The design, synthesis and development of a new class of potent antineoplastic anthraquinones

Rational Design, Synthesis and Binding Affinity Studies of Anthraquinone Derivatives Conjugated to Gonadotropin-Releasing Hormone (GnRH) Analogues towards Selective Immunosuppression of Hormone-Dependent Cancer

Gonadotropin-releasing hormone (GnRH) is pivotal in regulating human reproduction and fertility through its specific receptors. Among these, gonadotropin-releasing hormone receptor type I (GnRHR I), which is a member of the G-protein-coupled receptor family, is expressed on the surface of both healthy and malignant cells. Its presence in cancer cells has positioned this receptor as a primary target for the development of novel anti-cancer agents. Moreover, the extensive regulatory functions of GnRH have underscored decapeptide as a prominent vehicle for targeted drug delivery, which is accomplished through the design of appropriate conjugates. On this basis, a rationally designed series of anthraquinone/mitoxantrone-GnRH conjugates (con1-con8) has been synthesized herein. Their in vitro binding affinities range from 0.06 to 3.42 nM, with six of them (con2-con7) demonstrating higher affinities for GnRH than the established drug leuprolide (0.64 nM). Among the mitoxantrone based GnRH conjugates, con3 and con7 show the highest affinities at 0.07 and 0.06 nM, respectively, while the disulfide bond present in the conjugates is found to be readily reduced by the thioredoxin (Trx) system. These findings are promising for further pharmacological evaluation of the synthesized conjugates with the prospect of performing future clinical studies.

Nanocrystalline ZnO: A Competent and Reusable Catalyst for the Preparation of Pharmacology Relevant Heterocycles in the Aqueous Medium

:

Nanoparticle catalyzed synthesis is a green and convenient method to achieve most of the chemical transformations in water or other green solvents. Nanoparticle ensures an easy isolation process of catalyst as well as products from the reaction mixture avoiding the hectic work up procedure. Zinc oxide is a biocompatible, environmentally benign and economically viable nanocatalyst with effectivity comparable to the other metal nanocatalyst employed in several reaction strategies. This review mainly focuses on the recent applications of zinc oxide in the synthesis of biologically important heterocyclic molecules under sustainable reaction conditions.

:

Application of zinc oxide in organic synthesis: Considering the achievable advantages of this nanocatalyst, presently several research groups are paying attention in anchoring zincoxide or its modified structure in several types of organic conversions e.g. multicomponent reactions, ligand-free coupling reactions, cycloaddition reaction, etc. The advantages and limitations of this nanocatalyst are also demonstrated. The present study aims to highlight the recent multifaceted applications of ZnO towards the synthesis of diverse heterocyclic motifs. Being a promising biocompatible nanoparticle, this catalyst has an important contribution in the fields of synthetic chemistry and medicinal chemistry.

Bbr 2778, an Aza-anthracenedione Endowed with Preclinical Anticancer Activity and Lack of Delayed Cardiotoxicity

With the aim to provide second-generation anthracenedione analogues endowed with reduced side effects and a wider spectrum of action than mitoxantrone and doxorubicin, a large number of new molecules bearing nitrogen atoms in the chromophore was synthesized and screened in vitro and in vivo. From this screening, BBR 2778 (6,9-bis[(2-aminoethyl)amino] benzo[g]isoquinoline-5,10-dione dimaleate) emerged as the most interesting compound. BBR 2778 was tested in vitro on several murine and human tumor cell lines and showed cytotoxic potency lower than that of mitoxantrone and doxorubicin. BBR 2778 was more cytotoxic in leukemia and lymphoma cell lines than in solid tumor cell lines. Although against in vivo models BBR 2778 was less potent than mitoxantrone and doxorubicin, its antitumor activity was equal or superior (in certain tumor models) to that of the above standard compounds. In particular, BBR 2778 was curative against L1210 murine leukemia and YC-8 murine lymphoma. Moreover, it showed an antitumor activity comparable to that of mitoxantrone and doxorubicin on solid tumors. No cardiotoxic effect of BBR 2778 in animals not pretreated with anthracyclines was observed compared to standards. In light of its spectrum of activity and marked efficacy against lymphomas and leukemias over a wide dose range, together with its lack of delayed cardiotoxicity, BBR 2778 has been entered in clinical studies.

