Towards Understanding Drugs on the Molecular Level to Design Drugs of Desired Profiles

Abstract

The process of drug development proceeds through several stages including discovery, product characterisation, formulation, delivery and packaging development, pharmacokinetics and drug disposition, preclinical toxicology testing and IND (Investigational New Drug) application; bioanalytical testing and clinical trials. In general this process is time-consuming and expensive. According to statistical data, from among 50 thousand to 5 million of compounds subjected to screening only 6 become prospective drugs and the whole process from discovery to implementation takes from 12 to 24 years and costs even up to 800 million USD [1]. The number of new approved drugs partially reflects the progress in research and development. Despite enormous financial outlays, there has been a steady decrease in the number of drugs introduced each year into therapy. While in the 1960s about 70-100 new drugs was introduced in the market, in the 1970s, 60-70, in the 1980s 50, in the 1990s 40 while in 2000th only 20. On the one hand, this is a result of increased demands on safety (average number of clinical trials per new drug increased from 30 in the 1970s through 40 in the 1980s, to 70 in the 1990s), which prolonged the development process from 8 years in the 1960s, 12 in 1970s, 14 in 1980s, 15 in 1990s and 21 currently. On the other hand, the so-called "easy" to discover drugs have already been discovered. Currently 75% of expenditures is absorbed by the research ended in failure and as much as 90% of candidates for drug never reach the market. Therefore, much effort is directed towards development of new theoretical and experimental tools that would increase the effectiveness of the above process, in particular in its first stages leading to a decision whether a given compound is a prospective drug or not. The necessary and reliable data needed to take such a decision are provided first of all by the methods of analytical characterisation of compounds (identification, physical and chemical properties, structure), methods permitting optimisation of the leading structure (structure-activity relation) and pre-clinical study (toxicity). These early stages of pharmacological studies sometimes (but not always) reveal the whole mechanism of action of a future drug. Recent research work towards drug development has been conducted in two independent directions. On the one hand, completely new drugs or pro-drugs (drug precursors that become drugs only as a result of metabolic transformations in vivo) are searched for, while on the other hand, drugs of second and third generation are proposed that are the improved