The process starts with a drug sponsor, usually a pharmaceutical company, seeking to develop a new drug it hopes will find a useful and profitable place in the market. Before clinical testing begins, researchers analyze the drug's main physical and chemical properties in the laboratory and study its pharmacologic and toxic effects in laboratory animals. If the laboratory and animal study results show promise, the sponsor can apply to FDA to begin testing in people. These phase 1 studies assess the most common acute adverse effects and examine the size of doses that patients can take safely without a high incidence of side effects. If phase 1 studies don't reveal major problems, such as unacceptable toxicity, the next step is to conduct a clinical study in which the drug is given to patients who have the condition it's intended to treat.
Researchers then assess whether the drug has a favorable effect on the condition.
Sounds easy enough, and sometimes it is. In what may be medicine's most celebrated clinical trial, Louis Pasteur treated patients exposed to rabies with an experimental anti-rabies vaccine. All the treated patients survived. Since scientists knew that untreated rabies was 100 percent fatal, it wasn't hard to conclude that Pasteur's treatment was effective. But that was a highly unusual case.