Mass spectrometry in the pharmacokinetic studies of anticancer natural products

In the history of medicine, nature has represented the main source of medical products. Indeed, the therapeutic use of plants certainly goes back to the Sumerian and Hippocrates and nowadays nature still represents the major source for new drugs discovery. Moreover, in the cancer treatment, drugs are either natural compounds or have been developed from naturally occurring parent compounds firstly isolated from plants and microbes from terrestrial and marine environment. A critical element of an anticancer drug is represented by its severe toxicities and, after administration, the drug concentrations have to remain in an appropriate range to be effective. Anyway, the drug dosage defined during the clinical studies could be inappropriate for an individual patient due to differences in drug absorption, metabolism and excretion. For this reason, personalized medicine, based on therapeutic drug monitoring (TDM), represents one of most important challenges in cancer therapy. Mass spectrometry sensitivity, specificity and fastness lead to elect this technique as the Golden Standard for pharmacokinetics and drug metabolism studies therefore for TDM. This review focuses on the mass spectrometry-based methods developed for pharmacokinetic quantification in human plasma of anticancer drugs derived from natural sources and already used in clinical practice. Particular emphasis was placed both on the pre-analytical and analytical steps, such as: sample preparation procedures, sample size required by the analysis and the limit of quantification of drugs and metabolites to give some insights on the clinical practice applicability. © 2015 Wiley Periodicals, Inc. Mass Spec Rev. 36:213-251, 2017.

Pathways of cardiac toxicity: comparison between chemotherapeutic drugs doxorubicin and mitoxantrone

Anthracyclines, e.g., doxorubicin (DOX), and anthracenediones, e.g., mitoxantrone (MTX), are drugs used in the chemotherapy of several cancer types, including solid and non-solid malignancies such as breast cancer, leukemia, lymphomas, and sarcomas. Although they are effective in tumor therapy, treatment with these two drugs may lead to side effects such as arrhythmia and heart failure. At the same clinically equivalent dose, MTX causes slightly reduced cardiotoxicity compared with DOX. These drugs interact with iron to generate reactive oxygen species (ROS), target topoisomerase 2 (Top2), and impair mitochondria. These are some of the mechanisms through which these drugs induce late cardiomyopathy. In this review, we compare the cardiotoxicities of these two chemotherapeutic drugs, DOX and MTX. As described here, even though they share similarities in their modes of toxicant action, DOX and MTX seem to differ in a key aspect. DOX is a more redox-interfering drug, while MTX induces energy imbalance. In addition, DOX toxicity can be explained by underlying mechanisms that include targeting of Top2 beta, mitochondrial impairment, and increases in ROS generation. These modes of action have not yet been demonstrated for MTX, and this knowledge gap needs to be filled.

PCL–F68–PCL/PLGA–PEG–PLGA mixed micelles mediated delivery of mitoxantrone for reversing multidrug resistant in breast cancer

Mitoxantrone-loaded PCL–F68–PCL/PLGA–PEG–PLGA mixed micelles for reversing multidrug resistant in breast cancer.

Synthesis and antiproliferative activity of 1,4-bis(dimethylamino)-9,10-anthraquinone derivatives against P388 mouse leukemic tumor cells

A series of 2-substituted-1,4-bis(dimethylamino)-9,10-anthraquinone derivatives were synthesized and their in vitro antiproliferative activities against p388 mouse leukemic tumor cells were evaluated. In addition, the effect of substituents on the phenyl ring was investigated. Among the derivatives tested, seven showed a high antiproliferative effect and three showed a moderate effect. In addition, introduction of a series of substituted phenyl groups into 1,4-bis(dimethylamino)-9,10-anthraquinone at 2-position were shown to enhance its antiproliferative activity. The antiproliferative activity also increased upon substitution of the benzene ring by an electron donating group such as an amine or methoxyl group.

Asymmetric enzymatic glycosylation of mitoxantrone

Using a uniquely promiscuous engineered glycosyltransferase (GT) derived from the macrolide-inactivating GT OleD, a single-step asymmetric glucosylation of one 'arm' of the drug mitoxantrone was efficiently achieved in high stereo- and regiospecificity. The synthesis, structural elucidation, and anticancer activity of the corresponding mitoxantrone 4'-β-D-glucoside are described.

