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In 2019, the emergence of the seventh known coronavirus to cause severe illness in humans triggered a global effort towards the development of new drugs and vaccines for the SARS-CoV-2 virus. These efforts are still ongoing in 2024, including the present work where we conducted a ligand-based virtual screening of terpenes with potential anti-SARS-CoV-2 activity. We constructed a Quantitative Structure-Activity Relationship (QSAR) model from compounds with known activity against SARS-CoV-2 with a model accuracy of 0.71. We utilized this model to predict the activity of a series of 217 terpenes isolated from the Fabaceae family. Four compounds, predominantly triterpenoids from the lupane series, were subjected to an in vitro phenotypic screening in Vero CCL-81 cells to assess their inhibitory activity against SARS-CoV-2. The compounds which showed high rates of SARS-CoV-2 inhibition along with substantial cell viability underwent molecular docking at the SARS-CoV-2 main protease, papain-like protease, spike protein and RNA-dependent RNA polymerase. Overall, virtual screening through our QSAR model successfully identified compounds with the highest probability of activity, as validated using the in vitro study. This confirms the potential of the identified triterpenoids as promising candidates for anti-SARS-CoV-2 therapeutics.

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Amongst the potential contribution of protein or peptide-display systems to study epitopes with relevant immunological features, the RAD display system stands out as a highly stable scaffold protein that allows the presentation of constrained target peptides. Here, we employed the RAD display system to present peptides derived from the SARS-CoV-2 Spike (S) protein as a tool to detect specific serum antibodies and to generate polyclonal antibodies capable of inhibiting SARS-CoV-2 infectivity in vitro. 44 linear S-derived peptides were genetically fused with the RAD scaffold (RAD-SCoV-epitopes) and screened for antigenicity with sera collected from COVID-19-infected patients. In a second step, selected RAD-SCoV-epitopes were used to immunize mice and generate antibodies. Phenotypic screening showed that some of these antibodies were able to recognize replicating viral particles in VERO CCL-81 and most notably seven of the RAD-SCoV-epitopes were able to induce antibodies that inhibited viral infection. Our findings highlight the RAD display system as an useful platform for the immunological characterization of peptides and a potentially valuable strategy for the design of antigens for peptide-based vaccines, for epitope-specific antibody mapping, and for the development of antibodies for diagnostic and therapeutic purposes.

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The compound 3a,10b-dihydro-1H-cyclopenta[b]naphtho[2,3-d]furan-5,10-dione (IVS320) is a naphthoquinone with antifungal and antichagasic potential, which however has low aqueous solubility. To increase bioavailability, inclusion complexes with ß-cyclodextrin (ßCD) and methyl-ß-cyclodextrin (MßCD) were prepared by physical mixture (PM), kneading (KN) and rotary evaporation (RE), and their in vitro anti-SARS-CoV-2 and antichagasic potential was assessed. The formation of inclusion complexes led to a change in the physicochemical characteristics compared to IVS320 alone as well as a decrease in crystallinity degree that reached 74.44% for the IVS320-MßCD one prepared by RE. The IVS320 and IVS320-MßCD/RE system exhibited anti-SARS-CoV-2 activity, showing half maximal effective concentrations (EC50) of 0.47 and 1.22 µg/mL, respectively. Molecular docking simulation suggested IVS320 ability to interact with the SARS-CoV-2 viral protein. Finally, the highest antichagasic activity, expressed as percentage of Tripanosoma cruzi growth inhibition, was observed with IVS320-ßCD/KN (70%) and IVS320-MßCD/PM (72%), while IVS320 alone exhibited only approximately 48% inhibition at the highest concentration (100 µg/mL).

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High genetic and phenotypic variability between Leishmania species and strains within species make the development of broad-spectrum antileishmanial drugs challenging. Thus, screening panels consisting of several diverse Leishmania species can be useful in enabling compound prioritization based on their spectrum of activity. In this study, a robust and reproducible high content assay was developed, and 1280 small molecules were simultaneously screened against clinically relevant cutaneous and visceral species: L. amazonensis, L. braziliensis, and L. donovani. The assay is based on THP-1 macrophages infected with stationary phase promastigotes and posterior evaluation of both compound antileishmanial activity and host cell toxicity. The profile of compound activity was species-specific, and out of 51 active compounds, only 14 presented broad-spectrum activity against the three species, with activities ranging from 52% to 100%. Notably, the compounds CB1954, Clomipramine, Maprotiline, Protriptyline, and ML-9 presented pan-leishmanial activity, with efficacy greater than 70%. The results highlight the reduced number of compound classes with pan-leishmanial activity that might be available from diversity libraries, emphasizing the need to screen active compounds against a panel of species and strains. The assay reported here can be adapted to virtually any Leishmania species without the need for genetic modification of parasites, providing the basis for the discovery of broad spectrum anti-leishmanial agents.

