Goals of early phase clinical trials

Early clinical trials used in new drug development typically have the following goals  

Although somewhat overly simplistic (especially to readers who are students of pharmacy) we can consider pharmacokinetic effects as what the body does to the drug and pharmacodynamic effects as what the drug does to the body. For those readers who are less familiar with pharmacokinetics and pharmacodynamics, Tozer and Roland (2006) provide an excellent and very readable introduction to these topics. 

Patients with diseases or conditions of interest can have a number of attributes that, although 

The employment of healthy participants in early clinical studies provides essential information about the pharmacokinetics, pharmacodynamics, and safety of the new drug. This chapter focuses on the research questions relevant to early human studies, the designs used to address them, the data and analysis approaches commonly encountered, and the development decisions that are made as a result of these studies. 

We should note here that there are some special cases for which the use of healthy participants is not justified in early studies. For particularly invasive therapies (for example, implantation of a medical device) or therapies with known toxicity (for example, oncologies) it is not ethical to study healthy participants. The use of healthy participants in early studies may also provide a misleading result for future studies of participants with disease. For example, the maximum tolerated dose of new antidepressants or anxiolytics may differ quite markedly between healthy participants and those with the disease. 

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