1,8-Bis(tos-yloxy)-9,10-anthraquinone

In the crystal structure of the title compound, C₂₈H₂₀O₈S₂, adjacent anthracene skeletons are parallel or inclined at an angle of 20.6 (1)°. In the mol­ecular structure, the mean plane of the anthracene skeleton makes dihedral angles of 49.6 (1) and 76.8 (1)° with the tosyl rings, and the two terminal benzene rings are oriented at an angle of 74.5 (1)° with respect to each other. The crystal structure is stabilized by inter­molecular C—H⋯O and C—O⋯π inter­actions.

Assessment of DNA double-strand breaks and gammaH2AX induced by the topoisomerase II poisons etoposide and mitoxantrone

Double-strand breaks (DSBs) are highly deleterious DNA lesions as they lead to chromosome aberrations and/or apoptosis. The formation of nuclear DSBs triggers phosphorylation of histone H2AX on Ser-139 (defined as gammaH2AX), which participates in the repair of such DNA damage. Our aim was to compare the induction of gammaH2AX in relation to DSBs induced by topoisomerase II (TOPO II) poisons, etoposide (ETOP) and mitoxantrone (MXT), in V79 cells. DSBs were measured by the neutral comet assay, while gammaH2AX was quantified using immunocytochemistry and flow cytometry. Stabilized cleavage complexes (SCCs), lesions thought to be responsible for TOPO II poison-induced genotoxicity, were measured using a complex of enzyme-DNA assay. In the case of ETOP, a no observed adverse effect level (NOAEL) and lowest observed effect level (LOEL) for genotoxicity was determined; gammaH2AX levels paralleled DSBs at all concentrations but significant DNA damage was not detected below 0.5 microg/ml. Furthermore, DNA damage was dependent on the formation of SCCs. In contrast, at low MXT concentrations (0.0001-0.001 microg/ml), induction of gammaH2AX was not accompanied by increases in DSBs. Rather, DSBs were only significantly increased when SCCs were detected. These findings suggest MXT-induced genotoxicity occurred via at least two mechanisms, possibly related to DNA intercalation and/or redox cycling as well as TOPO II inhibition. Our findings also indicate that gammaH2AX can be induced by DNA lesions other than DSBs. In conclusion, gammaH2AX, when measured using immunocytochemical and flow cytometric methods, is a sensitive indicator of DNA damage and may be a useful tool in genetic toxicology screens. ETOP data are consistent with the threshold concept for TOPO II poison-induced genotoxicity and this should be considered in the safety assessment of chemicals displaying an affinity for TOPO II and genotoxic/clastogenic effects.

Synthesis and Human Telomerase Inhibition of a Series of Regioisomeric Disubstituted Amidoanthraquinones

Telomerase is the enzymatic activity that maintains the ends of eukaryotic chromosomes. Telomerase activity is detected in most tumor cells whereas it is low or undetectable in most normal somatic cells. Expression of the telomerase catalytic component, the human telomerase reverse transcriptase (hTERT), is believed to be controlled primarily at the level of transcription. Because of this selective expression property of telomerase, it has been touted as a specific target for antitumor chemotherapeutics. However, a concern for the applicability of telomerase inhibitors is that they require a long lag time for telomeres to be shortened to critical length before cancer cells stop proliferating. Here we investigate telomerase inhibitory, cytotoxicity and the hTERT repressing effects on a number of synthesized 2,6-diamidoanthraquinones and 1,5-diamidoanthraquinones as compared to their disubstituted homologues. We found that several of the 1,5-diamidoanthraquinones and 2,6-diamidoanthraquinones inhibited telomerase activity effectively with IC50 at the sub-micro to micro molar range and caused acute cytotoxicity to cancer cells with EC50 similar or better than that of mitoxantrone. Particularly, 2,6-diamidoanthraquinone with 2-ethylaminoacetamido side chains 33, even though not affecting cell proliferation, showed to be endowed with a strong telomerase effect, probably related to a marked stabilization of the G-quadruplex-binding structure. The results suggested that these compounds caused multiple effects to cancer cells. More significantly, they overcome the long lag period problem of classical telomerase inhibitors that they are also potent cytotoxic agents. These results greatly expand the potential of tricyclic anthraquinone pharmacophore in preventive and/or curative therapy.

