Phenothiazine- and Carbazole-Cyanochalcones as Dual Inhibitors of Tubulin Polymerization and Human Farnesyltransferase.

In the search for innovative approaches to cancer chemotherapy, a chemical library of 49 cyanochalcones, 1a-r, 2a-o, and 3a-p, was designed as dual inhibitors of human farnesyltransferase (FTIs) and tubulin polymerization (MTIs) (FTIs/MTIs), two important biological targets in oncology. This approach is innovative since the same molecule would be able to interfere with two different mitotic events of the cancer cells and prevent these cells from developing an emergency route and becoming resistant to anticancer agents. Compounds were synthesized by the Claisen-Schmidt condensation of aldehydes with N-3-oxo-propanenitriles under classical magnetic stirring and under sonication. Newly synthesized compounds were screened for their potential to inhibit human farnesyltransferase, tubulin polymerization, and cancer cell growth in vitro. This study allowed for the identification of 22 FTIs and 8 dual FTIs/MTIs inhibitors. The most effective molecule was carbazole-cyanochalcone 3a, bearing a 4-dimethylaminophenyl group (IC50 (h-FTase) = 0.12 µM; IC50 (tubulin) = 0.24 µM) with better antitubulin activity than the known inhibitors that were previously reported, phenstatin and (-)-desoxypodophyllotoxin. The docking of the dual inhibitors was realized in both the active site of FTase and in the colchicine binding site of tubulin. Such compounds with a dual inhibitory profile are excellent clinical candidates for the treatment of human cancers and offer new research perspectives in the search for new anti-cancer drugs.

7-Chloroquinolinehydrazones as First-in-Class Anticancer Experimental Drugs in the NCI-60 Screen among Different Investigated Series of Aryl, Quinoline, Pyridine, Benzothiazole and Imidazolehydrazones.

In the context of a continuously increasing global cancer risk, the search for new effective and affordable anticancer drugs remains a constant demand. This study describes chemical experimental drugs able to destroy cancer cells by arresting their growth. New hydrazones with quinoline, pyridine, benzothiazole and imidazole moieties have been synthesized and evaluated for their cytotoxic potential against 60 cancer cell lines. 7-Chloroquinolinehydrazones were the most active in the current study and exhibited good cytotoxic activity with submicromolar GI50 values on a large panel of cell lines from nine tumor types (leukemia, non-small cell lung cancer, colon cancer, CNS cancer, melanoma, ovarian cancer, renal cancer, prostate cancer and breast cancer). This study provided consistent structure-activity relationships in this series of experimental antitumor compounds.

Attempts to Access a Series of Pyrazoles Lead to New Hydrazones with Antifungal Potential against Candida species including Azole-Resistant Strains.

The treatment of benzylidenemalononitriles with phenylhydrazines in refluxing ethanol did not provide pyrazole derivatives, but instead furnished hydrazones. The structure of hydrazones was secured by X-ray analysis. The chemical proof was also obtained by direct reaction of 3,4,5-trimethoxybenzaldehyde with 2,4-dichlorophenylhydrazine. Newly synthesized hydrazones were tested against eight Candida spp. strains in a dose response assay to determine the minimum inhibitory concentration (MIC99). Five compounds were identified as promising antifungal agents against Candida spp. (C. albicans SC5314, C. glabrata, C. tropicalis, C. parapsilosis and C. glabrata (R azoles)), with MIC99 values ranging from 16 to 32 µg/mL and selective antifungal activity over cytotoxicity.

Indolizine-phenothiazine hybrids as the first dual inhibitors of tubulin polymerization and farnesyltransferase with synergistic antitumor activity.

