Antimalarial hit 1SR (TCMDC-134674) identified in a GlaxoSmithKline cell based screening campaign was evaluated for inhibitory activity against the digestive vacuole plasmepsins (Plm I, II, and IV). It was found to be a potent Plm IV inhibitor with no selectivity over Cathepsin D. A cocrystal structure of 1SR bound to Plm II was solved, providing structural insight for the design of more potent and selective analogues. Structure-guided optimization led to the identification of structurally simplified analogues 17 and 18 as low nanomolar inhibitors of both, plasmepsin Plm IV activity and P. falciparum growth in erythrocytes.

2-Aminoquinazolin-4(3H)-ones were identified as a novel class of malaria digestive vacuole plasmepsin inhibitors by using NMR-based fragment screening against Plm II. Initial fragment hit optimization led to a submicromolar inhibitor, which was cocrystallized with Plm II to produce an X-ray structure of the complex. The structure showed that 2-aminoquinazolin-4(3H)-ones bind to the open flap conformation of the enzyme and provided clues to target the flap pocket. Further improvement in potency was achieved via introduction of hydrophobic substituents occupying the flap pocket. Most of the 2-aminoquinazolin-4(3H)-one based inhibitors show a similar activity against digestive Plms I, II, and IV and >10-fold selectivity versus CatD, although varying the flap pocket substituent led to one Plm IV selective inhibitor. In cell-based assays, the compounds show growth inhibition of Plasmodium falciparum 3D7 with IC50 ∼ 1 μM. Together, these results suggest 2-aminoquinazolin-4(3H)-ones as perspective leads for future development of an antimalarial agent.

Viral mRNA cap methyltransferases (MTases) are emerging targets for the development of broad-spectrum antiviral agents. In this work, we designed potential SARS-CoV-2 MTase Nsp14 and Nsp16 inhibitors by using bioisosteric substitution of the sulfonium and amino acid substructures of the cosubstrate S-adenosylmethionine (SAM), which serves as the methyl donor in the enzymatic reaction. The synthetically accessible target structures were prioritized using molecular docking. Testing of the inhibitory activity of the synthesized compounds showed nanomolar to submicromolar IC 50 values for five compounds. To evaluate selectivity, enzymatic inhibition of the human glycine N -methyltransferase involved in cellular SAM/SAH ratio regulation was also determined, which indicated that the discovered compounds are nonselective inhibitors of the studied MTases with slight selectivity for Nsp16. No cytotoxic effects were observed; however, this is most likely a result of the poor cell permeability of all evaluated compounds.

The highly infectious disease COVID-19 caused by the Betacoronavirus SARS-CoV-2 poses a severe threat to humanity and demands the redirection of scientific efforts and criteria to organized research projects. The international COVID19-NMR consortium seeks to provide such new approaches by gathering scientific expertise worldwide. In particular, making available viral proteins and RNAs will pave the way to understanding the SARS-CoV-2 molecular components in detail. The research in COVID19-NMR and the resources provided through the consortium are fully disclosed to accelerate access and exploitation. NMR investigations of the viral molecular components are designated to provide the essential basis for further work, including macromolecular interaction studies and high-throughput drug screening. Here, we present the extensive catalog of a holistic SARS-CoV-2 protein preparation approach based on the consortium’s collective efforts. We provide protocols for the large-scale production of more than 80% of all SARS-CoV-2 proteins or essential parts of them. Several of the proteins were produced in more than one laboratory, demonstrating the high interoperability between NMR groups worldwide. For the majority of proteins, we can produce isotope-labeled samples of HSQC-grade. Together with several NMR chemical shift assignments made publicly available on covid19-nmr.com, we here provide highly valuable resources for the production of SARS-CoV-2 proteins in isotope-labeled form.

Following up the open initiative of anti-malarial drug discovery, a GlaxoSmithKline (GSK) phenotypic screening hit was developed to generate hydroxyethylamine based plasmepsin (Plm) inhibitors exhibiting growth inhibition of the malaria parasite Plasmodium falciparum at nanomolar concentrations. Lead optimization studies were performed with the aim of improving Plm inhibition selectivity versus the related human aspartic protease cathepsin D (Cat D). Optimization studies were performed using Plm IV as a readily accessible model protein, the inhibition of which correlates with anti-malarial activity. Guided by sequence alignment of Plms and Cat D, selectivity-inducing structural motifs were modified in the S3 and S4 sub-pocket occupying substituents of the hydroxyethylamine inhibitors. This resulted in potent anti-malarials with an up to 50-fold Plm IV/Cat D selectivity factor. More detailed investigation of the mechanism of action of the selected compounds revealed that they inhibit maturation of the P. falciparum subtilisin-like protease SUB1, and also inhibit parasite egress from erythrocytes. Our results indicate that the anti-malarial activity of the compounds is linked to inhibition of the SUB1 maturase plasmepsin subtype Plm X.

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The cyclization of arylalkynes under selenobromination conditions, combined with an acid-induced 3,2-aryl shift, was elaborated as a general synthetic pathway for the preparation of polyhydroxy-2- and -3-arylbenzo[b]selenophenes from the same starting materials. The redox properties, free-radical-scavenging ability, and cytotoxicity against malignant cell lines (MCF-7, MDA-MB-231, HepG2, and 4T1) of the synthesized compounds were explored, and the obtained results were used to consider the structure-activity relationships (SARs) in these compounds. Consequently, the structural features that were responsible for the highly potent peroxyl-radical-scavenging activity were established.

The majority of nonantibacterial activities discovered for beta-lactam derivatives during the last 15 years are based on their ability to form a stable covalent complex with nucleophile in the active site of enzymes regulating fundamental physiological processes in mammalian organism such as serine and cysteine proteases, LDL phospholipase A(2), A-independent transacylase and some still indeciphered enzymes. Regulation of their catalytic activity both in vitro and in vivo by compounds designed on the cephalosporin, penicillin and 2-azetidinone base was successfully exploited in the treatment of inflammatory, respiratory, cardiovascular disorders, cancer and other pathologic processes. Availability of X-ray crystallographic data for target enzymes and computational molecular modelling in combination with wide possibilities of structural modifications for commercial natural and synthetic beta-lactams and the chiral blocks allow to consider this class of organic compounds as a perspective source of mechanism based nonantibacterial drugs.