Synthesis and biological evaluation of new carbohydrate-substituted indenoisoquinoline topoisomerase I inhibitors and improved syntheses of the experimental anticancer agents indotecan (LMP400) and indimitecan (LMP776)

Design, synthesis and anticancer evaluation of 4-Substituted 5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidines as dual topoisomerase I and II inhibitors

In this study, we herein report the design, synthesis, and anticancer assessment of a series of new 4-substituted 5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidines. The synthesis involved key intermediates such as the 2-aminoester derivative, which underwent a series of reactions to produce compounds 7a-7t. The optimized SNAr reactions, utilizing microwave irradiation in DMF, led to high yields and efficient preparation of the desired compounds. The biological evaluation revealed significant cytotoxicity of compounds 7b and 7t against MCF-7 breast cancer cell lines with IC50 values of 8.80 ± 0.08 and 7.45 ± 0.26 µM, respectively, demonstrating superior activity to standard controls like camptothecin and etoposide. Both the compounds exhibited dual topoisomerase I and II inhibition (7t > 7b), enhanced reactive oxygen species (ROS) generation in cancer cells, and halted cell cycle at the G2/M phase. Molecular docking and dynamics simulations further supported the higher binding affinity of compound 7t to topoisomerase enzymes compared to 7b and standard compounds. In silico ADME profiling of 7b and 7t confirmed their drug-likeness, while DFT calculations provided insight into their electronic properties.

Flexible and Convergent Enantioselective Total Synthesis of (R)-Juglanaloids A and B: Two Phthalide Spiro Alkaloids with Potential Alzheimer's Disease Inhibitory Activity

Juglanaloids A and B are recently isolated natural products characterized by an unprecedented spiro bicyclic isobenzofuranone-tetrahydrobenzazepinone framework and a promising antiamyloid activity. Here reported is a straightforward convergent total synthesis of these natural products, which were obtained in high enantiomeric purity (94% and >99% ee for juglanaloids A and B, respectively) through an eight-step longest linear sequence, based on an efficient and reliable enantioselective phase-transfer-catalyzed alkylation step. Considering the interesting biological activity of juglanaloids, this convenient, highly enantioselective, flexible, and predictable synthetic strategy promises to be a powerful tool for accessing potentially bioactive spiro bicyclic phthalide-tetrahydrobenzazepinone derivatives.

Camptothecin structure simplification elaborated new imidazo[2,1-b]quinazoline derivative as a human topoisomerase I inhibitor with efficacy against bone cancer cells and colon adenocarcinoma

Camptothecin is a pentacyclic natural alkaloid that inhibits the hTop1 enzyme involved in DNA transcription and cancer cell growth. Camptothecin structure pitfalls prompted us to design new congeners using a structure simplification strategy to reduce the ring extension number from pentacyclic to tetracyclic while maintaining potential stacking of the new compounds with the DNA base pairs at the Top1-mediated cleavage complex and aqueous solubility, as well as minimizing compound-liver toxicity. The principal axis of this study was the verification of hTop1 inhibiting activity as a possible mechanism of action and the elaboration of new simplified inhibitors with improved pharmacodynamic and pharmacokinetic profiling using three structure panels (A-C) of (isoquinolinoimidazoquinazoline), (imidazoquinazoline), and (imidazoisoquinoline), respectively. DNA relaxation assay identified five compounds as hTop1 inhibitors belonging to the imidazoisoquinolines 3a,b, the imidazoquinazolines 12, and the isoquinolinoimidazoquinazolines 7a,b. In an MTT cytotoxicity assay against different cancer cell lines, compound 12 was the most potent against HOS bone cancer cells (IC50 = 1.47 μM). At the same time, the other inhibitors had no detectable activity against any cancer cell type. Compound (12) demonstrated great penetrating power in the HOS cancer cells' 3D-multicellular tumor spheroid model. Bioinformatics research of the hTop1 gene revealed that the TP53 cell proliferative gene is in the network of hTop1. The finding is confirmed empirically using the gene expression assay that proved the increase in p53 expression. The impact of structure simplification on compound 12 profile, characterized by the absence of acute oral liver toxicity when compared to Doxorubicin as a standard inhibitor, the lethal dose measured on Swiss Albino female mice and reported at LD50 = 250 mg/kg, and therapeutic significance in reducing colon adenocarcinoma tumor volume by 75.36 % after five weeks of treatment with compound 12. The molecular docking solutions of the active CPT-based derivative 12 and the inactive congener 14 into the active site of hTop1 and the activity cliffing of such MMP directed us to recommend the addition of HBD and HBA variables to compound 12 imidazoquinazoline core scaffold to enhance the potency via hydrogen bond formation with the major groove amino acids (Asp533, Lys532) as well as maintaining the hydrogen bond with the minor groove amino acid Arg364.

