Textbook in PDF format This English-language textbook, based on the successful German edition 'Wirkstoffdesign', brings the subject of drug design back to the cutting edge of research. The reader learns about new methods in genetic engineering and the expanded range of structural biological methods. Especially in the last 10 years, many complex target structures such as G-protein coupled receptors or ion channels have been elucidated by using these methods. The reader learns how these long-sought complex structures with classical drugs look like and how the therapeutic effect is achieved. This textbook is aimed at students of pharmacy, chemistry and the life sciences, but also at career changers and medicinal chemists in research and development departments of the pharmaceutical industry. Conceptually, it is very different from classical textbooks on pharmaceutical chemistry. It focuses on the path to a new drug substance. The selection of case studies is based on didactic aspects and attempts to give a broad overview of methods and strategies without forgetting to look back at the beginnings of this field of work. Thus, the arc spans from the history of drug research, the mechanisms of action of drugs and the methods for lead structure search and optimisation to structure determination methods, modelling, molecular dynamics and QSAR methods to structure- and computer-aided design. Foundations in Drug Research Drug Research: Yesterday, Today, and Tomorrow In the Beginning, There Was Serendipity Classical Drug Research Protein–Ligand Interactions as the Basis for Drug Action Optical Activity and Biological Effect The Search for the Lead Structure The Classical Search for Lead Structures Screening Technologies for Lead Structure Discovery. Optimization of Lead Structures Designing Prodrugs Peptidomimetics Experimental and Theoretical Methods Combinatorics: Chemistry with Big Numbers Gene Technology in Drug Research Experimental Methods of Structure Determination Three-Dimensional Structure of Biomolecules Molecular Modeling Conformational Analysis Quantitative Structure-Activity Relationships and Design Approaches Pharmacophore Hypotheses and Molecular Comparisons Quantitative Structure–Activity Relationships From In Vitro to In Vivo: Optimization of ADME and Toxicology Properties Protein Modeling and Structure-Based Drug Design A Case Study: Structure-Based Inhibitor Design for tRNA-Guanine Transglycosylase Drugs and Drug Action: Sucesses of Structure-Based Design How Drugs Act: Concepts for Therapy Inhibitors of Hydrolases with an Acyl–Enzyme Intermediate Aspartic Protease Inhibitors Inhibitors of Hydrolyzing Metalloenzymes Transferase Inhibitors Oxidoreductase Inhibitors Agonists and Antagonists of Nuclear Receptors Agonists and Antagonists of Membrane-Bound Receptors Ligands for Channels, Pores, and Transporters Ligands for Surface Receptors Biologicals: Peptides, Proteins, Nucleotides, and Macrolides as Drugs