In the incessant search for innovative cancer control strategies, this study was devoted to the design, synthesis and pharmacological evaluation of dual inhibitors of farnesyltransferase and tubulin polymerization (FTI/MTIs). A series of indolizine-phenothiazine hybrids 16 (amides) and 17 (ketones) has been obtained in a 4-step procedure. The combination of the two heterocycles provided potent tubulin polymerization inhibitors with similar efficiency as the reference phenstatin and (-)-desoxypodophyllotoxin. Ketones 17 were also able to inhibit human farnesyltransferase (FTase) in vitro. Interestingly, three molecules 17c, 17d and 17f were very effective against both considered biological targets. Next, nine indolizine-phenothiazine hybrids 16c, 16f, 17a-f and 22b were evaluated for their cell growth inhibition potential on the NCI-60 cancer cell lines panel. Ketones 17a-f were the most active and displayed promising cellular activities. Not only they arrested the cell growth of almost all tested cancer cells, but they displayed cytotoxicity potential with GI50 values in the low nanomolar range. The most sensitive cell lines upon treatment with indolizine-phenothiazine hybrids were NCI-H522 (lung cancer), COLO-205 and HT29 (colon cancer), SF-539 (human glioblastoma), OVCAR-3 (ovarian cancer), A498 (renal cancer) and especially MDA-MB-435 (melanoma). Demonstrating the preclinical effectiveness of these dual inhibitors can be crucial. A single dual molecule could induce a synergy of antitumor activity, while increasing the effectiveness and reducing the toxicity of the classical combo treatments currently used in chemotherapy.

Novel amphiphilic dextran esters with antimicrobial activity.

New amphiphilic dextran esters were obtained by polysaccharide functionalization with different substituted 1,2,3-triazoles-4-carboxylic acid via in situ activation with N, N'-carbonyldiimidazole. Nitrogen-containing heterocyclic derivatives were achieved by copper(I)-catalyzed cycloaddition reaction between organic azides and ethyl propiolate. Structural characteristics of the compounds were studied by elemental analysis, Fourier transform infrared and nuclear magnetic resonance spectroscopy (1H and 13C-NMR). Thermogravimetric analysis, differential scanning calorimetry and wide-angle X-ray diffraction were used for esters characterization. Properties of polymeric self-associates, formed in aqueous solution, were studied by dynamic light scattering and transmission electron microscopy. The critical aggregation concentration values for dextran esters, determined by fluorescence spectroscopy, were in the range of 4.1-9.5 mg/dL. Antimicrobial activity, investigated for some of the polymers by disc-diffusion method, pointed out that polysaccharide esters were active.

Exploring isoxazoles and pyrrolidinones decorated with the 4,6-dimethoxy-1,3,5-triazine unit as human farnesyltransferase inhibitors.

Unprecedented triazinyl-isoxazoles were afforded via an effective cycloaddition reaction between nitrile oxides and the scarcely described 2-ethynyl-4,6-dimethoxy-1,3,5-triazine as dipolarophile. The biological evaluation of the newly synthesized compounds showed that the inhibition of human farnesyltransferase by zinc complexation could be improved with triazine-isoxazole moieties. The replacement of the isoxazole unit by a pyrrolidin-2-one was detrimental to the inhibitory activity while the pyrrolidin-2-thione derivatives conserved the biological potential. The potential of selected compounds to disrupt protein farnesylation in Chinese hamster ovary (CHO) cells transfected with pEGFP-CAAX was also evaluated.

Methylene versus carbonyl bridge in the structure of new tubulin polymerization inhibitors with tricyclic A-rings.

The phenothiazine group has been identified as a suitable A ring in the structure of tubulin polymerization inhibitors. In our search to identify more potent inhibitors, a study of different isosteric tricyclic groups as new potential A rings was first realized and permitted to identify 1-azaphenothiazine and iminodibenzyl as favorable modulations providing compounds with improved activity against tubulin. An investigation of the methylene group as the connector between the A and B rings revealed that the "CH2" bridge was tolerated, improving the biological potency when the A unit was of phenothiazine, 1-azaphenothiazine or iminodibenzyl type. Molecules 6-8 and 12 showed increased biological activity in comparison to parent phenstatin 2 on COLO 205 colon cancer cell line. The most antineoplastic agent in the current study was phenothiazine 5 displaying a GI50 of 25nM against the melanoma MDA-MB-435 cell line.

New indolizine-chalcones as potent inhibitors of human farnesyltransferase: Design, synthesis and biological evaluation.

A new family of indolizine-chalcones was designed, synthesized and screened for the inhibitory potential on human farnesyltransferase in vitro to identify potent antitumor agents. The most active compound was phenothiazine 2a, exhibiting an IC50 value in the low nanomolar range, similar to that of known FTI-276, highly potent farnesyltransferase inhibitor. The newly synthesized indolizine-chalcones 2a-d constitute the most efficient inhibitors of farnesyltransferase bearing a phenothiazine unit known to date.

