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The subject of this dissertation is the search for new therapeutic strategies for pancreatic cancer and aims to implement a Drug Discovery process for the rational design and synthesis of molecules active in the modulation of pathways related to the regulation of pre-mRNA splicing process. This research project is the result of a joint PhD between the University of Palermo, Italy, and the Department of Medical Oncology, VU University Medical Center, Amsterdam, The Netherlands. It integrates complementary skills in pharmaceutical chemistry and translational cancer research with a special focus on the rational design of new anticancer compounds potentially active on SF3B1 (Splicing Factor 3B subunit 1), an effective therapeutic target involved in the pre-mRNA splicing process. Furthermore, SF3B1 is a frequently mutated gene in haematological malignancies and some solid tumors, including pancreatic cancer. Specifically, pancreatic ductal adenocarcinoma (PDAC) is the most common type of exocrine pancreatic cancer with a highly poor prognosis and an increasing incidence. The urgent need to find effective therapeutic strategies for the treatment of this disease prompted us to evaluate the antitumor activity of these compounds on preclinical models of PDAC. Based on the interesting anticancer properties described for the imidazothiadiazole nucleus as a scaffold for the development of pharmacologically active derivatives, we were encouraged to continue with the same approach. A preliminary computational study led us to the realization of a common pharmacophore that was used for the virtual screening of an in-house molecular library and commercially available molecular libraries, in order to identify the molecular scaffold of interest and then select the most promising molecules that were tested in vitro on PDAC cell lines. We also tested for the first time two splicing modulators targeting SF3B1, in order to identify new potential therapeutic targets for the treatment of PDAC. Furthermore, the status of the transmembrane protein hENT-1 (human Equilibrative Nucleoside Transporter-1) as a potential biomarker in PDAC is explored in detail in the present Thesis. In conclusion, the need to find new diagnostic biomarkers and the interesting antiproliferative activity previously shown by imidazothiadiazole compounds prompted us to extend the evaluation of the biological activity in vitro concerning a new class of imidazothiadiazole compounds.

The subject of this dissertation is the search for new therapeutic strategies for pancreatic cancer and aims to implement a Drug Discovery process for the rational design and synthesis of molecules active in the modulation of pathways related to the regulation of pre-mRNA splicing process. This research project is the result of a joint PhD between the University of Palermo, Italy, and the Department of Medical Oncology, VU University Medical Center, Amsterdam, The Netherlands. It integrates complementary skills in pharmaceutical chemistry and translational cancer research with a special focus on the rational design of new anticancer compounds potentially active on SF3B1 (Splicing Factor 3B subunit 1), an effective therapeutic target involved in the pre-mRNA splicing process. Furthermore, SF3B1 is a frequently mutated gene in haematological malignancies and some solid tumors, including pancreatic cancer. Specifically, pancreatic ductal adenocarcinoma (PDAC) is the most common type of exocrine pancreatic cancer with a highly poor prognosis and an increasing incidence. The urgent need to find effective therapeutic strategies for the treatment of this disease prompted us to evaluate the antitumor activity of these compounds on preclinical models of PDAC. Based on the interesting anticancer properties described for the imidazothiadiazole nucleus as a scaffold for the development of pharmacologically active derivatives, we were encouraged to continue with the same approach. A preliminary computational study led us to the realization of a common pharmacophore that was used for the virtual screening of an in-house molecular library and commercially available molecular libraries, in order to identify the molecular scaffold of interest and then select the most promising molecules that were tested in vitro on PDAC cell lines. We also tested for the first time two splicing modulators targeting SF3B1, in order to identify new potential therapeutic targets for the treatment of PDAC. Furthermore, the status of the transmembrane protein hENT-1 (human Equilibrative Nucleoside Transporter-1) as a potential biomarker in PDAC is explored in detail in the present Thesis. In conclusion, the need to find new diagnostic biomarkers and the interesting antiproliferative activity previously shown by imidazothiadiazole compounds prompted us to extend the evaluation of the biological activity in vitro concerning a new class of imidazothiadiazole compounds.