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Introduction and objectives Direct antiviral agents (DAAs) are very efficient in inhibiting hepatitis C virus and might be used to treat infections caused by other flaviviruses whose worldwide detection has recently increased. The aim of this study was to verify the efficacy of DAAs in inhibiting yellow fever virus (YFV) by using drug repositioning (a methodology applied in the pharmaceutical industry to identify new uses for approved drugs). Materials and methods Three DAAs were evaluated: daclatasvir, sofosbuvir and ledipasvir or their combinations. For in vitro assays, the drugs were diluted in 100% dimethyl sulfoxide. Vaccine strain 17D and a 17D strain expressing the reporter fluorescent protein were used in the assays. A fast and reliable cell-based screening assay using Vero cells or Huh-7 cells (a hepatocyte-derived carcinoma ell line) was carried out. Two patients who acquired yellow fever virus with acute liver failure were treated with sofosbuvir for one week as a compassionate use. Results Using a high-content screening assay, we verified that sofosbuvir presented the best antiviral activity against YFV. Moreover, after an off-label treatment with sofosbuvir, the two female patients diagnosed with yellow fever infection displayed a reduction in blood viremia and an improvement in the course of the disease, which was observed in the laboratory medical parameters related to disease evolution. Conclusions Sofosbuvir may be used as an option for treatment against YFV until other drugs are identified and approved for human use. These results offer insights into the role of nonstructural protein 5 (NS5) in YFV inhibition and suggest that nonstructural proteins may be explored as drug targets for YFV treatment.

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The current methodologies used to identify promising new anthelmintic compounds rely on subjective microscopic examination of worm motility or involve genetic modified organisms. We describe a new methodology to detect worm viability that takes advantage of the differential incorporation of the fluorescent molecular marker propidium iodide and the 2,1,3-benzothiadiazole core, which has been widely applied in light technology. The new assay developed could be validated using the "Pathogen Box" library. By use of this bioassay, it was possible to identify three molecules with activity against Caenorhabditis elegans that were previously described as effective in in vitro assays against other pathogens, such as Schistosoma mansoni, Mycobacterium tuberculosis, and Plasmodium falciparum, accelerating the identification of molecules with anthelmintic potential. The current fluorescence-based bioassay may be used for assessing C. elegans viability. The described methodology replaces the subjectivity of previous assays and provides an enabling technology that is useful for rapid in vitro screens of both natural and synthetic compound libraries. It is expected that the results obtained from these robust in vitro screens would select the most effective compounds for follow-up in vivo experimentation with pathogenic helminths.

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Protozoan infections caused by Plasmodium, Leishmania, and Trypanosoma spp. contribute significantly to the burden of infectious diseases worldwide, causing severe morbidity and mortality. The inadequacy of available treatments calls for cost- and time-effective drug discovery endeavors. To this end, we envisaged the triazole linkage of privileged structures as an effective drug design strategy to generate a focused library of high-quality compounds. The versatility of this approach was combined with the feasibility of a phenotypic assay, integrated with early ADME-tox profiling. Thus, an 18-membered library was efficiently assembled via Huisgen cycloaddition of phenothiazine, biphenyl, and phenylpiperazine scaffolds. The resulting 18 compounds were then tested against seven parasite strains, and counter-screened for selectivity against two mammalian cell lines. In parallel, hERG and cytochrome P450 (CYP) inhibition, and mitochondrial toxicity were assessed. Remarkably, 10-((1-(3-([1,1-biphenyl]-3-yloxy)propyl)-1H-1,2,3-triazol-5-yl)methyl)-10H-phenothiazine (7) and 10-(3-(1-(3-([1,1-biphenyl]-3-yloxy)propyl)-1H-1,2,3-triazol-4-yl)propyl)-10H-phenothiazine (12) showed respective IC50 values of 1.8 and 1.9gmL(-1) against T.cruzi, together with optimal selectivity. In particular, compound 7 showed a promising ADME-tox profile. Thus, hit 7 might be progressed as an antichagasic lead.

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Basing on a library of thiadiazole derivatives showing anti-trypanosomatidic activity, we have considered the thiadiazoles opened forms and reaction intermediates, thiosemicarbazones, as compounds of interest for phenotypic screening against Trypanosoma brucei (Tb), intracellular amastigote form of Leishmania infantum (Li) and Trypanosoma cruzi (Tc). Similar compounds have already shown interesting activity against the same organisms. The compounds were particularly effective against T. brucei and T. cruzi. Among the 28 synthesized compounds, the best one was (E)-2-(4-((3.4-dichlorobenzyl)oxy)benzylidene) hydrazinecarbothioamide (A14) yielding a comparable anti-parasitic activity against the three parasitic species (TbEC50=231 mu M, LiEC50 = 6.14 mu M, TcEC50 = 1.31 mu M) and a Selectivity Index higher than 10 with respect to human macrophages, therefore showing a pan-anti-trypanosomatidic activity. (E)-2-((3'.4'-dimethoxy-[1.1'-biphenyl]-3-yl)methyle ne) hydrazinecarbothioamide (A12) and (E)-2-(4-((3.4-dichlorobenzyl)oxy)benzylidene)hydrazine carbothioamide (A14) were able to potentiate the anti parasitic activity of methotrexate (MTX) when evaluated in combination against T. brucei, yielding a 6 fold and 4-fold respectively Dose Reduction Index for MTX. The toxicity profile against four human cell lines and a panel of in vitro early-toxicity assays (comprising hERG, Aurora B, five cytochrome P450 isoforms and mitochondrial toxicity) demonstrated the low toxicity for the thosemicarbazones class in comparison with known drugs. The results confirmed thiosemicarbazones as a suitable chemical scaffold with potential for the development of properly decorated new anti-parasitic drugs.

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