Preliminary Biological Evaluation Research Articles

Interrogating alkyl and arylalkylpolyamino (bis)urea and (bis)thiourea isosteres as potent antimalarial chemotypes against multiple lifecycle forms of Plasmodium falciparum parasites

A new series of potent potent aryl/alkylated (bis)urea- and (bis)thiourea polyamine analogues were synthesized and evaluated in vitro for their antiplasmodial activity. Altering the carbon backbone and terminal substituents increased the potency of analogues in the compound library 3-fold, with the most active compounds, 15 and 16, showing half-maximal inhibitory concentrations (IC50 values) of 28 and 30nM, respectively, against various Plasmodium falciparum parasite strains without any cross-resistance. In vitro evaluation of the cytotoxicity of these analogues revealed marked selectivity towards targeting malaria parasites compared to mammalian HepG2 cells (>5000-fold lower IC50 against the parasite). Preliminary biological evaluation of the polyamine analogue antiplasmodial phenotype revealed that (bis)urea compounds target parasite asexual proliferation, whereas (bis)thiourea compounds of the same series have the unique ability to block transmissible gametocyte forms of the parasite, indicating pluripharmacology against proliferative and non-proliferative forms of the parasite. In this manuscript, we describe these results and postulate a refined structure–activity relationship (SAR) model for antiplasmodial polyamine analogues. The terminally aryl/alkylated (bis)urea- and (bis)thiourea–polyamine analogues featuring a 3-5-3 or 3-6-3 carbon backbone represent a structurally novel and distinct class of potential antiplasmodials with activities in the low nanomolar range, and high selectivity against various lifecycle forms of P. falciparum parasites.

Tough biohydrogels with interpenetrating network structure by bienzymatic crosslinking approach

Enzymatically crosslinked biohydrogels have increasingly attracted attention mainly due to the mildness of this type of reaction. However, their mechanical strength is usually so weak that their applications are limited in the field of medicine. In order to improve their mechanical properties and degradation resistance, bienzymatic crosslinking approach was utilized to prepare biohydrogels of gelatin and chitosan with an interpenetrating polymer network (IPN) structure in this report. First of all, chitosan was grafted with phloretic acid (chitosan-PA) used as a substrate of horseradish peroxidase (HRP). After that, the gelation process of gelatin/chitosan-PA IPN hydrogels was monitored by a rheometer. The results indicated the formation of dual networks: one gelatin network crosslinked by transglutaminase (TG) and another chitosan-PA network crosslinked by HRP in the presence of a low concentration of H2O2. In addition, the mechanical performances of the hydrogels were measured by a universal testing machine. It was found that the mechanical properties of the IPN gels were significantly improved compared with gelatin hydrogel crosslinked by TG. Moreover, the swelling ratio, degradation behavior, and cytocompatibility of the IPN hydrogels were investigated in detail. The preliminary biological evaluation indicated that the IPN hydrogels can support L929 cell adhesion and proliferation. Overall, the gelatin/chitosan IPN hydrogels prepared by bienzymatic crosslinking approach have excellent biocompatibility and mechanical properties. Therefore, dual enzyme-mediated crosslinking of natural polymer hydrogels is promising for the development of tissue engineering scaffolds and wound dressing.

Synthesis and preliminary biological evaluation of S-11C-methyl-D-cysteine as a new amino acid PET tracer for cancer imaging.

