What is a clinical trial?

Clinical trials (also known as clinical studies) help researchers answer important medical questions, providing information that may help with the development of future treatment options. For example, a trial could help us learn more about the effects of an investigational drug, understand if it is safe, and whether it works better than other currently available options.

Clinical trials are conducted to test investigational drugs so that regulatory authorities can decide if they can be approved for use. But these trials wouldn’t have been possible without the help of people like you. After all, taking part in a clinical trial is entirely optional.

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How are clinical trials staged?

Phase 1: 20-80 participants

This is the first time an investigational drug is tested in people. Because of this, phase 1 trials often recruit just a small group of healthy volunteers. The primary aim is to learn about the safety of the investigational drug, determine a safe dose, and identify side effects.

Note: This information is about clinical trials in general – not all clinical trials follow exactly the same process, however, all clinical trials undergo scientific review by an ethics committee before being approved by a government agency. The safety of participants is always the first priority.

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How are clinical trials staged?

Phase 2: 100-300 participants

Phase 2 trials test how safe and potentially effective an investigational drug is for a larger group of people with the relevant condition or disease. These trials also help us begin to understand if it may be effective and further test its safety.

Note: This information is about clinical trials in general – not all clinical trials follow exactly the same process, however, all clinical trials undergo scientific review by an ethics committee before being approved by a government agency. The safety of participants is always the first priority.

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How are clinical trials staged?

Phase 3: larger groups of participants

Phase 3 trials usually involve even larger groups to look for statistical patterns in any changes seen. This helps us as we work to understand if the investigational drug is effective and can be used safely. During this phase, it is often compared to a placebo. The trial may also investigate how it compares to any existing standard of care, the best dose and any side effects.

Note: This information is about clinical trials in general – not all clinical trials follow exactly the same process, however, all clinical trials undergo scientific review by an ethics committee before being approved by a government agency. The safety of participants is always the first priority.

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How are clinical trials staged?

Phase 4

After an investigational drug has been approved and made available to the public, phase 4 trials help researchers gather information on how it impacts various groups of people and any long-term side effects.

Note: This information is about clinical trials in general – not all clinical trials follow exactly the same process, however, all clinical trials undergo scientific review by an ethics committee before being approved by a government agency. The safety of participants is always the first priority.

Phase 1 Phase 2 Phase 3 Phase 4
Why take part in a trial?

Choosing to participate in a clinical trial is personal, and everyone has their own individual reasons for doing so. For example, they may be motivated by:

  • The possibility of advancing medical science
  • The opportunity to receive regular health monitoring
  • A desire to learn more about their disease or condition
  • Feeling part of a community
  • The chance of accessing an investigational drug
Do you have to pay to take part?

No. All trial-related investigational drugs and assessments are provided at no cost. Often, trial-related expenses (such as travel) are reimbursed too. It’s also important to note that if you’re in the US, health insurance is not required in order to participate.

Do I have to take part?

Taking part is completely voluntary and participants can decide to leave at any time.

Are trials safe?

As with any medication, participants may experience unwanted side effects. Any potential side effects that are already known are listed in full in the informed consent form (the legal document that participants must carefully read and sign). However, there may be some side effects that investigators don’t know about yet. But please be reassured that each team of trial investigators monitors its participants’ health closely for any unexpected changes.

Why do some trials use a placebo?

In some trials, a group of participants will be randomly (by chance) assigned to take a placebo. These trials are known as ‘placebo-controlled.’ A placebo looks exactly like the investigational drug but does not contain any active ingredients. It is also taken in the same way. Researchers compare the results of the group receiving the investigational drug to the group receiving a placebo to understand if the investigational drug is having the desired effect. Using a placebo helps speed up a clinical trial, as researchers can more quickly see any differences between the groups.

What is randomization?

The process that determines whether a participant will be assigned to the group receiving the investigational drug or the group receiving a placebo is called randomization. This process is done by chance, like flipping a coin.

What do blinding and double-blinding mean?

In some clinical trials, neither the participant nor the researchers know to which group the participant has been assigned. This is called ‘double-blinding’ and it is designed to eliminate potential bias on the part of the researchers. In other clinical trials, only the participant does not know to which group they have been assigned. These are called ‘blinded’ trials.