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Different molecular mechanisms contribute to the development of multidrug resistance in cancer, including increased drug efflux, enhanced cellular repair mechanisms and alterations of drug metabolism or drug targets. ABCG2 is a member of the ATP-binding cassette superfamily transporters that promotes drug efflux, inducing chemotherapeutic resistance in malignant cells. In this context, the development of selective ABCG2 inhibitors might be a suitable strategy to improve chemotherapy efficacy. Thus, through a multidisciplinary approach, we identified a new ABCG2 selective inhibitor (8), highlighting its ability to increase mitoxantrone cytotoxicity in both hepatocellular carcinoma (EC50from 8.67 ± 2.65 to 1.25 ± 0.80 μM) and transfected breast cancer cell lines (EC50from 9.92 ± 2.32 to 2.45 ± 1.40 μM). Moreover, mitoxantrone co-administration in both transfected and non-transfected HEK293 revealed that compound 8 notably lowered the mitoxantrone EC50, demonstrating its efficacy along with the importance of the ABCG2 extrusion pump overexpression in MDR reversion. These results were corroborated by evaluating the effect of inhibitor 8 on mitoxantrone cell uptake in multicellular tumor spheroids and via proteomic experiments.

Trypanosomiases are neglected tropical diseases caused by Trypanosoma (sub)species. Available treatments are limited and have considerable adverse effects and questionable efficacy in the chronic stage of the disease, urgently calling for the identification of new targets and drug candidates. Recently, we have shown that impairment of glycosomal protein import by the inhibition of the PEX5-PEX14 protein-protein interaction (PPI) is lethal to Trypanosoma. Here, we report the development of a novel dibenzo[b,f][1,4]oxazepin-11(10H)-one scaffold for small molecule inhibitors of PEX5-PEX14 PPI. The initial hit was identified by a high throughput screening (HTS) of a library of compounds. A bioisosteric replacement approach allowed to replace the metabolically unstable sulphur atom from the initial dibenzo[b,f][1,4]thiazepin-11(10H)-one HTS hit with oxygen. A crystal structure of the hit compound bound to PEX14 surface facilitated the rational design of the compound series accessible by a straightforward chemistry for the initial structure-activity relationship (SAR) analysis. This guided the design of compounds with trypanocidal activity in cell-based assays providing a promising starting point for the development of new drug candidates to tackle trypanosomiases.

Procedures for producing and exploring Trypanosoma cruzi farnesyl pyrophosphate synthase (tcFPPS) for surface plasmon resonance (SPR) biosensor‐driven fragment‐based discovery have been established. The method requires functional sensor surfaces with high sensitivity for extended times and appropriate controls. Initial problems with protein stability and lack of useful reference compounds motivated optimization of experimental procedures and conditions. The improved methods enabled the production of pure, folded and dimeric protein, and identified procedures for storage and handling. A new coupled enzymatic assay, using luciferase for detection of pyrophosphate, was developed and used to confirm that the purified enzyme was active after purification and storage. It also confirmed that sensor surfaces prepared with structurally intact protein was active. An SPR‐biosensor assay for fragment library screening and hit confirmation was developed. A thermal shift assay was used in parallel. A library of 90 fragments was efficiently screened by both assays at a single concentration in the presence and absence of the catalytic cofactor Mg2+. Hits were selected on the basis of response levels or ΔT m > 1°C and selectivity for tcFPPS in the presence of Mg2+. Characterization of hits by SPR showed that all had low affinities and the relationships between steady‐state responses and concentrations were not sufficiently hyperbolic for determination of KD‐values. Instead, ranking could be performed from the slope of the linear relationship at low concentrations. This pilot screen confirms that the procedures developed herein enables SPR‐biosensor driven fragment‐based discovery of leads targeting tcFPPS, despite the lack of a reference compound. Significance Statement To enable the discovery of drugs, it is essential to have access to relevant forms of the target protein and valid biochemical methods for studying the protein and effects of compounds that may be evolved into drugs. We have established methods for the discovery of drugs for treatment of American Trypanosomiasis (Chagas disease), using farnesyl pyrophosphate synthase from Trypanosoma cruzi as a target.

We show that a water envelope network plays a critical role in protein-protein interactions (PPI). The potency of a PPI inhibitor is modulated by orders of magnitude on manipulation of the solvent envelope alone. The structure-activity relationship of PEX14 inhibitors was analyzed as an example using in silico and X-ray data.

The COVID-19 pandemic caused by SARS-CoV-2 has been socially and economically devastating. Despite an unprecedented research effort and available vaccines, effective therapeutics are still missing to limit severe disease and mortality. Using high-throughput screening, we identify acriflavine (ACF) as a potent papain-like protease (PLpro) inhibitor. NMR titrations and a co-crystal structure confirm that acriflavine blocks the PLpro catalytic pocket in an unexpected binding mode. We show that the drug inhibits viral replication at nanomolar concentration in cellular models, in vivo in mice and ex vivo in human airway epithelia, with broad range activity against SARS-CoV-2 and other betacoronaviruses. Considering that acriflavine is an inexpensive drug approved in some countries, it may be immediately tested in clinical trials and play an important role during the current pandemic and future outbreaks., Graphical abstract, Napolitano et al. discovered acriflavine (ACF), a clinically approved drug, as an effective inhibitor of SARS-CoV-2 papain-like protease (PLpro). ACF inhibits viral replication at nanomolar concentrations in vitro and ex vivo, as well as in vivo. These findings open a promising therapeutic approach against COVID-19 and other betacoronaviruses.

