The elements of luck and inspiration

Despite this, programmes have been designed to try and solve these problems. 

For example, by considering the various conformations of a range of active compounds, it is possible to find the common volume or space into which the active compounds can be placed in order to interact with the receptor. These spaces can then be compared with no go areas —areas which must not be occupied. These areas are determined by considering similar structures which do not fit the binding site. By subtracting one from the other, a more accurate shape or volume is obtained, which, in turn, can reveal which conformations are not permitted for active drugs. Clearly, the more drugs studied, the more accurate the picture. 

Therefore, finding the ideal drug for a protein target is still only part of the overall battle. A great deal of fine-tuning still requires to be done, and the compound with the most effective interactions at the protein target will not necessarily be the most effective drug. 

It is true to say that drug design is becoming more rational, but it has not yet eliminated the role of chance or the need for hard-working, mentally alert bench chemists. 

The vast majority of drugs still on the market were developed by a mixture of rational design, trial and error, hard graft, and pure luck. The drugs which were achieved by purely rational design are severely limited and are exemplified by cimeti-dine (Chapter 13) and pralidoxime (Chapter 11). 

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