SECTION II
Drug Discovery
and Development
Introduction
How does a chemical become a medicine? A better
question, given the huge attrition rates in drug
development, might be: What governswhethera
chemical becomes a medicine? This section of the
book covers all those disciplines and processes that
are needed for this putative transmogrification.
This can also be called the ‘pre-marketing’
phase of the drug life cycle. It should be noted
that although all this is necessary, it is certainly
not sufficient for commercial success.
Importantly, these chapters have had to be
designed to present the general case. Two major
limitations then automatically arise. The larger
limitation is that whole disciplines can be essen-
tially product specific; hence, there is little about
preclinical pharmacology in this section because a
general case cannot be extensively presented. The
smaller limitation is well illustrated by the disci-
pline of toxicology. In this case, the general prin-
ciples are fairly easily to enunciate, and have been
codified by the International Conference on Har-
monization. However, the toxicology program for
almost every new chemical entity deviates from
these general principles because special studies are
needed in pursuit of product-specific issues that are
uncovered while doing the ‘standard’ tests. Neither
can such custom-designed studies be generalized
here.
Regulatory affairs are so fundamental to precli-
nical and clinical development that it deserves a
section of this book to itself. However, this is a
purely artificial distinction which must not be
allowed to obscure the crucial, intimate and inter-
active relationship between regulation and the
other disciplines that are described in this section.
Lastly, there is some cross-referencing and over-
laps between some of the chapters in this section.
Much in this section would also apply to late phase
III and phase IV drug development. This is inten-
tional and again reinforces how an integrated
approach must be taken in drug development for
there to be any chance at all of eventual success.