Single Bead Labeling Method for Combining Confocal Fluorescence On-Bead Screening and Solution Validation of Tagged One-Bead One-Compound Libraries

SummaryScreening of one-bead one-compound libraries by incubating beads with fluorescently labeled target protein requires isolation and structure elucidation of a large number of primary hit beads. However, the potency of the identified ligands is only revealed after time consuming and expensive larger scale resynthesis and testing in solution. Often, many of the resynthesized compounds turn out to be weak target binders in solution due to large differences between surface and solution binding affinities. For an industry style high-throughput screening (HTS) process a high false positive rate is detrimental. We have therefore combined single bead and single molecule/single cell techniques into an integrated HTS process in which the picomole amount of substance contained on one isolated hit bead is sufficient for quality control, structure determination, and precise affinity determination to the target protein in solution

Peptide folding induces high and selective affinity of a linear and small β-peptide to the human somatostatin receptor 4

β-Peptides with side chains in the 2- and 3-positions on neighboring residues (of (S) configuration) are known to fold and form a turn (similar to an alpha-peptidic β-turn). Thus, the authors have synthesized an appropriately substituted β-tetrapeptide deriv. to mimic the hormone somatostatin in its binding to the human receptors hsst1-5, which is known to rest upon a turn contg. the amino acid residues Thr, Lys, Trp, and Phe. The N-acetyl-peptide amide Ac-β3-HThr-β2-HLys-β3-HTrp-β3-HPhe-NH2 indeed shows all characteristics of the targeted turn-mimic: Lys CH2 groups are in the shielding cone of the Trp indole ring (by NMR anal.) and there is high and specific nanomolar affinity for hsst4 receptor. In contrast, the isomer 2 bearing the Lys side chain in 3-, rather than in the 2-position, has a 1000-fold smaller affinity to hsst4. The syntheses of the required Fmoc-protected β-amino acids are described. Coupling of the β-amino acids was achieved by the manual solid-phase technique, on Rink resin

The Screening Compound Collection: A Key Asset for Drug Discovery

In this case study on an essential instrument of modern drug discovery, we summarize our successful efforts in the last four years toward enhancing the Actelion screening compound collection. A key organizational step was the establishment of the Compound Library Committee (CLC) in September 2013. This cross-functional team consisting of computational scientists, medicinal chemists and a biologist was endowed with a significant annual budget for regular new compound purchases. Based on an initial library analysis performed in 2013, the CLC developed a New Library Strategy. The established continuous library turn-over mode, and the screening library size of 300'000 compounds were maintained, while the structural library quality was increased. This was achieved by shifting the selection criteria from 'druglike' to 'leadlike' structures, enriching for non-flat structures, aiming for compound novelty, and increasing the ratio of higher cost 'Premium Compounds'. Novel chemical space was gained by adding natural compounds, macrocycles, designed and focused libraries to the collection, and through mutual exchanges of proprietary compounds with agrochemical companies. A comparative analysis in 2016 provided evidence for the positive impact of these measures. Screening the improved library has provided several highly promising hits, including a macrocyclic compound, that are currently followed up in different Hit-to-Lead and Lead Optimization programs. It is important to state that the goal of the CLC was not to achieve higher HTS hit rates, but to increase the chances of identified hits to serve as the basis of successful early drug discovery programs. The experience gathered so far legitimates the New Library Strategy

Discovery and Optimization of Isoquinoline Ethyl Ureas as Antibacterial Agents

Our strategy to combat resistant bacteria consisted of targeting the GyrB/ParE ATP-binding sites located on bacterial DNA gyrase and topoisomerase IV and not utilized by marketed antibiotics. Screening around the minimal ethyl urea binding motif led to the identification of isoquinoline ethyl urea <b>13</b> as a promising starting point for fragment evolution. The optimization was guided by structure-based design and focused on antibacterial activity in vitro and in vivo, culminating in the discovery of unprecedented substituents able to interact with conserved residues within the ATP-binding site. A detailed characterization of the lead compound highlighted the potential for treatment of the problematic fluoroquinolone-resistant MRSA, VRE, and <i>S. pneumoniae</i>, and the possibility to offer patients an intravenous-to-oral switch therapy was supported by the identification of a suitable prodrug concept. Eventually, hERG K-channel block was identified as the main limitation of this chemical series, and efforts toward its minimization are reported