Synthesis of 3-(Imidazo[2,1-b]thiazol-6-yl)-2H-chromen-2-one Derivatives and Study of Their Antiviral Activity against Parvovirus B19.

Parvovirus B19 (B19V) is a human pathogenic virus associated with a wide range of clinical conditions. Currently, there are no recognized antiviral drugs for B19V treatment; therefore, efforts in the search for compounds inhibiting B19V replication are now being pursued. Coumarins (chromen-2-ones) are considered a privileged structure for designing novel orally bioavailable and non-peptidic antiviral agents. To further contribute to the development of new drugs against B19V, our research was focused on the synthesis, characterization and evaluation of antiviral activity of some new 3-(imidazo[2,1-b]thiazol-6-yl)-2H-chromen-2-one derivatives. The effects of the synthesized compounds on cell viability and viral replication were investigated by employing two relevant cellular systems, the myeloblastoid cell line UT7/EpoS1 and primary erythroid progenitor cells (EPCs). Some of the tested compounds showed inhibitory activity both on cell viability and on viral replication, depending on the cellular system. These results suggest that the mechanism involved in biological activity is sensitive to small structural changes and that it is possible to direct the activity of the 3-(imidazo[2,1-b]thiazol-6-yl)-2H-chromen-2-one core.

Synthesis and antiproliferative activity of imidazo[2,1-b][1,3,4]thiadiazole derivatives.

A series of 2,5,6-substituted imidazo[2,1-b][1,3,4]thiadiazole derivatives have been prepared and were tested for antiproliferative activity on cancer cells at the National Cancer Institute. Results showed that molecules with a benzyl group at position 2, exhibited an increase in activity for the introduction of a formyl group at the 5 position. The compound 2-benzyl-5-formyl-6-(4-bromophenyl)imidazo[2,1-b][1,3,4]thiadiazole 22 has been chosen for understanding the mechanism of action by various molecular and cellular biology studies. Results obtained from cell cycle evaluation analysis, analysis of mitochondrial membrane potential and Annexin V-FITC by flow cytometric analysis, ROS production and expression of apoptotic and DNA-repair proteins suggested that compound 22 induced cytotoxicity by activating extrinsic pathway of apoptosis, however, without affecting cell cycle progression.

Inhibition of MDR1 activity and induction of apoptosis by analogues of nifedipine and diltiazem: an in vitro analysis.

We report herein the reversal of multidrug resistance-1 (MDR1) in A2780/DX3 cells by the two nifedipine-like compounds 1 and 2 that are part of a library of 1,4-dihydropyridines (1,4-DHPs) calcium-channel modulators bearing in C-4 a different substituted imidazo[2,1-b]thiazole system. By methylthiazol tetrazolium (MTT) assay, cytofluorimetry, and fluorescence microscopy we evaluated their ability to reverse MDR in our cell system. Moreover, together with compound 3 (the diltiazem-like 8-(4-chlorophenyl)-5-methyl-8-[(2Z)-pent-2-en-1-yloxy]-8H-[1,2,4]oxadiazolo[3,4-c][1,4]thiazin-3-one) we analyzed their ability to potentiate the triggering of apoptosis after exposure to doxorubicin, through the nuclear morphological analysis after 4',6-diamidino-2-phenylindole (DAPI), the fluorescein isothiocyanate (FITC)-Annexin-V/propidium iodide (PI) staining and the caspase activity determination. Our results demonstrate that compounds 1 and 2, at concentrations showing a very low (5%) or absent inhibition of cell proliferation, in combination with doxorubicin enhance its antiproliferative activity (from 30% to 54% IC(50) reduction) in A2780/DX3 cells through an increase of doxorubicin intracellular accumulation. These compounds together with compound 3, which has already been demonstrated to act as a potent inhibitor of MDR1 function, were also able to significantly potentiate the activation of the apoptosis machinery triggered by the exposure to doxorubicin. In conclusion, our results identify two new molecules structurally related to the calcium-channel blocker nifedipine, but characterized by a very low LTCC blockers activity, able to potentiate the antiproliferative and apoptotic activities of doxorubicin through an increase of its intracellular concentration likely caused by the inhibition of MDR1 function.

Antitumor activity and COMPARE analysis of bis-indole derivatives.

This paper reports the synthesis of new derivatives (formed by two indole systems separated by a central moiety) analogous of potent antitumor agents previously described. The activity of the bis-indoles bearing a pyridine core confirms the good result described in the previous paper and compound 4c was chosen for the first in vivo experiment (Hollow Fiber Assay). COMPARE analysis and structure-activity relationships were also considered. Contrary to data reported by other Authors, no correlations were found between antitumor activity and NQO1 induction.

