Book Description

This book is aimed at, from students to advanced researchers, for anyone that is interested or works with current experimental and theoretical methods in medicinal chemistry and biological physics, with particular interest in chemoinformatics, bioinformatics, molecular modeling, QSAR, spectrometry, molecular biology and combinatorial chemistry for many therapeutic purposes. This book attempts to convey something of the fascination of working in these multidisciplinar areas, which overlap knowledge of chemistry, physics, biochemistry, biology and pharmacology. This second volume, in particular, contains 11 chapters, of which 6 are related to theoretical methods in medicinal chemistry and at least 5 deal with experimental/mixed methods. In the modern computational medicinal chemistry, quantum mechanics (QM) plays an important role since the associated methods can describe molecular energies, bond breaking or forming, charge transfer and polarization effects. Historically in drug design, QM ligand-based applications were devoted to investigations of electronic features, and they have also been routinely used in the development of quantum descriptors in quantitative structure-activity relationships (QSAR) approaches. In chapter 1, we present an overview of the state-of-the-art of quantum methods currently used in medicinal chemistry. Molecular Dynamics (MD) simulation is a sophisticated molecular modeling technique useful to describe molecular structures and macroscopic properties in very large molecular systems comprising hundreds or even thousands of atoms. In the field of drug discovery, MD simulation has been widely used to understand the biomolecule structure, drug and biomolecule interactions. The chapter 2 outlines the theory and practical details of MD approach and focuses on its application in studies of prediction of binding affinities for putative receptor-ligand complexes. In chapter 3 we discuss the important role of the homology modeling procedure in the drug discovery process. This strategy, associated with computational power and more sophisticated and robust algorithms, has been used to predict properties, energies, conformations and support the binding modes of ligands inside their receptor sites. This approach is vital in structure-based drug design (SBBD), since it can quickly predict the tertiary structure of the target whose structure has not been experimentally solved. In drug discovery research, a massive dataset of information is involved and the high throughput screening of typically millions of compounds plays an important role. Different docking protocols can be combined in order to predict binding models and affinities of a ligand with a target receptor, selecting as example the best drug-like compound candidates to further experimental assays, leading to a reduction in the time and cost of the drug discovery process. In the chapter 4, we discuss the general basis and aspects of this approach, presenting some successful cases in drug discovery. Structure-based approaches have increasingly demonstrated their value in drug design. The impact of these technologies on early discovery and lead optimization is significant. Although there is a multiplicity of different approaches being employed in early stages of drug discovery, structure-based drug design (SBDD) is one of the most powerful techniques, and has been used quite frequently by scientists in the pharmaceutical industry as well as in academic laboratories over the past twenty years. The evolution of medicinal chemistry has resulted in an increase in the number of successful applications of structure-based approaches. Some case studies are presented in chapter 5, exploring the value of structure-based virtual screening (SBVS) approaches in drug design, highlighting the identification of novel, potent and selective receptor modulators with drug like properties. Drug discovery has moved toward more rational strategies based on our increasing understanding of the fundamental principles of protein-ligand interactions. The combination of available knowledge of several 3D protein structures with hundreds of thousands of commercially available small molecules has attracted the attention of scientists from all over the world for the application of structure-based pharmacophore strategies. Pharmacophore approaches offer timely and cost-effective ways to identify new drug-like ligands for a variety of biological targets, and their utility in drug design is unquestionable. In the chapter 6, the understanding and limitations of this approach in drug R&D are discussed. Modern molecular biology has inundated drug discovery organizations with countless potential novel drug targets. A foremost challenge for the researchers is to validate this asset of targets with bioactive small molecules (bioproducts can also be included). Eventually, they will be developed into drugs for the more promising targets. The difficulty of finding a good small-molecule starting point is at the beginning of the searching for a proper chemical space that is well related to biological space. Drugs that are small molecules and act at enzyme targets account for over 50% of all medicines in therapeutically use in the marketplace. It is for this reason that chapter 7 take thermodynamics of the small molecule-target enzyme interactions into account to a limited scope. So far, the main purpose of this chapter is to provide a guidance profile of biocalorimetry and its role in drug discovery and development. The chapter 8 intends to describe how proteomes can be analyzed and studied. It addresses some available databases and bioinformatics tools. The description of certain instrumentation, such as mass spectrometry is also presented, but not highly detailed. The aim of chapter 9 is to introduce the reader to the wide spectrum of tools currently available in the drug validation process. With the conclusion of the human genome sequencing, an increase demand for target validation follows the development of high throughput techniques used in the identification of potential new drugs. In vitro technology as the RNA interference (RNAi) and recombinant protein array together with advances on the in vivo technology as the development of transgenic animals, including here the humanized ones, will certainly improve the safety of future clinical trials processes and ultimately play an important role in the treatment of several human diseases. A therapeutically significant drug may have limited utilization in clinical practice because of various shortcomings like poor organoleptic properties (chloranphenicol), poor bioavailability (ampicilin), lack of site specificity (antineoplastic agents), incomplete absorption (epinephrine), poor aqueous solubility (corticosteroids), high first-pass metabolism (propranolol), low chemical stability (penicillin), high toxicity (thalidomide) or other adverse effects. Sometimes, an adequate pharmaceutical formulation can overcome these drawbacks, but often the galenic formulation is inoperant and a chemical modification of active molecule is necessary to correct its pharmacokinetic profile. This chemical formulation process, whose objective is to convert an interesting active molecule into a clinically acceptable drug, often involves the so-called prodrug design , which is extensively discussed in chapter 10. The dominant role of synthetic chemistry has been increasingly challenged by knowledge of the structure and functions of enzymes, receptors, channels, membrane pumps, nucleic acids and by the exponential growth of information about biology, genetics and pathology, giving paramount importance to the dialogue between chemists and biologists. Nevertheless, as in the old days, the development of new chemical entities is still highly dependent on the ability of chemists to obtain, with simple, reliable, fast and possibly inexpensive methods, the molecules that have been designed. Even if it is an undisputed fact that biology has become exceedingly important in drug research, it is reasonable to imagine that chemistry, and in particular synthetic organic chemistry, will continue to play a fundamental role in academic research and in the R&D departments of drug companies of the third millennium. In chapter 11, we describe synthetic routes that have been used to synthesize the structures of top drugs in current usage. This provides an ideal way of introducing students to a wide range of applied chemistry with brief descriptions of the modes of action of these drugs. Some contents of this book therefore reflect our own ideas and personal experiences, which are presented in reviews of different topics here investigated. It is interesting to consider the information described in this book as the starting point to access available and varied knowledge in Medicinal Chemistry and Biological Physics or related areas.