"Fragment-based drug discovery has developed into one of the sound pillars forproviding small molecule lead compounds. Mostoften medicinal che mists are faced with thechallenge of using information from high-throughput screening as well as othe r efforts to optimize and develop compounds with the best drug potential. However, with more than thirty compounds in clinical trialsand at least one drug on the market whose origins can be traced to fragment-based approaches, the knowledge and pplicabilit y of this methodology has matured over the years."

"Since fragments usually have a low molecular weight they tend to be more polar and soluble than larger drug-like molecules and are therefore thought to translate into compounds with favourable physicochemical properties. Commonly, fragments are defined as smallmolecules obeying the Congreve ‘Rule of three’ in which MW ≤ 300, the number of hydrogen donors &acceptors ≤ 3 and cLogP ≤ 3 rather than the more traditional Lipinski ‘Rule of five’.