A Convenient Route to New (Radio)Fluorinated and (Radio)Iodinated Cyclic Tyrosine Analogs.

The use of radiolabeled non-natural amino acids can provide high contrast SPECT/PET metabolic imaging of solid tumors. Among them, radiohalogenated tyrosine analogs (i.e., [123I]IMT, [18F]FET, [18F]FDOPA, [123I]8-iodo-L-TIC(OH), etc.) are of particular interest. While radioiodinated derivatives, such as [123I]IMT, are easily available via electrophilic aromatic substitutions, the production of radiofluorinated aryl tyrosine analogs was a long-standing challenge for radiochemists before the development of innovative radiofluorination processes using arylboronate, arylstannane or iodoniums salts as precursors. Surprisingly, despite these methodological advances, no radiofluorinated analogs have been reported for [123I]8-iodo-L-TIC(OH), a very promising radiotracer for SPECT imaging of prostatic tumors. This work describes a convenient synthetic pathway to obtain new radioiodinated and radiofluorinated derivatives of TIC(OH), as well as their non-radiolabeled counterparts. Using organotin compounds as key intermediates, [125I]5-iodo-L-TIC(OH), [125I]6-iodo-L-TIC(OH) and [125I]8-iodo-L-TIC(OH) were efficiently prepared with good radiochemical yield (RCY, 51-78%), high radiochemical purity (RCP, >98%), molar activity (Am, >1.5-2.9 GBq/µmol) and enantiomeric excess (e.e. >99%). The corresponding [18F]fluoro-L-TIC(OH) derivatives were also successfully obtained by radiofluorination of the organotin precursors in the presence of tetrakis(pyridine)copper(II) triflate and nucleophilic [18F]F- with 19-28% RCY d.c., high RCP (>98.9%), Am (20-107 GBq/µmol) and e.e. (>99%).

Determination of eumelanin and pheomelanin in melanomas using solid-phase extraction and high performance liquid chromatography-diode array detection (HPLC-DAD) analysis.

Determination of eumelanin and pheomelanin in melanomas that exhibit different pigmentation was carried using a solid-phase extraction (SPE) preparation method based on weak anion exchange chemistry. This extraction significantly enhanced the chromatographic profile obtained by reverse phase high performance liquid chromatography-diode array detection (RP-HPLC-DAD). The SPE method was developed using aqueous standards of melanin markers: thiazole-2,4,5-tricarboxylic acid (TTCA), thiazole-4,5-dicarboxylic acid (TDCA), pyrrole-2,3-dicarboxylic acid (PDCA) and pyrrole-2,3,5-tricarboxylic acid (PTCA) and non-pigmented cell lines spiked with those markers. An excellent average recovery, above 90%, was obtained for the four markers with a relative standard deviation below 7%. We have also optimized the stationary phase and the mobile phase (phosphate concentration and pH) to improve sensitivity and to reduce the analysis time. Elution of the four markers is achieved in 5 min and total analysis of biological samples is completed in 15 min. The quantification limits for TDCA, TTCA, PDCA and PTCA are 60, 50, 47 and 48 ng/mL respectively. Furthermore, DAD detection improves the marker identification in complex matrices through the analysis of UV spectra. We have successfully applied this method to melanoma tumors and cells. Murine B16BL6 tumor are highly pigmented with mostly eumelanin (98.1% of eumelanin) while human SK-MEL-3 tumor contain about 30% pheomelanin. B16BL6 and B16F10 are eumelanic cells lines and NHEM melanocytes contain about 24% of pheomelanin.

Linker structure-activity relationships in fluorodeoxyglucose chlorambucil conjugates for tumor-targeted chemotherapy.

Nitrogen mustards, such as chlorambucil (CLB), can cause adverse side-effects due to ubiquitous distribution in non-target organs. To minimize this toxicity, strategies of tumor-targeting drug delivery have been developed, where a cytotoxic warhead is linked to a tumor-cell-specific small ligand. Malignant cells exhibit marked glucose avidity and an accelerated metabolism by aerobic glycolysis, known as the Warburg effect, and recognized as a hallmark of cancer. A targeting approach exploiting the Warburg effect by conjugation of CLB to 2-fluoro-2-deoxyglucose (FDG) was previously reported and identified two peracetylated glucoconjugates 2 and 3 with promising antitumor activities in vivo. These results prompted us to investigate the importance of the spacer in this tumor-targeting glucose-based conjugates. Here we report the chemical synthesis and an in vitro cytotoxicity evaluation, using a 5-member panel of human tumor cell lines and human fibroblasts, of 16 new CLB glucoconjugates in which the alkylating drug is attached to the C-1 position of FDG via different linkages. We studied the structure-activity relationships in the linker, and evidenced the positive impact of an aromatic linker on in vitro cytotoxicity: compound 51 proved to be the most active FDG-CLB glucoside, characterized by a bis-aromatic spacer tethered to CLB through an amide function.

