Phthalimido-thiazole as privileged scaffold: activity against immature and adult worms of Schistosoma mansoni.

Phthalimide, 1,3-thiazole, and thiazolidinone cores are considered privileged scaffolds and represent an attractive starting point to design new bioactive compounds for neglected tropical disease (NTD). Schistosomiasis is a NTD, caused by Schistosoma worms which praziquantel (PZQ) is the only drug used to treat humans, but the decrease in the effect after treatment has been reported. Recently, some phthalimide-thiazole derivatives exhibited in vitro antischistosomal activity against adult worms with significant ultrastructural changes and a lower cytotoxic effect on splenocytes. This new biological phthalimido-thiazole profile has motivated us to evaluate a new generation of such molecules in immature and adult worms. Thus, a phthalimido-thiazolidinone derivative, (3c), and three phthalimido-thiazoles (6c, 7a, and 7h) were evaluated concerning their in vitro activity on schistosomulae and adult worms. The results showed that these compounds brought a significant reduction on the mortality, inhibited oviposition, and then induced mortality in immature and adult worms alike. According to scanning electron microscopy, the tegument was the principal target for 7a and 7h and revealed gradual damage to the tegument surface, inducing destruction and decomposition of the tegument in the same areas and exposition of subtegumental tissue and of muscle tissue. Furthermore, they caused less toxicity in splenocytes than PZQ. Compounds 7a and 7h revealed to possess promising activity against larval forms. According to the present study, the privileged structure phthalimido-thiazoles act as a molecular framework that has antischistosomal activity and most form the basis to the next pre-clinical tests. Graphical abstract.

Compound profiling and 3D-QSAR studies of hydrazone derivatives with activity against intracellular Trypanosoma cruzi.

Chagas disease is a tropical disease caused by the parasite Trypanosoma cruzi, which is endemic in Central and South America. Few treatments are available with effectiveness limited to the early (acute) stage of disease, significant toxicity and widespread drug resistance. In this work we report the outcome of a HTS-ready assay chemical library screen to identify novel, nontoxic, small-molecule inhibitors of T. cruzi. We have selected 50 compounds that possess hydrazone as a common group. The compounds were screened using recombinant T. cruzi (Tulahuen strain) expressing beta-galactosidase. A 3D quantitative structure-activity relationship (QSAR) analysis was performed using descriptors calculated from comparative molecular field analysis (CoMFA). Our findings show that of the fifty selected hydrazones, compounds LpQM-19, 28 and 31 displayed the highest activity against T. cruzi, leading to a selectivity index (SI) of 20-fold. The 3D-QSAR analysis indicates that a particular electrostatic arrangement, where electron-deficient atoms are aligned along the molecule main axis positively correlates with compound biological activity. These results provide new candidate molecules for the development of treatments against Chagas disease.

Structural design, synthesis and pharmacological evaluation of 4-thiazolidinones against Trypanosoma cruzi.

Chagas disease is an infection caused by protozoan Trypanosoma cruzi, which affects approximately 8-10million people worldwide. Benznidazole is the only drug approved for treatment during the acute and asymptomatic chronic phases of Chagas disease; however, it has poor efficacy during the symptomatic chronic phase. Therefore, the development of new pharmaceuticals is needed. Here, we employed the bioisosterism to modify a potent antiparasitic and cruzain-inhibitor aryl thiosemicarbazone (4) into 4-thiazolidinones (7-21). Compounds (7-21) were prepared by using a straightforward synthesis and enabled good to excellent yields. As a chemical elucidation tool, X-ray diffraction of compound (10) revealed the geometry and conformation of this class compounds. The screening against cruzain showed that 4-thiazolidinones were less active than thiosemicarbazone (4). However, the antiparasitic activity in Y strain trypomastigotes and host cell cytotoxicity in J774 macrophages revealed that compounds (10 and 18-21) are stronger and more selective antiparasitic agents than thiosemicarbazone (4). Specifically, compounds (18-20), which carry a phenyl at position N3 of heterocyclic ring, were the most active ones, suggesting that this is a structural determinant for activity. In infected macrophages, compounds (18-20) reduced intracellular amastigotes, whereas Benznidazole did not. In T. cruzi-infected mice treated orally with 100mg/kg of compound (20), a decreased of parasitemia was observed. In conclusion, we demonstrated that the conversation of thiosemicarbazones into 4-thiazolidinones retains pharmacological property while enhances selectivity.

Cytotoxic and toxicological effects of phthalimide derivatives on tumor and normal murine cells.

