Cristina Fonseca-Berzal

Synthesis, biological evaluation and chemometric analysis of indazole derivatives. 1,2-Disubstituted 5-nitroindazolinones, new prototypes of antichagasic drug

Chagas disease chemotherapy, currently based on only two drugs, nifurtimox and benznidazole, is far from satisfactory and therefore the development of new antichagasic compounds remains an important goal. On the basis of antichagasic properties previously described for some 1,2-disubstituted 5-nitroindazolin-3-ones (21, 33) and in order to initiate the optimization of activity of this kind of compounds, we have prepared a series of related analogs (22-32, 34-38, 58 and 59) and tested in vitro these products against epimastigote forms of Trypanosoma cruzi. 2-Benzyl-1-propyl (22), 2-benzyl-1-isopropyl (23) and 2-benzyl-1-butyl (24) derivatives have shown high trypanocidal activity and low unspecific toxicity. Other indazole derivatives with different substitution patterns (1-substituted 3-alkoxy-1H-indazoles and 2-substituted 3-alkoxy-2H-indazoles), arising from the synthetic procedures used to prepare the mentioned indazolinones, have moderate to low effectiveness. The exploration of SAR information using the concept of an activity landscape has been carried out with SARANEA software. We have also searched for structural similarities between 225 known antiprotozoan drugs and compound 22. The results confirm that compounds 22-24 constitute promising leads and that 5-nitroindazolin-3-one system is a novel anti-T. cruzi scaffold which may represent an important therapeutic alternative for the treatment of Chagas disease.

Development of novel benznidazole formulations: Physicochemical characterization and in vivo evaluation on parasitemia reduction in Chagas disease

This work aims to develop novel benznidazole (BZN) solid dispersions (SD) to improve its solubility and bioavailability properties. Low-substituted hydroxypropylcellulose (L-HPC) and sodium deoxycholate (NaDC) were evaluated as carriers. BZN solid dispersions containing different ratios of carrier were prepared by a freeze-drying process and characterized by SEM, powder X-ray diffraction (XRD), differential scanning calorimetry (DSC) and dissolution studies. The reduced BNZ crystallinity in the new formulations was confirmed by XRD, and supported by DSC. BNZ:L-HPC solid dispersion at a 1:3 ratio (w/w) (SD-1:3 L-HPC) improved the BNZ dissolution rate (85% at 5 min) in comparison with BNZ raw material (23% at 5 min). However, NaDC formulations showed a prolonged release (24% at 30 min for SD-1:3 NaDC), due to the formation of a sustained release matrix in acidic medium. In vivo studies performed in a murine model of Chagas disease showed that the formulation achieving the highest parasitemia suppression at a low dose of 25mg/kg/day after five days of treatment was SD-1:3 L-HPC (60% of parasitemia suppression versus 33% of suppression exerted by BNZ), suggesting that BNZ:L-HPC systems enhance the bioavailability of the drug.

In vitro phenotypic screening of 7-chloro-4-amino(oxy)quinoline derivatives as putative anti-Trypanosoma cruzi agents

In this study, a series of 22 pre-synthesized 7-chloro-4-amino(oxy)quinoline derivatives was assayed in vitro as potential antichagasic agents. A primary screening against Trypanosoma cruzi epimastigotes and a non-specific cytotoxicity assay on murine fibroblasts were simultaneously performed, resulting quinolines 3, 7 and 12 with great selectivity (SI) on the extracellular parasite (SI7, SI3, SI12 and SIBZ >9.44). Therefore, the activity of these derivatives was evaluated on intracellular amastigotes, achieving derivative 7 the best SI (SI=12.73). These results, supported by the in silico prediction of a good oral bioavailability and a suitable risk profile, propose the 4-amino-7-chloroquinoline scaffold as a potential template for designing trypanocidal prototypes.

Novel solid dispersions of benznidazole: preparation, dissolution profile and biological evaluation as alternative antichagasic drug delivery system.

Solid dispersions (SD) of benznidazole (BNZ) in sodium deoxycholate (NaDC) or low-substituted hydroxypropylcellulose (L-HPC) were developed by freeze-drying process to improve the solubility of this low water-soluble drug and consequently, its trypanocidal activity. Although the dissolution studies showed a progressive decrease in the release rate of BNZ when formulated in the presence of NaDC, the increase in the surfactant concentration resulted in a better trypanocidal profile on epimastigotes, as well as in an enhancement of the unspecific cytotoxicity. However, such an effect was not so evident on amastigotes and in vivo (blood-trypomastigotes), where high concentrations of surfactant (BNZ:NaDC ≥ 1:6) experimented a loss of activity, correlating this fact with the minor cession of BNZ these formulations accomplished in acidic locations (i.e., dissolution test medium). According to the in vitro results, we reformulated the promising SD-1:3 (IC₅₀ epimastigotes = 33.92 ± 6.41 µM, IC₅₀ amastigotes = 0.40 ± 0.05 µM and LC₅₀ = 183.87 ± 12.30 µM) replacing NaDC by L-HPC, which achieved the fastest dissolution profile. This fact, together with the safety this carrier ensures (LC₅₀ > 256 µM), prompted us to evaluate the cellulose SD in vivo, improving the effectiveness of its NaDC equivalent (%AUPC = 96.65% and 91.93%, respectively). The results compiled in the present work suggest these solid dispersions as alternative drug delivery systems to improve the limited chemotherapy of Chagas disease.