Synthesis and Biological Activity of a New Indenoisoquinoline Copper Derivative as a Topoisomerase I Inhibitor

Topoisomerases are interesting targets in cancer chemotherapy. Here, we describe the design and synthesis of a novel copper(II) indenoisoquinoline complex, WN198. The new organometallic compound exhibits a cytotoxic effect on five adenocarcinoma cell lines (MCF-7, MDA-MB-231, HeLa, HT-29, and DU-145) with the lowest IC50 (0.37 ± 0.04 μM) for the triple-negative MDA-MB-231 breast cancer cell line. Below 5 µM, WN198 was ineffective on non-tumorigenic epithelial breast MCF-10A cells and Xenopus oocyte G2/M transition or embryonic development. Moreover, cancer cell lines showed autophagy markers including Beclin-1 accumulation and LC3-II formation. The DNA interaction of this new compound was evaluated and the dose-dependent topoisomerase I activity starting at 1 μM was confirmed using in vitro tests and has intercalation properties into DNA shown by melting curves and fluorescence measurements. Molecular modeling showed that the main interaction occurs with the aromatic ring but copper stabilizes the molecule before binding and so can putatively increase the potency as well. In this way, copper-derived indenoisoquinoline topoisomerase I inhibitor WN198 is a promising antitumorigenic agent for the development of future DNA-damaging treatments.

New benzothienopyran and benzothienopyranopyrimidine derivatives as topoisomerase I inhibitors: Design, synthesis, anticancer screening, apoptosis induction and molecular modeling studies

New benzothienopyran and benzothienopyranopyrimidine derivatives were synthesized based on the structural requirements of topoisomerase I inhibitors. All target compounds exhibited strong cytotoxic activity with GI₅₀ range of 70.62 %-87.29 % in one dose NCI (USA) screening against 60 human tumor cell lines. Among the tested derivatives, eight compounds namely 4d, 4e, 4f, 5b, 5e, 6b, 6d, and 6f demonstrated broad spectrum and potent anticancer efficacy in five dose screening against all tested panels. DNA relaxation assay for the latter compounds showed that 4d, 5b, and 6f exhibited excellent inhibitory activity with IC₅₀ range of 2.553-4.495 µM as compared to indenoisoquinoline reference drug (IC₅₀ = 3.911 ± 0.21 µM). Moreover, the most active compounds were investigated for being topoisomerase poisons or catalytic inhibitors using DNA nicking assay. Compounds 4d and 6f were found to be potential Topo I poisons, whereas compound 5b has acted as Topo I suppressor. Analyzing cell cycle and induction of apoptosis for the most active compound 4d, revealed growth arrest at the S phase in MDA-MB-435 cells similarly to indenoisoquinoline reference drug. Additionally, in silico molecular modeling study for eight most active cytotoxic compounds in five dose screening demonstrated interaction with DNA as well as distinctive binding pattern similar to the reference indenoisoquinoline, indicating that the newly discovered targets are supposed to be promising candidates as Topo I inhibitors.

Novel Pyrido[2',1':2,3]imidazo[4,5-c]quinoline Derivative Selectively Poisons Leishmania donovani Bisubunit Topoisomerase 1 to Inhibit the Antimony-Resistant Leishmania Infection in Vivo

The unique bisubunit structure of Leishmania donovani topoisomerase 1B (LdTop1) is a potential drug target in the parasites unlike the monomeric Top1 from its human host counterpart. Here, we report the design, synthesis, and validation of a chimeric pyrido[2',1':2,3]imidazo[4,5-c]quinoline derivative (C17) as a novel antileishmanial agent that poisons topoisomerase 1-DNA covalent complexes (LdTop1cc) inside the parasites and inhibits Top1 religation activity both in the drug sensitive and antimony-resistant L. donovani clinical isolates. Importantly, the human Top1 is not sensitive to C17. Further, C17 overcomes the chemical instability of camptothecin (CPT) by generating persistent LdTop1cc-induced DNA breaks inside the parasites even after 12 h of drug removal. Intraperitoneal administration of C17 results in marked reduction of the Leishmania amastigotes from the infected spleen and liver of BALB/c mice. C17 confers a host protective immune-response up-regulating the Th1 cytokines facilitating parasite clearance which can be exploited for treating drug-resistant leishmaniasis.

Dual Targeting Topoisomerase/G-Quadruplex Agents in Cancer Therapy-An Overview

Topoisomerase (Topo) inhibitors have long been known as clinically effective drugs, while G-quadruplex (G4)-targeting compounds are emerging as a promising new strategy to target tumor cells and could support personalized treatment approaches in the near future. G-quadruplex (G4) is a secondary four-stranded DNA helical structure constituted of guanine-rich nucleic acids, and its stabilization impairs telomere replication, triggering the activation of several protein factors at telomere levels, including Topos. Thus, the pharmacological intervention through the simultaneous G4 stabilization and Topos inhibition offers a new opportunity to achieve greater antiproliferative activity and circumvent cellular insensitivity and resistance. In this line, dual ligands targeting both Topos and G4 emerge as innovative, efficient agents in cancer therapy. Although the research in this field is still limited, to date, some chemotypes have been identified, showing this dual activity and an interesting pharmacological profile. This paper reviews the available literature on dual Topo inhibitors/G4 stabilizing agents, with particular attention to the structure-activity relationship studies correlating the dual activity with the cytotoxic activity.

