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SARS-CoV-2 is a spherical, positive-sense, single-stranded RNA virus with a large genome, responsible for encoding both structural proteins, vital for the viral particle's architecture, and non-structural proteins, critical for the virus's replication cycle. Among the non-structural proteins, two cysteine proteases emerge as promising molecular targets for the design of new antiviral compounds. The main protease (Mpro) is a homodimeric enzyme that plays a pivotal role in the formation of the viral replication–transcription complex, associated with the papain-like protease (PLpro), a cysteine protease that modulates host immune signaling by reversing post-translational modifications of ubiquitin and interferon-stimulated gene 15 (ISG15) in host cells. Due to the importance of these molecular targets for the design and development of novel anti-SARS-CoV-2 drugs, the purpose of this review is to address aspects related to the structure, mechanism of action and strategies for the design of inhibitors capable of targeting the Mpro and PLpro. Examples of covalent and non-covalent inhibitors that are currently being evaluated in preclinical and clinical studies or already approved for therapy will be also discussed to show the advances in medicinal chemistry in the search for new molecules to treat COVID-19. [ABSTRACT FROM AUTHOR]

Heterocyclic compounds such as pyrrole and pyrrolidine derivatives have a broad spectrum of biological activity, being widely used as pharmacophore to design novel bioactive compounds. In this work, sixteen pyrrole and pyrrolidine derivatives were synthesized and evaluated for their growth inhibitory activity on two human cancer cells lines: breast cancer MDA‐MB‐231 and chronic myelogenous leukemia (K562). Eight compounds showed activity against at least one tumor cell line (IC50=49.15–195.9 μM). The compounds were tested in non‐cancerous human lung fibroblasts WI‐26VA4 to evaluate their selectivity index. In addition, Hierarchical Cluster Analysis (HCA) studies were carried out in attempt to establish a structure‐activity relationship. [ABSTRACT FROM AUTHOR]

The search for an effective small molecule against the severe acute respiratory syndrome related coronavirus 2 (SARS-CoV-2) is a challenge that remains even after the end of the Coronavirus disease 2019 (COVID-19) global health emergency. The indole-based ferulic acid derivatives were synthesized in this work and evaluated for their in vitro cytotoxic profiles and anti-SARS-CoV-2 activity. Compounds 1 and 2 decreased the number of genomic copies of SARS-CoV-2 in a dose-dependent manner, with IC50 values of 70.85 µM and 68.28 µM, respectively, with no significant cytotoxicity up to 100 µM against uninfected Vero cells. In order to search for a possible molecular target of these compounds, their activity against the two SARS-CoV-2 cysteine proteases, Mpro and PLpro, in addition to the human cysteine protease cathepsin L (hCatL) was investigated. However, they did not display significant activity against any of these proteases and, therefore, their mechanism of action remains unclear. Our findings suggest that the activity may be related to antioxidant properties of 1 and 2, since the presence of a phenolic group is critical for the antiviral activity. [ABSTRACT FROM AUTHOR]

Arboviral diseases caused by flaviviruses, such as dengue, are a continuing threat and major concern worldwide, with over three billion people estimated to be living with the risk of dengue virus (DENV) infections. There are thus far no antiviral drugs available for treatment, and limited or no vaccines are available. Curcumin and seven synthetic analogues were evaluated for their antiviral activity against dengue virus serotype 2, yellow fever virus and Zika virus, as well as for their cytotoxicity in Vero cells, both by employing MTT assays. Compounds 6 and 7, which present a thiazolylhydrazone moiety, showed moderate activity against all three flaviviruses, with selectivity index (SI) values up to 4.45. In addition, the envelope protein (E) was predicted as the potential target inhibited by both compounds, supported by molecular docking and dynamics simulation analysis. We hope that this data can contribute to the development of new curcumin antiviral analogues in the near future and can help in the search for new promising compounds as potential therapeutic agents to treat flaviviruses infections. [ABSTRACT FROM AUTHOR]

Chagas disease and Human African Trypanosomiasis, caused by Trypanosoma cruzi and T. brucei, respectively, pose relevant health challenges throughout the world, placing 65 to 70 million people at risk each. Given the limited efficacy and severe side effects associated with current chemotherapy, new drugs are urgently needed for both diseases. Here, we report the screening of the Pathogen Box collection against cruzain and TbrCatL, validated targets for Chagas disease and Human African Trypanosomiasis, respectively. Enzymatic assays were applied to screen 400 compounds, validate hits, determine IC50 values and, when possible, mechanisms of inhibition. In this case, 12 initial hits were obtained and ten were prioritized for follow-up. IC50 values were obtained for six of them (hit rate = 1.5%) and ranged from 0.46 ± 0.03 to 27 ± 3 µM. MMV687246 was found to be a mixed inhibitor of cruzain (Ki = 57 ± 6 µM) while MMV688179 was found to be a competitive inhibitor of cruzain with a nanomolar potency (Ki = 165 ± 63 nM). A putative binding mode for MMV688179 was obtained by docking. The six hits discovered against cruzain and TbrCatL are of great interest for further optimization by the medicinal chemistry community. [ABSTRACT FROM AUTHOR]