Objectives To synthesize and characterize 2-[[6-(4-bromophenyl)imidazo[2,1-b]thiazol-3-yl]acetyl]-N-alkyl/arylhydrazinecarbothioamide and 3-alkyl/aryl-2-[((6-(4-bromophenyl)imidazo[2,1-b]thiazol-3-yl)acetyl)hydrazono]-5-nonsubstituted/methyl-4-thiazolidinone derivatives and evaluate them for their aldose reductase (AR) inhibitory effect. Materials and methods 2-[[6-(4-bromophenyl)imidazo[2,1-b]thiazol-3-yl]acetyl]-N-alkyl/arylhydrazinecarbothioamides (3a-f) and 3-alkyl/aryl-2-[((6-(4-bromophenyl)imidazo[2,1-b]thiazol-3-yl)acetyl)hydrazono]-5-nonsubstituted/methyl-4-thiazolidinones (4a-j) were synthesized from 2-[6-(4-bromophenyl)imidazo[2,1-b]thiazole-3-yl]acetohydrazide (2). Their structures were elucidated by elemental analyses and spectroscopic data. The synthesized compounds were tested for their ability to inhibit rat kidney AR. Results Among the synthesized compounds, 2-[[6-(4-bromophenyl)imidazo[2,1-b]thiazol-3-yl]acetyl]-N-benzoylhydrazinecarbothioamide (3d) showed the best AR inhibitory activity. Conclusion The findings of this study indicate that the different derivatives of the compounds in this study may be considered interesting candidates for future research.

International audience; In continuation of our pharmacomodulation work on the nitroimidazooxazole series, we report the synthesis of new 5-substituted 6-nitroimidazooxazole derivatives. Our aim was to evaluate how func-tionalization of the 5-position of the 6-nitroimidazooxazole scaffold affects antileishmanial and anti-trypanosomal in vitro activities. Twenty-one original compounds were synthesized and evaluated for their in vitro antileishmanial (L. donovani) and antitrypanosomal (T. cruzi) properties. Pallado-catalyzed cross-coupling reactions were used to introduce an aryl or ethynyl aryl substituent in 5-position from a 5-brominated-6-nitroimidazooxazole starting product. Unfortunately, the first series of compounds bearing an aryl group in 5-position presented limited in vitro activities against L. donovani and T. cruzi, with IC 50 > 10 mM (vs 0.18 mM and 2.31 mM for the reference drugs amphotericin B and benznidazole respectively). Interestingly, the second series of compounds bearing an ethynyl aryl substituent in 5-position showed more promising, particularly against T. cruzi. Compounds 6a, 6b, 6c, 6g and 6h had better activity than the reference drug benznidazole (0.92 mM IC 50 2.18 mM vs IC 50 ¼ 2.31 mM), whereas the non-functionalized 2-methyl-6-nitro-2,3-dihydroimidazo [2,1-b]oxazole 2 was not active against T. cruzi (IC 50 > 10 mM).

Objectives: The aim of this study was to determine the probable antibacterial, antitubercular, and antiviral activities of some N2-arylidene-(6-(4-chlorophenyl)imidazo[2,1-b]thiazol-3-yl) acetic acid hydrazides (3a-j). Further structural optimization of the identified lead structures can lead us to new more active potential antibacterial, antitubercular, and antiviral agents. Materials and Methods: Antibacterial activities of the title compounds against Staphylococcus aureus ATCC 29213, Pseudomonas aeruginosa ATCC 27853 and Escherichia coli ATCC 25922. These molecules were also evaluated for their in vitro antitubercular activity against Mycobacterium tuberculosis H37Rv (ATCC 27294) using the BACTEC 460 radiometric system and BACTEC 12B medium. Moreover, all the compounds (3a-j) were also evaluated against some DNA and RNA viruses in Madin-Darby Canine Kidney, Crandell-Rees Feline Kidney (CRFK), Vero, human embryonic lung (HEL) and HeLa cells. Results: Among the tested compounds, 3i displayed the highest efficacy against S. aureus and E. coli. Compound 3j, 5-nitro-2-furfurylidene derivative showed the highest antituberculosis activity (IC50: 6.16 µg/mL and IC90: 14.390 µg/mL). Compound 3i showed the most potent antiviral activity against feline corona virus in CRFK cell cultures (antiviral EC50: 7.5 µM and SI>13). Furthermore, compounds 3c and 3g displayed activity against herpes simplex virus-1 and vaccinia virus in HEL cell cultures (antiviral EC50 values of 9; 16 and 20; 14 µM, respectively). Conclusion: On the basis of aforementioned results, it can be conluded that imidazo[2,1-b]thiazole derivatives bearing hydrazone moieties serve as promising chemical probes to design therapeutic agents with antibacterial, antitubercular, and antiviral properties.