A Novel Copper(II) Indenoisoquinoline Complex Inhibits Topoisomerase I, Induces G2 Phase Arrest, and Autophagy in Three Adenocarcinomas

Topoisomerases, targets of inhibitors used in chemotherapy, induce DNA breaks accumulation leading to cancer cell death. A newly synthesized copper(II) indenoisoquinoline complex WN197 exhibits a cytotoxic effect below 0.5 µM, on MDA-MB-231, HeLa, and HT-29 cells. At low doses, WN197 inhibits topoisomerase I. At higher doses, it inhibits topoisomerase IIα and IIβ, and displays DNA intercalation properties. DNA damage is detected by the presence of γH2AX. The activation of the DNA Damage Response (DDR) occurs through the phosphorylation of ATM/ATR, Chk1/2 kinases, and the increase of p21, a p53 target. WN197 induces a G2 phase arrest characterized by the unphosphorylated form of histone H3, the accumulation of phosphorylated Cdk1, and an association of Cdc25C with 14.3.3. Cancer cells die by autophagy with Beclin-1 accumulation, LC3-II formation, p62 degradation, and RAPTOR phosphorylation in the mTOR complex. Finally, WN197 by inhibiting topoisomerase I at low concentration with high efficiency is a promising agent for the development of future DNA damaging chemotherapies.

Design and Synthesis of Indenoisoquinolines Targeting Topoisomerase I and Other Biological Macromolecules for Cancer Chemotherapy

The discovery that certain indenoisoquinolines inhibit the religation reaction of DNA in the topoisomerase I-DNA-indenoisoquinoline ternary complex led to a structure-based drug design research program which resulted in three representatives that entered Phase I clinical trials in cancer patients at the National Cancer Institute. This has stimulated a great deal of interest in the design and execution of new synthetic pathways for indenoisoquinoline production. More recently, modulation of the substitution pattern and chemical nature of substituents on the indenoisoquinoline scaffold has resulted in a widening scope of additional biological targets, including RXR, PARP-1, MYC promoter G-quadruplex, topoisomerase II, estrogen receptor, VEGFR-2, HIF-1α, and tyrosyl DNA phosphodiesterases 1 and 2. Furthermore, convincing evidence has been advanced supporting the potential use of indenoisoquinolines for the treatment of diseases other than cancer. The rapidly expanding indenoisoquinoline knowledge base has provided a firm foundation for further advancements in indenoisoquinoline chemistry, pharmacology, and therapeutics.

Recent Advances in Copper-Catalyzed C-N Bond Formation Involving N-Centered Radicals

C-N bonds are pervasive throughout organic-based materials, natural products, pharmaceutical compounds, and agricultural chemicals. Considering the widespread importance of C-N bonds, the development of greener and more convenient ways to form C-N bonds, especially in late-stage synthesis, has become one of the hottest research goals in synthetic chemistry. Copper-catalyzed radical reactions involving N-centered radicals have emerged as a sustainable and promising approach to build C-N bonds. As a chemically popular and diverse radical species, N-centered radicals have been used for all kinds of reactions for C-N bond formation by taking advantage of their inherently incredible reactive flexibility. Copper is also the most abundant and economic catalyst with the most relevant activity for facilitating the synthesis of valuable compounds. Therefore, the aim of the present Review was to illustrate recent and significant advances in C-N bond formation methods and to understand the unique advantages of copper catalysis in the generation of N-centered radicals since 2016. To provide an ease of understanding for the readers, this Review was organized based on the types of nitrogen sources (amines, amides, sulfonamides, oximes, hydrazones, azides, and tert-butyl nitrite).

Epigenetic modulation and apoptotic induction by a novel imidazo-benzamide derivative in human lung adenocarcinoma cells

PURPOSE

Lung cancer is the most commonly diagnosed and leading cause of cancer death worldwide. Imidazo-benzamides are considered to be good anti-cancer agents. The present study was aimed to investigate the cytotoxicity of a novel imidazo-benzamide derivative N-(2-(3-(tert-butyl)ureido)ethyl)-4-(1H-imidazol-1-yl)benzamide (TBUEIB) in lung cancer cell line A549.

METHODS

The antiproliferative activity of TBUEIB was investigated using MTT, LDH and trypan blue assay. The apoptotic potential was investigated using various staining techniques and further confirmed by DNA fragmentation assay and western blotting.

RESULTS

TBUEIB inhibited fifty precent A549 cells at a dose of 106 μM. The novel compound was found to exert a modulatory effect on apoptotic marker caspase-3 as well as epigenetic regulatory proteins like DNA Methyltransferase 1 (DNMT1). In silico studies with the compound and other epigenetic proteins such as Histone deacetylase (HDAC) and ubiquitin-like with PHD (plant homeodomain) and RING (Really Interesting New Gene) finger domains 1(UHRF1) showed good modulatory effects.

CONCLUSION

The overall results obtained in the study conclude that the novel compound TBUEIB has potential anti-cancer activities, mainly by targeting the expression of DNMT1 enzyme, which may have re-activated the major tumor suppressor genes involved in the cell cycle, leading to the apoptosis of the cancer cells. The results also indicate that the compound has more than one target in the epigenetic pathway implying that the compound may be a potential multi-target compound.

Proteins from the DNA Damage Response: Regulation, Dysfunction, and Anticancer Strategies

Cells respond to genotoxic stress through a series of complex protein pathways called DNA damage response (DDR). These monitoring mechanisms ensure the maintenance and the transfer of a correct genome to daughter cells through a selection of DNA repair, cell cycle regulation, and programmed cell death processes. Canonical or non-canonical DDRs are highly organized and controlled to play crucial roles in genome stability and diversity. When altered or mutated, the proteins in these complex networks lead to many diseases that share common features, and to tumor formation. In recent years, technological advances have made it possible to benefit from the principles and mechanisms of DDR to target and eliminate cancer cells. These new types of treatments are adapted to the different types of tumor sensitivity and could benefit from a combination of therapies to ensure maximal efficiency.