Development and Preliminary Evaluation of TFIB, a New Bimodal Prosthetic Group for Bioactive Molecule Labeling.

The new readily available prosthetic group, tetrafluorophenyl 4-fluoro-3-iodobenzoate (TFIB), designed for both molecular imaging and targeted radionuclide therapy purposes was radiolabeled either with fluorine or iodine radionuclides with excellent radiochemical yields and purities. These radiolabeled tags were conjugated to N,N-diethylethylenediamine to give melanin-targeting radiotracers [ (125) I]9 and [ (18) F]9, which were successfully evaluated by PET and gamma scintigraphic imaging in B16F0 pigmented melanoma-bearing C57BL/6J mice. Then, radiolabeled [ (125) I]/[ (18) F]TFIB was used to tag tumor-targeting peptides (i.e., PEG3[c(RGDyK)]2 and NDP-MSH targeting αvß3 integrin and MC1R receptors, respectively) in mild conditions and with good radiochemical yields (47-83% d.c.) and purities (>99%). The resulting radiolabeled peptides were assessed both in vitro and by PET imaging in animal models.

Spacer optimization of new conjugates for a melanoma-selective delivery approach.

In the search for more selective anticancer drugs, we designed and synthesized seven conjugates varying the structure of the linker connecting the 5-iodo-2'-deoxyuridine (IUdR) to the ICF 01012 melanoma-carrier for potential intratumoural specific drug release. Chemical and in vitro metabolic stability evaluations showed that, except for the ester conjugate (1), the ketal (2b), acetal (2a), carbonate (4) and carbamate (3) conjugates were compatible with our approach. The acetal (2a) and its PEGylated derivative (2c) were of particular interest for further in vivo development owing to their respective pH-dependent stability and limited metabolic degradation in order to exploit the acidic subcellular environment of malignant melanocytes to trigger the release of therapeutics upon internalization in cells.

In vitro biological effects of two anti-diabetic medicinal plants used in Benin as folk medicine.

BACKGROUND: Extracts from Polygonum senegalensis (Polygonaceae) and Pseudocedrela kotschyi (Meliaceae) are two important traditionally used medicinal plants in rural Benin to treat many diseases and notably type 2 diabetes. The aim of the study was to investigate the α-glucosidase inhibition, antioxidant and antibacterial activities of those plants extract: Polygonum senegalensis leaves, and Pseudocedrela kotschyi root. METHODS: Hydro-alcoholic (50%) extracts were analyzed for their phytochemical content and tested for their inhibition potency on α-glucosidase from Saccharomyces cerevisiae. Antioxidant activities were assessed using the DPPH, ORAC, FRAP and DCFH-DA (cell based) assay. Finally, the antibacterial activity was evaluated using MIC determination on four Gram-positive cocci (Bacillus subtilis, Clostridium difficile, Enterococcus faecalis, Staphylococcus aureus), three Gram-negative bacilli (Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae), and the yeast Candida albicans. RESULTS: Each extract presented significant α-glucosidase inhibition and antioxidant activities. Polygonum senegalensis leaf extracts were the most active in each in vitro assay with an IC50 = 1.5 µg/ml for α-glucosidase inhibition and an IC50 = 6.8 µg/ml for DPPH scavenging, - 4.5 µmol Fe II/g of dry matter - 9366 µmol Trolox / g DW - for FRAP and ORAC values, respectively. IC50 = 2.3 µg GA / ml for DCFH-DA assay. Concerning its antibacterial activity, a growth inhibitory effect was observed only against three Gram negative bacilli: B. subtilis, E. faecalis, S. aureus and the yeast C. albicans at high concentration. CONCLUSION: The results showed that the semi alcoholic extract of the two studied plants possess α-glucosidase inhibitory activity, antioxidant potency, and low antibacterial effect.

Synthesis and biological activities of 4-substituted pyrrolo[2,3-a]carbazole Pim kinase inhibitors.

