Sébastien Combes

Synthesis and Biological Evaluation of 4-Arylcoumarin Analogues of Combretastatins. Part 2

A series of A-ring variously methoxylated 4-(3-hydroxy-4-methoxyphenyl)coumarins related to combretastatin A-4 was prepared by cross-coupling reactions. Cytotoxicity studies indicated a potent activity against HBL100 cell line. Substitution patterns on A-ring had only a slight effect on antiproliferative activity. For most cytotoxic compounds, the activity as potential modulators of P-gp and BCRP efflux pumps was evaluated. The results show that compounds 2 and 7 were able to restore mitoxantrone accumulation (BCRP) at concentrations similar to that of cyclosporine A. Compound 7 was the most efficient to reverse P-gp activity. All compounds were found to potently inhibit in vitro microtubule formation via a substoichiometric mode of action for the most part. Compounds 1 and 2 were found to have an apparent affinity binding constant similar to that of combretastatin A-4, i.e., 1 × 10 (6) M(-1). The molecular modeling of coumarin derivatives was performed on the basis of the molecular structure of 7, as determined by single-crystal X-ray crystallography. The calculations suggested that the presence of a methoxy group out of the plane of the chromenone moiety is an important steric hindrance factor embedding the accessibility of those molecules inside the binding pocket on tubulin.

Synthesis and biological evaluation of polymethoxylated 4-heteroarylcoumarins as tubulin assembly inhibitor

A series of syn-restricted polymethoxylated 4-heteroarylcoumarins--the isostuctural analogs of combretastatin A-4--was synthesized by Suzuki-Miyaura cross-coupling reaction and evaluated for antiproliferative activity. The 4-(1-methyl-1H-indol-5-yl)chromen-2-ones exhibit a potent cytotoxicity against HBL100 epithelial cell line with an IC(50) value amounting to 0.098 and 0.078 microM, respectively. The two compounds, having an indolyl moiety, potent inhibit in vitro microtubule assembly with a substoichiometric mode of action. A structure-activity relationship was discussed and the indolyl moiety was proved to be a good surrogate for the 3-hydroxy-4-methoxyphenyl ring of CA-4.

Exploring Selective Inhibition of the First Bromodomain of the Human Bromodomain and Extra-terminal Domain (BET) Proteins.

A midthroughput screening follow-up program targeting the first bromodomain of the human BRD4 protein, BRD4(BD1), identified an acetylated-mimic xanthine derivative inhibitor. This compound binds with an affinity in the low micromolar range yet exerts suitable unexpected selectivity in vitro against the other members of the bromodomain and extra-terminal domain (BET) family. A structure-based program pinpointed a role of the ZA loop, paving the way for the development of potent and selective BET-BRDi probes.

Synthesis and Biological Evaluation of Furanoallocolchicinoids

A series of conformationally flexible furan-derived allocolchicinoids was prepared from commercially available colchicine in good to excellent yields using a three-step reaction sequence. Cytotoxicity studies indicated the potent activity of two compounds against human epithelial and lymphoid cell lines (AsPC-1, HEK293, and Jurkat) as well as against Wnt-1 related murine epithelial cell line W1308. The results of in vitro experiments demonstrated that the major effect of these compounds was the induction of cell cycle arrest in the G2/M phase as a direct consequence of effective tubulin binding. In vivo testing of the most potent furanoallocolchicinoid 10c using C57BL/6 mice inoculated with Wnt-1 tumor cells indicated significant inhibition of the tumor growth.

2P2Ichem: focused chemical libraries dedicated to orthosteric modulation of protein–protein interactions

We have recently developed a 2P2IHUNTER learning machine tool for filtering potential orthosteric PPI modulators. In the present research article we applied our algorithm to 8.3 million compounds representing the main chemical providers commercially available to design a PPI-focused library, 2P2IREF, composed of 143 218 small molecules. Compounds corresponding to medicinally important privileged structures identified as core structures in numerous therapeutics were prioritized in a medicinal oriented version of this database (2P2IPRIV – 51 476 compounds). A diverse chemical library was generated using 2D molecular fingerprints (2P2IDIV – 8217 diverse compounds). The carbon bond saturation index (Fsp3) was used as a final filter (Fsp3 ≥ 0.4) to escape from flatland, another hurdle in the long path to the gold mine. We analyzed the resulting chemical space of this final library of 1683 compounds, 2P2I3D and discuss the chemical moieties proposed to the community. This library will now be tested to evaluate its ability to enhance hit rates in general screening campaigns and is open to academic and private companies for collaborative prospects.

New Ianthelliformisamine Derivatives as Antibiotic Enhancers against Resistant Gram-Negative Bacteria

A series consisting of ianthelliformisamimes A, B, and C as well as its synthetic analogues was prepared in high chemical yield, from 27 to 91%, using peptide coupling as the key step, and the compounds were evaluated for their in vitro antibiotic enhancer properties against resistant Gram-negative bacteria and clinical isolates. The mechanism of action of one of these derivatives against Pseudomonas aeruginosa when combined with doxycycline was precisely evaluated utilizing bioluminescence to measure ATP efflux and fluorescence to evaluate membrane depolarization.