S-(11)C-methyl-L-cysteine (LMCYS) is an attractive amino acid tracer for clinical tumor positron emission tomography (PET) imaging. D-isomers of some radiolabeled amino acids are potential PET tracers for tumor imaging. In this work, S-(11)C-methyl-D-cysteine (DMCYS), a D-amino acid isomer of S-(11)C-methyl-cysteine for tumor imaging was developed and evaluated. DMCYS was prepared by (11)C-methylation of the precursor D-cysteine, with an uncorrected radiochemical yield over 50% from (11)CH3I within a total synthesis time from (11)CO2 about 12min. In vitro competitive inhibition studies showed that DMCYS uptake was primarily transported through the Na(+)-independent system L, and also the Na(+)-dependent system B(0,+) and system ASC, with almost no system A. In vitro incorporation experiments indicated that almost no protein incorporation was found in Hepa 1-6 hepatoma cell lines. Biodistribution studies demonstrated higher uptake of DMCYS in pancreas and liver at 5min post-injection, relatively lower uptake in brain and muscle, and faster radioactivity clearance from most tissues than those of L-isomer during the entire observation time. In the PET imaging of S180 fibrosarcoma-bearing mice and turpentine-induced inflammatory model mice, 2-(18)F-fluoro-2-deoxy-D-glucose (FDG) exhibited significantly high accumulation in both tumor and inflammatory lesion with low tumor-to-inflammation ratio of 1.40, and LMCYS showed low tumor-to-inflammation ratio of 1.64 at 60min post-injection. By contrast, DMCYS showed moderate accumulation in tumor and very low uptake in inflammatory lesion, leading to relatively higher tumor-to-inflammation ratio of 2.25 than (11)C-methyl-L-methionine (MET) (1.85) at 60min post-injection. Also, PET images of orthotopic transplanted glioma models demonstrated that low uptake of DMCYS in normal brain tissue and high uptake in brain glioma tissue were observed. The results suggest that DMCYS is a little better than the corresponding L-isomers as a potential PET tumor-detecting agent and is superior to MET and FDG in the differentiation of tumor from inflammation.

In vitro studies of antimicrobial activity of Gly-His-Lys conjugates as potential and promising candidates for therapeutics in skin and tissue infections

In this Letter, we presented in vitro studies of antimicrobial activity of Gly-His-Lys conjugates that are important point in preliminary biological evaluation of their potential application in skin and tissue therapies. The novel compounds include the conjugation of fatty acids with a modification of the amino acid sequence in the primary structure of Gly-His-Lys (6i). All the compounds exhibited strong to moderate activity. Compound 1d had the most potent antimicrobial activity at MIC ranges 31.3–125.0μg/mL (against Escherichia coli spp. and Staphylococcus aureus spp.), 375.0–500.0μg/mL (against Pseudomonas aeruginosa spp.). Conjugate 5b expressed activity against Staphylococcus aureus spp. and Escherichia coli spp. at MIC ranges 250.0–500.0μg/mL and 62.5–125.0μg/mL, respectively. Both conjugates 1d and 5b possessed rapid bactericidal activity against Gram-positive bacteria at 2MIC or 4MIC. Conjugates 1b–c, 1e, 2a–b and 4b showed noticeable effect against both Gram-positive and Gram-negative bacteria. Compounds 1d, 1e and 2e were the most active against fungus.

Synthesis and preliminary biological evaluation of potent and selective 2-(3-alkoxy-1-azetidinyl) quinolines as novel PDE10A inhibitors with improved solubility

We report the discovery of a novel series of 2-(3-alkoxy-1-azetidinyl) quinolines as potent and selective PDE10A inhibitors. Structure–activity studies improved the solubility (pH 7.4) and maintained high PDE10A activity compared to initial lead compound 3, with select compounds demonstrating good oral bioavailability. X-ray crystallographic studies revealed two distinct binding modes to the catalytic site of the PDE10A enzyme. An ex vivo receptor occupancy assay in rats demonstrated that this series of compounds covered the target within the striatum.

Preparation and preliminary biological evaluation of radiogallium-labeled DTPA-amlodipine complex for possible L-type calcium channel imaging

Abstract A DTPA-conjugated amlodipine analog (DTPA-AMLO) 3, was prepared for possible voltage gated calcium channel imaging after radiolabeling with Ga-67. [67Ga]-DTPA-AMLO complex was prepared starting [67Ga]gallium chloride and DTPA-AMLO in 60–90 min at 50–60 ℃ in phosphate buffer. The partition co-efficient and stability of the tracer was determined in final solution (25 ℃) and presence of human serum (37 ℃) up to 24 h. The biodistribution of the labeled compound in wild-type rats were determined up to 72 h using organ counting and SPECT. The radiolabled complex was prepard in high radiochemical purity (>96%, RTLC and >98% HPLC) and significant specific activity (7–10 GBq/mmol). The log P for the complex was calculated as − 0.594, consistent with a water soluble complex. The tracer is mostly washed out through kidneys which were in full compliance with the amlodipine metabolism and imaging studies demonstrated the same behavior. The tracer uptake in organs with smooth muscles was observed in stomach, colon as well as intestine.