Studies on phenothiazines: New microtubule-interacting compounds with phenothiazine A-ring as potent antineoplastic agents.

New phenothiazine derivatives 6-20 have been designed, synthesized and evaluated in vitro for their ability to inhibit tubulin polymerization and antiproliferative activity against 60 cancer cell lines, including several multi-drug resistant (MDR) tumor cell lines. The phenothiazine unit may successfully replace the classical 3,4,5-trimethoxyphenyle A ring of parent combretastatin A-4 or phenstatin, confirming previous studies. The most promising structural modulations have been realized on the B ring, the 2'-fluoro-4'-methoxy substitution in compound 6 and the 2'-trifluoromethyl-4'-methoxy substitution in compound 7 providing the best antitubulin and antitumor activity in the current study. Compounds 6-8 and 16 exhibited more important cell growth inhibition than parent phenstatin 2 on human colon Duke's type D, colorectal adenocarcinoma COLO 205 and on human kidney adenocarcinoma A498 cell lines. 10-Methylphenothiazine derivatives 19 and 20 did not show biological activity but exerted bright fluorescence and solvatochromism effects. These molecules deserve further chemical efforts in order to provide valuable tools for biophysical studies.

Phenothiazine-based CaaX competitive inhibitors of human farnesyltransferase bearing a cysteine, methionine, serine or valine moiety as a new family of antitumoral compounds.

A new family of CaaX competitive inhibitors of human farnesyltransferase based on phenothiazine and carbazole skeleton bearing a l-cysteine, l-methionine, l-serine or l-valine moiety was designed, synthesized and biologically evaluated. Phenothiazine derivatives proved to be more active than carbazole-based compounds. Phenothiazine 1b with cysteine residue was the most promising inhibitor of human farnesyltransferase in the current study.

Discovery of indolizines containing triazine moiety as new leads for the development of antitumoral agents targeting mitotic events.

A new family of 3-aroylindolizines bearing a dimethoxytriazine unit in their position 1 was designed, synthesized and evaluated for their ability to inhibit tubulin polymerization and cellular growth in vitro. Compound 39 was the best candidate in the current study with a GI50 value of 870 nM on SNB-75 CNS cancer cells and of 920 nM on MDA-MB-231/ATCC breast cancer cells. The standard NCI Compare results indicated that indolizine 39 may target PLK1 (polo-like kinase 1).

Studies on indolizines. Evaluation of their biological properties as microtubule-interacting agents and as melanoma targeting compounds.

With the aim of investigating new analogues of phenstatin with an indolizin-3-yl unit, in particular as the B-ring, three new series of compounds (6-8, 9-34 and 54) were synthesized and tested for interactions with tubulin polymerization and evaluated for cytotoxicity on an NCI-60 human cancer cell lines panel. The replacement of the 3'-hydroxy-4'-methoxyphenyl B-ring of phenstatin with substituted indolizine unit results in the conservation of both antitubulin and cytotoxic effect. Indolizines 9 and 17 were the most effective in the present study and showed the highest antiproliferative effect on melanoma cell lines MDA-MB-435 (GI50 = 30 nM) and could serve as new lead compounds for the development of anti-cancer therapeutics.

Novel indolizine derivatives with unprecedented inhibitory activity on human farnesyltransferase.

The rational structural modification of new substituted indolizin-3-yl(phenyl)methanones 1a-i, 2a-i and 3a-i has greatly improved human farnesyltransferase inhibition. The para-bromophenyl analog 2f bearing an ester unit on the indolizine ring demonstrates the highest inhibition potential, with IC50 value of 1.3±0.2 µM. The amidic series 1a-i proves to be the most promising for future modulations, particularly at the triple bond level.

Eaton's reagent-mediated domino π-cationic arylations of aromatic carboxylic acids to Iasi-red polymethoxylated polycyclic aromatic hydrocarbons: products with unprecedented biological activities as tubulin polymerization inhibitors.