Synthesis and calculated properties of some 1,4-bis(amino)anthracene-9,10-diones

The synthesis of a number of 1,4-bis(amino)anthracene-9,10-diones containing chlorine or sulfur which are related to the anti-cancer drugs Ametantrone and Mitoxantrone are reported. 1,4-Dichloro-2,3-dihydro-5,8-dihydroxyanthracene-9,10-dione reacts readily with a series of alkylamines to yield the corresponding 1,4-bis(alkylamino)-5,8-dichloroanthracene-9,10-dione after oxidation. The subsequent reaction of the products with ethanethiol or thiophenol gives the corresponding 1,4-bis(alkylamino)-5,8-bis(sulfanyl)anthracene-9,10-dione in good yield. Theoretical calculations at the RHF 6-31G** level indicate that the introduction of either chlorine or the phenylsulfanyl group into the 5- and 8-positions of 1,4-bis(alkylamino)anthracene-9,10-diones results in a lowering of the LUMO energies suggesting that related functionalised derivatives might have lower cardiotoxicities than Mitoxantrone.

New benzo[g]isoquinoline-5,10-diones and dihydrothieno [2,3-b]naphtho-4,9-dione derivatives: synthesis and biological evaluation as potential antitumoral agents

Novel antitumoral agents with quinonic structure were synthesized and evaluated for their in vitro cytotoxic activities. This study examines the cytotoxic activities of several aryl benzo[g]isoquinoline-5,10-dione derivatives and a number of aminoacyl dihydrothieno[2,3-b]naphtho-4,9-dione (DTNQ) derivatives containing amino acids in position 3 of the ring system. Compound 6 showed remarkable cytotoxic activity at submicromolar concentration not only against several human leukaemia and solid tumour cell lines, but also toward sensitive and resistant human cell lines.

Effect of modification of 6-[(aminoalkyl)amino]-7H-benzo[e]-perimidin-7-ones on their cytotoxic activity toward sensitive and multidrug resistant tumor cell lines. Synthesis and biological evaluation

Benzoperimidines, a novel group of antitumor anthracenedione analogues, are of interest due to their ability to overcome multidrug resistance of tumor cells (Stefańska, B., Dzieduszycka, M., Bontemps-Gracz, M. M., Borowski, E., Martelli, S., Supino, R., Pratesi, G., De Cesare, MA., Zunino, F., Kuśnierczyk, H., Radzikowski, Cz. J. Med. Chem. 1999, 42, 3494). Although the structural factor essential for exhibiting this desirable property is the presence in the molecule of a fused heterocyclic ring, the cytotoxicity against resistant cells is highly influenced by the nature and location of the substituents. A series of novel synthetic derivatives, comprising monohydroxylated benzoperimidines and 2-aminobenzoperimidines, allowed the establishment of an in vitro structure-activity relationship for a panel of leukemia sensitive, as well as P-gp dependent multidrug resistance (MDR) and multidrug resistance associated protein dependent resistance (MRP) resistant cell lines. The membrane affinity for the compounds has also been determined.

Novel anthraquinone derivatives with redox-active functional groups capable of producing free radicals by metabolism: are free radicals essential for cytotoxicity?

The mode of action of antitumour anthraquinone derivatives (i.e. mitoxantrone) is not clearly established yet. It includes, among others, intercalation and binding to DNA, bioreduction and aerobic redox cycling. A series of anthraquinone derivatives, with potentially bioreducible groups sited in the side chain, have been synthesized and biologically evaluated. Their redox and cytotoxic activities were screened. Derivatives which bear a 2-(dimethylamino)ethylamino substituent, known to confer high DNA affinity, demonstrated cytotoxicity but not redox activity (beside the anthraquinone reduction). Conversely, derivatives which showed redox activity were not cytotoxic toward the P388 cell line. The results suggest that bioreduction is not the main mode of action in the cytotoxicity of anthraquinones.