The Brazilian Compound Library (BraCoLi) is a novel open access and manually curated electronic library of compounds developed by Brazilian research groups to support further computer-aided drug design works, available on https://www.farmacia.ufmg.br/qf/downloads/. Herein, the first version of the database is described comprising 1176 compounds. Also, the chemical diversity and drug-like profiles of BraCoLi were defined to analyze its chemical space. A significant amount of the compounds fitted Lipinski and Veber's rules, alongside other drug-likeness properties. A comparison using principal component analysis showed that BraCoLi is similar to other databases (FDA-approved drugs and NuBBEDB) regarding structural and physicochemical patterns. Furthermore, a scaffold analysis showed that BraCoLi presents several privileged chemical skeletons with great diversity. Despite the similar distribution in the structural and physicochemical spaces, Tanimoto coefficient values indicated that compounds present in the BraCoLi are generally different from the two other databases, where they showed different kernel distributions and low similarity. These facts show an interesting innovative aspect, which is a desirable feature for novel drug design purposes. [ABSTRACT FROM AUTHOR]

Aim: All-trans retinoic acid (ATRA) shows erratic oral bioavailability when administered orally against leukemia, which can be solved through its incorporation in self-nanoemulsifying drug-delivery systems (SEDDS). The SEDDS developed contained a hydrophobic ion pair between benzathine (BZT) and ATRA and was enriched with tocotrienols by the input of a palm oil tocotrienol rich fraction (TRF) in its composition. Results: SEDDS-TRF-ATRA-BZT allowed the formation of emulsions with nanometric size that retained ATRA within their core after dispersion. Pharmacokinetic parameters after oral administration of SEDDS-TRF-ATRA-BZT in mice were improved compared with what was seen for an ATRA solution. Moreover, SEDDS-TRF-ATRA-BZT had improved activity against HL-60 cells compared with SEDDS without TRF. Conclusion: SEDDS-TRF-ATRA-BZT is a promising therapeutic choice over ATRA conventional medicine. SEDDS-TRF-ATRA-BZT after dispersion in ultrapure water produces nanoemulsions that have improved ATRA oral pharmacokinetics in Swiss male mice and improved its differentiation and cytotoxic properties against HL-60 cells. [ABSTRACT FROM AUTHOR]

Chagas disease remains a major health problem in South America, and throughout the world. The two drugs clinically available for its treatment have limited efficacy and cause serious adverse effects. Cruzain is an established therapeutic target of Trypanosoma cruzi, the protozoan that causes Chagas disease. Our group recently identified a competitive cruzain inhibitor (compound 1) with an IC50 = 15 µM that is also more synthetically accessible than the previously reported lead, compound 2. Prior studies, however, did not propose a binding mode for compound 1, hindering understanding of the structure-activity relationship and optimization. Here, the cruzain binding mode of compound 1 was investigated using docking, molecular dynamics (MD) simulations with ab initio derived parameters, ab initio calculations, and MM/PBSA. Two ligand protonation states and four binding poses were evaluated. A careful ligand parameterization method was employed to derive more physically meaningful parameters than those obtained by automated tools. The poses of unprotonated 1 were unstable in MD, showing large conformational changes and diffusing away from the binding site, whereas the protonated form showed higher stability and interaction with negatively charged residues Asp161 and Cys25. MM/PBSA also suggested that these two residues contribute favorably to binding of compound 1. By combining results from MD, ab initio calculations, and MM/PBSA, a binding mode of 1 is proposed. The results also provide insights for further optimization of 1, an interesting lead compound for the development of new cruzain inhibitors. [ABSTRACT FROM AUTHOR]

The nitroaromatic compound 4-bromomethyl-3-nitrobenzoic acid (ANB) is a promising antitumoral agent whose activity has recently been investigated. Forced degradation studies were conducted on ANB with a high-performance liquid chromatography–ultraviolet assay to establish its stability and selectivity. ANB was subjected to degradation studies under hydrolytic (acid and alkaline), oxidative and light exposition conditions. The compound showed greater lability only in acid and alkaline conditions by forming a major degradation product. The chromatographic separation of ANB and its degradation product was achieved on an octadecylsilane column using a mobile phase of methanol–water (80:20, v/v), pH 4.0 adjusted with formic acid, flow rate of 0.7 mL/min, ultraviolet diode array detection at λ 271 nm, injection volume of 20 µL and temperature of 30°C. The method was validated according to International Conference on Harmonization guidelines with respect to precision (average relative standard deviation 0.67%), accuracy (average 99.97%), linearity (y = 118730x + 12912; coefficient of determination > 0.999), specificity and robustness (p > 0.05). The degradation product formed as a result from the hydrolysis of nitrobenzyl bromide, corresponded to its benzyl alcohol, 4-hydroxymethyl-3-nitrobenzoic acid (ANOH) and was characterized by co-elution with a synthetic ANOH working standard. [ABSTRACT FROM PUBLISHER]

In our search for new anticancer therapies, some compounds synthesized in our lab were selected and their potential cytotoxic activity was evaluated in vitro against two cancer cells lines including a solid tumor (UACC-62, melanoma) and a human lymphoma (JURKAT). Compounds showing cytotoxic activity were subjected to an apoptosis assay. Two compounds showed promising results. [ABSTRACT FROM AUTHOR]