Matteo Incerti

Synthesis and biological evaluation of benzo[d]isothiazole, benzothiazole and thiazole Schiff bases.

Three new series of benzo[d]isothiazole, benzothiazole and thiazole Schiff bases were synthesized and tested in vitro with the aim of identifying novel lead compounds active against emergent and re-emergent human and cattle infectious diseases (AIDS, hepatitis B and C, tuberculosis, bovine viral diarrhoea) or against drug-resistant cancers (leukaemia, carcinoma, melanoma, MDR tumors) for which no definitive cure or efficacious vaccine is available at present. In particular, these compounds were evaluated in vitro against representatives of different virus classes, such as a HIV-1 (Retrovirus), a HBV (Hepadnavirus) and the single-stranded RNA(+) viruses Yellow fever virus (YFV) and Bovine viral diarrhoea virus (BVDV), both belonging to Flaviviridae. Title compounds were also tested against representatives of Gram-positive and Gram-negative bacteria (Staphylococcus aureus, Salmonella spp.), various atypic mycobacterial strains (Mycobacterium fortuitum and Mycobacterium smegmatis), yeast (Candida albicans) and mould (Aspergillus fumigatus). None of the compounds showed antiviral or antimicrobial activity. The benzo[d]isothiazole compounds showed a marked cytotoxicity (CC(50)=4-9 microM) against the human CD4(+) lymphocytes (MT-4) that were used to support HIV-1 growth. For this reason, the most cytotoxic compounds of this series were evaluated for their antiproliferative activity against a panel of human cell lines derived from haematological and solid tumors. The results highlighted that all the benzo[d]isothiazole derivatives inhibited the growth of leukaemia cell lines, whereas only one of the above mentioned compounds (1e) showed antiproliferative activity against two solid tumor-derived cell lines.

2-Heteroarylimino-5-benzylidene-4-thiazolidinones analogues of 2-thiazolylimino-5-benzylidene-4-thiazolidinones with antimicrobial activity: synthesis and structure-activity relationship.

2-Heteroarylimino-5-benzylidene-4-thiazolidinones, unsubstituted or carrying hydroxy, methoxy, nitro and chloro groups on the benzene ring, were synthesised and assayed in vitro for their antimicrobial activity against gram positive and gram negative bacteria, yeasts and mould. The antimicrobial activity of the 2-benzo[d]thiazolyl- and of the 2-benzo[d]isothiazolyl-imino-5-benzylidene-4-thiazolidinones is, on the whole, lower in comparison with the high activity detected for the derivatives of the 2-thiazolylimino-5-benzylidene-4-thiazolidinone class. Nevertheless most of the benzo[d]thiazole analogues display good inhibition of the growth of gram positive bacilli and staphylococci, including methicillin-resistant Staphylococcus strains. Among the 2-benzo[d]isothiazole analogues a few derivatives show a strong and selective activity against bacilli. Moreover, it is worth noting that the replacement of the thiazole nucleus for the benzo[d]thiazole bicyclic system in the parent 2-(benzo[d]thiazol-2-ylimino)thiazolidin-4-one leads to significant antifungal properties against both yeasts and moulds, properties not shown by the analogous 2-thiazolyl- and 2-benzo[d]isothiazolyl-imino)thiazolidin-4-ones. The structure-activity relationship of 33 analogues possessing the 2-heteroarylimino-4-thiazolidinone structure is analysed through QSAR models.

Anti-HIV evaluation of benzo[d]isothiazole hydrazones.

The synthesis and the anti-HIV-1 activity of novel benzo[d]isothiazole hydrazones are reported. Target compounds tested in MT-4 cells cultures for their anti-HIV properties against wild type HIV-1 and HIV strains carrying clinically relevant mutations (EFV(R), Y181C and K103/Y181C) showed good activity against wild type HIV-1 and against the EFV(R) mutant. In terms of SAR the relevant result was that, in the class of benzisothiazole hydrazones, the benzo[d]isothiazol-3(2H)-one moiety (compounds 1 and 4) is an essential structural requirement for the antiretroviral activity.

