What Are Clinical Trials?

Clinical trials are a type of research in which people are studied to better understand what makes us healthy…and what makes us sick. In a clinical trial, participants receive specific interventions, such as drugs, devices, digital therapies, or vaccines, that are being developed to help diagnose, treat, or prevent a specific disease or medical condition. Health authorities, such as the Food and Drug Administration, look at the data collected in clinical trials to determine whether a new treatment should be approved for use. Before a new treatment can be prescribed by a doctor, it needs to be studied in clinical trials. Every clinical trial is conducted according to a research plan, which is also called a protocol, that is created by the trial investigators or the trial sponsor before the trial begins. The purpose of the trial, the types of treatment the participants will receive, the instructions for using the study treatment, the duration of treatment, and every step involved in the clinical trial process are all planned out in the trial protocol.

Clinical Trial Phases

When a new drug is being studied in clinical research, it is tested in stages, or “phases.” During the early phases, researchers may study the effects of a single dose of an experimental treatment in a trial that includes only a small number of participants. During the later phases, researchers may study the long-term effects of an experimental treatment in a clinical trial that may include thousands of participants in multiple countries. Each phase is designed to learn more about how a new drug works and how safe it is. If a drug is successful in one phase, it will move to the next. A clinical trial is usually described by its phase because the trial phase gives you some idea of what the trial is designed to learn and how many participants will be enrolled. There are four phases of clinical trials.

What are the Four Phases of Clinical Trials?

Phase I clinical trials: Is the treatment safe?

Phase I trials usually include a small number of people. This number varies from one trial to the next, but there are usually fewer than 100 participants in a Phase I trial. The participants may be people with a specific disease or condition or healthy volunteers. Researchers conduct Phase I trials to learn more about how a treatment behaves in the human body, to learn about any side effects that might happen when someone takes a treatment, or to find the right dose of a treatment to use in Phase II. In some Phase I trials, such as cancer trials, researchers will also look at how each participant’s disease responds to treatment.

Phase II clinical trials: Does the treatment work?

Phase II trials usually include more participants, up to several hundred people. While researchers continue to study a treatment’s safety in Phase II trials, they also begin to collect data about if and how well a treatment works in people who have the disease or condition that it is being developed to treat.

Phase III clinical trials: Is it better than what’s already available?

Phase III trials usually include large numbers of participants. Some Phase III trials are conducted in multiple countries and may include thousands of people. Phase III trials are used to collect more information about how safe a drug is and how well it works. Phase III trials will often compare an experimental treatment with the current standard of care to see if it works as well or better, or has fewer side effects, than what is already available to patients. To do this, researchers will assign participants to different treatment groups – participants in one treatment group will receive the new treatment, while participants in another group will receive standard-of-care therapy. Alternatively, participants in one group might receive the new drug plus standard therapy, while participants in another treatment group might receive standard therapy alone.

Phase IV clinical trials: What else do we need to know?

Phase IV trials may be conducted after a drug or device has been approved for use. Phase IV trials are done to study how safe a drug is and how well it works in large, diverse populations over long periods of time. Phase IV trials might identify side effects that were not seen in smaller, shorter trials.