A patent review of topoisomerase I inhibitors (2016-present)

INTRODUCTION

Topoisomerases are important targets for therapeutic improvement in the treatment of some diseases, including cancer. Inhibitors and poisons of topoisomerase I can limit the activity of this enzyme in its enzymatic cycle. This fact implies an anticancer effect of these drugs, since most cancer cells are characterized by both a higher activity of topoisomerase I and a higher replication rate compared to non-cancerous cells. Clinically approved inhibitors include camptothecin (CPT) and its derivatives. However, their limitations have encouraged different research groups to prepare new compounds, proof of which are the numerous research works and patents, some of them in the last five years.

AREAS COVERED

This review covers patent literature on topoisomerase I inhibitors and their application published between 2016-present.

EXPERT OPINION

The highest contribution toward patent development has been obtained from academics or small biotechnology companies. The most important fields of innovation include the preparation of prodrugs or inhibitors combined with other agents, as biocompatible polymers or antibodies. A promising development of topoisomerase I inhibitors is expected in the next years, directed to the treatment of diverse diseases, specifically toward different types of cancer and infectious diseases, among others.

Isoquinolines: Important Cores in Many Marketed and Clinical Drugs

BACKGROUND

Isoquinoline analogs are an important, structurally diverse class of compounds that are extensively used as pharmaceuticals. Derivatives containing the isoquinoline scaffold have become a focus of therapeutic research because of their wide range of biological characteristics. Examples of these drugs, many of which are in clinical application or at the pre-clinical stage, are used to treat a broad swathe of ailments, such as tumors, respiratory diseases, infections, nervous system diseases, cardiovascular and cerebrovascular diseases, endocrine and metabolic diseases.

METHODS

Data were collected from PubMed, Web of Science, and SciFinder, through searches of drug names.

RESULTS

At least 38 isoquinoline-based therapeutic drugs are in clinical application or clinical trials, and their chemical structure and pharmacokinetics are described in detail.

CONCLUSION

The isoquinoline ring is a privileged scaffold which is often preferred as a structural basis for drug design, and plays an important role in drug discovery. This review provides a guide for pharmacologists to find effective preclinical/clinical drugs and examines recent progress in the application of the isoquinoline scaffold.

Novel 3-benzylidene/benzylphthalide Mannich base derivatives as potential multifunctional agents for the treatment of Alzheimer's disease

To discover novel multifunctional agents for the treatment of Alzheimer's disease, a series of 3-benzylidene/benzylphthalide Mannich base derivatives were designed, synthesized and evaluated. The biological screening results indicated that most of these derivatives exhibited good multifunctional activities. Among them, compound (Z)-13c raised particular interest because of its excellent multifunctional bioactivities. It displayed excellent EeAChE and HuAChE inhibition (IC₅₀ = 9.18 × 10^-5 and 6.16 × 10^-4 μM, respectively), good MAO-B inhibitory activity (IC₅₀ = 5.88 μM) and high antioxidant activity (ORAC = 2.05 Trolox equivalents). Additionally, it also exhibited good antiplatelet aggregation activity, moderate self- and Cu²⁺-induced Aβ_1-42 aggregation inhibitory potency, disaggregation ability on Aβ_1-42 fibrils, biometal chelating ability, appropriate BBB permeability and significant neuroprotective effect. Furthermore, (Z)-13c can also ameliorate the learning and memory impairment induced by scopolamine in mice. These multifunctional properties highlight compound (Z)-13c as a promising candidate for further development of multifunctional drug against AD.

Synthesis of Oxygen-Containing Heterocyclic Compounds by Iron-Catalyzed Alkylative Cyclization of Unsaturated Carboxylic Acids and Alcohols

Iron-catalyzed alkylative cyclization of alkenes bearing oxygen nucleophiles with secondary and tertiary alkyl bromides through carbon-carbon and carbon-oxygen bond formations has been developed. A broad substrate scope is an attractive feature of this synthetic method, providing a variety of potentially bioactive five- and six-membered oxygen-containing heterocycles. The reaction pathway is proposed to involve a radical addition of the in situ-formed alkyl radical to an alkene followed by carbon-oxygen bond-forming intramolecular cyclization.

Fluoral Hydrate: A Perspective Substrate for the Castagnoli-Cushman Reaction

The reactivity of azomethines based on trifluoroacetaldehyde hydrate in the Castagnoli-Cushman reaction (CCR) was researched. The impact of the nature of anhydrides explored on the reaction route was determined. The preparative procedures for the synthesis of N-substituted (3R*,4R*)-1-oxo-3-(trifluoromethyl)-1,2,3,4-tetrahydroisoquinoline-4-carboxylic and (1R*,2R*)-4-oxo-2-(trifluoromethyl)-2,3,4,5-tetrahydro-1H-benzo[d]azepine-1-carboxylic acids in gram scales were elaborated. It was shown that the trifluoromethyl group remarkably decreased the reactivity of azomethines in CCR. The mechanism for the formation of different products depending on the anhydride's nature was proposed.

Benefits and applications of microwave-assisted synthesis of nitrogen containing heterocycles in medicinal chemistry

Nitrogen containing heterocycles are of immense research interest because they are often found as naturally occurring bioactive compounds.