Lithocholic Acid Is an Eph-ephrin Ligand Interfering with Eph-kinase Activation

Eph-ephrin system plays a central role in a large variety of human cancers. In fact, alterated expression and/or de-regulated function of Eph-ephrin system promotes tumorigenesis and development of a more aggressive and metastatic tumour phenotype. In particular EphA2 upregulation is correlated with tumour stage and progression and the expression of EphA2 in non-trasformed cells induces malignant transformation and confers tumorigenic potential. Based on these evidences our aim was to identify small molecules able to modulate EphA2-ephrinA1 activity through an ELISA-based binding screening. We identified lithocholic acid (LCA) as a competitive and reversible ligand inhibiting EphA2-ephrinA1 interaction (Ki = 49 µM). Since each ephrin binds many Eph receptors, also LCA does not discriminate between different Eph-ephrin binding suggesting an interaction with a highly conserved region of Eph receptor family. Structurally related bile acids neither inhibited Eph-ephrin binding nor affected Eph phosphorylation. Conversely, LCA inhibited EphA2 phosphorylation induced by ephrinA1-Fc in PC3 and HT29 human prostate and colon adenocarcinoma cell lines (IC50 = 48 and 66 µM, respectively) without affecting cell viability or other receptor tyrosine-kinase (EGFR, VEGFR, IGFR1β, IRKβ) activity. LCA did not inhibit the enzymatic kinase activity of EphA2 at 100 µM (LANCE method) confirming to target the Eph-ephrin protein-protein interaction. Finally, LCA inhibited cell rounding and retraction induced by EphA2 activation in PC3 cells. In conclusion, our findings identified a hit compound useful for the development of molecules targeting ephrin system. Moreover, as ephrin signalling is a key player in the intestinal cell renewal, our work could provide an interesting starting point for further investigations about the role of LCA in the intestinal homeostasis.

Amino Acid Conjugates of Lithocholic Acid As Antagonists of the EphA2 Receptor

The Eph receptor-ephrin system is an emerging target for the development of novel antiangiogenetic agents. We recently identified lithocholic acid (LCA) as a small molecule able to block EphA2-dependent signals in cancer cells, suggesting that its (5β)-cholan-24-oic acid scaffold can be used as a template to design a new generation of improved EphA2 antagonists. Here, we report the design and synthesis of an extended set of LCA derivatives obtained by conjugation of its carboxyl group with different α-amino acids. Structure-activity relationships indicate that the presence of a lipophilic amino acid side chain is fundamental to achieve good potencies. The l-Trp derivative (20, PCM126) was the most potent antagonist of the series disrupting EphA2-ephrinA1 interaction and blocking EphA2 phosphorylation in prostate cancer cells at low μM concentrations, thus being significantly more potent than LCA. Compound 20 is among the most potent small-molecule antagonists of the EphA2 receptor.

Structure-activity relationships and mechanism of action of Eph-ephrin antagonists: interaction of cholanic acid with the EphA2 receptor

The Eph–ephrin system, including the EphA2 receptor and the ephrinA1 ligand, plays a critical role in tumor and vascular functions during carcinogenesis. We previously identified (3α,5β)‐3‐hydroxycholan‐24‐oic acid (lithocholic acid) as an Eph–ephrin antagonist that is able to inhibit EphA2 receptor activation; it is therefore potentially useful as a novel EphA2 receptor‐targeting agent. Herein we explore the structure–activity relationships of a focused set of lithocholic acid derivatives based on molecular modeling investigations and displacement binding assays. Our exploration shows that while the 3‐α‐hydroxy group of lithocholic acid has a negligible role in recognition of the EphA2 receptor, its carboxylate group is critical for disrupting the binding of ephrinA1 to EphA2. As a result of our investigation, we identified (5β)‐cholan‐24‐oic acid (cholanic acid) as a novel compound that competitively inhibits the EphA2–ephrinA1 interaction with higher potency than lithocholic acid. Surface plasmon resonance analysis indicates that cholanic acid binds specifically and reversibly to the ligand binding domain of EphA2, with a steady‐state dissociation constant (KD) in the low micromolar range. Furthermore, cholanic acid blocks the phosphorylation of EphA2 as well as cell retraction and rounding in PC3 prostate cancer cells, two effects that depend on EphA2 activation by the ephrinA1 ligand. These findings suggest that cholanic acid can be used as a template structure for the design of effective EphA2 antagonists, and may have potential impact in the elucidation of the role played by this receptor in pathological conditions.