Eleven phthalimide derivatives were evaluated with regards to their antiproliferative activity on tumor and normal cells and possible toxic effects. Cytotoxic analyses were performed against murine tumors (Sarcoma 180 and B-16/F-10 cells) and peripheral blood mononuclear cells (PBMC) using MTT and Alamar Blue assays. Following, the investigation of cytotoxicity was executed by flow cytometry analysis and antitumoral and toxicological potential by in vivo techniques. The molecules 3b, 3c, 4 and 5 revealed in vitro cytotoxicity against Sarcoma 180, B-16/F-10 and PBMC. Since compound 4 was the most effective derivative, it was chosen to detail the mechanism of action after 24, 48 and 72 h exposure (22.5 and 45 µM). Sarcoma 180 cells treated with compound 4 showed membrane disruption, DNA fragmentation and mitochondrial depolarization in a time- and dose-dependent way. Compounds 3c, 4 and 5 (50 mg/kg/day) did not inhibit in vivo tumor growth. Compound 4-treated animals exhibited an increase in total leukocytes, lymphocytes and spleen relative weight, a decreasing in neutrophils and hyperplasia of spleen white pulp. Treated animals presented reversible histological changes. Molecule 4 had in vitro antiproliferative action possibly triggered by apoptosis, reversible toxic effects on kidneys, spleen and livers and exhibited immunostimulant properties that can be explored to attack neoplasic cells.

Evaluation of the anti-Schistosoma mansoni activity of thiosemicarbazones and thiazoles.

Schistosomiasis is a chronic and debilitating disease caused by a trematode of the genus Schistosoma and affects over 207 million people. Chemotherapy is the only immediate recourse for minimizing the prevalence of this disease and involves predominately the administration of a single drug, praziquantel (PZQ). Although PZQ has proven efficacy, there is a recognized need to develop new drugs as schistosomicides since studies have shown that repeated use of this drug in areas of endemicity may cause a temporary reduction in susceptibility in isolates of Schistosoma mansoni. Hydrazones, thiosemicarbazones, phthalimides, and thiazoles are thus regarded as privileged structures used for a broad spectrum of activities and are potential candidates for sources of new drug prototypes. The present study determined the in vitro schistosomicidal activity of 10 molecules containing these structures. During the assays, parameters such motility and mortality, oviposition, morphological changes in the tegument, cytotoxicity, and immunomodulatory activity caused by these compounds were evaluated. The results showed that compounds formed of thiazole and phthalimide led to higher mortality of worms, with a significant decline in motility, inhibition of pairing and oviposition, and a mortality rate of 100% starting from 144 h of exposure. These compounds also stimulated the production of nitric oxide and tumor necrosis factor alpha (TNF-α), thereby demonstrating the presence of immunomodulatory activity. The phthalyl thiazole LpQM-45 caused significant ultrastructural alterations, with destruction of the tegument in both male and female worms. According to the present study, phthalyl thiazole compounds possess antischistosomal activities and should form the basis for future experimental and clinical trials.

Synthesis, ADMET Prediction, and Antitumor Profile of Phenoxyhydrazine- 1,3-thiazoles Derivatives.

BACKGROUND: Cancer is one of the most important barriers to increasing life expectancy in all countries in the 21st century. Investigations of new anti-cancer drugs with low side effects are an urgent demand for medicinal chemists. Considering the known antitumor and immunomodulatory activity of thiazoles, this work presents the synthesis and antineoplastic activity of new thiazoles. METHODS: The 22 new compounds (2a-v) were synthesized from different thiosemicarbazones and 2-bromoacetophenone. The compounds were evaluated on: MOLT-4, HL-60, HL-60/MX1, MM1S, SKMEL-28, DU145, MCF-7, and T47d. RESULTS: Compound 2b induced cellular viability on MOLT-4 (37.1%), DU145 (41.5%), and HL- 60/MX1 (58.8%) cells. On MOLT-4 cells, compound 2b exhibited an IC50 of 8.03 µM, and against DU145 cells, an IC50 of 6.04µM. Besides, at IC50 and fold of IC50, 20% to 30% of dead cells were found, most due to necrosis/late apoptosis. Most compounds no showed cytotoxicity against fibroblast cells L929 at the concentrations tested. The compound did not alter the cell cycle of DU145 cells when compared to the negative control. Therefore, compound 2b stands out against DU145 and MOLT-4 cells. CONCLUSION: Our study reinforced the importance of 1,3-thiazoles nuclei in antitumor activity. In addition, derivative 2b stands out against DU145 and MOLT-4 cells and could be a starting point for developing new antineoplastic agents.

A Novel High-Content Screening-Based Method for Anti-Trypanosoma cruzi Drug Discovery Using Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes.