Trypanosomiases are life-threatening infections of humans and livestock, and novel effective therapeutic approaches are needed. Trypanosoma compartmentalize glycolysis into specialized organelles termed glycosomes. Most of the trypanosomal glycolytic enzymes harbor a peroxisomal targeting signal-1 (PTS1) which is recognized by the soluble receptor PEX5 to facilitate docking and translocation of the cargo into the glycosomal lumen. Given its pivotal role in the glycosomal protein import, the PEX5–PTS1 interaction represents a potential target to inhibit import of glycolytic enzymes and thus kill the parasite. We developed a fluorescence polarization (FP)-based assay for monitoring the PEX5–PTS1 interaction and performed a High Throughput Screening (HTS) campaign to identify small molecule inhibitors of the interaction. Six of the identified hits passed orthogonal selection criteria and were found to inhibit parasite growth in cell culture. Our results validate PEX5 as a target for small molecule inhibitors and provide scaffolds suitable for further pre-clinical development of novel trypanocidal compounds.

African and American trypanosomiases are estimated to affect several million people across the world, with effective treatments distinctly lacking. New, ideally oral, treatments with higher efficacy against these diseases are desperately needed. Peroxisomal import matrix (PEX) proteins represent a very interesting target for structure- and ligand-based drug design. The PEX5-PEX14 protein-protein interface in particular has been highlighted as a target, with inhibitors shown to disrupt essential cell processes in trypanosomes, leading to cell death. In this work, we present a drug development campaign that utilizes the synergy between structural biology, computer-aided drug design, and medicinal chemistry in the quest to discover and develop new potential compounds to treat trypanosomiasis by targeting the PEX14-PEX5 interaction. Using the structure of the known lead compounds discovered by Dawidowski et al. as the template for a chemically advanced template search (CATS) algorithm, we performed scaffold-hopping to obtain a new class of compounds with trypanocidal activity, based on 2,3,4,5-tetrahydrobenzo[f][1,4]oxazepines chemistry. The initial compounds obtained were taken forward to a first round of hit-to-lead optimization by synthesis of derivatives, which show activities in the range of low- to high-digit micromolar IC50 in the in vitro tests. The NMR measurements confirm binding to PEX14 in solution, while immunofluorescent microscopy indicates disruption of protein import into the glycosomes, indicating that the PEX14-PEX5 protein-protein interface was successfully disrupted. These studies result in development of a novel scaffold for future lead optimization, while ADME testing gives an indication of further areas of improvement in the path from lead molecules toward a new drug active against trypanosomes. ISSN:1549-9596 ISSN:0095-2338 ISSN:1520-5142

International audience; The interaction between the Shiga toxin B-subunit (STxB) and its globotriaosylceramide receptor (Gb3) has a high potential for being exploited for targeted cancer therapy. The primary goal of this study was to evaluate the capacity of STxB to carry small molecules and proteins as cargo into cells. For this purpose, an assay was designed to provide real-time information about the StxB-Gb3 interaction as well as the dynamics and mechanism of the internalization process. The assay revealed the ability to distinguish the process of binding to the cell surface from internalization and presented the importance of receptor and STxB clustering for internalization. The overall setup demonstrated that the binding mechanism is complex, and the concept of affinity is difficult to apply. Hence, time-resolved methods, providing detailed information about the interaction of STxB with cells, are critical for the optimization of intracellular delivery.

Trypanosoma protists are pathogens leading to a spectrum of devastating infectious diseases. The range of available chemotherapeutics against Trypanosoma is limited, and the existing therapies are ...

Despite aptamers are very promising alternative to antibodies, very few of them are under clinical trials or are used as drugs. Among them, NU172 is currently in Phase II as anticoagulant in heart disease treatments. It inhibits thrombin activity much more effectively than TBA, the best-known thrombin binding aptamer. The crystal structure of thrombin-NU172 complex reveals a bimodular duplex/quadruplex architecture for the aptamer, which binds thrombin exosite I through a highly complementary surface involving all three loops of the G-quadruplex module. Although the duplex domain does not interact directly with thrombin, the features of the duplex/quadruplex junction and the solution data on two newly designed NU172 mutants indicate that the duplex moiety is important for the optimization of the protein-ligand interaction and for the inhibition of the enzyme activity. Our work discloses the structural features determining the inhibition of thrombin by NU172 and put the basis for the design of mutants with improved properties.

Mixed duplex/quadruplex oligonucleotides have attracted great interest as therapeutic targets as well as effective biomedical aptamers. In the case of thrombin-binding aptamer (TBA), the addition of a duplex motif to the G-quadruplex module improves the aptamer resistance to biodegradation and the affinity for thrombin. In particular, the mixed oligonucleotide RE31 is significantly more effective than TBA in anticoagulation experiments and shows a slower disappearance rate in human plasma and blood. In the crystal structure of the complex with thrombin, RE31 adopts an elongated structure in which the duplex and quadruplex regions are perfectly stacked on top of each other, firmly connected by a well-structured junction. The lock-and-key shape complementarity between the TT loops of the G-quadruplex and the protein exosite I gives rise to the basic interaction that stabilizes the complex. However, our data suggest that the duplex motif may have an active role in determining the greater anti-thrombin activity in biological fluids with respect to TBA. This work gives new information on mixed oligonucleotides and highlights the importance of structural data on duplex/quadruplex junctions, which appear to be varied, unpredictable, and fundamental in determining the aptamer functional properties.

The essay invites to read the book edited in 2010 by Maura Striano, Pratiche educative per l’inclusione sociale, focalising some international and European initiatives aimed at promoting lifelong learning interventions addressed to “weak” categories of peoples. Compared to these, is the adoption of a gender perspective, according to which the limited recognition of the rights of citizenship of women in terms of education, employment status and political participation is linked to symbolic discrimination of a culture called “universal”, but deeply rooted in male values.

Analisi della misura di sicurezza che si aggiunge alla pena per il delitto di usura e la natura eccentrica della prescrizione del reato