Synthesis, in vitro and in vivo biological evaluation of substituted 3-(5-imidazo[2,1-b]thiazolylmethylene)-2-indolinones as new potent anticancer agents.

A small library of 3-(5-imidazo[2,1-b]thiazolylmethylene)-2-indolinones has been synthesized and screened according to protocols available at the National Cancer Institute (NCI). Some derivatives were potent antiproliferative agents, showing GI50 values in the nanomolar range. Remarkably, when most active compounds against leukemia cells were tested in human peripheral blood lymphocytes from healthy donors, were 100-200 times less cytotoxic. Some compounds, selected by the Biological Evaluation Committee of NCI, were examined to determine tubulin assembly inhibition. Furthermore, flow cytometric studies performed on HeLa, HT-29, and A549 cells, showed that compounds 14 and 25 caused a block in the G2/M phase. Interestingly, these derivatives induced apoptosis through the mitochondrial death pathway, causing in parallel significant activation of both caspase-3 and -9, PARP cleavage and down-regulation of the anti-apoptotic proteins Bcl-2 and Mcl-1. Finally, compound 25 was also tested in vivo in the murine BL6-B16 melanoma and E0771 breast cancer cells, causing in both cases a significant reduction in tumor volume.

New antitumor imidazo[2,1-b]thiazole guanylhydrazones and analogues.

The synthesis of new antitumor 6-substituted imidazothiazole guanylhydrazones is described. Moreover, a series of compounds with a different basic chain at the 5 position were prepared. Finally, the replacement of the thiazole ring in the imidazothiazole system was also considered. All the new compounds prepared were submitted to the NCI cell line screen for evaluation of their antitumor activity. A few selected compounds were submitted to additional biological studies concerning effects on the cell cycle, apoptosis, and mitochondria.

Diphenidol-related diamines as novel muscarinic M4 receptor antagonists.

A series of hydrochloride derivatives 2a-9a and quaternary ammonium derivatives 3b-9b of diphenidol have been synthesized and characterized in receptor binding and cellular functional assays versus human muscarinic M(1)-M(5) receptors expressed in CHO cells. Compound 8b, a methiodide derivative with a bipiperidinyl moiety and a second diphenidol framework, showed a potent and selective M(4) activity as competitive antagonist. Moreover 8b, acting as an allosteric modulator, was able to retard the dissociation rate of [(3)H]-N-methylscopolamine from CHO-M(4) cell membranes exposed to atropine. Taken together, these data suggest that 8b might open new avenues to the discovery of novel multivalent antagonists for the muscarinic receptors.

Chemiluminescent high-throughput microassay applied to imidazo[2,1-b]thiazole derivatives as potential acetylcholinesterase and butyrylcholinesterase inhibitors.

The synthesis of a new series of imidazo[2,1-b]thiazole derivatives is described. They were tested as potential acetylcholinesterase and butyrylcholinesterase inhibitors by means of a chemiluminescent microassay. Although most of the new compounds did not show significant cholinesterase inhibition potency, three of them displayed selective antiacetylcholinesterase activity in the micromolar range.

Investigation on the Effects of Antimicrobial imidazo[2,1-b]thiazole Derivatives on the Genitourinary Microflora.

BACKGROUND: Fused five-membered heterocyclic rings containing bridgehead nitrogen atom are particularly versatile in the field of medicinal chemistry because of their different biological activities. Among them, the imidazo[2,1-b]thiazole is an attractive fused heterocyclic core that has been extensively studied. OBJECTIVE: The aim of the current study was to study the therapeutic applications of imidazo[2,1- b]thiazole derivatives as antimicrobial agents for the treatment of genitourinary infections. METHOD: A traditional synthetic methodology was involved to obtain a small series of imidazothiazole derivatives. RESULTS: Herein, we report the antimicrobial activity of the imidazo[2,1-b]thiazole or imidazo[2,1- b]thiazolidine derivatives against selected fungi, Gram-positive and Gram-negative bacteria. Moreover, experiments were carried out to investigate the interference towards the endogenous microbiota. CONCLUSION: The most interesting of the series are the thiocyano derivatives (19, 23) showing a good profile for the treatment of genitourinary infections: a spectrum of activity covering both bacteria and fungi together with a reduced impact versus critical lines of Lactobacillus exerting defense against pathogens.

Substituted E-3-(2-chloro-3-indolylmethylene)1,3-dihydroindol-2-ones with antitumor activity. Effect on the cell cycle and apoptosis.

