The Future of Drug Development for Neglected Tropical Diseases: How the European Commission Can Continue to Make a Difference

In this article, the four coordinators of neglected tropical disease (NTD) drug development projects funded under the European Commission (EC) Framework Programme 7 argue that the EC should reassess their funding strategy to cover the steps necessary to translate a lead compound into a drug candidate for testing in clinical trials, and suggest ways in which this might be achieved

Homogeneous, Real-Time NanoBRET Binding Assays for the Histamine H₃ and H₄ Receptors on Living Cells

Receptor-binding affinity and ligand-receptor residence time are key parameters for the selection of drug candidates and are routinely determined using radioligand competition-binding assays. Recently, a novel bioluminescence resonance energy transfer (BRET) method utilizing a NanoLuc-fused receptor was introduced to detect fluorescent ligand binding. Moreover, this NanoBRET method gives the opportunity to follow fluorescent ligand binding on intact cells in real time, and therefore, results might better reflect in vivo conditions as compared with the routinely used cell homogenates or purified membrane fractions. In this study, a real-time NanoBRET-based binding assay was established and validated to detect binding of unlabeled ligands to the histamine H3 receptor (H3R) and histamine H4 receptor on intact cells. Obtained residence times of clinically tested H3R antagonists were reflected by their duration of H3R antagonism in a functional receptor recovery assay

Growth, maturity, and diet of the pearl whipray (<i>Fontitrygon margaritella</i>) from the Bijagós Archipelago, Guinea-Bissau

The pearl whipray Fontitrygon margaritella (Compagno & Roberts, 1984) is a common elasmobranch in coastal western African waters. However, knowledge on their life-history and trophic ecology remains limited. Therefore, we aimed to determine the growth, maturity and diet of F. margaritella from the Bijagós Archipelago in Guinea-Bissau. Growth was modelled with: von Bertalanffy, Gompertz and logistic functions. Model selection revealed no model significantly outperformed another. The sampled age ranged from less than 1 to 7 years (1.8 ± 1.9 cm, mean ± standard deviation) and size (disc width) ranged from 12.2 to 30.6 cm (18.7 ± 5.2 cm). Size-at-maturity was estimated at 20.3 cm (95% CI [18.8–21.8 cm]) for males and 24.3 cm for females (95% CI [21.9–26.5 cm]), corresponding ages of 2.2 and 3.9 years. The diet differed significantly among young-of-the-year (YOY), juveniles and adults (p = 0.001). Diet of all life stages consisted mainly of crustaceans (27.4%, 28.5%, 33.3%) and polychaetes (12.5%, 26.7%, 20.3%), for YOY, juveniles and adults respectively. This study shows that F. margaritella is relatively fast-growing, matures early and experiences ontogenetic diet shifts. These results contribute to status assessments and conservation efforts of F. margaritella and closely related species

Label-Free Analysis with Multiple Parameters Separates G Protein-Coupled Receptor Signaling Pathways

Real-time label-free techniques are used to profile G protein-coupled receptor (GPCR) signaling pathways in living cells. However, interpreting the label-free signal responses is challenging, and previously reported methods do not reliably separate pathways from each other. In this study, a continuous angular-scanning surface plasmon resonance (SPR) technique is utilized for measuring label-free GPCR signal profiles. We show how the continuous angular-scanning ability, measuring up to nine real-time label-free parameters simultaneously, results in more information-rich label-free signal profiles for different GPCR pathways, providing a more accurate pathway separation. For this, we measured real-time full-angular SPR response curves for Gs, Gq, and Gi signaling pathways in living cells. By selecting two of the most prominent label-free parameters: the full SPR curve angular and intensity shifts, we present how this analysis approach can separate each of the three signaling pathways in a straightforward single-step analysis setup, without concurrent use of signal inhibitors or other response modulating compounds

3-nitroimidazo[1,2-b]pyridazine as a novel scaffold for antiparasitics with sub-nanomolar anti-Giardia lamblia activity.