Synthesis of indole-derived allocolchicine congeners exhibiting pronounced anti-proliferative and apoptosis-inducing properties

Based on the natural antimitotic agent allocolchicine as a lead structure, a series of novel indole-based allocolchicine congeners was synthesized and assessed in vitro for their cytostatic properties. Several compounds exhibited potent anti-proliferative and apoptosis-inducing activity towards lymphoma cells along with low unspecific cytotoxicity. The observed activity is supposed to result from the inhibition of microtubule assembly, as indicated by the tubulin polymerisation assay.

The Indolylcoumarin COUFIN Exhibits Potent Activity Against Renal Carcinoma Cells without Affecting Hematopoietic System

The present work describes the anticancer activity of a new indolylcoumarin named COUFIN and more specifically, its efficiency against clear cell renal carcinoma (CCRC). COUFIN inhibited microtubule formation and bound on tubulin to or near the colchicine site. In vitro, COUFIN showed potent anticancer activity on renal carcinoma cells (RCC) both in monolayer (2D culture) (IC50 of 88 ± 8 nM) and multicellular tumor spheroid (3D culture) (IC50 of 180 ± 20 nM). The compound blocked cell cycle transition at G2/M phase, induced a subsequent apoptotic process but did not modulate clonal growth of CFU-GM. On the other hand, the coumarin derivative decreased the activity of P-gp and BCRP but was not substrate for these ABC pumps. In vivo, the indolylcoumarin increased the survival rate after 3 weeks of treatment. Based on the present study, COUFIN was identified as a bifunctional molecule able to inhibit renal carcinoma cells proliferation without being effluxed by ABC proteins. Thus COUFIN could be a promising chemotherapeutic agent for treating tumor cells over-expressing efflux pumps and tumor cells irrigated by vessels lined with endothelial cells responsible of poor distribution of conventional anticancer agents.

Tumor Selective Cytotoxic Action of a Thiomorpholin Hydroxamate Inhibitor (TMI-1) in Breast Cancer

Background Targeted therapies, associated with standard chemotherapies, have improved breast cancer care. However, primary and acquired resistances are frequently observed and the development of new concepts is needed. High-throughput approaches to identify new active and safe molecules with or without an “a priori” are currently developed. Also, repositioning already-approved drugs in cancer therapy is of growing interest. The thiomorpholine hydroxamate compound TMI-1 has been previously designed to inhibit metalloproteinase activity for the treatment of rheumatoid arthritis. We present here the repositioning of TMI-1 drug in breast cancer. Methodology/Principal Findings We tested the effect of TMI-1 on luminal, basal and ERBB2-overexpressing breast tumor cell lines and on MMTV-ERBB2/neu tumor evolution. We measured the effects on i) cell survival, ii) cell cycle, iii) extrinsic and intrinsic apoptotic pathways, iv) association with doxorubicin, docetaxel and lapatinib, v) cancer stem cells compartment. In contrast with conventional cytotoxic drugs, TMI-1 was highly selective for tumor cells and cancer stem cells at submicromolar range. All non-malignant cells tested were resistant even at high concentration. TMI-1 was active on triple negative (TN) and ERBB2-overexpressing breast tumor cell lines, and was also highly efficient on human and murine “primary” ERBB2-overexpressing cells. Treatment of transgenic MMTV-ERBB2/neu mice with 100 mg/kg/day TMI-1 alone induced tumor apoptosis, inhibiting mammary gland tumor occurrence and development. No adverse effects were noticed during the treatment. This compound had a strong synergistic effect in association with docetaxel, doxorubicin and lapatinib. We showed that TMI-1 mediates its selective effects by caspase-dependent apoptosis. TMI-1 was efficient in 34/40 tumor cell lines of various origins (ED50: 0.6 µM to 12.5 µM). Conclusions/Significance This is the first demonstration of the tumor selective cytotoxic action of a thiomorpholin hydroxamate compound. TMI-1 is a novel repositionable drug not only for the treatment of adverse prognosis breast cancers but also for other neoplasms.

Dual protein kinase and nucleoside kinase modulators for rationally designed polypharmacology

Masitinib, a highly selective protein kinase inhibitor, can sensitise gemcitabine-refractory cancer cell lines when used in combination with gemcitabine. Here we report a reverse proteomic approach that identifies the target responsible for this sensitisation: the deoxycytidine kinase (dCK). Masitinib, as well as other protein kinase inhibitors, such as imatinib, interact with dCK and provoke an unforeseen conformational-dependent activation of this nucleoside kinase, modulating phosphorylation of nucleoside analogue drugs. This phenomenon leads to an increase of prodrug phosphorylation of most of the chemotherapeutic drugs activated by this nucleoside kinase. The unforeseen dual activity of protein kinase inhibition/nucleoside kinase activation could be of great therapeutic benefit, through either reducing toxicity of therapeutic agents by maintaining effectiveness at lower doses or by counteracting drug resistance initiated via down modulation of dCK target.Masitinib is a protein kinase inhibitor that sensitises refractory pancreatic adenocarcinoma cells to treatment with the nucleoside analog gemcitabine. Here the authors show that Masitinib activates deoxycytidine kinase to enhance phosphorylation of nucleoside analogue pro-drugs, increasing their potency.