Application of NMR screening in drug discovery

The application of NMR screening in drug discovery has recently attained heightened importance throughout the pharmaceutical industry. NMR screening can be applied at various points in a drug discovery program, ranging from very early in the program, when new targets can be screened long before an HTS enzymatic assay is developed, to later in the program, as in the case where no useful hits have been detected by HTS using biological assays. The binders determined in primary NMR screens are used to guide secondary screens, which can be either completely NMR driven or use NMR in combination with other biophysical techniques. In this review we briefly discuss the methods and techniques used in NMR screening. Then, we describe in detail the NMR screening strategies and their applications to specific targets, including successful examples from actual drug design programs at our own and other pharmaceutical companies.     

Recent applications of isotopic labeling for protein NMR in drug discovery

Introduction: Nuclear magnetic resonance (NMR) applications in drug discovery are classified into two categories: ligand-based methods and protein-based methods. The latter is based on the observation of the ¹H-¹⁵N HSQC spectra of a protein with and without lead compounds. However, in order to take this strategy, isotopic labeling is an absolute necessity. Given that each ¹H-¹⁵N HSQC signal corresponds to a residue of the target protein, signal changes provide specific information on whether a compound will fit into a pocket. Thus, this protein-based method is particularly suitable for fragment-based approaches, such as “SAR-by-NMR” and “fragment-growing.” Alternatively, the information from a protein interface may be used to develop inhibitors for protein–protein interactions.

Areas covered: This review discusses at the experimental procedures for preparing isotopically labeled protein and introduces selected topics on atom-specific and residue-selective isotope labeling, which may facilitate the development of PPI/PA inhibitors. Furthermore, the author reviews the recent applications of “in-cell” NMR spectroscopy, which is now considered as an important tool in drug delivery research.

Expert opinion: Many recent advances in labeling methods have succeeded in expanding NMR's potential for drug discovery. In addition to those methods, another new technique called “in-cell NMR” allows the observation of protein–ligand interactions inside living cells. In other words, “in-cell NMR” may become a pharmaceutical NMR technique for drug delivery.     

Aptamers and aptazymes: accelerating small molecule drug discovery

Synthetic nucleic acid ligands, known as aptamers, are versatile tools that can greatly enhance the efficiency of modern drug development. Exhibiting binding characteristics comparable to or even better than monoclonal antibodies, these ligands can be used as detection probes, highly efficient inhibitors of protein function or specific competitors in high-throughput screening (HTS) assays. Thus, aptamer technology can be exploited to address the growing demand for multi-parallel analysis of proteomes, functional prioritization of potential drug targets and accelerated small molecule lead identification. The unique advantages of this technology are the rapid automated generation of sophisticated ligands against almost any target molecule and the convenient structural or chemical modification of the nucleic acid probes. Depending on the strategy, an RNA aptamer can be expressed transgenically to investigate and inactivate an endogenous protein in an animal model, or it can be designed to function as a highly sensitive nucleic acid biosensor. More recently, the technology has been extended to directly link functional target validation with HTS, accelerating the process of drug discovery.     

High-throughput screening of small molecule libraries using SAMDI mass spectrometry

High-throughput screening is a common strategy used to identify compounds that modulate biochemical activities, but many approaches depend on cumbersome fluorescent reporters or antibodies and often produce false-positive hits. The development of "label-free" assays addresses many of these limitations, but current approaches still lack the throughput needed for applications in drug discovery. This paper describes a high-throughput, label-free assay that combines self-assembled monolayers with mass spectrometry, in a technique called SAMDI, as a tool for screening libraries of 100,000 compounds in one day. This method is fast, has high discrimination, and is amenable to a broad range of chemical and biological applications.     

Design of diversity and focused combinatorial libraries in drug discovery

Using well-characterized chemical reactions and readily available monomers, chemists are able to create sets of compounds, termed libraries, which are useful in drug discovery processes. The design of combinatorial chemical libraries can be complex and there has been much information recently published offering suggestions on how the design process can be carried out. This review focuses on literature with the goal of organizing current thinking. At this point in time, it is clear that benchmarking of current suggested methods is required as opposed to further new methods.     

Crystallography,NMR and virtual screening: integrated tools for drug discovery

Crystallography, nuclear magnetic resonance and virtual ligand screening have become common tools in structural approaches to drug discovery. Appropriately used, these techniques are highly complementary and synergistic, significantly enhancing the pace of the discovery process and the quality of compounds selected for further development. The integration of these discovery tools will be discussed, and examples in which the combination of these technologies has impacted on the drug discovery cycle will be highlighted.     