A rapid domino π-cationic arylation of aromatic carboxylic acids, mediated by Eaton's reagent, has been developed for the synthesis of Iasi-red polymethoxylated polycyclic aromatic hydrocarbons (PAHs). This route is currently the easiest method to obtain such popular PAH compounds, which bear in addition numerous methoxy groups. The domino process was generalized, the structure of the obtained red products and the mechanism of their formations were elucidated, and some of their photophysical properties were determined. Newly synthesized polymethoxylated-PAHs were tested for their interaction with tubulin polymerization as well as for their cytotoxicity on a panel of NCI-60 human cancer cell lines. Interestingly, one of these rubicene derivatives exhibited remarkable cytotoxicity in vitro, including inhibition of leukemia, colon, melanoma, CNS, and ovarian cancer cell lines with GI50 values in the low nanomolar range (GI50 < 10 nM).

Peptide chemistry applied to a new family of phenothiazine-containing inhibitors of human farnesyltransferase.

Novel phenothiazine derivatives bearing an amino acid residue were synthesized via peptide chemistry, and evaluated for their inhibitory potential on human farnesyltransferase. The phenothiazine unit proved to be an important bulky unit in the structure of the synthesized inhibitors. Propargyl ester 20 bearing a tyrosine residue exhibited the best biological potential in vitro in the present study. Further syntheses and biological evaluation of phenothiazine derivatives are necessary in order to gain a full view of SAR in this family of farnesyltransferase inhibitors.

A facile synthesis of Pechmann dyes.

A facile synthesis of Pechmann dyes has been accomplished by the reaction of substituted N-phenacyl-4-dimethylaminopyridinium halides with dimethyl maleate in the presence of DBU. Based on a related 4-DMAP elimination product and an isolated monolactone intermediate a reaction mechanism has been proposed. The scope of this synthetic method is determined by the availability of α-haloaroyl or heteroaroyl derivatives. DBU=1,8-diazabicycloundec-7-ene, DMAP=4-dimethylaminopyridine.

Synthesis and biological evaluation of a new series of N-ylides as protein farnesyltransferase inhibitors.

A new family of 30 benzoylated N-ylides 4 and 5 was synthesized and evaluated for the inhibitory activity on human protein farnesyltransferase. Most of these novel compounds possessed in vitro inhibition potencies in the micromolar range. The nature of the substituents on the pyridine and phenyl units proved to be important in determining inhibitory activity and generally, the replacement of the cyanoacrylonitrile function by a cyanoethylacrylate group decreased the biological potential on farnesyltransferase. These results completed our SAR study on this original class of N-ylides.

Synthesis and biological evaluation of a new series of phenothiazine-containing protein farnesyltransferase inhibitors.

Two new families of human farnesyltransferase inhibitors 13a-m and 14a-d, based on a phenothiazine scaffold, were synthesized. Compounds 14a and 14b were the most promising inhibitors of human farnesyltransferase with IC(50) values of 0.7 and 0.6 µM, respectively.

Synthesis and anticancer activity of analogues of phenstatin, with a phenothiazine A-ring, as a new class of microtubule-targeting agents.

A new family of microtubule-targeting agents with a phenothiazine A-ring was synthesized and evaluated for anti-proliferative activity and interaction with tubulin. These new derivatives showed significant activities against cellular proliferation and tubulin polymerization, rather similar to those of phenstatin. Phenothiazine derivative 21 proved to be the most potent compound synthesized with GI(50) values ranging from 29 to 93 nM on different cell lines. The same compound showed a better inhibition of COLO 205, A498, and MCF7 cell lines than the parent phenstatin.

Synthesis and biological evaluation of new phenothiazine derivatives bearing a pyrazole unit as protein farnesyltransferase inhibitors.

A new family of protein farnesyltransferase inhibitors, based on a phenothiazine scaffold, was designed and synthesized. The biological evaluation of these products showed that compounds 28 and 30 were the most active, with protein farnesyltransferase inhibition potencies in the low micromolar range. Compounds were also evaluated for their antiproliferative activity on a NCI-60 cancer cell line panel. Indenopyrazole 30 exhibited the most potent in vitro cytostatic activity inhibiting the growth of HCT-116, LOX IMVI and SK-MEL-5 cell lines.