Heterocyclic rings are recognized as key components of many natural, semi-synthetic and synthetic molecules with a broad spectrum of biological activities. Among these molecules, the indole and imidazo[2,1-b][1,3,4]thiadiazole systems have recently been described as useful scaffolds for the design of anticancer agents. Herein the antitumor activity of a series of 3-(6-phenylimidazo[2,1-b][1,3,4]thiadiazol-2-yl)-1H-indoles, designed as hybrid structures, was assessed. Seven out of 10 compounds (1a-g) were submitted to National Cancer Institute (NCI). Remarkably, compound 1g showed antiproliferative activity against the full panel of sixty human cancer lines, with half-maximal inhibitory concentration of between 1.67 and 10.3 μM. Further studies showed antiproliferative activity of 1a-g and of three additional compounds 1h, 1i and 1l, with different substituents on the indole nucleus and phenyl ring, against three pancreatic cancer cell lines. In particular, derivatives 1g and 1h inhibited both proliferation and migration of SUIT-2 cells at concentrations lower than 10 μM. In conclusion, new indole derivatives are characterized by in vitro antitumor activity, supporting future mechanistic studies.

In the present work we describe the synthesis, characterization and evaluation of neuroprotective effects of a focused library of 4-imidazo[2,1-b]thiazole-1,4-dihydropyridines. Furthermore, the new dihydropyridines were subjected to functional in vitro assays in cardiac tissues and vascular smooth muscle to determine their possible selectivity in counteracting the effects of neurodegeneration. In particular the strategy adopted for designing the compounds involves the imidazo[2,1-b]thiazole nucleus. The observed properties show that substituents at C2 and C6 of the bicyclic scaffold are able to influence the cardiovascular parameters and the neuroprotective activity. In comparison to nifedipine, a set of derivatives such as compound 6, showed a neuroprotective profile of particular interest.

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.

A new series of imidazo[2,1-b]thiazole analogs containing a methyl sulfonyl COX-2 pharmacophore was synthesized and evaluated for their COX-2 inhibitory activity. According to in-vitro COX-1/COX-2 inhibition data, all compounds (6a-g) were selective inhibitors of COX-2 isoenzyme with IC50 values in the highly potent 0.08-0.16 µM range. These results indicated that both potency and selectivity of COX-2 inhibitory activity were affected by the type and size of amine on C-5 of imidazo[2,1-b]thiazole ring. Our data identified N,N-dimethyl-1-(6-(4-(methylsulfonyl)phenyl)imidazo[2,1-b]thiazol-5-yl)methanamine (6a) as a potent and selective COX-2 inhibitor (IC50 COX-1 >100 µM; IC50 COX-2 = 0.08 µM; selectivity index = 313.7). Our results indicated that both potency and selectivity of COX-2 inhibitory activity were affected by the type and size of amine on C-5 of imidazo[2,1-b]thiazole ring.

A class of 36 new 2-(6-phenylimidazo[2,-1-b][1,3,4]thiadiazol-2-yl)-1H-indoles was efficiently synthesized and evaluated for their anti-biofilm properties against the Gram-positive bacterial reference strains Staphylococcus aureus ATCC 25923, S. aureus ATCC 6538 and Staphylococcus epidermidis ATCC 12228, and the Gram-negative strains Pseudomonas aeruginosa ATCC 15442 and Escherichia coli ATCC 25922. Many of these new compounds, were able to inhibit biofilm formation of the tested staphylococcal strains showing BIC50 lower than 10 μg/ml. In particular, derivatives 9c and 9h showed remarkable anti-biofilm activity against S. aureus ATCC 25923 with BIC50 values of 0.5 and 0.8 μg/ml, respectively, whereas compound 9aa was the most potent against S. aureus ATCC 6538, with a BIC50 of 0.3 μg/ml. Remarkably, these compounds showed effects in the early stages of the biofilm formation without affecting the mature biofilm of the same strains and the viability of the planktonic form. Their ability in counteracting a virulence factor (biofilm formation) without interfering with the bacterial growth in the free life form make them novel valuable anti-virulence agents.

