Anti-cancer drug design最新文献

A series of bisbenzimidazoles bearing a variety of alkylating agents [ortho- and meta-mustards, imidazolebis(hydroxymethyl), imidazolebis(methylcarbamate) and pyrrolebis(hydroxymethyl)], appended by a propyl linker chain, were prepared and investigated for sequence-specificity of DNA alkylation and their cytotoxicity. Previous work has shown that, for para-aniline mustards, a propyl linker is optimal for cytotoxicity. Alkaline cleavage assays using a variety of different labelled oligonucleotides showed that the preferred sequences for adenine alkylation were 5'-TTTANANAANN and 5'-ATTANANAANN (underlined bases show the drug alkylation sites), with AT-rich sequences required on both the 5' and 3' sides of the alkylated adenine. The different aniline mustards showed little variation in alkylation pattern and similar efficiencies of DNA cross-link formation despite the changes in orientation and positioning of the mustard, suggesting that the propyl linker has some flexibility. The imidazole- and pyrrolebis(hydroxymethyl) alkylators showed no DNA strand cleavage following base treatment, indicating that no guanine or adenine N3 or N7 adducts were formed. Using the PCR-based polymerase stop assay, these alkylators showed PCR blocks at 5'-C*G sites (the * nucleotide indicates the blocked site), particularly at 5'-TAC*GA 5'-AGC*GGA, and 5'-AGCC*GGT sequences, caused by guanine 2-NH2 lesions on the opposite strand. Only the (more reactive) imidazolebis(methylcarbamoyl) and pyrrolebis(hydroxymethyl) alkylators demonstrated interstrand cross-linking ability. All of the bifunctional mustards showed large (approximately 100-fold) increases in cytotoxicity over chlorambucil, with the corresponding monofunctional mustards being 20- to 60-fold less cytotoxic. These results suggest that in the mustards the propyl linker provides sufficient flexibility to achieve delivery of the alkylator to favoured (adenine N3) sites in the minor groove, regardless of its exact geometry with respect to the bisbenzimidazole carrier. The 'targeted' bisbenzimidazole bis(hydroxymethyl)pyrrole- and imidazole analogues showed very similar patterns of alkylation to the corresponding 'untargeted' compounds, with little evidence of additional selectivity imposed by this AT-preferring carrier.

The mitogenic action of EGF is mediated by ligand-induced autophosphorylation of the EGF receptor (EGF-R), which is commonly overexpressed in numerous human cancers. Inhibitors of receptor tyrosine kinase (RTK) activity could therefore be considered as effective potential antitumor agents. For this purpose, 4-aminoquinazoline derivatives were prepared and evaluated for their ability to inhibit RTK activity and the autophosphorylation of EGF-R. In addition, these compounds were tested on A431 cell growth to estimate their antiproliferative effect. The results showed that the substituent at the 4-position of the quinazoline ring must be an aromatic amine carrying small lipophilic electron-withdrawing groups on the 3- (or 2-) position of the phenyl ring. This aromatic moiety might be far from the quinazoline provided that the linking group is conformationally restricted, such as with piperazine. Hydrophilic and non-aromatic substituents such as morpholine gave completely inactive compounds. Introduction of a bulk at the 2-position of the quinazoline ring in 2,4-diaminoquinazolines or tricyclic compounds led to inactive products. This study reports additional structure-activity relationships of a well-characterized series to develop new inhibitors of EGF-R-associated tyrosine kinase activity.

The design and synthesis of the mustard pro-prodrugs which can be used in ADEPT is reported. Prodrugs 1 and 2 include a glucuronide group which is connected to the drug via an aromatic and/or aliphatic bis-carbamate spacer. The design of these new prodrugs takes advantage of a spontaneous 1,6-elimination and/or an intramolecular cyclization reaction after enzymatic cleavage. Thus, enzymatic-catalyzed hydrolysis of the glucuronyl moiety of 1 by Escherichia coli beta-glucuronidase results in the liberation of the parent mustard drug 20 with formation of CO2, 2-nitro-4-hydroxymethylphenol 19 and dimethylimidazolidinone 21. Surprisingly, prodrug 2 was not cleaved under the same conditions. According to in vitro experiments, prodrugs 1 and 2 were approximately 50- and 80-fold less cytotoxic than the parent drug and, when treated with beta-glucuronidase, the level of cytotoxic activity of 1 became comparable to that of the drug. Stability of 1 in phosphate buffer was satisfactory. These results demonstrate that 1 is a prodrug that can be specifically activated to release the cytotoxic agent.

Some N-sulphonated-2-substituted benzimidazoles and imidazo[4,5-b]-pyridines were synthesized and tested in vitro for antiviral and antiproliferative activity. None of the compounds had antiviral properties. However, three of them inhibited the proliferation of leukaemia and lymphoma cell lines at micromolar concentrations. The maximum potency of antiproliferative activity is correlated with the presence of an ethylenic spacer between the two heterocycles.