As there is a continuous need for novel anti-infectives, the present study aimed to fuse two modes of action into a novel 3-nitroimidazo[1,2-b]pyridazine scaffold to improve antiparasitic efficacy. For this purpose, we combined known structural elements of phosphodiesterase inhibitors, a target recently proposed for Trypanosoma brucei and Giardia lamblia, with a nitroimidazole scaffold to generate nitrosative stress. The compounds were evaluated in vitro against a panel of protozoal parasites, namely Giardia lamblia, Trypanosoma brucei, T. cruzi, Leishmania infantum and Plasmodium falciparum and for cytotoxicity on MRC-5 cells. Interestingly, selective sub-nanomolar activity was obtained against G. lamblia, and by testing several analogues with and without the nitro group, it was shown that the presence of a nitro group, but not PDE inhibition, is responsible for the low IC50 values of these novel compounds. Adding the favourable drug-like properties (low molecular weight, cLogP (1.2-4.1) and low polar surface area), the key compounds from the 3-nitroimidazo[1,2-b]pyridazine series can be considered as valuable hits for further anti-giardiasis drug exploration and development

Modulators of CXCR4 and CXCR7/ACKR3 Function

Copyright © 2019 by The Author(s). The two G protein-coupled receptors (GPCRs) C-X-C chemokine receptor type 4 (CXCR4) and atypical chemokine receptor 3 (ACKR3) are part of the class A chemokine GPCR family and represent important drug targets for human immunodeficiency virus (HIV) infection, cancer, and inflammation diseases. CXCR4 is one of only three chemokine receptors with a US Food and Drug Administration approved therapeutic agent, the small-molecule modulator AMD3100. In this review, known modulators of the two receptors are discussed in detail. Initially, the structural relationship between receptors and ligands is reviewed on the basis of common structural motifs and available crystal structures. To date, no atypical chemokine receptor has been crystallized, which makes ligand design and predictions for these receptors more difficult. Next, the selectivity, receptor activation, and the resulting ligand-induced signaling output of chemokines and other peptide ligands are reviewed. Binding of pepducins, a class of lipid-peptides whose basis is the internal loop of a GPCR, to CXCR4 is also discussed. Finally, small-molecule modulators of CXCR4 and ACKR3 are reviewed. These modulators have led to the development of radio- and fluorescently labeled tool compounds, enabling the visualization of ligand binding and receptor characterization both in vitro and in vivo. SIGNIFICANCE STATEMENT: To investigate the pharmacological modulation of CXCR4 and ACKR3, significant effort has been focused on the discovery and development of a range of ligands, including small-molecule modulators, pepducins, and synthetic peptides. Imaging tools, such as fluorescent probes, also play a pivotal role in the field of drug discovery. This review aims to provide an overview of the aforementioned modulators that facilitate the study of CXCR4 and ACKR3 receptors

Probe dependency in the determination of ligand binding kinetics at a prototypical G protein-coupled receptor

© 2019, The Author(s). Drug-target binding kinetics are suggested to be important parameters for the prediction of in vivo drug-efficacy. For G protein-coupled receptors (GPCRs), the binding kinetics of ligands are typically determined using association binding experiments in competition with radiolabelled probes, followed by analysis with the widely used competitive binding kinetics theory developed by Motulsky and Mahan. Despite this, the influence of the radioligand binding kinetics on the kinetic parameters derived for the ligands tested is often overlooked. To address this, binding rate constants for a series of histamine H1 receptor (H1R) antagonists were determined using radioligands with either slow (low koff) or fast (high koff) dissociation characteristics. A correlation was observed between the probe-specific datasets for the kinetic binding affinities, association rate constants and dissociation rate constants. However, the magnitude and accuracy of the binding rate constant-values was highly dependent on the used radioligand probe. Further analysis using recently developed fluorescent binding methods corroborates the finding that the Motulsky-Mahan methodology is limited by the employed assay conditions. The presented data suggest that kinetic parameters of GPCR ligands depend largely on the characteristics of the probe used and results should therefore be viewed within the experimental context and limitations of the applied methodology

Principals in Programming Languages: Technical Results

This is the companion technical report for ``Principals in Programming Languages'' [20]. See that document for a more readable version of these results. In this paper, we describe two variants of the simply typed $\lambda$-calculus extended with a notion of {\em principal}. The results are languages in which intuitive statements like ``the client must call $\mathtt{open}$ to obtain a file handle'' can be phrased and proven formally. The first language is a two-agent calculus with references and recursive types, while the second language explores the possibility of multiple agents with varying amounts of type information. We use these calculi to give syntactic proofs of some type abstraction results that traditionally require semantic arguments