How clinical trials work

Clinical trials help people in the medical community create better ways to treat diseases and health issues. The research done through clinical trials helps doctors, specialists, and other medical professionals learn important information about diseases and chronic conditions, their treatments, and medications. Clinical trials help us understand which potential treatments are safe and effective.

patient listening to a healthcare provider explain something

Clinical trial phases

Types of clinical trials

Randomization and placebos

Clinical trial phases

Clinical trials are done in a series of four steps, called phases. Each phase has a specific purpose and helps us learn more about a potential treatment. The United States Food and Drug Administration (FDA) must approve a trial before it can move from one phase to the next.

The first time a potential treatment or prevention option is tested in people is in a phase 1 trial. This phase may include small groups of people. And the clinical trials in phase 1 often look to enroll healthy people. Before researchers conduct tests in large groups of people with a specific disease or health condition, they want to learn more about:

Safety of the potential treatment or prevention
Potential side effects in people
Different doses that may be given to people (if applicable)

The FDA reviews phase 1 results to decide if the next phase can start. Phase 2 clinical trials continue the work that starts in phase 1. But most phase 2 clinical trials enroll people living with a specific disease or health condition. They might also enroll a larger group of people. This phase typically includes:

Continued testing for safety
Ongoing collection of information about side effects
Testing to find out what effects the potential treatment or prevention may have on the disease or health condition

Phase 3 clinical trials are a lot like phase 2 clinical trials. Safety tests continue. Side effects are tracked closely. And researchers learn more about how effective a potential treatment or prevention may be. But this phase might enroll an even larger group of people. It may also help researchers compare options. In other words, researchers can find out if a potential treatment or prevention:

Is more effective than current options
Has fewer or less severe side effects
Can be administered less frequently or in a different way

After phase 3, the FDA reviews all results. They decide if the potential treatment or prevention should be approved. This is based on how safe and effective it is when given to people. But the research doesn’t necessarily end there. Phase 4 clinical trials collect more data after approval. This phase typically includes:

Assessment of long-term safety and effectiveness
Information collected when the approved treatment or prevention is given to patients under the care of their healthcare providers (rather than the trial medical team)

Types of clinical trials

You might already know about clinical trials. Maybe you’ve been in one or know someone who has. But you might not realize how many types of trials there are. The types described here share common features, but each has its own special focus. In some cases, a clinical trial can be a combination of more than one type.

Potential treatment clinical trials

When most people think of clinical trials, they might think of the search for potential treatments. These clinical trials may test a new medicine or therapy. Sometimes they look for new ways to use a current medicine. Or they might test a combination of medicines. Some clinical trials test medical procedures. The goal is to find more ways to treat diseases and health conditions.

Prevention clinical trials

These clinical trials test ways to keep people from getting sick. They may also help find ways to stop a disease or health condition from coming back. This could include a vaccine, a medicine, or a lifestyle change.

Screening clinical trials

Routine screenings can be a big part of living your healthiest life. Screening clinical trials test ways to detect a disease or health condition before symptoms appear.

Diagnostic clinical trials

Learning what’s causing your symptoms is a key step on your health journey. It can be the first step to finding a potential treatment that may be right for you. Diagnostic clinical trials test ways to learn which disease or health condition may cause a set of symptoms.

Device clinical trials

Medical devices can play a big role in helping someone on their health journey. They can also be used to help diagnose someone. A medical device can be as simple as a cast for a broken bone. Or it can be as complex as a new machine that creates pictures of the inside of your body. Device clinical trials test devices to learn more about how safe and effective they may be when used by different people.

Stages of testing for medical device clinical trials:

Clinical trials that test medical devices are a bit different. Devices are tested in three stages (rather than four phases). But the approach is similar. Results are reviewed after each stage to decide if the next stage should start. And the focus is still on safety and effectiveness.

Pilot/feasibility stage: Test the device to find out if it works
Pivotal stage: Use the device in a healthcare setting to find out if it is safe and effective
Post-market stage: Collect additional information after approval to confirm the device is effective

Behavioral clinical trials

Behavior can have a big impact on health. Some clinical trials test changes in behavior. For example, a trial might test changes in:

What you eat or drink
Your physical activity
Other daily activities and habits

This type of trial can also be a prevention or potential treatment trial. The goal is to see if the changes can help improve health.

Quality of life clinical trials

Helping people live their healthiest lives is about more than just treating a disease or health condition. We also need to think about quality of life. That’s why some clinical trials test ways to reduce the impact of a disease or health condition. They may also look for ways to address side effects of current or potential treatments.

Randomization and placebos in clinical trials

In clinical trials, people are randomly put into different groups. A computer assigns people to groups at random (by chance). You can’t choose your group. And the trial team can’t choose your group. This randomization helps make sure that everyone has a fair chance and that the results are fair, too.

People in some trial groups receive a potential medicine or procedure. People in other groups receive a placebo.

A placebo can be a medicine or procedure. But it has no true physical effects. Using a placebo can help identify the effects of a potential medicine or procedure by comparing the effects of someone who is taking a placebo with someone who has been given a potential new treatment or procedure.

Placebos are a key part of some clinical trials. But many clinical trials don’t include a placebo.

Before you join a trial, you will know if there’s a chance you might get a placebo. You will also know what other care is provided in the trial. No matter if you get the potential treatment or the placebo, you’ll receive attention from healthcare providers during the trial.