When drug trials are performed, there is a standard protocol and language for how they are to be designed so that the clinicians can be sure that what they are measuring is truly the effect of the drug in question and not any other extraneous data.
Preclinical Phase: This research is not done with people. It is either done on growing tissue or in animals to test toxicity.
Phase 0: This is the very first trial in people where the drug is assessed to determine how the drug affects body tissues for harm. A small dose is administered to 10-15 healthy people.
Phase 1: The testing of the drug on healthy volunteers for safety. This involves multiple dose testing to rule out side effects. This means they determine the best dose titrating up until they reach severe side effects or the desired effect. This phase usually consists of 15-30 people. Participants are usually paid, and it can take several months to complete.
Phase 2: Testing the drug on patients to assess efficacy and side effects more thoroughly. Does it do what it is proposed to do? This study is done with a much larger group of people. There is almost always a “control” group that gets a placebo. Participants don’t know which group they are in until after the trial is over. The trial can take years because all participants are not all done at the same time.
Phase 3: Testing of the drug on patients to assess effectiveness, and safety. The new drug is compared to the standard-of-care. These trials are randomized and people participating must be alike so you rule out differences in everything except the drug, usually performed double-blind meaning neither the clinician nor the patient knows whether they are getting placebo, or the drug. This trial will involve 100’s-1000’s of people and last for a year or more for each participant.
Phase 4: After licensing by the FDA, this may be done to check the drug’s performance in the real world, to study possible long term risks and uncover any rare side effects that are only found in very large groups, or how it performs in combination with other drugs. It is in this trial where the new drug is compared to drugs already on the market, and the cost effectiveness of the new drug. This trial will involve hundreds to thousands of people.
Before any trials are done, the trials must be planned and approved before the start. Funding may come from the federal government such as National Institute of Health, the Department of Defense, or the Department of Veteran’s Affairs, and private industry (pharmaceutical and biotech companies). All human trials must be approved by the Food and Drug Administration.
The above was summarized from the National Comprehensive Cancer Network (NCCN)