- Resistance-modifying agents. 9. Synthesis and biological properties of benzimidazole inhibitors of the DNA repair enzyme poly(ADP-ribose) polymerase
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The nuclear enzyme poly(ADP-ribose) polymerase (PARP) facilitates the repair of DNA strand breaks and is implicated in the resistance of cancer cells to certain DNA-damaging agents. Inhibitors of PARP have clinical potential as resistance-modifying agents capable of potentiating radiotherapy and the cytotoxicity of some forms of cancer chemotherapy. The preclinical development of 2-aryl-1H-benzimidazole-4-carboxamides as resistance-modifying agents in cancer chemotherapy is described. 1H-Benzimidazole-4-carboxamides, particularly 2-aryl derivatives, are identified as a class of potent PARP inhibitors. Derivatives of 2-phenyl-1H-benzimidazole-4-carboxamide (23, K(i) = 15 nM), in which the phenyl ring contains substituents, have been synthesized. Many of these derivatives exhibit K(i) values for PARP inhibition 10 nM, with 2-(4-hydroxymethylphenyl)-1H-benzimidazole-4-carboxamide (78, K(i) = 1.6 nM) being one of the most potent. Insight into structure-activity relationships (SAR) for 2-aryl-1H-benzimidazole-4-carboxamides has been enhanced by studying the complex formed between 2-(3-methoxyphenyl)-1H-benzimidazole-4-carboxamide (44, K(i) = 6 nM) and the catalytic domain of chicken PARP. Important hydrogen-bonding and hydrophobic interactions with the protein have been identified for this inhibitor. 2-(4-Hydroxyphenyl)-1H-benzimidazole-4-carboxamide (45, K(i) = 6 nM) potentiates the cytotoxicity of both temozolomide and topotecan against A2780 cells in vitro (by 2.8- and 2.9-fold, respectively).
- White,Almassy,Calvert,Curtin,Griffin,Hostomsky,Maegley,Newell,Srinivasan,Golding
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p. 4084 - 4097
(2007/10/03)
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- Benzimidazole compounds
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Benzimidazole-4-carboxamide compounds (I) which can act as potent inhibitors of the DNA repair enzyme poly(ADP-ribose) polymerase or PARP enzyme (EC 2.4.2.30), and which thereby can provide useful therapeutic compounds for use in conjunction with DNA-damaging cytotoxic drugs or radiotherapy to potentiate the effects of the latter. In formula (I), R and R' may each be selected independently from hydrogen, alkyl, hydroxyalkyl (e.g. CH2CH2OH), acyl (e.g. acetyl or benzoyl) or an optionally substituted aryl (e.g. phenyl) or aralkyl (e.g. benzyl or carboxybenzyl) group. R is generally a substituted phenyl group in the most preferred compounds. The compounds may also be used in the form of pharmaceutically acceptable salts or pro-drugs.
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- Novel benzimidazole and quinazolinone inhibitors of the DNA repair enzyme Poly(ADP-ribose)polymerase
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Two novel series of inhibitors of the DNA repair enzyme poly(ADP-ribose)polymerase (PARP) were synthesized and evaluated for biological activity. In the benzimidazole-4-carboxamide series, the carbamoyl function was restricted into the putative biologically active conformation via an intramolecular hydrogen bond, while for quinazolin-4-[3H]-ones this was achieved by incorporation of the group into a heterocyclic ring. For both series of compounds, syntheses involved acylation of substituted anthranilic acid derivatives, followed by acid- or base-catalysed cyclization. 8-Hydroxyquinazolin-4-[3H]-ones were prepared from the corresponding 8-methoxy compounds by dealkylation with boron tribromide. PARP inhibitory activity was determined in permeabilized L1210 murine leukaemia cells, in comparison with the established inhibitor 3-hydroxybenzamide (IC50 = 8.3 μM). For both series, inhibitory activity varied with the nature of the 2-substituent, with benzimidazole-4-carboxamides proving approximately tenfold more potent than the previously prepared benzoxazole-4-carboxamides. 2-Arylbenzimidazoles were especially active, and 2-(4-methoxyphenyl)benzimidazole-4-carboxamide (IC50 = 60 nM) is the most potent PARP inhibitor reported to date. In the quinazolinone series, a 2-(4-nitrophenyl) substituent, and either an 8-methyl or 8-hydroxy group conferred potent inhibitory activity, with IC50 values of 0.13 and 0.23 μM, respectively, being observed.
- Griffin,Srinivasan,White,Bowman,Calvert,Curtin,Newell,Golding
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