Docking and scoring in virtual screening for drug discovery: methods and applications

Computational approaches that 'dock' small molecules into the structures of macromolecular targets and 'score' their potential complementarity to binding sites are widely used in hit identification and lead optimization. Indeed, there are now a number of drugs whose development was heavily influenced by or based on structure-based design and screening strategies, such as HIV protease inhibitors. Nevertheless, there remain significant challenges in the application of these approaches, in particular in relation to current scoring schemes. Here, we review key concepts and specific features of small-molecule-protein docking methods, highlight selected applications and discuss recent advances that aim to address the acknowledged limitations of established approaches.     

NMR in drug discovery

NMR spectroscopy has evolved into an important technique in support of structure-based drug design. Here, we survey the principles that enable NMR to provide information on the nature of molecular interactions and, on this basis, we discuss current NMR-based strategies that can identify weak-binding compounds and aid their development into potent, drug-like inhibitors for use as lead compounds in drug discovery.     

Antibody libraries in drug and target discovery

Antibody libraries have come of age in the generation and evolution of monoclonal antibodies for therapeutic applications. Here, with an emphasis on cancer therapy, several examples are presented that illustrate the ability to design, engineer and select antibody libraries for different rationales in drug and target discovery.     

Advances in encoding of colloids for combinatorial libraries: applications in genomics, proteomics and drug discovery

The creation of enormous libraries of chemicals and their subsequent screening for bioactivity has been accelerated through recent developments in encoding solid supports. The ability to accurately identify the structure of a biomolecule that has exhibited activity is invaluable and is closer to realisation in the advent of smart nanoscience. In this review the evolution of encoding solid supports as platforms for combinatorial synthesis is traced. Current approaches to encoding solid supports are reviewed and their potential for use as supports for the high-throughput screening of split and mix libraries explored. Finally, a brief consideration of the status of the application of encoded libraries is provided including creative chemical and colloidal encoding.     

Fragment analysis in small molecule discovery

Cheminformatics is playing an ever-increasing role in small molecule drug discovery. The widespread use of high-throughput screening (HTS) and combinatorial chemistry techniques has led to the generation of large amounts of pharmacological data which, in turn, has catalyzed the development of computational methods designed to reduce the time and cost in identifying molecules suitable for pharmaceutical development. This review focuses on recent advances in the field of substructure analysis, an increasingly popular data mining technique with applications at many levels of the discovery process, including HTS, compound library design, virtual screening and the prediction of biological activity.     

Receptorome screening for CNS drug discovery

An estimated 50% of currently marketed drugs target G protein-coupled receptors (GPCRs) for a wide variety of indications, including central nervous system (CNS) disorders. Although drug discovery efforts have focused on GPCRs, less than 10% of GPCRs are currently used as drug targets. Thus, GPCRs continue to represent a significant opportunity for future CNS drug development. Identifying the molecular targets of psychoactive compounds may result in the elucidation of novel targets for CNS drug discovery. This commentary will describe discovery-based approaches and provide several recent examples of novel ligand-receptor interactions discovered through systematic screening of the 'receptorome'.     

Applications of NMR in drug discovery

In the half-century since its discovery, nuclear magnetic resonance (NMR) has become the single most powerful form of spectroscopy in both chemistry and structural biology. The dramatic technical advances over the past 10-15 years, which continue apace, have markedly increased the range of applications for NMR in the study of protein-ligand interactions. These form the basis for its most exciting uses in the drug discovery process, which range from the simple identification of whether a compound (or a component of a mixture) binds to a given protein, through to the determination of the full three-dimensional structure of the complex, with all the information this yields for structure-based drug design.     

NMR spectroscopy and protein structure determination: applications to drug discovery and development

Recent technological advances in NMR methods and instrumentation are having a significant impact in structural biology. These innovations are also impacting pharmaceutical biotechnology as it is now possible to use NMR spectroscopy to rapidly characterize a growing number of prospective protein drugs and protein drug targets. This review provides a general summary of how solution-state NMR can be used to determine protein structures. It also focuses on exploring how advances in solution state NMR are changing the way in which protein structures can be determined and protein-ligand interactions can be characterized. Recent innovations in protein sample preparation, in instrumentation and data collection, in spectral assignment and in structure generation are highlighted. The impact of solution-state NMR on pharmaceutical biotechnology is also discussed, with a special emphasis on describing how NMR has been used to study a number of pharmaceutically important proteins and how NMR is currently being used to rapidly screen and to map the binding sites of small molecules to a range of protein targets.