Radiolabelling and preliminary biological evaluation of NOTA-cRGD dimer labelled with Ga-68

Radiolabelling and preliminary biological evaluation of NOTA-cRGD dimer labelled with Ga-68

Fused heterocycles bearing bridgehead nitrogen as potent HIV-1 NNRTIs. Part 2: Discovery of novel [1,2,4]Triazolo[1,5-a]pyrimidines using a structure-guided core-refining approach

Guided by crystal structures of HIV-1 RT/DAPY complex and molecular modeling studies, a series of novel [1,2,4]triazolo[1,5-a]pyrimidine derivatives were rationally designed via structure-based core refining approach, synthesized through the readily accessible synthetic methods and evaluated for their anti-HIV activities in MT-4 cells. Preliminary biological evaluation indicated that most of the compounds exhibited marked inhibitory activity against the wild-type HIV-1 IIIB. Particularly, compound 7n was the most potent inhibitor against wild-type and K103N/Y181C double resistant mutant strain of HIV-1, possessing EC50 values of 0.02 μM and 7.6 μM, respectively, which were much better than or similar to nevirapine (NVP, EC50 = 0.15 μM, 2.9 μM) and delavirdine (DLV, EC50 = 0.07 μM, >36 μM). Besides, some other compounds, 5b, 7c, 7e, 7f, and 7m, were also endowed with favorable anti-HIV-1 potency (EC50 = 0.07, 0.05, 0.05, 0.07, and 0.05 μM, respectively), which were better than or similar to those of NVP and DLV, suggesting a high potential to further develop this type of bridgehead nitrogen heterocycle as a novel class of NNRTIs with improved antiviral efficacy and resistance profile. The selected compound, 7i, was found moderately inhibitory towards RT (IC50 = 0.39 μM), which was higher than for ETV (IC50 = 0.56 μM). Preliminary structure–activity relationships (SARs) and molecular modeling of these new analogues were detailed in this manuscript.

Synthesis and preliminary biological evaluation of new antiproliferative aromatic analogues of 1α,25-dihydroxyvitamin D3

In an effort to develop novel vitamin D3 analogues, a series of aromatic compounds was synthetized, using efficient Negishi cross coupling between alkenylzinc reagents of the C,D-ring moiety of vitamin D3, and various substituted aromatic halides as A-ring mimics. The study aimed at exploring the influence of the replacement of the original vitamin D3 diene by a styrene unit on the biological activities. Potency in the induction of the differentiation of HL-60 cells for the lead compound 36 was 12 fold less important than calcitriol correlating with a weaker binding affinity for VDR.

Synthesis and biological evaluation of substituted 4-(thiophen-2-ylmethyl)-2H-phthalazin-1-ones as potent PARP-1 inhibitors

We have developed a series of substituted 4-(thiophen-2-ylmethyl)-2H-phthalazin-1-ones as potent PARP-1 inhibitors. Preliminary biological evaluation indicated that most compounds possessed inhibitory potencies comparable to, or higher than AZD-2281. Among these compounds, 18q appeared to be the most notable one, which displayed an 8-fold improvement in enzymatic activity compared to AZD-2281. These efforts lay the foundation for our further investigation.

Synthesis and Preliminary Biological Evaluation of Polyamine-aniline Acridines as P-glycoprotein Inhibitors

We have synthesized a series of polyamine-based anilinoacridine derivatives. The preliminary biological evaluation indicated that the 9-anilinoacridine-polyamine derivatives had low or insignificant in vitro cytotoxicity against K562 cell line and K562/ADM, the drug-resistant cell line. However, the evaluation for P-gp modulation showed that they held potent P-gp inhibitory ability. Among them, the effect of compound 7c on P-gp was even greater than that of Verapamil, the known P-gp modulator. The results suggest that 9-anilinoacridine-polyamine derivatives can be employed as effective P-gp modulators.

Synthesis and preliminary biological evaluation of O-2((2-[(18)F]fluoroethyl)methylamino)ethyltyrosine ([(18)F]FEMAET) as a potential cationic amino acid PET tracer for tumor imaging.