Topoisomerase Inhibitors and Targeted Delivery in Cancer Therapy

DNA topoisomerases are enzymes that catalyze the alteration of DNA topology with transiently induced DNA strand breakage, essential for DNA replication. Topoisomerases are validated cancer chemotherapy targets. Anticancer agents targeting Topoisomerase I and II have been in clinical use and proven to be highly effective, though with significant side effects. There are tremendous efforts to develop new generation of topoisomerase inhibitors. Targeted delivery of topoisomerase inhibitors is another way to reduce the side effects. Conjugates of topoisomerases inhibitors with antibody, polymer, or small molecule are developed to target these inhibitors to tumor sites.

Indenoisoquinoline Topoisomerase Inhibitors Strongly Bind and Stabilize the MYC Promoter G-Quadruplex and Downregulate MYC

MYC is one of the most important oncogenes and is overexpressed in the majority of cancers. G-Quadruplexes are noncanonical four-stranded DNA secondary structures that have emerged as attractive cancer-specific molecular targets for drug development. The G-quadruplex formed in the proximal promoter region of the MYC oncogene (MycG4) has been shown to be a transcriptional silencer that is amenable to small-molecule targeting for MYC suppression. Indenoisoquinolines are human topoisomerase I inhibitors in clinical testing with improved physicochemical and biological properties as compared to the clinically used camptothecin anticancer drugs topotecan and irinotecan. However, some indenoisoquinolines with potent anticancer activity do not exhibit strong topoisomerase I inhibition, suggesting a separate mechanism of action. Here, we report that anticancer indenoisoquinolines strongly bind and stabilize MycG4 and lower MYC expression levels in cancer cells, using various biochemical, biophysical, computer modeling, and cell-based methods. Significantly, a large number of active indenoisoquinolines cause strong MYC downregulation in cancer cells. Structure-activity relationships of MycG4 recognition by indenoisoquinolines are investigated. In addition, the analysis of indenoisoquinoline analogues for their MYC-inhibitory activity, topoisomerase I-inhibitory activity, and anticancer activity reveals a synergistic effect of MYC inhibition and topoisomerase I inhibition on anticancer activity. Therefore, this study uncovers a novel mechanism of action of indenoisoquinolines as a new family of drugs targeting the MYC promoter G-quadruplex for MYC suppression. Furthermore, the study suggests that dual targeting of MYC and topoisomerase I may serve as a novel strategy for anticancer drug development.

Discovery and Mechanistic Study of Tailor-Made Quinoline Derivatives as Topoisomerase 1 Poison with Potent Anticancer Activity

To overcome chemical limitations of camptothecin (CPT), we report design, synthesis, and validation of a quinoline-based novel class of topoisomerase 1 (Top1) inhibitors and establish that compound 28 ( N-(3-(1 H-imidazol-1-yl)propyl)-6-(4-methoxyphenyl)-3-(1,3,4-oxadiazol-2-yl)quinolin-4-amine) exhibits the highest potency in inhibiting human Top1 activity with an IC₅₀ value of 29 ± 0.04 nM. Compound 28 traps Top1-DNA cleavage complexes (Top1ccs) both in the in vitro cleavage assays and in live cells. Point mutation of Top1-N722S fails to trap compound 28-induced Top1cc because of its inability to form a hydrogen bond with compound 28. Unlike CPT, compound 28 shows excellent plasma serum stability and is not a substrate of P-glycoprotein 1 (permeability glycoprotein) advancing its potential anticancer activity. Finally, we provide evidence that compound 28 overcomes the chemical instability of CPT in human breast adenocarcinoma cells through generation of persistent and less reversible Top1cc-induced DNA double-strand breaks as detected by γH2AX foci immunostaining after 5 h of drug removal.

A comprehensive review of topoisomerase inhibitors as anticancer agents in the past decade

The topoisomerase enzymes play an important role in DNA metabolism, and searching for enzyme inhibitors is an important target in the search for new anticancer drugs. Discovery of new anticancer chemotherapeutical capable of inhibiting topoisomerase enzymes is highlighted in anticancer research. Therefore, biologists, organic chemists and medicinal chemists all around the world have been identifying, designing, synthesizing and evaluating a variety of novel bioactive molecules targeting topoisomerase. This review summarizes types of topoisomerase inhibitors in the past decade, and divides them into nine classes by structural characteristics, including N-heterocycles compounds, quinone derivatives, flavonoids derivatives, coumarin derivatives, lignan derivatives, polyphenol derivatives, diterpenes derivatives, fatty acids derivatives, and metal complexes. Then we discussed the application prospect and development of these anticancer compounds, as well as concluded parts of their structural-activity relationships. We believe this review would be invaluable in helping to further search potential topoisomerase inhibition as antitumor agent in clinical usage.

Synthesis and Investigation of Phthalazinones as Antitubercular Agents

A series of 2- and 7-substituted phthalazinones was synthesised and their potential as anti-tubercular drugs assessed via Mycobacterium tuberculosis (mc² 6230) growth inhibition assays. All phthalazinones tested showed growth inhibitory activity (MIC <100 μm), and those compounds containing lipophilic and electron-withdrawing groups generally exhibited better anti-tubercular activity. Several lead compounds were identified, including 7-((2-amino-6-(4-fluorophenyl)pyrimidin-4-yl)amino)-2-heptylphthalazin-1(2H)-one (MIC=1.6 μm), 4-tertbutylphthalazin-2(1H)-one (MIC=3 μm), and 7-nitro-phthalazin-1(2H)-one (MIC=3 μm). Mode of action studies indicated that selected pyrimidinyl-phthalazinones may interfere with NADH oxidation, however, the mode of action of the lead compound is independent of this enzyme. MIC=minimum inhibitory concentration.