Chagas disease is caused by Trypanosoma cruzi infection and remains a relevant cause of chronic heart failure in Latin America. The pharmacological arsenal for Chagas disease is limited, and the available anti-T. cruzi drugs are not effective when administered during the chronic phase. Cardiomyocytes derived from human-induced pluripotent stem cells (hiPSC-CMs) have the potential to accelerate the process of drug discovery for Chagas disease, through predictive preclinical assays in target human cells. Here, we aimed to establish a novel high-content screening- (HCS-) based method using hiPSC-CMs to simultaneously evaluate anti-T. cruzi activity and cardiotoxicity of chemical compounds. To provide proof-of-concept data, the reference drug benznidazole and three compounds with known anti-T. cruzi activity (a betulinic acid derivative named BA5 and two thiazolidinone compounds named GT5A and GT5B) were evaluated in the assay. hiPSC-CMs were infected with T. cruzi and incubated for 48 h with serial dilutions of the compounds for determination of EC50 and CC50 values. Automated multiparametric analyses were performed using an automated high-content imaging system. Sublethal toxicity measurements were evaluated through morphological measurements related to the integrity of the cytoskeleton by phalloidin staining, nuclear score by Hoechst 33342 staining, mitochondria score following MitoTracker staining, and quantification of NT-pro-BNP, a peptide released upon mechanical myocardial stress. The compounds showed EC50 values for anti-T. cruzi activity similar to those previously described for other cell types, and GT5B showed a pronounced trypanocidal activity in hiPSC-CMs. Sublethal changes in cytoskeletal and nucleus scores correlated with NT-pro-BNP levels in the culture supernatant. Mitochondrial score changes were associated with increased cytotoxicity. The assay was feasible and allowed rapid assessment of anti-T. cruzi action of the compounds, in addition to cardiotoxicity parameters. The utilization of hiPSC-CMs in the drug development workflow for Chagas disease may help in the identification of novel compounds.

Privileged Structures in the Design of Potential Drug Candidates for Neglected Diseases.

BACKGROUND: Privileged motifs are recurring in a wide range of biologically active compounds that reach different pharmaceutical targets and pathways and could represent a suitable start point to access potential candidates in the neglected diseases field. The current therapies to treat these diseases are based in drugs that lack of the desired effectiveness, affordable methods of synthesis and allow a way to emergence of resistant strains. Due the lack of financial return, only few pharmaceutical companies have been investing in research for new therapeutics for neglected diseases (ND). METHODS: Based on the literature search from 2002 to 2016, we discuss how six privileged motifs, focusing phthalimide, isatin, indole, thiosemicarbazone, thiazole, and thiazolidinone are particularly recurrent in compounds active against some of neglected diseases. RESULTS: It was observed that attention was paid particularly for Chagas disease, malaria, tuberculosis, schistosomiasis, leishmaniasis, dengue, African sleeping sickness (Human African Trypanosomiasis - HAT) and toxoplasmosis. It was possible to verify that, among the ND, antitrypanosomal and antiplasmodial activities were between the most searched. Besides, thiosemicarbazone moiety seems to be the most versatile and frequently explored scaffold. As well, phthalimide, isatin, thiazole, and thiazolidone nucleus have been also explored in the ND field. CONCLUSION: Some described compounds, appear to be promising drug candidates, while others could represent a valuable inspiration in the research for new lead compounds.

Structural improvement of new thiazolidinones compounds with antinociceptive activity in experimental chemotherapy-induced painful neuropathy.

Chemotherapy-induced neuropathy is a disabling pain condition resulting from chemotherapy for cancers. Up to now, no drug is available to cure chemotherapy-induced neuropathy. In the present study, we describe the structural design, synthesis, chemical and pharmacological characterization of 15 thiazolidinones, a class of potential analgesic compounds. The synthesis of new thiazolidinones was achieved by using the thiazolidinone heterocyclic as main structural pharmacophoric group and varying the substituents attached to the phenyl near to the iminic bond. The analgesic potential of the compounds was investigated in a mice model of oxaliplatin-induced neuropathic pain, using von Frey, rota-rod and open-field tests. Except for compound 14, these thiazolidinones exhibited antinociceptive property without causing motor impairment. Thiazolidinones 12, 15 and 16 displayed a dose-dependent antinociceptive effect, with similar efficacy and enhanced potency than gabapentin, the gold standard drug used for neuropathic pain. In addition, the antinociceptive activity of 16 lasted longer than gabapentin. The antinociceptive effect of thiazolidinones was prevented by GW9662, a PPARγ antagonist. The main antinociceptive compounds exhibited positive Lipinski's index, predicting their oral bioavailability. In conclusion, the structural design performed here led to the identification of new compounds endowed with potent antinociceptive activity, potentially useful to treat chemotherapy-induced neuropathic pain.

Structural design, synthesis and pharmacological evaluation of thiazoles against Trypanosoma cruzi.