Rationale for the use of aliphatic N-oxides of cytotoxic anthraquinones as prodrug DNA binding agents: a new class of bioreductive agent

NAD(P)H dependent cytochrome P450's and other haemoproteins under hypoxia, mediate two-electron reduction of a wide range of structurally dissimilar N-oxides to their respective tertiary amines. Metabolic reduction can be utilised, in acute and chronic hypoxia, to convert N-oxides of DNA affinic agents to potent and persistent cytotoxins. In this respect a knowledge of N-oxide bioreduction and the importance of the cationic nature of agents that bind to DNA by intercalation can be combined to rationalise N-oxides as prodrugs of DNA binding agents. The concept is illustrated using the alkylaminoanthraquinones which are a group of cytotoxic agents with DNA binding affinity that is dependent on the cationic nature of these compounds. The actions of the alkylaminoanthraquinones involve drug intercalation into DNA (and double stranded RNA) and inhibition of both DNA and RNA polymerases and topoisomerase Type I and II. A di-N-oxide analogue of mitoxantrone, 1,4-bis([2-(dimethylamino-N-oxide)ethyl]amino)5,8-dihydroxyanthracene -9,10- dione (AQ4N) has been shown to possess no intrinsic binding affinity for DNA and has low toxicity. Yet in the absence of air AQ4N can be reduced in vitro to a DNA affinic agent with up to 1000-fold increase in cytotoxic potency. Importantly the reduction product, AQ4, is stable under oxic conditions. Studies in vivo indicate that antitumour activity of AQ4N is manifest under conditions that promote transient hypoxia and/or diminish the oxic tumour fraction. The advantage of utilising the reductive environment of hypoxic tumours to reduce N-oxides is that, unlike conventional bioreductive agents, the resulting products will remain active even if the hypoxia that led to bioactivation is transient or the active compounds, once formed, diffuse away from the hypoxic tumour regions. Furthermore, the DNA affinic nature of the active compounds should ensure their localisation in tumour tissue.

Structural modification study of anthracyclinones: synthesis and biological activity of several derivatives of eta-pyrromycinone

On the basis of the N-O-O triangular pharmacophore hypothesis postulated earlier in our laboratory, selected side chains with or without the nitrogen atom at the strategic position were incorporated to eta-pyrromycinone, one of the anthracyclinones derived from the antibiotic cinerubins. Since none of the anthracyclinones (the aglycones of anthracyclines) were reported to have antineoplastic activity, the validity of the proposed hypothesis could be tested. Results indicated that a compound designed in this manner, 1,4-bis[2-(2,2-dimethyloxazolidin-3-yl)ethylamino]-1,4-didehydr oxy-eta- pyrromycinone (9c) possessed both in vitro and in vivo antineoplastic activity comparable to that of mitoxantrone. The structure-activity relationship of this class of compounds is discussed.

DNA strand breakage by peroxidase-activated mitoxantrone

Spectroscopic evidence demonstrate that the alkylaminoanthraquinone mitoxantrone is a substrate for horseradish peroxidase in the presence of hydrogen peroxide and that the result of this interaction is the formation of an air-stable mitoxantrone-derived free radical. The mitoxantrone-derived free radicals or their further oxidation products appear to extensively cross-link with plasmid DNA by a reaction that is mitoxantrone concentration-dependent. Oxidative activation of mitoxantrone to a DNA-damaging species may contribute to the mechanism of action of this antitumour agent.

Mechanism(s) for the metabolism of mitoxantrone: electron spin resonance and electrochemical studies

Mitoxantrone has been reported to lack certain properties that characterize quinone containing antitumor agents that undergo enzymatic reduction. These properties are the stimulation of NADPH oxidation, the stimulation of oxygen consumption by microsomes and reductases and, the absence of oxygen free radicals during these reactions. Having these properties implies the presence of a futile redox cycle that requires the generation and the oxidation of a semiquinone free radical. It would follow that if mitoxantrone does not redox cycle in the presence of reductases, then the semiquinone free radical is not produced or, if it is formed, it reacts quickly to form diamagnetic products. However, using liver microsomes, there are reports of the formation of the mitoxantrone free radial anion. In this paper we investigated the mitoxantrone free radical anion generated electrochemically and found that in the presence of oxygen it behaved like other semiquinones. That is, it is oxidized to the parent compound (presumably generating oxygen free radicals), indicating the ability to redox cycle. The reduction potential to generate such free radical in aqueous medium is very high (-0.79 V) when compared to diaziquone (-0.36 V) and Adriamycin (-0.6 V). This suggests that mitoxantrone may not be a substrate for reductases. Under reductive conditions with purified NADPH cytochrome P-450 reductase which very easily reduces diaziquone and Adriamycin, mitoxantrone was not reduced. However, under the same conditions, mitoxantrone was oxidized by the prototype oxidase horseradish peroxidase with the production of a mitoxantrone free radical. This oxidation was accompanied by a drastic change in color and the formation of a dark precipitate. Because microsomes contain a variety of enzymes, we suggest that the previously observed free radical in microsomes is probably due to the oxidation of mitoxantrone. In this theory, this product is probably a polymer which would not require oxygen to be formed. Thus, under oxidative conditions, the mitoxantrone free radical cation will also display impaired redox activity.

