor does not form cleavable DNA-enzyme complex because its function attributes to inhibition of the catalytic steps of the enzyme such as before generating DNA DSBs or in the last step of the catalytic cycle after religation. It has been reported that the stabilizing effect of etoposide on transient cleavable DNA-topoisomerase IIß complex attributes to its secondary malignancy. Therefore, topoisomerase IIα has been considered as more attractive target than topoisomerase IIß for the development of chemotherapeutic agents. In the previous work, we reported compounds I and II as novel topoisomerase IIα catalytic inhibitors targeting for ATP binding site of human topoisomerase IIα ATP-binding domain. As a continuous work, we have designed and synthesized 43 compounds of C1-O-alkyl and arylalkyl substitiuted compounds with or without methoxy group on ring A. In the topoisomerase IIα inhibitory test, among the tested C1-O-4-chlorophenethyl substituted compounds 37 and 47 were more active than others, and compound 37 showed strongest topoisomerase IIα inhibitory activity with 94.4% and 23.0% inhibition, respectively, at 100 and 20 µM. Compounds 37 and 47 have also showed much enhanced cytotoxic activity against T47D cells; IC50 (µM): 0.63 ± 0.01 and 0.19 ± 0.02, respectively, which are stronger than reference drugs. Band depletion assay and cleavage complex assay results showed compounds 37 and 47 were potential topoisomerase IIα catalytic inhibitor with low DNA damage.

Neuroprotective effect of synthetic chalcone derivatives as competitive dual inhibitors against µ-calpain and cathepsin B through the downregulation of tau phosphorylation and insoluble Aß peptide formation.

A series of chalcone derivatives were synthesized and evaluated for their µ-calpain and cathepsin B inhibitory activities. Among the tested chalcone derivatives, two compounds, 7 and 11, showed potent inhibitory activities against µ-calpain and cathepsin B and were selected for further evaluation. Compounds 7 and 11 showed enzyme inhibitory activities at the cellular level and displayed neuroprotective effects against oxidative stress-induced apoptosis in SH-SY5Y cells, a human neuroblastoma cell line. Moreover, compounds 7 and 11 reduced p25 formation, tau phosphorylation and insoluble Aß peptide formation. Enzyme kinetic experiments and docking studies revealed that compounds 7 and 11 competitively inhibited both µ-calpain and cathepsin B enzymes.

A new series of 2-phenol-4-aryl-6-chlorophenyl pyridine derivatives as dual topoisomerase I/II inhibitors: Synthesis, biological evaluation and 3D-QSAR study.

As a continuous effort to develop novel antitumor agents, a new series of forty-five 2-phenol-4-aryl-6-chlorophenyl pyridine compounds were synthesized and evaluated for cytotoxicity against four different human cancer cell lines (DU145, HCT15, T47D, and HeLa), and topoisomerase I and II inhibitory activity. Several compounds (10-15, 20, 22, 24, 28, 42, and 49) displayed strong to moderate dual topoisomerase I and II inhibitory activity at 100 µM. It was observed that hydroxyl and chlorine moiety at meta or para position of phenyl ring is favorable for dual topoisomerase inhibitory activity and cytotoxicity. Most of the compounds displayed stronger cytotoxicities than those of all positive controls against the HCT15 and T47D cell lines. For investigation of the structure-activity relationships, a 3D-QSAR analysis using the method of comparative molecular field analysis (CoMFA) was performed. The generated 3D contour maps can be used for further rational design of novel terpyridine derivatives as highly selective and potent cytotoxic agents.