Anthraquinone compounds belong to the most important class of clinical antitumour agents. However, their use is limited by their peroxidating activity, being the consequence of free radical formation initiated by three oxyreductases. This activity is considered to be the main cause of cardiotoxic effects. The affinity of anthraquinone compounds to these enzymes is an essential factor governing the rate of one-electron transfer and the generation of oxygen radicals. A series of novel derivatives and analogues of natural and synthetic anthraquinones has been examined with the aim of identifying the structural factors essential for the ability to stimulate oxygen radical formation catalysed by NADH dehydrogenase. Functional groups and moieties favouring or disfavouring the interaction of the compounds with the enzyme have been determined. The quinonoid moiety as well as at least two phenolic groups in peri positions favoured the affinity of these compounds for NADH dehydrogenase. The modification of the quinonoid structure to iminoquinonoid or carboquinonoid forms dramatically decreased interaction with the enzyme. The O'-substitution by a bulky group in the sugar moiety of daunorubicin decreased the ability of the derivatives to stimulate oxygen radical formation. It has also been shown that the presence of an ionizable amino group on the sugar moiety of daunorubicin favours interaction with the NADH dehydrogenase. However, its location is not essential for this effect.

The DNA sequence-specific binding ability of polybenzamide minor groove binding ligands was investigated. These ligands were compared with the known minor groove binder Hoechst 33258, using both DNase I footprinting and chlorambucil interference footprinting. The monocationic derivative showed some sequence specific binding to A/T-rich sequences, as shown by DNase I footprinting, but results for the biscationic polybenzamide were inconclusive. A general non-specific inhibition of cleavage at high drug concentrations was observed, suggesting these compounds had a low DNA binding affinity compared to Hoechst 33258. Using a complementary technique, chlorambucil interference footprinting, the biscationic derivative displayed a clear preference for sites containing at least three consecutive adenines and in contrast with the monocationic analogue, a lesser affinity for mixed A/T sequences.

Some flavone-2'-carboxylic acid analogues are described. Direct in vitro toxicity of the synthesized compounds was evaluated towards four tumoral cell lines, and the ability of these compounds to stimulate mouse peritoneal macrophages in culture to become tumoricidal (indirect toxicity) was also studied. Direct cytotoxic activity was very low for all derivatives. However, almost all compounds showed a remarkable increase of indirect cytotoxicity. In particular, compound 3i, which has an F atom in the 7 position of the flavone ring, was able to increase significantly the macrophage's lytic properties, and has been selected for further investigations.

We have explored the potential antitumour activity of DNA-intercalating free radical generators based on compounds constructed from 9-anilinoacridine and chelidamic acid as an iron (II) binding centre. Here we describe their synthesis, DNA cleaving ability and activity against a panel of human tumour cell lines in culture. We also investigate their potential for use as DNA footprinting agents. Previous work has shown that the parent compound, FTP1, cleaves DNA in an essentially sequence neutral fashion and has modest cytotoxicity [Searcey, M., McClean, S., Madden, B. & Wakelin, L.P.G. (1997) Journal of the Chemical Society. Perkin Transactions, 2, 523]. Here we have equipped the acridine chromophore with an N,N-dimethylaminoethyl-4-carboxamide substituent, giving the threading agent FTP2, which confers selectivity for cleaving in GC-rich sequences, avoidance for binding to AT-tracts and 8-fold enhanced cytotoxicity compared with FTP1. Although this side chain bestows slow dissociation kinetics on DNA complexes of 9-anilinoacridines, it does not enhance the overall cutting efficiency of FTP2, implying that free-radical generation, DNA hydrogen abstraction and sugar fragmentation are fast compared with DNA-ligand complex lifetimes. FTP2 does not appear to be susceptible to resistance by the mdr phenotype in human ovarian carcinoma cells. We also report that FTP2 is an effective footprinting agent for GC-selective binding ligands and that it has some advantages over FTP1 in this regard.

The three new hydrophilic prodrugs 2, 3 and 4 have been prepared from methyl (4-hydroxymethyl-2-nitrophenyl 2,3,4-tri-O-acetyl-beta-D-glucopyranosid)uronate (5) and doxorubicin. Their low cytotoxicity, efficient release of doxorubicin after hydrolysis by beta-D-glucuronidase, and in the cases of 2 and 3 stability at pH 7.2 fulfil the preliminary requirement for their use in antibody-directed enzyme prodrug therapy or prodrug monotherapy.

The (E)-stilbene isomer (2a) of the (Z)-combretastatin A-4 prodrug (1b) was efficiently prepared from (E)-combretastatin A-4 by a reaction sequence employing phosphorylation (dibenzyl chlorophosphite), cleavage (trimethyliodosilane) of the benzyl ester and reaction of the resulting phosphoric acid with sodium methoxide. The sodium phosphate product (2c) was also found to be an important side-product, presumably from iodine-catalyzed isomerization, when the analogous synthetic route was used to obtain the combretastatin A-4 prodrug (1b). The phosphoric acid precursor of prodrug 1b derived from (Z)-combretastatin A-4 (1a) was converted into a series of metal cation and ammonium cation salts to evaluate effects on human cancer cell growth, antimicrobial activities and solubility behavior.