How fragments are optimized? A retrospective analysis of 145 fragment optimizations.

Fragment optimizations in nearly 150 fragment-based drug discovery programs reported in the literature during the last fifteen years were investigated. Analyzing physico-chemical properties and ligand efficiency indices we found that biochemical detection methods yield hits with superior ligand efficiency and lipophilicity indices than do X-ray and NMR. These advantageous properties are partially preserved in the optimization since higher affinity starting points allow optimizations better balanced between affinity and physico-chemical property improvements. Size-independent ligand efficiency (SILE) and lipophilic indices (primarily LELP) were found to be appropriate metrics to monitor optimizations. Small and medium enterprises (SME) produce optimized compounds with better properties than do big pharma companies and universities. It appears that the use of target structural information is a major reason behind this finding. Structure-based optimization was also found to dominate successful fragment optimizations that result in clinical candidates. These observations provide optimization guidelines for fragment-based drug discovery programs

Is there a link between selectivity and binding thermodynamics profiles?

Thermodynamics of ligand binding is influenced by the interplay between enthalpy and entropy contributions of the binding event. The impact of these binding free energy components, however, is not limited to the primary target only. Here, we investigate the relationship between binding thermodynamics and selectivity profiles by combining publicly available data from broad off-target assay profiling and the corresponding thermodynamics measurements. Our analysis indicates that compounds binding their primary targets with higher entropy contributions tend to hit more off-targets compared with those ligands that demonstrated enthalpy-driven binding

Structure-Based beta-Secretase (BACE1) Inhibitors

Alois Alzheimer identified first abnormal deformation in the brain of diseased people with mental disorder. The disorder is clinically characterized by a progression from episodic memory problems to a slow global decline of cognitive function, ending with the final stage when patients become bedridden and death occurs on average 9 years after diagnosis. The current standard of care does not cover the approved and effective treatment of both cognitive and non-cognitive symptoms. Tremendous effort was put in investigation of the disease development. The uncovered molecular mechanism shed light on aspartic proteases, the smallest protease class with about 15 members in the human genome. Here we summarise the most important structure-based developments on one of the most popular aspartic protease target BACE1

Calmodulin in Complex with Proteins and Small Molecule Ligands: Operating with the Element of Surprise. Implications for Structure-Based Drug Design

Calmodulin plays a role in several life processes, its flexibility allows binding of a number of different ligands from small molecules to amphiphilic peptide helices and proteins. Through the diversity of its functions, it is quite difficult to find new drugs, which bind to calmodulin as a target. We present available structural information on the protein, obtained by X-ray diffraction, nuclear magnetic resonance spectroscopy and molecular modeling and try to derive some conclusions on structureactivity relationships

Virtual fragment screening on GPCRs: A case study on dopamine D3 and histamine H4 receptors

Prospective structure based virtual fragment screening methodologies on two GPCR targets namely the dopamine D3 and the histamine H4 receptors with a library of 12,905 fragments were evaluated. Fragments were docked to the X-ray structure and the homology model of the D3 and H4 receptors, respectively. Representative receptor conformations for ensemble docking were obtained from molecular dynamics trajectories. In vitro confirmed hit rates ranged from 16% to 32%. Hits had high ligand efficiency (LE) values in the range of 0.31-0.74 and also acceptable lipophilic efficiency. The X-ray structure, the homology model and structural ensembles were all found suitable for docking based virtual screening of fragments against these GPCRs. However, there was little overlap among different hit sets and methodologies were thus complementary to each other. (C) 2014 Elsevier Masson SAS. All rights reserved