Amino acid transport is an attractive target for oncologic imaging. Despite a high demand of cancer cells for cationic amino acids, their potential as PET probes remains unexplored. Arginine, in particular, is involved in a number of biosynthetic pathways that significantly influence carcinogenesis and tumor biology. Cationic amino acids are transported by several cationic transport systems including, ATB(0,+) (SLC6A14), which is upregulated in certain human cancers including cervical, colorectal and estrogen receptor-positive breast cancer. In this work, we report the synthesis and preliminary biological evaluation of a new cationic analog of the clinically used PET tumor imaging agent O-(2-[(18)F]fluroethyl)-L-tyrosine ([(18)F]FET), namely O-2((2-[(18)F]fluoroethyl)methylamino)ethyltyrosine ([(18)F]FEMAET). Reference compound and precursor were prepared by multi-step approaches. Radiosynthesis was achieved by no-carrier-added nucleophilic [(18)F]fluorination in 16-20% decay-corrected yields with radiochemical purity >99%. The new tracer showed good stability in vitro and in vivo. Cell uptake assays demonstrated that FEMAET and [(18)F]FEMAET accumulate in prostate cancer (PC-3) and small cell lung cancer cells (NCI-H69), with an energy-dependent mechanism. Small animal PET imaging with NCI-H69 xenograft-bearing mice revealed good tumor visualization comparable to [(18)F]FET and low brain uptake, indicating negligible transport across the blood-brain barrier. In conclusion, the non-natural cationic amino acid PET probe [(18)F]FEMAET accumulates in cancer cells in vitro and in vivo with possible involvement of ATB(0,+).

Cell-penetrable lysine dendrimers for anti-cancer drug delivery: synthesis and preliminary biological evaluation.

Improving the cell penetration and enhancing the cell selectivity of drugs have been approved for overcoming the major drawbacks of chemotherapeutic agents: the toxicity to normal cells and the drug resistance in tumors. In this paper, lysine dendrimers (G1-G3) were chosen as novel cell-penetrating carriers for anti-cancer drugs based on the internalization mechanism of cell-penetrating peptides and the characteristics of dendritic peptides. After labeling with fluorescein isothiocyanate (FITC), the cell-penetrable capacity of lysine dendrimers was certified by flow cytometric analysis. In a preliminary biological evaluation, the conjugates of lysine dendrimers and 5-fluorouracil showed the expected advantages: stable drug release, low toxicity to normal cells, and moderate inhibition of tumor cells. These results imply that cell-penetrable lysine dendrimers could be potential carriers in drug delivery of anti-cancer medicine.

Novel liver-specific nitric oxide (NO) releasing drugs with bile acid as both NO carrier and targeting ligand

Abstract Novel liver-specific nitric oxide (NO) releasing drugs with bile acid as both the NO carrier and targeting ligand were designed and synthesized by direct nitration of the hydroxyl group in bile acids or the 3- O -hydroxyl alkyl derivatives, with the intact 24-COOH being preserved for hepatocyte specific recognition. Preliminary biological evaluation revealed that oral administrated targeted conjugates could protect mice against acute liver damage induced by acetaminophen or carbon tetrachloride. The nitrate level in the liver significantly increased after oral administration of 1e while nitrate level in the blood did not significantly change. Co-administration of ursodeoxycholic acid (UDCA) significantly antagonized the increase of nitrate in the liver resulted by administration of 1e .

Synthesis of 6-cinnamoyl-2H-benzo[b][1,4]oxazin-3(4H)-ones and their effects on A549 lung cancer cell growth

A series of novel 6-cinnamoyl-2H-benzo[b][1,4]oxazin-3(4H)-one derivatives was synthesized. The structures of compounds were characterized by 1H NMR, IR, and MS. Moreover, representative crystal structure was determined by X-ray diffraction analysis. The preliminary biological evaluation of all these compounds showed that compounds 3a–3d would suppress the growth of A549 lung cells effectively by inducing autophagy and cell cycle arrest.