Topoisomerase 1B poisons: Over a half-century of drug leads, clinical candidates, and serendipitous discoveries

Topoisomerases are DNA processing enzymes that relieve supercoiling (torsional strain) in DNA, are necessary for normal cellular division, and act by nicking (and then religating) DNA strands. Type 1B topoisomerase (Top1) is overexpressed in certain tumors, and the enzyme has been extensively investigated as a target for cancer chemotherapy. Various chemical agents can act as "poisons" of the enzyme's religation step, leading to Top1-DNA lesions, DNA breakage, and eventual cellular death. In this review, agents that poison Top1 (and have thus been investigated for their anticancer properties) are surveyed, including natural products (such as camptothecins and indolocarbazoles), semisynthetic camptothecin and luotonin derivatives, and synthetic compounds (such as benzonaphthyridines, aromathecins, and indenoisoquinolines), as well as targeted therapies and conjugates. Top1 has also been investigated as a therapeutic target in certain viral and parasitic infections, as well as autoimmune, inflammatory, and neurological disorders, and a summary of literature describing alternative indications is also provided. This review should provide both a reference for the medicinal chemist and potentially offer clues to aid in the development of new Top1 poisons.

Characterization and structure-activity relationships of indenoisoquinoline-derived topoisomerase I inhibitors in unsilencing the dormant Ube3a gene associated with Angelman syndrome

Background

Angelman syndrome (AS) is a severe neurodevelopmental disorder lacking effective therapies. AS is caused by mutations in ubiquitin protein ligase E3A (UBE3A), which is genomically imprinted such that only the maternally inherited copy is expressed in neurons. We previously demonstrated that topoisomerase I (Top1) inhibitors could successfully reactivate the dormant paternal allele of Ube3a in neurons of a mouse model of AS. We also previously showed that one such Top1 inhibitor, topotecan, could unsilence paternal UBE3A in induced pluripotent stem cell-derived neurons from individuals with AS. Although topotecan has been well-studied and is FDA-approved for cancer therapy, its limited CNS bioavailability will likely restrict the therapeutic use of topotecan in AS. The goal of this study was to identify additional Top1 inhibitors with similar efficacy as topotecan, with the expectation that these could be tested in the future for safety and CNS bioavailability to assess their potential as AS therapeutics.

Methods

We tested 13 indenoisoquinoline-derived Top1 inhibitors to identify compounds that unsilence the paternal allele of Ube3a in mouse neurons. Primary cortical neurons were isolated from embryonic day 14.5 (E14.5) mice with a Ube3a-YFP fluorescent tag on the paternal allele (Ube3a^m+/pYFP mice) or mice that lack the maternal Ube3a allele and hence model AS (Ube3a^m-/p+ mice). Neurons were cultured for 7 days, treated with drug for 72 h, and examined for paternal UBE3A protein expression by Western blot or fluorescence immunostaining. Dose responses of the compounds were determined across a log range of drug treatments, and cytotoxicity was tested using a luciferase-based assay.

Results

All 13 indenoisoquinoline-derived Top1 inhibitors unsilenced paternal Ube3a. Several compounds exhibited favorable paternal Ube3a unsilencing properties, similar to topotecan, and of these, indotecan (LMP400) was the most effective based on estimated E_max (maximum response of unsilencing paternal Ube3a) and EC₅₀ (half maximal effective concentration).

Conclusions

We provide pharmacological profiles of indenoisoquinoline-derived Top1 inhibitors as paternal Ube3a unsilencers. All 13 tested compounds were effective at unsilencing paternal Ube3a, although with variable efficacy and potency. Indotecan (LMP400) demonstrated a better pharmacological profile of Ube3a unsilencing compared to our previous lead compound, topotecan. Taken together, indotecan and its structural analogues are potential AS therapeutics whose translational potential in AS treatment should be further assessed.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2013-2014

This review is the eighth update of the original article published in 1999 on the application of Matrix-assisted laser desorption/ionization mass spectrometry (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2014. Topics covered in the first part of the review include general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation, and arrays. The second part of the review is devoted to applications to various structural types such as oligo- and poly- saccharides, glycoproteins, glycolipids, glycosides, and biopharmaceuticals. Much of this material is presented in tabular form. The third part of the review covers medical and industrial applications of the technique, studies of enzyme reactions, and applications to chemical synthesis. © 2018 Wiley Periodicals, Inc. Mass Spec Rev 37:353-491, 2018.