Amidinobenzisothiazole derivatives with antidegenerative activity on cartilage

N-(Benzo[d]isothiazol-3-yl)amidines were synthesised and evaluated for their antiinflammatory activity. Encouraging results led us to evaluate these derivatives on the prevention of cartilage destruction in articular disease. Antidegenerative activity was assayed on culture of porcine nasal cartilage and diarthroidal joint human cartilage in the presence of interleukin-1beta (IL-1beta). The amount of glycosaminoglycans (GAGs) and the production of nitric oxide (NO) in the culture medium were determined. The obtained results showed that all the compounds, in the presence of IL-beta, blocked the cartilage breakdown, with different behaviour. The antidegenerative activity is more evident in human cartilage.

UniPR129 is a competitive small molecule Eph‐ephrin antagonist blocking in vitro angiogenesis at low micromolar concentrations

The Eph receptor tyrosine kinases and their ephrin ligands are key players in tumorigenesis and many reports have correlated changes in their expression with a poor clinical prognosis in many solid tumours. Agents targeting the Eph‐ephrin system might emerge as new tools useful for the inhibition of different components of cancer progression. Even if different classes of small molecules targeting Eph‐ephrin interactions have been reported, their use is hampered by poor chemical stability and low potency. Stable and potent ligands are crucial to achieve robust pharmacological performance.

Heteroarylimino-4-thiazolidinones as inhibitors of cartilage degradation.

2-Benzo[d]thiazolyl- and 2-benzo[d]isothiazolyl-imino-5-benzylidene-4-thiazolidinone derivatives were investigated as potential metalloproteinases (MMPs) inhibitors and evaluated for their antidegenerative activity on human chondrocyte cultures stimulated by IL-1β, using an experimental model that reproduces the mechanisms involved in osteoarthritic (OA) diseases. Cell viability, the amount of glycosaminoglycans (GAGs) and the production of nitric oxide (NO) were measured. The most potent compound, 5-(4-methoxy-benzylidene)-2-(benzo[d]isothiazol-3-ylimino)-thiazolidin-4-one (4b), a MMP-13 inhibitor at nanomolar concentration (IC(50)=0.036 μM), could be considered as a lead compound for the development of novel clinical agents, inhibitors of cartilage degradation, for the treatment of OA.

Dual-Acting Drugs: an in vitro Study of Nonimidazole Histamine H3 Receptor Antagonists Combining Anticholinesterase Activity

Dual‐acting compounds that combine H3 antagonism with anticholinesterase properties are currently emerging as a novel and promising therapeutic approach in the treatment of multifactorial disorders primarily characterized by cholinergic deficits such as Alzheimers disease. A series of novel nonimidazole H3 ligands was developed from the chemical manipulation of 1,1′‐octa‐, ‐nona‐, and ‐decamethylene‐bis‐piperidines—H3 antagonists that had been the subject of previous investigations. These compounds were evaluated for in vitro binding affinity, antagonistic potency, and selectivity at rodent and human histamine H3 receptors, inhibitory activity at rat brain cholinesterase, and in vivo CNS access and cholinomimetic effects. Within the present series, the tetrahydroaminoacridine hybrid 18 stands out as one of the most attractive molecules, synergistically combining nanomolar and selective H3 antagonism with remarkable anticholinesterase activity. From this original starting point, it is hoped that future investigations will lead to dual‐acting compounds that can selectively enhance central cholinergic neurotransmission and thus facilitate the treatment of cognitive disorders.