The synthesis and antitumor activity of new E-3-(2-chloro-3-indolylmethylene)1,3-dihydroindol-2-ones is described. They were studied at the National Cancer Institute, taking into consideration the 50% growth inhibitory power (pGI50), the cytostatic effect (pTGI = total growth inhibition), and the cytotoxic effect (pLC50). All the compounds were potent growth inhibitors, with mean pGI50 ranging from 5.26 to 7.72. They were also analyzed with NCI COMPARE algorithm. Further studies were dedicated to the effects on the cell cycle and apoptosis.

Antitumor activity of substituted E-3-(3,4,5-trimethoxybenzylidene)-1,3-dihydroindol-2-ones1.

The design and synthesis of anticancer E-3-(3,4,5-trimethoxybenzylidene)-1,3-dihydroindol-2-ones is reported. Strong COMPARE correlations among the cell line responses suggest that these compounds may be acting similarly through a combination of different mechanisms of action. The 5-methoxy derivative (2h) was the most active compound with a mean pGI50 of 6.34, and it is now under review by Biological Evaluation Committee of the National Cancer Institute for possible further studies.

Synthesis and antitumor activity of guanylhydrazones from 6-(2,4-dichloro-5-nitrophenyl)imidazo[2,1-b]thiazoles and 6-pyridylimidazo[2,1-b]thiazoles(1).

The design and synthesis of antitumor imidazothiazole guanylhydrazones are reported. The compounds were submitted to NCI for testing. All but one were more active than methyl-GAG. A few compounds were selected for further studies in search of a possible mechanism of action. The results from these studies and a final search with the NCI COMPARE algorithm suggest that the guanylhydrazones described in this paper are acting through a novel mechanism of action.

2-Indolinone a versatile scaffold for treatment of cancer: a patent review (2008-2014).

INTRODUCTION: 2-Indolinone is a well-known aromatic heterocyclic organic compound. A lot of work has been done on this bicyclic structure by academic and company researchers to synthesize compounds directed to a plethora of molecular targets in order to discover new drug leads. This review presents up-to-date information in the field of cancer therapy research based on this small building block. AREAS COVERED: The present review gives an account of the recent patent literature (2008-2014) describing the discovery of 2-indolinone derivatives with selected therapeutic activities. In this period, a large amount of patents were published on this topic. We have limited the analysis to 37 patents on 2-indolinone derivatives having potential clinical application as chemotherapeutic agents. In this review, the therapeutic applications of 2-indolinone derivatives for the treatment of cancer reported in international patents have been discussed. EXPERT OPINION: 2-Indolinone is the scaffold of the compounds considered from a medicinal chemistry perspective. Many of them have been developed and marketed for therapeutic use. In cancer chemotherapy, progress has been made in designing selective 2-indolinone derivatives. Some of them show preclinical efficacy. However, 2-indolinone has not exhausted all of its potential in the development of new compounds for clinical applications and remains a great tool for future research.

Small-Molecules Targeting Kinases Involved in Pulmonary Hypertension: a Patent Review (2010-2015).

BACKGROUND: Despite the fact that in recent years, a substantial progress has been made in the treatment of pulmonary hypertension, it is still a severe disease characterized by poor prognosis, and the search for new drugs remains a priority. Current remedies address mainly the vasoconstrictor/ vasodilator imbalance in the pulmonary circulation, while the causes of the disease are only moderately affected. Recently, the role of receptor and non receptor kinases in pulmonary hypertension has emerged and these targets were extensively considered for the development of new therapeutic strategies. This review discusses the patents on small-molecules targeting kinases involved in the proliferation/apoptosis imbalance, typically present in pulmonary hypertension. METHODS: Bibliographic research for the inventions was carried out using Espacenet and Sci-Finder databases, "pulmonary hypertension and kinases" as research query and the range from 2010 to 2015. Only patents published in English were considered. A qualitative analysis of the contents of each patent was made to examine the reported compounds, the studies performed and the resulting conclusions. RESULTS: The review includes about thirty applications. Moreover, in order to illustrate the pathophisiology of the disease and the mechanisms of the targets, about forty additional papers were reported. Considering that imatinib, a PDGF receptor inhibitor, entered the clinical trials for the treatment of pulmonary hypertension, the first patents were devoted to inhibitors of tyrosine kinase receptors, such as PDGFR and c-Kit. Subsequently, in addition to kinase receptors, the role of other pathways involved in pulmonary hypertension has emerged, and some research groups have focused their attention also on non-receptor kinases. Fifteen patents on this topic reported these new targets and new derivatives. However, in most of the inventions, although the pulmonary hypertension is among the treatable diseases, the compounds were subjected only to antiproliferative assays and not to specific tests on animal models. CONCLUSION: The studies reported in this review confirm the continuous research efforts aimed to identify new targets and new drugs for the treatment of pulmonary hypertension. Several inhibitors of kinase were described. These compounds could inhibit mainly important branching processes and pathological growth of blood vessels, thereby might increase the lifespan of patients.