Development of a quantitative pharmacodynamic assay for apoptosis in fixed tumor tissue and its application in distinguishing cytotoxic drug-induced DNA double strand breaks from DNA double strand breaks associated with apoptosis

DNA double strand breaks (DSBs) induced by cancer therapeutic agents can lead to DNA damage repair or persistent DNA damage, which can induce apoptotic cell death; however, apoptosis also induces DSBs independent of genotoxic insult. γH2AX is an established biomarker for DSBs but cannot distinguish between these mechanisms. Activated cleaved caspase-3 (CC3) promotes apoptosis by enhancing nuclear condensation, DNA fragmentation, and plasma membrane blebbing. Here, we describe an immunofluorescence assay that distinguishes between apoptosis and drug-induced DSBs by measuring coexpression of γH2AX and membrane blebbing−associated CC3 to indicate apoptosis, and γH2AX in the absence of CC3 blebbing to indicate drug-induced DNA damage. These markers were examined in xenograft models following treatment with topotecan, cisplatin, or birinapant. A topotecan regimen conferring tumor regression induced tumor cell DSBs resulting from both apoptosis and direct DNA damage. In contrast, a cisplatin regimen yielding tumor growth delay, but not regression, resulted in tumor cell DSBs due solely to direct DNA damage. MDA-MB-231 xenografts exposed to birinapant, which promotes apoptosis but does not directly induce DSBs, exhibited dose-dependent increases in colocalized γH2AX/CC3 blebbing in tumor cells. Clinical feasibility was established using formalin-fixed, paraffin-embedded biopsies from a canine cancer clinical trial; γH2AX/CC3 colocalization analysis revealed apoptosis induction by two novel indenoisoquinoline topoisomerase I inhibitors, which was consistent with pathologist-assessed apoptosis and reduction of tumor volume. This assay is ready for use in clinical trials to elucidate the mechanism of action of investigational agents and combination regimens intended to inflict DNA damage, apoptotic cell death, or both.

Imidazoles as potential anticancer agents

Cancer is a black spot on the face of humanity in this era of science and technology. Presently, several classes of anticancer drugs are available in the market, but issues such as toxicity, low efficacy and solubility have decreased the overall therapeutic indices. Thus, the search for new promising anticancer agents continues, and the battle against cancer is far from over. Imidazole is an aromatic diazole and alkaloid with anticancer properties. There is considerable interest among scientists in developing imidazoles as safe alternatives to anticancer chemotherapy. The present article describes the structural, chemical, and biological features of imidazoles. Several classes of imidazoles as anticancer agents based on their mode of action have been critically discussed. A careful observation has been made into pharmacologically active imidazoles with better or equal therapeutic effects compared to well-known imidazole-based anticancer drugs, which are available on the market. A brief discussion of the toxicities of imidazoles has been made. Finally, the current challenges and future perspectives of imidazole based anticancer drug development are conferred.

Synthesis of indolo[4,3-bc]phenanthridine-6,11(2H,12H)-diones using the Schiff base-homophthalic anhydride cyclization reaction

A novel indolophenanthridine ring system has been synthesized via the Schiff base-homophthalic anhydride cyclization followed by thionyl chloride-mediated dehydrogenation and intramolecular Friedel-Crafts acylation. This adds to the array of heterocyclic systems that are available through the cycloaddition reaction of imines with cyclic dicarboxylic acid anhydrides. The cytotoxicities of the indolophenanthridines were investigated in human cancer cell cultures, and the results documented significant antitumor activity in a variety of human cancer cell lines. This provides a new heterocyclic scaffold for anticancer drug design.

Clinical and pharmacologic evaluation of two dosing schedules of indotecan (LMP400), a novel indenoisoquinoline, in patients with advanced solid tumors

PURPOSE

Indenoisoquinolines are non-camptothecin topoisomerase I (TopI) inhibitors that overcome the limitations of camptothecins: chemical instability and camptothecin resistance. Two dosing schedules of the novel indenoisoquinoline, indotecan (LMP400), were evaluated in patients with advanced solid tumors.

METHODS

The maximum tolerated dose (MTD), toxicities, and pharmacokinetics of two indotecan drug administration schedules (daily for 5 days or weekly) were investigated. Modulation of TopI and the phosphorylation of histone H2AX (γH2AX) were assayed in tumor biopsies; γH2AX levels were also evaluated in circulating tumor cells (CTCs) and hair follicles to assess DNA damage response.

RESULTS

An MTD of 60 mg/m(2)/day was established for the daily regimen, compared to 90 mg/m(2) for the weekly regimen. The TopI response to drug showed target engagement in a subset of tumor biopsies. Pharmacokinetics profiles demonstrated a prolonged terminal half-life and tissue accumulation compared to topotecan. Dose-dependent decreases in total CTCs were measured in seven patients. Formation of γH2AX-positive foci in CTCs (day 3) and hair follicles (4-6 h) was observed following treatment.

CONCLUSIONS

We established the MTD of two dosing schedules for a novel TopI inhibitor, indotecan. Target engagement was demonstrated as Top1 downregulation and γH2AX response. No objective responses were observed on either schedule in this small patient cohort. The principal toxicity of both schedules was myelosuppression; no significant gastrointestinal problems were observed. Increased DNA damage response was observed in CTCs, hair follicles, and a subset of tumor biopsies.

Indenopyrans - synthesis and photoluminescence properties

New indeno[1,2-c]pyran-3-ones bearing different substituents at the pyran moiety were synthesized and their photophysical properties were investigated. In solution all compounds were found to be blue emitters and the trans isomers exhibited significantly higher fluorescence quantum yields (relative to 9,10-diphenylanthracene) as compared to the corresponding cis isomers. The solid-state fluorescence spectra revealed an important red shift of λ_max due to intermolecular interactions in the lattice, along with an emission-band broadening, as compared to the solution fluorescence spectra.