Chagas disease is one of the most significant health problems in the American continent. benznidazole (BDZ) and nifurtimox (NFX) are the only drugs approved for treatment and exhibit strong side effects and ineffectiveness in the chronic stage, besides different susceptibility among T. cruzi DTUs (Discrete Typing Units). Therefore, new drugs to treat this disease are necessary. Thiazole compounds have been described as potent trypanocidal agents. Here we report the structural planning, synthesis and anti-T. cruzi evaluation of a new series of 1,3-thiazoles (7-28), which were designed by placing this heterocycle instead of thiazolidin-4-one ring. The synthesis was conducted in an ultrasonic bath with 2-propanol as solvent at room temperature. By varying substituents attached to the phenyl and thiazole rings, substituents were observed to retain, enhance or greatly increase their anti-T. cruzi activity. In some cases, methyl at position 5 of the thiazole (compounds 9, 12 and 23) increased trypanocidal property. The exchange of phenyl for pyridinyl heterocycle resulted in increased activity, giving rise to the most potent compound against the trypomasigote form (14, IC50trypo = 0.37 µM). Importantly, these new thiazoles were toxic for trypomastigotes without affecting macrophages and cardiomyoblast viability. The compounds were also evaluated against cruzain, and five of the most active compounds against trypomastigotes (7, 9, 12, 16 and 23) inhibited more than 70% of enzymatic activity at 10 µM, among which compound 7 had an IC50 in the submicromolar range, suggesting a possible mechanism of action. In addition, examination of T. cruzi cell death showed that compound 14 induces apoptosis. We also examined the activity against intracellular parasites, revealing that compound 14 inhibited T. cruzi infection with potency similar to benznidazole. The antiparasitic effect of 14 and benznidazole in combination was also investigated against trypomastigotes and revealed that they have synergistic effects, showing a promising profile for drug combination. Finally, in mice acutely-infected with T. cruzi,14 treatment significanty reduced the blood parasitaemia and had a protective effect on mortality. In conclusion, we report the identification of compounds (7), (12), (15), (23) and (26) with similar trypanocidal activity of benznidazole; compounds (9) and (21) as trypanocidal agents equipotent with BDZ, and compound 14 with potency 28 times better than the reference drug without affecting macrophages and cardiomyoblast viability. Mechanistically, the compounds inhibit cruzain, and 14 induces T. cruzi cell death by an apoptotic process, being considered a good starting point for the development of new anti-Chagas drug candidates.

Improvement of in vivo anticancer and antiangiogenic potential of thalidomide derivatives.

The strategy of antiangiogenic drugs is based on inhibiting formation of new blood vessels as alternative to limit cancer progression. In this work, we investigated the antitumor and antiangiogenic potential of eight thalidomide derivatives. Most of the molecules was not cytotoxic but 2a, 2d and 3d revealed weak antiproliferative activity on HL-60, Sarcoma 180 (S180) and normal peripheral blood mononuclear cells. Thalidomide, 2a and 2b were able to inhibit tumor growth (53.5%, 67.9% and 67.4%, respectively) in S180-bearing mice and presented moderate and reversible toxicity on liver, kidneys and spleens. Both analogs (2a and 2b) inhibited cell migration of endothelial (HUVEC) and melanoma cells (MDA/MB-435) at 50µg/mL. Immunohistochemistry labeling assays with CD-31 (PECAM-1) antibody showed microvascular density (MVD) was significantly reduced in thalidomide, 2a and 2b groups (30±4.9, 64.6±1.8 and 46.5±19.5%, respectively) (p<0.05). Neovascularization evaluated by Chorioallantoic Membrane Assay (CAM) with compounds 2a and 2b showed reduction of vessels' number (12. 9±2.3 and 14.8±3.3%), neovascularization area (13.1±1.7 and 14.3±1.7%) and total length of vessels (9.2±1.5 and 9.9±1.9%). On the other hand, thalidomide did not alter vascularization parameters. Consequently, addition of thiosemicarbazone pharmacophore group into the phthalimidic ring improved the in vivo antitumor and antiangiogenic potential of the analogs 2a and 2b.

Structural investigation of anti-Trypanosoma cruzi 2-iminothiazolidin-4-ones allows the identification of agents with efficacy in infected mice.

We modified the thiazolidinic ring at positions N3, C4, and C5, yielding compounds 6-24. Compounds with a phenyl at position N3, 15-19, 22-24, exhibited better inhibitory properties for cruzain and against the parasite than 2-iminothiazolidin-4-one 5. We were able to identify one high-efficacy trypanocidal compound, 2-minothiazolidin-4-one 18, which inhibited the activity of cruzain and the proliferation of epimastigotes and was cidal for trypomastigotes but was not toxic for splenocytes. Having located some of the structural determinants of the trypanocidal properties, we subsequently wished to determine if the exchange of the thiazolidine for a thiazole ring leaves the functional properties unaffected. We therefore tested thiazoles 26-45 and observed that they did not inhibit cruzain, but they exhibited trypanocidal effects. Parasite development was severely impaired when treated with 18, thus reinforcing the notion that this class of heterocycles can lead to useful cidal agents for Chagas disease.