Novel multi-targeting anthra[2,3-b]thiophene-5,10-diones with guanidine-containing side chains: Interaction with telomeric G-quadruplex, inhibition of telomerase and topoisomerase I and cytotoxic properties

Novel generations of antitumor anthraquinones are expected to be advantageous over the conventional chemotherapeutic agents. Previous structure-activity relationship studies demonstrated an importance of the positively charged side chains conjugated to anthra[2,3-b]thiophene-5,10-dione scaffolds. Exploring a role of individual side chain moieties in binding to the duplex and G-quadruplex DNA, modulation of telomerase and topoisomerase I activities, intracellular accumulation and cytostatic potency, we herein analyzed a series of reported and newly synthesized guanidine-containing derivatives of anthra[2,3-b]thiophene-5,10-dione. We found that the number of cationic side chains (namely, two) is critical for a tight interaction with human telomeric G-quadruplex (TelQ). Along with a larger drug-TelQ association constant, the telomerase attenuation by anthrathiophenediones with two basic groups in the side chains was more pronounced than by the analogs bearing one basic group. For mono-guanidinated compounds the substituent with the amino group in the side chain provided better TelQ affinity than the methylamine residue. The intracellular uptake of the mono-guanidino derivative with two side chains was >2-fold higher than the respective value for the bis(guanidino) derivative. This difference can explain a lower antiproliferative potency of bis(guanidine) containing compounds. Thus, the modifications of side chains of anthra[2,3-b]thiophene-5,10-dione differently modulated drug-target interactions and cellular effects. Nevertheless, the selected compound 11-(3-aminopropylamino)-4-(2-guanidinoethylamino)anthra[2,3-b]thiophene-5,10-dione 13 demonstrated a high affinity to TelQ and the ability to stabilize the quadruplex structure. These properties were paralleled by reasonable potency of 13 as a telomerase/topoisomerase I inhibitor and an antiproliferative agent. These results indicate that the structural elements of anthra[2,3-b]thiophene-5,10-dione derivatives can be balanced to yield a candidate for further preclinical study.status: publishe

Discovery of antitumor anthra[2,3-b]furan-3-carboxamides: Optimization of synthesis and evaluation of antitumor properties

Anthraquinones and their analogues, in particular heteroarene-fused anthracendiones, are prospective scaffolds for new compounds with improved antitumor characteristics. We herein report the use of a 'scaffold hopping' approach for the replacement of the core structure in the previously discovered hit compound naphtho[2,3-f]indole-5,10-dione 2 with an alternative anthra[2,3-b]furan-5,10-dione scaffold. Among 13 newly synthesized derivatives the majority of 4,11-dihydroxy-2-methyl-5,10-dioxoanthra[2,3-b]furan-3-carboxamides demonstrated a high antiproliferative potency against a panel of wild type and drug resistant tumor cell lines, a property superior over the reference drug doxorubicin or lead naphtho[2,3-f]indole-5,10-dione 2. At low micromolar concentrations the selected derivative of (R)-3-aminopyrrolidine 3c and its stereoisomer (S)-3-aminopyrrolidine 3d caused an apoptotic cell death preceded by an arrest in the G2/M phase. Studies of intracellular targets showed that 3c and 3d formed stable intercalative complexes with the duplex DNA as determined by spectral analysis and molecular docking. Both 3c and 3d attenuated topoisomerase 1 and 2 mediated unwinding of the supercoiled DNA via a mechanism different from conventional DNA-enzyme tertiary complex formation. Furthermore, 3d decreased the activity of selected human protein kinases in vitro, indicating multiple targeting by the new chemotype. Finally, 3d demonstrated an antitumor activity in a model of murine intraperitoneally transplanted P388 leukemia, achieving the increase of animal life span up to 262% at tolerable doses. Altogether, the 'scaffold hopping' demonstrated its productivity for obtaining new perspective antitumor drug candidates.publisher: Elsevier articletitle: Discovery of antitumor anthra[2,3-b]furan-3-carboxamides: Optimization of synthesis and evaluation of antitumor properties journaltitle: European Journal of Medicinal Chemistry articlelink: http://dx.doi.org/10.1016/j.ejmech.2016.01.050 content_type: article copyright: Copyright © 2016 Elsevier Masson SAS. Published by Elsevier Masson SAS All rights reserved.status: publishe