Synthesis and cytotoxic evaluation of novel indenoisoquinoline-substituted triazole hybrids

The synthesis of various substituted triazole-indenoisoquinoline hybrids was performed based on a CuI-catalyzed 1,3-cycloaddition between propargyl-substituted derivatives and the azide-containing indenoisoquinoline. Besides, a variety of N-(alkyl)propargylindenoisoquinolines was used as substrates for the construction of triazole-indenoisoquinoline-AZT conjugated via a click chemistry-mediated coupling with 3'-azido-3'-deoxythymidine (AZT). Thus, twenty three new indenoisoquinoline-substituted triazole hybrids were successfully prepared and evaluated as cytotoxic agents, revealing an interesting anticancer activity of four triazole linker-indenoisoquinoline-AZT hybrids in KB and HepG2 cancer cell lines.

Investigation of the Structure-Activity Relationships of Aza-A-Ring Indenoisoquinoline Topoisomerase I Poisons

Several indenoisoquinolines have shown promise as anticancer agents in clinical trials. Incorporation of a nitrogen atom into the indenoisoquinoline scaffold offers the possibility of favorably modulating ligand-binding site interactions, physicochemical properties, and biological activities. Four series of aza-A-ring indenoisoquinolines were synthesized in which the nitrogen atom was systematically rotated through positions 1, 2, 3, and 4. The resulting compounds were tested to establish the optimal nitrogen position for topoisomerase IB (Top1) enzyme poisoning activity and cytotoxicity to human cancer cells. The 4-aza compounds were the most likely to yield derivatives with high Top1 inhibitory activity. However, the relationship between structure and cytotoxicity was more complicated since the potency was influenced strongly by the side chains on the lactam nitrogen. The most cytotoxic azaindenoisoquinolines 45 and 46 had nitrogen in the 2- or 3-positions and a 3'-dimethylaminopropyl side chain, and they had MGM GI50 values that were slightly better than the corresponding indenoisoquinoline 64.

Synthesis and biological evaluation of new fluorinated and chlorinated indenoisoquinoline topoisomerase I poisons

Fluorine and chlorine are metabolically stable, but generally less active replacements for a nitro group at the 3-position of indenoisoquinoline topoisomerase IB (Top1) poisons. A number of strategies were employed in the present investigation to enhance the Top1 inhibitory potencies and cancer cell growth inhibitory activities of halogenated indenoisoquinolines. In several cases, the new compounds' activities were found to rival or surpass those of similarly substituted 3-nitroindenoisoquinolines, and several unusually potent analogs were discovered through testing in human cancer cell cultures. A hydroxyethylaminopropyl side chain on the lactam nitrogen of two halogenated indenoisoquinoline Top1 inhibitors was found to also impart inhibitory activity against tyrosyl DNA phosphodiesterases 1 and 2 (TDP1 and TDP2), which are enzymes that participate in the repair of DNA damage induced by Top1 poisons.

A new [4 + 1]/[4 + 2]bicycliaztion strategy for accessing functionalized indeno[1,2-b]pyran-2-ones

A new base-promoted bicyclization strategy for the synthesis of functionalized indeno[1,2-b]pyran-2-ones has been established from readily accessible o-phthalaldehydes (OPA) and the preformed 1-arylethylidenemalononitriles.

Developing a Novel Indolocarbazole as Histone Deacetylases Inhibitor against Leukemia Cell Lines

A novel indolocarbazole (named as ZW2-1) possessing HDAC inhibition activity was synthesized and evaluated against human leukemia cell lines HL-60 and NB4. ZW2-1 performed anti-population growth effect which was in a concentration-dependent manner (2-12 μM) by inducing both apoptosis and autophagy in cells. The compound also caused differentiation of HL-60 and NB4 cells as shown by increasing expression of CD11b, CD14, and CD38 at moderate concentration (4 μM). At relatively high concentration (8 μM), ZW2-1 significantly decreased intracellular histone deacetylase 1 level which was also observed. All the results indicated that ZW2-1 could be a novel antileukemia lead capable of simultaneously inducing apoptosis, autophagy, and differentiation.

Single-Molecule Supercoil Relaxation Assay as a Screening Tool to Determine the Mechanism and Efficacy of Human Topoisomerase IB Inhibitors

Human nuclear type IB topoisomerase (Top1) inhibitors are widely used and powerful anticancer agents. In this study, we introduce and validate a single-molecule supercoil relaxation assay as a molecular pharmacology tool for characterizing therapeutically relevant Top1 inhibitors. Using this assay, we determined the effects on Top1 supercoil relaxation activity of four Top1 inhibitors; three clinically relevant: camptothecin, LMP-400, LMP-776 (both indenoisoquinoline derivatives), and one natural product in preclinical development, lamellarin-D. Our results demonstrate that Top1 inhibitors have two distinct effects on Top1 activity: a decrease in supercoil relaxation rate and an increase in religation inhibition. The type and magnitude of the inhibition mode depend both on the specific inhibitor and on the topology of the DNA substrate. In general, the efficacy of inhibition is significantly higher with supercoiled than with relaxed DNA substrates. Comparing single-molecule inhibition with cell growth inhibition (IC50) measurements showed a correlation between the binding time of the Top1 inhibitors and their cytotoxic efficacy, independent of the mode of inhibition. This study demonstrates that the single-molecule supercoil relaxation assay is a sensitive method to elucidate the detailed mechanisms of Top1 inhibitors and is relevant for the cellular efficacy of Top1 inhibitors.