Design, quality and validation of the EU-OPENSCREEN fragment library poised to a high-throughput screening collection.

The EU-OPENSCREEN (EU-OS) European Research Infrastructure Consortium (ERIC) is a multinational, not-for-profit initiative that integrates high-capacity screening platforms and chemistry groups across Europe to facilitate research in chemical biology and early drug discovery. Over the years, the EU-OS has assembled a high-throughput screening compound collection, the European Chemical Biology Library (ECBL), that contains approximately 100 000 commercially available small molecules and a growing number of thousands of academic compounds crowdsourced through our network of European and non-European chemists. As an extension of the ECBL, here we describe the computational design, quality control and use case screenings of the European Fragment Screening Library (EFSL) composed of 1056 mini and small chemical fragments selected from a substructure analysis of the ECBL. Access to the EFSL is open to researchers from both academia and industry. Using EFSL, eight fragment screening campaigns using different structural and biophysical methods have successfully identified fragment hits in the last two years. As one of the highlighted projects for antibiotics, we describe the screening by Bio-Layer Interferometry (BLI) of the EFSL, the identification of a 35 µM fragment hit targeting the beta-ketoacyl-ACP synthase 2 (FabF), its binding confirmation to the protein by X-ray crystallography (PDB 8PJ0), its subsequent rapid exploration of its surrounding chemical space through hit-picking of ECBL compounds that contain the fragment hit as a core substructure, and the final binding confirmation of two follow-up hits by X-ray crystallography (PDB 8R0I and 8R1V).

Activity of alkoxyamide-based histone deacetylase inhibitors against Plasmodium falciparum malaria parasites.

There are more than 240 million cases of malaria and 600,000 associated deaths each year, most due to infection with Plasmodium falciparum parasites. While malaria treatment options exist, new drugs with novel modes of action are needed to address malaria parasite drug resistance. Protein lysine deacetylases (termed HDACs) are important epigenetic regulatory enzymes and prospective therapeutic targets for malaria. Here we report the antiplasmodial activity of a panel of 17 hydroxamate zinc binding group HDAC inhibitors with alkoxyamide linkers and different cap groups. The two most potent compounds (4a and 4b) were found to inhibit asexual P. falciparum growth with 50% inhibition concentrations (IC50's) of 0.07 µM and 0.09 µM, respectively, and demonstrated >200-fold more selectivity for P. falciparum parasites versus human neonatal foreskin fibroblasts (NFF). In situ hyperacetylation studies demonstrated that 4a, 4b and analogs caused P. falciparum histone H4 hyperacetylation, suggesting HDAC inhibition, with structure activity relationships providing information relevant to the design of new Plasmodium-specific aliphatic chain hydroxamate HDAC inhibitors.

Gefitinib-Tamoxifen Hybrid Ligands as Potent Agents against Triple-Negative Breast Cancer.

Anticancer drug conjugates may benefit from simultaneous action at two targets potentially overcoming the drawbacks of current cancer treatment, such as insufficient efficacy, high toxicity, and development of resistance. Compared to a combination of two single-target drugs, they may offer an advantage of pharmacokinetic simplicity and fewer drug-drug interactions. Here, we report a series of compounds connecting tamoxifen or endoxifen with the EGFR-inhibitor gefitinib via a covalent linkage. These hybrid ligands retain both ER antagonist activity and EGFR inhibition. The most potent analogues exhibited single-digit nanomolar activities at both targets. The amide-linked endoxifen-gefitinib drug conjugates 17b and 17c demonstrated the most favorable anti-cancer profile in cellular viability assays on MCF7, MDA-MB-231, MDA-MB-468, and BT-549 breast cancer cells. Most importantly, in TNBC cells 17b and 17c displayed nanomolar IC50-values (380 nM - 970 nM) and were superior in their anti-cancer activity compared to their control compounds and combinations thereof.