Since the publication of the first edition of Pharmaceutical Biotechnology over a decade ago, a not-so-subtle shift in the meaning of the term "biotechnology" has occurred. It has come to mean something very specific, namely the development of drug substances with large protein and polypeptide molecules. These substances can be used as drugs in their own right but may also be used to manipulate cellular DNA in order to produce a required molecule that is believed to have desirable properties in the treatment of a disease..