Testing of candidate drugs in humans is conducted to evaluate safety and the efficacy in treating, preventing, or diagnosing a specific disease or condition. The most important consideration in these studies is the safety of trial participants. Human testing occurs in FDA-supervised, phased clinical trials, along with further assays to characterize absorption, distribution, metabolism, and excretion (ADME) and toxicity associated with the lead candidate(s) that made it through earlier phases of testing. Show more
Clinical trials can take many forms and increasingly enroll a range of different populations. However, patient populations may be stratified in clinical trials when data suggest that a particular group may respond better to a specific treatment regimen. Generally, there are three or four phases during drug development. Phase 0 is increasingly included for investigational new drugs (INDs). This phase involves testing of subtherapeutic doses on a small number of subjects to confirm that the animal studies are valid in humans.
If a drug candidate passes Phase 0, the clinical trial will progress to Phase I, designed to evaluate drug safety, side effects, and dosage range in a small cohort. Phase II usually extends the trial to a larger cohort and compares the putative drug to a placebo. Typically, Phase III broadens the scope of Phase II to more study subjects, often with different populations, and includes comparisons to one or more existing treatments as well as further monitoring and evaluation of adverse events. Phase IV involves population studies after the market release of a new drug.Show less