ABSTRACT
Pharmaceutical companies invest considerable sums of money and time in the highly risky process of developing new drugs. Drug development goes through a number of stages, both for product development and regulatory approval, with each stage subject to many uncertainties, including whether the drug appears to be successful at treating a condition and whether there are adverse side effects that would prevent ultimate approval for use. These different development stages are clearly related: A company will only undertake the next stage of development if previous stages were all successful.