Enhancement of the antiviral activity of poly r(A-U) by ametantrone and mitoxantrone

The role of ametantrone (HAQ) and mitoxantrone (DHAQ) in modulating the antiviral and interferon-inducing activities of poly r(A-U) was examined using the human foreskin fibroblast-vesicular stomatitis virus (HSF-VSV) bioassay system in which the concentration of poly r(A-U) was fixed at 0.05 mM or 0.2 mM while the HAQ or DHAQ concentration was varied to produce variable HAQ (or DHAQ)/ribonucleotide ratios ranging from 1:16 to 2:1. HAQ, DHAQ and poly r(A-U) tested individually were not efficacious antiviral agents. When poly r(A-U) was combined with the ametantrone or mitoxantrone the antiviral activity was potentiated 10-fold at HAQ (or DHAQ)/ribonucleotide ratios in the region of 1/4 to 1/6. The interferon-inducing activity of the HAQ (or DHAQ)/poly r(A-U) combinations were equal to the sum of the interferon-inducing activity of the poly r(A-U) and the HAQ (or DHAQ). These results indicate that the HAQ and DHAQ potentiate the antiviral activity of the poly r(A-U) without the superinduction of interferon. The direct viral inactivation study demonstrated that HAQ, DHAQ, poly r(A-U) and the HAQ (or DHAQ)/poly r(A-U) combinations did not inactivate the VSV at concentrations near the viral 50% inhibitory dose.

Diethylaminopropionamido-hydroxy-anthraquinones as potential anticancer agents: synthesis and characterization

A number of new 9,10-anthracenediones were obtained, bearing one or two hydroxyl groups and one positively charged side chain at different positions of the aromatic ring system (compounds 1-5 in Chart 1). These derivatives resemble the anticancer agents mitoxantrone and ametantrone. The synthesis started from dihydroxy- or amino-hydroxy-9,10-anthracenediones, which were converted into the nitro-derivatives. After reduction to the corresponding amines and acylation with 3-chloropropionyl chloride, substitution with diethylamine led to the final diethylaminopropionamido derivatives. The new anthracenediones cause a quite relevant inhibition of cell growth in vitro and will be tested as possible anticancer agents.

Modification of radiation and dihydroxyanthraquinone-induced cell lethality by cysteamine and N-ethylmaleimide

The effect of alteration of sulfhydryl levels on the cell lethality induced by ionizing radiation and dihydroxyanthraquinone (DHAQ) was investigated in cultured Chinese hamster V79 cells. DHAQ produces a potentiation of radiation-induced cell lethality, both by increasing the slope and decreasing the shoulder of the survival curve. It has been suggested that DHAQ functions through the production of free radicals which then produce DNA strand breaks and crosslinks, resulting in cytotoxicity. If this mode of action predominates, then one would expect to be able to change the degree of cell kill by modifying conditions such that free radical processes were altered. This was accomplished by the addition of N-ethylmaleimide (NEM) or Cysteamine (CYS) to the culture medium during treatment with DHAQ. It was observed that the combination of DHAQ and NEM did not produce more cytotoxicity than would be expected from an additive interaction. Likewise, CYS did not reduce the cytotoxicity induced by DHAQ. When cells were treated with DHAQ and radiation plus either NEM or CYS, the resultant survival was consistent with an additive interaction between the potentiation of DHAQ for radiation-induced cell kill and the extra effect of NEM or CYS. These results indicate that alterations of sulfhydryl levels do not produce changes in the cytotoxicity induced by DHAQ, nor in the enhancement by DHAQ of radiation-induced lethality. More investigation is required before definite conclusions can be reached as to the mechanisms of action by which DHAQ, alone or in combination with ionizing radiation, induces mammalian cell lethality.