Pyrrolo[2,3-a]carbazole-3-carbaldehydes are potent Pim kinase inhibitors with in vitro antiproliferative activities. In the present study, we report the synthesis and biological activities (Pim kinase inhibition and in vitro antiproliferative potency) of new 4-substituted pyrrolo[2,3-a]carbazoles. The results demonstrated that the Pim kinase inhibitory potency (especially Pim-3) can be conserved for pyrrolo[2,3-a]carbazoles bearing a methoxycarbonyl group at the 4-position without a formyl at the 3-position. Moreover, compound 27 that was found to be active against Pim-1 and Pim-3 kinases showed antiproliferative activities in the micromolar range.

Kinase inhibitory potencies and in vitro antiproliferative activities of N-10 substituted pyrrolo[2,3-a]carbazole derivatives.

Development of potent and selective Pim kinase inhibitors has recently emerged as an important field for the design of new anti-cancer drugs. We report the synthesis of new N-10-substituted pyrrolo[2,3-a]carbazole derivatives and their evaluation as Pim kinase inhibitors. Moreover, in vitro antiproliferative activity of these compounds was evaluated toward a human fibroblast primary culture and three human solid cancer cell lines (PA1, PC3 and DU145). Compounds 3, 7 and 10 showed inhibitory potencies toward Pim-1 and Pim-3 in the nanomolar range. Additionally, dimethylamino analog 10 also demonstrated interesting sub-micromolar antiproliferative activities toward the cell lines tested.

Imidazonaphthyridine systems (part 2): Functionalization of the phenyl ring linked to the pyridine pharmacophore and its replacement by a pyridinone ring produces intriguing differences in cytocidal activity.

We recently discovered that five- and pseudo-five-fused-ring derivatives in an imidazonaphthyridine series were promising hit compounds for the development of new DNA-intercalators. In this study, novel (dihydro)imidazo[1,6] and [1,7]naphthyridi(no)nes were prepared including pseudo-pentacycles. All the compounds synthesized were screened against four tumor cell lines. Compounds 3(b-d) showed significant in vitro cytotoxicity, and DNA intercalation properties were demonstrated at 25 µM. Imidazonaphthyridinones exhibited no DNA binding affinity despite significant growth inhibition activity. Interestingly, when a pyridinone pharmacophore was linked to the imidazo[1,2-a]pyridine scaffold, the geometric orientation of the link had a strong impact on the growth inhibition activity. From these results we conclude that the moderate cytotoxicity observed for these compounds is independent of their DNA-binding and topoisomerase inhibition activities.

Synthesis, protein kinase inhibitory potencies, and in vitro antiproliferative activities of meridianin derivatives.

The synthesis of new meridianin derivatives is described. The indolic ring system was substituted at the C-4 to C-7 positions either by a bromine atom or by nitro or amino groups. Additionally, an iodine atom or various aryl groups were introduced at the C-5 position of the 2-aminopyrimidine ring. These compounds as well as some of their synthetic intermediates were tested for their kinase inhibitory potencies and for their in vitro antiproliferative activities. We found that this series of compounds is particularly interesting in the development of new inhibitors of DYRK1A and CLK1 kinases. The most effective compounds toward these two kinase families are the 6- and 7-bromo derivatives 30, 33, and 34 that showed more than 45-fold selectivity toward DYRK1A/CLK1 kinases over the other kinases tested. Meridianin derivatives could thus be developed toward potent and selective inhibitors of key RNA splicing regulators and potential therapeutic agents.

Design, synthesis and in vitro drug release investigation of new potential 5-FU prodrugs.

In order to identify new efficient prodrugs of 5-fluorouracil (5-FU) and to develop an original targeting approach using 2-fluoro-2-deoxyglucose (FDG) as a potential drug carrier, eight original 5-FU derivatives were synthesized: 5-FU was attached by the N1 position of the pyrimidinic ring to the C1 position of the FDG structure either by direct coupling (2a) or via various spacers (3, 6a-c, 10b and 19). A new sensitive high-performance liquid chromatography method was developed to simultaneously quantify 5-FU and its derivatives in human plasma and other relevant media at physiological temperatures. Half-lives were determined from the degradation profiles of these conjugates. Slow degradation of compounds 2a, 3, 10b and 19 was observed in vitro at 37 °C, but no 5-FU release was noticed. By contrast, the in vitro drug release profiles of compounds 6a-c followed pseudo-first-order kinetics, and 5-FU was found in all the media. The antiproliferative activity of the eight compounds was assessed in vitro by a fluorometric assay against two human solid cancer cell lines and one healthy cell line. A correlation was found between the activities of the compounds and their ability to release 5-FU efficiently.

