Developing trends in pharmaceutical patent claims

Pharmaceutical patents have traditionally defined the scope of monopoly by the clear and precise terminology which chemistry employs to characterise chemical structures. This defines particular compounds with precision, whilst at the same time also serving to define with precision numerous currently 'unknown' but similar molecules without actually having made or tested them. Such molecules, while different from each other, have a real prospect of having similar efficacy. However, this approach to patenting is now, with modern rational drug discovery techniques, starting to change, with claims formulated instead in terms of biological activity, receptor sites, or even the procedure by which a compound has been discovered. Examples are given of such claims and the rationale for them in patent law.