Synthesis and preliminary biological evaluation of 1,2,3-triazole-Jaspine B hybrids as potential cytotoxic agents

Two series of more available novel 1,2,3-triazole-Jaspine B hybrids were efficiently synthesized employing click chemistry approach and evaluated for their cytotoxic activities against three human cancer cell lines (EC-9706, MGC-803 and MCF-7). Among them, compound 14h showed excellent inhibition against MCF-7 (IC50 = 1.93 μM) and was more potent than 5-Fu and Jaspine B against all three cancer cell lines. Further investigation of apoptosis assay and cell cycle analysis demonstrated that compound 14h caused cellular early and late apoptosis and arrested the cell cycle at G2/M phase in a concentration- and time-independent manner. This was the first report about the synthesis and in vitro cytotoxic evaluation of 1,2,3-triazole-Jaspine B hybrids.

Synthesis and preliminary biological evaluation of 99mTc(CO)3-labeled pegylated 2-nitroimidazoles

This work reports the synthesis, radiolabeling and preliminary biodistribution results in tumor-bearing mice of Tc-99m(CO)(3)-labeled pegylated (PEG) 2-nitroimidazoles for tumor hypoxia imaging. The novel 2-nitroimidazole derivatives were successfully synthesized by conjugation of tridendate chelators to 2-nitroimidazole via PEG(3) linker. Radiolabeling was performed in high yield with [Tc-99m(CO)(3)](+) core to get cationic [Tc-99m(CO)(3)(BPA-PEG(3)-NIM)](+), neutral [Tc-99m(CO)(3)(AOPA-PEG(3)-NIM)] and anionic [Tc-99m(CO)(3)(IDA-PEG(3)-NIM)](-) respectively, all of which were hydrophilic and stable at room temperature. Biodistribution studies in tumor-bearing mice showed that Tc-99m(CO)(3)-labeled pegylated 2-nitroimidazoles accumulated in the tumor with low uptake. Tc-99m-chelate and charge had significant impact on partition coefficient, radiotracer tumor uptake and pharmacokinetic properties. The results indicate the need for synthetic modification of the parent 2-nitroimidazole derivatives and the Tc-99m-chelate with a view to improve the tumor targeting efficacy and in vivo kinetic profiles.

Design, Synthesis and Preliminary Biological Evaluation of a Biotin-S-S-Phosphine Reagent

Design, Synthesis and Preliminary Biological Evaluation of a Biotin-S-S-Phosphine Reagent

Discovery of nitropyridine derivatives as potent HIV-1 non-nucleoside reverse transcriptase inhibitors via a structure-based core refining approach

As a continuation of our efforts to discover and develop back-up analogs of DAPYs, novel substituted nitropyridine derivatives were designed via a structure-based core refining approach, synthesized and evaluated for their in vitro HIV-1 activity in MT-4 cells. Preliminary biological evaluation indicated that most of the compounds exhibited marked inhibitory activity against wild-type HIV-1 IIIB. Most notably, the compound 7b was identified as the most promising candidate in inhibiting HIV-1 replication with an EC50 value of 0.056 μM and a selective index (SI) of 1251, which were much better than those of NVP (EC50 = 0.23 μM) and DLV (EC50 = 0.51 μM). Some other compounds, 7k, 7c, 7j and 7e, were also endowed with a favorable anti-HIV-1 potency (EC50 = 0.034, 0.11, 0.11 and 0.16 μM, respectively). Some antivirally active compounds also showed moderate inhibitory activity against RT. Preliminary structure–activity relationships (SARs) and molecular modeling of these new analogs provide valuable avenues for future molecular optimization.

Towards a Tissue-Engineered Ligament: Design and Preliminary Evaluation of a Dedicated Multi-Chamber Tension-Torsion Bioreactor

Tissue engineering may constitute a promising alternative to current strategies in ligament repair, providing that suitable scaffolds and culture conditions are proposed. The objective of the present contribution is to present the design and instrumentation of a novel multi-chamber tension-torsion bioreactor dedicated to ligament tissue engineering. A preliminary biological evaluation of a new braided scaffold within this bioreactor under dynamic loading is reported, starting with the development of a dedicated seeding protocol validated from static cultures. The results of these preliminary biological characterizations confirm that the present combination of scaffold, seeding protocol and bioreactor may enable us to head towards a suitable ligament tissue-engineered construct.