Toward the Development of Specific G-Quadruplex Binders: Synthesis, Biophysical, and Biological Studies of New Hydrazone Derivatives.

G-Quadruplex-binding compounds are currently perceived as possible anticancer therapeutics. Here, starting from a promising lead, a small series of novel hydrazone-based compounds were synthesized and evaluated as G-quadruplex binders. The in vitro G-quadruplex-binding properties of the synthesized compounds were investigated employing both human telomeric and oncogene promoter G-quadruplexes with different folding topologies as targets. The present investigation led to the identification of potent G-quadruplex stabilizers with high selectivity over duplex DNA and preference for one G-quadruplex topology over others. Among them, selected derivatives have been shown to trap G-quadruplex structures in the nucleus of cancer cells. Interestingly, this behavior correlates with efficient cytotoxic activity in human osteosarcoma and colon carcinoma cells.

Potential antitumor agents. 37. Synthesis and antitumor activity of guanylhydrazones from imidazo[2,1-b]thiazoles and from the new heterocyclic system thiazolo[2',3':2,3]imidazo[4,5-c]quinoline.

This paper reports synthesis and antitumor activity of new guanylhydrazones from imidazo[2,1-b]thiazoles and from the new heterocyclic system thiazolo[2',3':2,3]imidazo[4,5-c]quinoline. The compounds were tested as potential antitumor agents at the National Cancer Institute. The effect of the guanylhydrazone of 2-chloro-6-(2,5-dimethoxy-4-nitrophenyl)imidazo[2,1-b]thiazole-5-carbaldehyde (41) was investigated, and it was found to be an inhibitor of Complex III of the mitochondrial respiratory chain and is able to induce apoptosis in the cell lines HT29 and HL60.

Antitumor activity of new substituted 3-(5-imidazo[2,1-b]thiazolylmethylene)-2-indolinones and study of their effect on the cell cycle.

This paper reports the synthesis of a new series of 3-(5-imidazo[2,1-b]thiazolylmethylene)-2-indolinones which were tested as potential antitumor agents at the National Cancer Institute. Two derivatives are now under review by BEC (Biological Evaluation Committee of NCI). To investigate the mechanism of action, the effect on cell cycle progression was studied by monitoring them in colon adenocarcinoma HT-29: both were able to block HT-29 in mitosis. 3-[(2,6-Dimethylimidazo[2,1-b]thiazol-5-yl)methylene]-5-chloro-2-indolinone was the most active compound.

Synthesis and chemiluminescent high throughput screening for inhibition of acetylcholinesterase activity by imidazo[2,1-b]thiazole derivatives.

The synthesis of a new series of imidazo[2,1-b]thiazole derivatives is described. They were tested as acetylcholinesterase inhibitors by means of a chemiluminescent method suitable for high throughput screening. The compounds without quaternization had no appreciable inhibitory potency probably because they are poorly soluble in water. The corresponding quaternized compounds were good inhibitors with activity related to the spacer employed.

Recent Patents on Thiazole Derivatives Endowed with Antitumor Activity.

Cancer is a disease of remarkable importance in the world today and is projected to become the primary cause of death within the coming years, therefore the design and development of new antitumor agents is one of the most pressing research areas in medicinal chemistry. Considering the importance of thiazole ring as scaffold present in a wide range of therapeutic agents, the medicinal chemists have been encouraged to synthesize a large number of novel antitumors bearing this heterocycle, which furnish extensive synthetic possibilities due to the presence of several reaction sites. The present review describes the patents from 2008 to present concerning new thiazole compounds useful for the development of new drug molecules. It has been divided according to the molecular target and describes the pathways involved in the biological activities and the structure of the most potent compounds, together with the screening results.

Synthesis and antitumor activity of 1,5,6-substituted E-3-(2-chloro-3-indolylmethylene)-1,3-dihydroindol-2-ones.

Synthesis and antitumor activity of new E-3-(2-chloro-3-indolylmethylene)-1,3-dihydroindol-2-ones are described. All compounds prepared were active in the primary test (three human cell lines) and entered the second level (60 human cell lines). The most active antitumor derivatives bear the same substituents in the chloroindole ring and are not CDK1 inhibitors. A COMPARE analysis showed that they could act as tubulin binders. In most cell lines, E-3-(2-chloro-5-methoxy-6-methyl-3-indolylmethylene)-1,3-dihydroindol-2-one was a growth inhibitor more potent than vincristine.