Preclinical investigation of tolerance and antitumour activity of new fluorodeoxyglucose-coupled chlorambucil alkylating agents.

Our strategy is to increase drug accumulation in target tumour cells using specific "vectors" tailored to neoplastic tissue characteristics, which ideally are not found in healthy tissues. The aim of this work was to use 2-fluoro-2-deoxyglucose (FDG) as a drug carrier, in view of its well-known accumulation by most primary and disseminated human tumours. We had previously selected two FDG-cytotoxic conjugates of chlorambucil (CLB), i.e. compounds 21a and 40a, on the basis of their in vitro profiles. Here we investigated the antitumour profile and tolerance of these compounds in vitro and in vivo in two murine cell lines of solid tumours. In vitro, we found that micromolar concentrations of compounds 21a and 40a inhibited proliferation of B16F0 and CT-26 cell lines. Interestingly, compounds 21a and 40a were found to act at different levels in the cell cycle: S and subG1 accumulation for 21a and G2 accumulation for 40a. In vivo, a single-dose-finding study to select the Maximum Tolerated Dose (MTD) by the intraperitoneal route (IP) showed that the two peracetylated glucoconjugates of CLB were less toxic than CLB itself. When given to tumour-bearing mice (melanoma and colon carcinoma models), according to a "q4d × 3" schedule (i.e., three doses at 4-day intervals) both compounds demonstrated a promising antitumour activity, with Log Cell Kill (LCK) values higher than 1.3 in both B16F0 and CT-26 models. Hence compounds 21a and 40a are good candidates for further works to develop new highly active antineoplastic compounds.

Synthesis and biological activities of pyrazolo[3,4-g]quinoxaline derivatives.

The synthesis of new pyrazolo[3,4-g]quinoxaline derivatives, as well as their Pim kinases (Pim-1, Pim-2, Pim-3) inhibitory potencies and in vitro antiproliferative activities toward a human fibroblast primary culture and three human solid cancer cell lines (PA1, PC3 and DU145) are described. The results obtained in this preliminary structure-activity relationship study have pointed out that most of the compounds in this series exhibited interesting in vitro Pim-3 kinase inhibitory potencies. Moreover, some of the tested compounds have demonstrated favorable antiproliferative potencies.

Synthesis and biological activities of aminopyrimidyl-indoles structurally related to meridianins.

The synthesis of new meridianin derivatives substituted at the C-5 position of the 2-aminopyrimidine ring by various aryl groups and substituted or not by a methyl group on the indole nitrogen is described. These compounds were tested for their kinase inhibitory potencies toward five kinases (CDK5/p25, CK1delta/epsilon, GSK-3alpha/beta, Dyrk1A and Erk2) as well as their in vitro antiproliferative activities toward a human fibroblast primary culture and two human solid cancer cell lines (MCF-7 and PA 1).

In-vitro antiproliferative activities and kinase inhibitory potencies of meridianin derivatives.

Marine alkaloid meridianin G derivatives, substituted on the pyrimidine ring by aryl groups, were evaluated for their kinase inhibitory potencies and their in-vitro antiproliferative activities. The derivatives were tested toward a panel of nine protein kinases (KDR, IGF-1R, c-Met, RET, c-Src, c-Abl, PKA, CDK2/cyclin A, and HER-1) and their in-vitro antiproliferative activities were evaluated toward a human fibroblast primary culture and two human solid cancer cell lines (MCF-7 and PA 1). Despite weak kinase inhibitory potencies, high in-vitro antiproliferative activities were found for compounds 5, 7, 12, and 14, which do not interfere with the PA 1 cell cycle and may be considered as direct cytolysis or apoptosis inducers.

Design, synthesis and preliminary biological evaluation of acridine compounds as potential agents for a combined targeted chemo-radionuclide therapy approach to melanoma.

Various iodo-acridone and acridine carboxamides have been prepared and evaluated as agents for targeted radionuclide and/or chemotherapy for melanoma, due to their structural similarity to benzamides which are known to possess specific affinity for melanin. Three of these carboxamides selected for their in vitro cytotoxic properties were radioiodinated with [(125)I]NaI at high specific activity. Biodistribution studies carried out in B16F0 murine melanoma tumour-bearing mice highlighted that acridone 8f and acridine 9d, presented high, long-lasting tumour concentrations together with an in vivo kinetic profile favourable to application in targeted radionuclide therapy.