Oxidative stress and apoptosis are both associated with various acute and chronic disorders. Thus, the aim of the present study is to synthesize imidazo[2,1-c][1,2,4]triazines derivatives and to evaluate their effects in H2O2-induced oxidative stress in human neuroblastoma cell line (SH-SY5Y cells). The effects of the compounds on cell viability were measured by MTT assay and the changes in stress and apoptosis-related proteins were investigated by PathScan® Stress and Apoptosis Signaling Antibody Array kit and Western Blot technique. In particular, four compounds were found to protect SH-SY5Y cells from H2O2-induced toxicity by increasing Bcl-2/Bax ratio, regulating PI3-K/Akt cascade and inhibiting the ERK pathway.

International audience; Glucocorticoid receptor (GCR) transactivation reporter gene assays were used as an initial high-throughput screening on a diversified library of 1200 compounds for their evaluation as GCR antagonists. A class of imidazo[2,1-b]benzothiazole and imidazo[2,1-b]benzoimidazole derivatives were identified for their ability to modulate GCR transactivation and anti-inflammatory transrepression effects utilizing GCR and NF-κB specific reporter gene assays. Modeling studies on the crystallographic structure of the GCR ligand binding domain provided three new analogues bearing the tetrahydroimidazo[2,1-b]benzothiazole scaffold able to antagonize the GCR in the presence of dexamethasone (DEX) and also defined their putative binding into the GCR structure. Both mRNA level measures of GCR itself and its target gene GILZ, on cells treated with the new analogues, showed a GCR transactivation inhibition, thus suggesting a potential allosteric inhibition of the GCR.

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.

Objectives: To synthesize and characterize 2-[[6-(4-bromophenyl)imidazo[2,1-b]thiazol-3-yl]acetyl]-N-alkyl/arylhydrazinecarbothioamide and 3-alkyl/aryl-2-[((6-(4-bromophenyl)imidazo[2,1-b]thiazol-3-yl)acetyl)hydrazono]-5-nonsubstituted/methyl-4-thiazolidinone derivatives and evaluate them for their aldose reductase (AR) inhibitory effect. Materials and Methods: 2-[[6-(4-bromophenyl)imidazo[2,1-b]thiazol-3-yl]acetyl]-N-alkyl/arylhydrazinecarbothioamides (3a-f) and 3-alkyl/aryl-2-[((6-(4-bromophenyl)imidazo[2,1-b]thiazol-3-yl)acetyl)hydrazono]-5-nonsubstituted/methyl-4-thiazolidinones (4a-j) were synthesized from 2-[6-(4-bromophenyl)imidazo[2,1-b]thiazole-3-yl]acetohydrazide (2). Their structures were elucidated by elemental analyses and spectroscopic data. The synthesized compounds were tested for their ability to inhibit rat kidney AR. Results: Among the synthesized compounds, 2-[[6-(4-bromophenyl)imidazo[2,1-b]thiazol-3-yl]acetyl]-N-benzoylhydrazinecarbothioamide (3d) showed the best AR inhibitory activity. Conclusion: The findings of this study indicate that the different derivatives of the compounds in this study may be considered interesting candidates for future research.

