SYNTHESIS OF NEW POLYCYCLIC COMPOUNDS WITH POTENTIAL ANTIMALARIAL AND/OR ANTILEISHMANIAL ACTIVITY

ABSTRACT Malaria and leishmaniasis are potentially lethal protozoan diseases affecting a huge number of people worldwide, especially in underdeveloped countries. The alarming spread of drug resistance concerning both Plasmodium and Leishmania parasites makes the search of novel antimalarial and antileishmanial agents an urgent need. Unfortunately, at the moment even the combination therapies are failing in many regions afflicted by the diseases and alternatives are scarcely found. In addition, the available antileishmanial drugs are quite toxic, expensive and very often need monitoring and hospitalization. In the light of this dramatic situation, the discovery of novel effective, safe and affordable molecules is vital. Thus far, several strategies have been developed to overcome resistance mechanisms; among them, of particular interest are the structural optimization of already known antiprotozoal molecules, the development of hybrid compounds and the search of new chemical scaffolds. Based on these considerations, the aim of the present thesis was the synthesis of different novel sets of molecules, potentially candidates for the treatment of malaria and/or leishmaniasis. On one hand I prepared derivatives of the antiprotozoal agents chloroquine and clofazimine, in order to improve the biological activity and to reduce resistance mechanisms. On the other hand, I explored the potenzialities of new chemical scaffolds, such as indeno[2,1-c]quinolines, to design new antimalarials. Moreover, I evaluated the possibility of creating hybrid molecules, combining moieties with different mechanism of action which could carry out a synergistic effect. In particular, the quinoline nucleus has been combined with different HDACs inhibiting structures to generate antiplasmodial hybrids, whereas aphidicolin (a fungal metabolite with antileishmanial activity) has been condensed with other molecules endowed with antileishmanial activity, such as ethyl 3-chloroacetamidobenzoate and eflornithine. Biological assays were in general quite encouraging and suggested that these new classes of compounds could be considered as potential leads for the synthesis of new effective antiprotozoal drugs that, in some cases, could hopefully overcome resistance mechanisms

Methanethiosulfonate derivatives as ligands of STAT3-SH2 domain

It is well known that inflammatory conditions in selected organs increase the risk of cancer. Compounds of the inflammatory tumor microenvironment include leukocytes, cytokines, complement components, are orchestrated by transcription factors, such as STAT-3 (Signal Transducer and Activator of Transcription 3) and NF-kB. Therefore drugs able to inhibit one or both transcription factors could be useful tools to treat cancer disease. Two main approaches have been explored to inhibit STAT-3 signalling: \u2022 indirect, inhibiting the upstream tyrosine kinases that are responsible for STAT-3 activation or blocking factors such as JAK, Src, Bcr-Abl, FLT3 and EGFR that are involved in the activation of STAT-3 signalling. This kind of inhibition induces tumour-cell apoptosis but is poor selective. \u2022 direct, by interaction of small molecules with the protein. In this selective approach the starting point is the crystallographic structure of STAT-3 SH2 domain. S-methyl methanethiosulfonate, isolated from cauliflower has been shown to inhibit colon tumor incidence when administered to rats during the post-initiation phase of carcinogenesis [1]. Recently, a new methanethiosulfonate derivative of valproic acid (ACS33) was reported by some of us to show good in vitro antiproliferative activity and to inhibit in vivo the growth of PC3 in subcutaneous xenograft mice models [2]. Fig.1: Structures of the studied thiosulfonate hybrids. Since the influence of methanethiosulfonates on STAT-3 activity has not been yet studied, we decided to synthesize a set of thiosulfonate-drug hybrids (Fig.1) and to submit them and their parent compounds to the AlphaScreen-based assay, to investigate their ability to bind STAT-3 SH2 domain. Moreover, in order to check the selectivity of our molecules on STAT-3, other SH2-containing proteins, such as STAT-1, exhibiting a high degree of sequence homology to STAT-3, have also been tested. Results showed that most of the synthesized thiosulfonate-hybrids are able to strongly and selectively bind STAT-3 SH2 domain, whereas the parent drugs were completely devoid of this ability. Studies are ongoing to better define the profile of our new methanethiosulfonate derivatives as potential dual STAT-3/NFkB inhibitors. References 1. Reddy, B. S.; Kawamori, T.; Lubet, R.; Steele, V.; Kelloff, G.; Rao, C. V. Chemopreventive effect of S-methylmethane thiosulfonate and sulindac administered together during the promotion/progression stages of colon carcinogenesis Carcinogenesis 1999, 20, 1645-8. 2. Wedel S. A.; Sparatore A.; Del Soldato P.; Al-Batran S. E.; Atmaca A.; Juengel E.; Hudak L.; Jonas D.; Blaheta R. A. New histone deacetylase inhibitors as potential therapeutics tools for advanced prostate carcinoma. J. Cell. Mol Med 2008, 12, 2457-66

Choroidal abnormalities detected by near-infrared reflectance imaging as a new diagnostic criterion for neurofibromatosis 1