Novel imidazo[1,2-a]naphthyridinic systems (part 1): synthesis, antiproliferative and DNA-intercalating activities.

Novel imidazo[1,2-a]naphthyridinic systems 6a-15a and 6b-15b were obtained from Friedländer's reaction in imidazo[1,2-a]pyridine series. Most of the compounds were evaluated for their antitumor activity in the NCIs in vitro human tumor cell line screening panel. Among them, pentacyclic derivatives 13b and 14a exhibited in vitro activity comparable to anticancer agent such as amsacrine. Their mechanism of cytotoxicity action was unrelated to poisoning or inhibiting abilities against topo1. On the contrary, we highlighted a direct intercalation of the drugs into DNA by electrophoresis on agarose gel.

Synthesis and cytotoxic properties of new fluorodeoxyglucose-coupled chlorambucil derivatives.

Frequently used in the treatment of malignant cells, alkylating agents, like most anticancer substances, produce adverse side effects caused by the toxicity of the agents toward normal tissues and lose efficiency through poor distribution to target sites. Our approach to developing more selective drugs with low systemic toxicity is based on the premise that the body distribution and cell uptake of a drug can be altered by attaching a neoplastic cell-specific uptake enhancer, such as 2-fluoro-2-deoxyglucose (FDG), the radiotracer most frequently used in PET for tumor imaging. Two properties of deoxyglucose, namely preferential accumulation in neoplastic cells and inhibition of glycolysis, underpin this targeting approach. Here, we report the synthesis of 19 new chlorambucil glycoconjugates in which the alkylating drug is attached to the C-1 position of FDG, directly or via different linkages. This set of compounds was evaluated for in vitro cytotoxicity against different human normal and tumor cell lines. There was a significant improvement in the in vitro cytotoxicity of peracetylated glucoconjugates compared with the free substance. Four compounds were finally selected for further in vivo studies owing to their lack of oxidative stress-inducing properties.

Reversal of P-glycoprotein-mediated drug efflux by eudesmin from Haplophyllum perforatum and cytotoxicity pattern versus diphyllin, podophyllotoxin and etoposide.

The present study focuses on eudesmin (bicyclic lignan, 0.15 % of dry leaves) and diphyllin (arylnaphthalene lignan, 0.1 % of dry roots), both isolated from H. perforatum Kar. et Kir, a Rutaceae species endemic to Uzbekistan. We first compared their specificity for cancer cells with those of etoposide and podophyllotoxin by screening their cytotoxicity on 3 healthy cell-lines and 7 sensitive or resistant human solid cancer lines. We then tested their capacity to reverse P-glycoprotein-mediated multidrug resistance (MDR) by assaying dye and drug uptake in MDR1-transfected Madin-Darby canine kidney (MDCK-MDR1) and doxorubicine-resistant human breast carcinoma cells (MCF7/Dox). Eudesmin displays IC (50) values > 100 microM on all tested lines. Our data provide the first demonstration that this non-toxic lignan reverses Pgp-mediated drug efflux and supports the hypothesis that it may inhibit resistance mediated by MDR1 and MRP proteins. Even if its reversal activity is insufficient for clinical application, its capacity to accumulate [(3)H]-vinblastine in MDCK/MDR1 and MCF7/Dox cells suggests that eudesmin may positively affect the bioavailability and, thereby, the therapeutic potency of anticancer drugs in Pgp-overexpressing cells. Diphyllin exhibits IC (50) values ranging from 10 (- 6) to 10 (- 4) M. It is markedly less toxic than podophyllotoxin (IC (50) : 13 - 61 nM), but exhibits tumoricidal effects close to those of etoposide. Unfortunatly, it is 65-fold more toxic than etoposide on human primary fibroblasts. Consequently, it has no value as an anticancer drug. Its value as raw material for the hemisynthesis of anticancer drugs is discussed.

Synthesis and PC3 androgen-independent prostate cells antiproliferative effect of fagaronine derivatives.

Fagaronine derivatives syntheses were optimized and their effect on PC3 androgen-independent prostate cell line was evaluated. An assessment of the lipophilicity of the benzo[c]phenanthridine derivatives was achieved at pH 7.4 and et 6.7 by determining log D.