Objectives: The aim of this study was to determine the probable antibacterial, antitubercular, and antiviral activities of some N2-arylidene-(6-(4-chlorophenyl)imidazo[2,1-b]thiazol-3-yl) acetic acid hydrazides (3a-j). Further structural optimization of the identified lead structures can lead us to new more active potential antibacterial, antitubercular, and antiviral agents. Materials and Methods: Antibacterial activities of the title compounds against Staphylococcus aureus ATCC 29213, Pseudomonas aeruginosa ATCC 27853 and Escherichia coli ATCC 25922. These molecules were also evaluated for their in vitro antitubercular activity against Mycobacterium tuberculosis H37Rv (ATCC 27294) using the BACTEC 460 radiometric system and BACTEC 12B medium. Moreover, all the compounds (3a-j) were also evaluated against some DNA and RNA viruses in Madin-Darby Canine Kidney, Crandell-Rees Feline Kidney (CRFK), Vero, human embryonic lung (HEL) and HeLa cells. Results: Among the tested compounds, 3i displayed the highest efficacy against S. aureus and E. coli. Compound 3j, 5-nitro-2-furfurylidene derivative showed the highest antituberculosis activity (IC50: 6.16 µg/mL and IC90: 14.390 µg/mL). Compound 3i showed the most potent antiviral activity against feline corona virus in CRFK cell cultures (antiviral EC50: 7.5 µM and SI>13). Furthermore, compounds 3c and 3g displayed activity against herpes simplex virus-1 and vaccinia virus in HEL cell cultures (antiviral EC50 values of 9; 16 and 20; 14 µM, respectively). Conclusion: On the basis of aforementioned results, it can be conluded that imidazo[2,1-b]thiazole derivatives bearing hydrazone moieties serve as promising chemical probes to design therapeutic agents with antibacterial, antitubercular, and antiviral properties.

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.

Synthesis of 6-(hydroxyphenyl)imidazo[2,1-b]thiazoles related to levamisole from the corresponding methoxy derivatives is reported. These compounds were tested on in vitro neutrophil activation, namely locomotion induced by chemoattractants, superoxide generation and lysozyme degranulation triggered by agonists. These functions were evaluated after cell pulse with different concentrations of the drugs. Several derivatives showed significant inhibitory effects, in some cases more potent than the parent compound.

The synthesis of new imidazo[2,1-b]thiazoles bearing phenolic groups is reported. These compounds and some previously described analogs were evaluated as antioxidant agents with three chemical model systems, and cancer chemopreventive potential was examined by inhibition of NO production, TNF-a activated NFkB activity, and aromatase activity, as well as induction of QR1 and RXRE binding. Two of the test compounds, 9 and 12, displayed promising activity by inhibiting iNOS, NFkB and aromatase in dose edependent manner, with IC50 values in low micromolar range. The same compounds activated QR1 in a bifunctional manner. When incubated with human liver microsomes, the active compounds were further hydroxylated on the parent ring system, suggesting the next logical step in the development of these promising leads will entail synthetic production of metabolites followed by additional assessment of biological activity.

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.

We report the synthesis of new guanylhydrazones from imidazo[2,1-b]thiazoles and of a bis-guanylhydrazone from diimidazo[1,2-a:1,2-c]pyrimidine. The compounds were tested as potential antitumor agents at the National Cancer Institute. Two derivatives are now under review by BEC: one of these was also subjected to a test for positive inotropic activity in view of a possible coanthracyclinic activity. Tyrosine kinase receptors may be involved as molecular targets in the mechanism of action of the guanylhydrazones described.

Some imidazo[2,1-b]thiazoles have been subjected to a 1H n.m.r. investigation. The aromatic character of this ring system, in connection with proton shielding, has been tested with coupled Hartree–Fock calculations of ring current effects, and it seems that the main differences in the chemical shifts relative to the single ring heterocycles are due to this kind of perturbation. A long-range coupling constant over six bonds has also been observed which implies a coupling mechanism involving the sulphur atom.

A series of ring-opened analogs of indomethacin was synthesized and tested in vitro (at concentrations ranging from 10-9 to 10-5 mol/l) on human neutrophil functions. Two compounds lacking the carboxylic group were subjected to the same tests and one of these showed unexpected activity. Among the acidic derivatives, compound 12 bearing the same substituents as indomethacin 10 (methoxy and 4-chlorobenzoyl groups) was the most active: it significantly lowered neutrophil responses in all five bioassays and at the three concentrations considered.