Objective: To investigate in a large sample of consecutive patients with neurofibromatosis type 1 (NF1) the possibility of including the presence of choroidal abnormalities detected by near-infrared reflectance (NIR) as a new diagnostic criterion for NF1. Design: Cross-sectional evaluation of a diagnostic test. Participants and Controls: Ninety-five consecutive adult and pediatric patients (190 eyes) with NF1, diagnosed based on the National Institutes of Health (NIH) criteria. Controls included 100 healthy age- and gender-matched control subjects. Methods: Confocal scanning laser ophthalmoscopy was performed for each subject, investigating the presence and the number of choroidal abnormalities. Main Outcome Measures: Sensitivity, specificity, and diagnostic accuracy for the different cutoff values of the criterion choroidal nodules detected by NIR compared with the NIH criteria. Results: Choroidal nodules detected by NIR imaging were present in 79 (82%) of 95 of the NF1 patients, including 15 (71%) of the 21 NF1 pediatric patients. Similar abnormalities were present in 7 (7%) of 100 healthy subjects, including 2 (8%) of the 25 healthy pediatric subjects. The highest accuracy was obtained at the cutoff value of 1.5 choroidal nodules detected by NIR imagery. Sensitivity and specificity of the examination at the optimal cutoff point were 83% and 96%, respectively. Diagnostic accuracy was 90% in the overall population and 83% in the pediatric population. Both of these values were in line with the most common NIH diagnostic criteria. Conclusions: Choroidal abnormalities appearing as bright patchy nodules detected by NIR imaging frequently occurred in NF1 patients. The present study shows that NIR examination to detect choroidal involvement should be considered as a new diagnostic criterion for NF1

Synthesis and evaluation of the antiplasmodial activity of novel indeno[2,1-c]quinoline derivatives

With the aim to explore the potentiality of new chemical scaffolds for the design of new antimalarials, a set of new indeno[2,1-c]quinolines bearing different basic heads has been synthesized and tested in vitro against chloroquine sensitive (CQ-S) and chloroquine resistant (CQ-R) strains of Plasmodium falciparum. Most of the synthesized compounds exhibited a moderate antiplasmodial activity, inhibiting the growth of both CQ-S and CQ-R strains of P. falciparum with IC50 ranging from 0.24 to 6.9\u3bcM and with a very low resistance index. The most potent compounds (1.2-1.3-fold the CQ on the W-2 strain) can be considered as promising 'lead compounds' to be further optimized to improve efficacy and selectivity against Plasmodia

Synthesis and antiplasmodial activity of new heteroaryl derivatives of 7-chloro-4-aminoquinoline

With the aim to investigate the effect of different heterocyclic rings linked to the 4-aminoquinoline nucleus on the antimalarial activity, a set of 7-chloro-N-(heteroaryl)-methyl-4-aminoquinoline and 7-chloro-N-(heteroaryl)-4-aminoquinoline was synthesized and tested in vitro against D-10 (CQ-S) and W-2 (CQ-R) strains of Plasmodium falciparum. All compounds exhibited from moderate to high antiplasmodial activities. The activity was strongly influenced both by the presence of a methylenic group, as a spacer between the 4-aminoquinoline and the heterocyclic ring, and by the presence of a basic head. The most potent molecules inhibited the growth of both CQ-S and CQ-R strains of P. falciparum with IC(50)<30nM and were not toxic against human endothelial cells. These results confirm that the presence of an heteroaryl moiety in the side chain of 7-chloro-4-aminoquinoline is useful for the design and development of new powerful antimalarial agents

CLOFAZIMINE ANALOGS WITH ANTILEISHMANIAL AND ANTIMALARIAL ACTIVITIES

Clofazimine is a fat-soluble riminophenazine dye used in combination with rifampicin and dapsone as multidrug therapy (MDT) for the treatment of leprosy. This agent is known to have antileishmanial effects both in vitro and in vivo.[1] Tetramethylpiperidine \u2013substituted phenazines, structurally related to clofazimine, have been described to be endowed with activity against multidrug resistant strains of Plasmodium falciparum.[2] In the search for more effective alternatives to the presently used antileishmanial drugs and with the aim to study more thorougly the antimalarial potentialities of this kind of structures, we synthesized a set of novel iminophenazines bearing a bicyclic basic head linked through an alkylic chain to the imino nitrogen in position 3 on the phenazine nucleus. The new compounds inhibited the growth of different strains of Leishmania promastigotes as well as chloroquine sensitive (CQ-S) and chloroquine resistant (CQ-R) strains of P. falciparum with IC50 in submicromolar range whereas clofazimine was 10-20 \u2013fold less active

Synthesis and antiplasmodial evaluation of new N-(imidazol-2-yl)-methyl-4-aminoquinolines

In order to develop new effective antimalarial agents, we have demonstrated that the replacement of the phenolic ring of amodiaquine-like compounds with an arylpyrrole nucleus is associated with a good antimalarial activity (M. Casagrande et al., Bioorg. Med. Chem. 2008, 16, 6813 and Bioorg. Med. Chem. 2010, 18, 6625). In addition, Chibale and co-workers recently reported a new potent antimalarial 4-aminoquinoline, termed phenylequine (PQ), characterized by a phenyl ring linked to 4-aminoquinoline nucleus through a methylenic group (M. A. L. Blackie et al., Bioorg. Med. Chem. Lett. 2010, 20, 1078). To test the effect on the antimalarial activity of the presence of other heterocyclic rings linked to the 7-chloro-4-aminoquinoline nucleus instead of the phenyl ring , a set of new 7-chloro-N-((1H-imidazol-2-yl)methyl)quinolin-4-amine and 7-chloro-N-((4-aryl-1H-imidazol-2-yl)methyl)quinolin-4-amine bearing at position 5 of imidazole a diethylaminomethyl or a pyrrolidinomethyl moiety as basic head, was synthesized and tested