Trypanocidal Activity of Long Chain Diamines and Aminoalcohols

Thirteen aminoalcohols and eight diamines were obtained and tested against Trypanosoma cruzi epimastigotes strains MG, JEM and CL-B5 clone. Some of them were equal or more potent (1.0–6.6 times) than the reference compound nifurtimox. From them, three aminoalcohols and two diamines were selected for amastigotes assays. Compound 5 was as potent as the reference drug nifurtimox against amastigotes of the CL-B5 strain (IC50 = 0.6 µM), with a selectivity index of 54.

Antichagasic, Leishmanicidal, and Trichomonacidal Activity of 2-Benzyl-5-nitroindazole-Derived Amines

Three different series of new 5‐nitroindazole derivatives—1‐(ω‐aminoalkyl)‐2‐benzylindazolin‐3‐ones (series A; ten compounds), 3‐(ω‐aminoalkoxy)‐2‐benzylindazoles (series B; four compounds) and 3‐alkylamino‐2‐benzylindazoles (series C; five compounds)—have been synthesized and evaluated against the protozoan parasites Trypanosoma cruzi, Leishmania amazonensis, and Trichomonas vaginalis: etiological agents of Chagas disease, cutaneous leishmaniasis, and trichomoniasis, respectively. Many indazoles of series A, B, and C were efficient against T. cruzi. Some compounds in series A, after successfully passing the preliminary screening for epimastigotes, exhibited activity values against amastigotes of several T. cruzi strains that were better than or similar to those shown by the reference drug benznidazole and displayed low nonspecific toxicity against mammalian cells. On the other hand, preliminary studies against promastigotes of L. amazonensis showed high leishmanicidal activity for some derivatives of series A and C. With regard to activity against T. vaginalis, some indazoles of series B and C were rather efficient against trophozoites of a metronidazole‐sensitive isolate and showed low nonspecific toxicities toward Vero cell cultures. Additionally, some of these compounds displayed similar activity against metronidazole‐sensitive and resistant isolates, showing the absence of cross‐resistance between these derivatives and the reference drug.

New imidazole-based compounds active against Trypanosoma cruzi

BACKGROUND Current drugs available for the treatment of Chagas disease are fraught with several challenges including severe toxicity and limited efficacy. These factors coupled with the absence of effective drugs for treating the chronic stage of the disease have rendered the development of new drugs against Chagas disease a priority. OBJECTIVE This study screened several imidazole-based compounds for anti-Trypanosoma potential. METHOD Using an in vitro experimental infection model, several imidazole-based compounds were screened for anti-proliferative effect on Trypanosoma cruzi epimastigotes. Additionally, all test compounds were evaluated for unspecific cytotoxicity on L929 murine fibroblasts. Benznidazole (BZN) served as reference drug. RESULTS All test compounds demonstrated interesting trypanocidal potential with IC50 values in the μM range (1< 1C50 <8 μM). The activities of the test compounds compared favorably with BZN, which had an IC50 value ca. 30 μM. Conversely, most of the test compounds were highly cytotoxic, resulting in selectivity lower than that of BZN (SI > 9.42). CONCLUSION We provide evidence which implicate the imidazole-based compounds as potential prototypes for the development of anti-parasitic agents. Findings have far-reaching relevance to drug discovery efforts for trypanosomiasis.

Experimental models in Chagas disease: a review of the methodologies applied for screening compounds against Trypanosoma cruzi

One of the main problems of Chagas disease (CD), the parasitic infection caused by Trypanosoma cruzi, is the lack of a completely satisfactory treatment, which is currently based on two old nitroheterocyclic drugs (i.e., nifurtimox and benznidazole) that show important limitations for treating patients. In this context, many laboratories look for alternative therapies potentially applicable to the treatment, and therefore, research in CD chemotherapy works in the design of experimental protocols for detecting molecules with activity against T. cruzi. Phenotypic assays are considered the most valuable strategy for screening these antiparasitic compounds. Among them, in vitro experiments are the first step to test potential anti-T. cruzi drugs directly on the different parasite forms (i.e., epimastigotes, trypomastigotes, and amastigotes) and to detect cytotoxicity. Once the putative trypanocidal drug has been identified in vitro, it must be moved to in vivo models of T. cruzi infection, to explore (i) acute toxicity, (ii) efficacy during the acute infection, and (iii) efficacy in the chronic disease. Moreover, in silico approaches for predicting activity have emerged as a supporting tool for drug screening procedures. Accordingly, this work reviews those in vitro, in vivo, and in silico methods that have been routinely applied during the last decades, aiming to discover trypanocidal compounds that contribute to developing more effective CD treatments.

Activity of 2-benzyl-1-(2-hydroxyethyl)-5-nitroindazolin-3-one on Trypanosoma cruzi Bloodstream Trypomastigotes (Y strain): In Vitro and In Vivo Studies

Benznidazole and nifurtimox, the currently available drugs for the specific treatment of Chagas disease, show limited effectiveness and high toxicity that prompt the identification of therapeutic alternatives. [...]