What are Clinical Trials

Before any new drug can be made available to the public, it must routinely go through three phases of clinical trials. A new drug advances from phase to phase as long as it continues to show promising results.

Clinical Trial Phases

Phase I

Phase I

Phase I studies test the drug in only a few people (usually 15 to 100). For example, patients with cancer may be invited to consider a Phase I trial if their cancer has come back or spread and there is no other standard treatment that could help them.

In this early phase, the trial aims to find out:

  • whether the treatment is safe to take
  • what dose can be given without causing serious side effects
  • if the drug has an adverse effect on the body
  • what side-effects it causes
  • whether the drug has any effect on stabilizing or shrinking the cancer
  • how the drug is metabolized or processed and eliminated from the body

Phase II

Phase II

Phase II studies are done to find out how well the investigational treatment works. For cancer treatments, the researchers usually want to better understand whether the drug has any effect on stabilizing or shrinking the cancer.

Phase II trials involve more patients (approximately 100-200).

The goal of Phase II trials is to find out:

  • more about the best treatment dose and schedule of administration
  • whether the drug has any effect on stabilizing or shrinking the cancer
  • which types and stages of cancer the investigational drug could treat
  • more about the drug’s side effects
  • if the treatment works well enough to be tested in a Phase III trial

Phase III

Phase III

After a drug’s safety and efficacy have been tested in Phase II trials, the drug must be tested in a large number of patients in a Phase III clinical trial.

Phase III trials involve several hundreds or thousands of patients at many different clinics and hospitals in a single country or around the world.

Phase III trials test how well the drug works compared to standard treatment(s) or best supportive care. Patients in Phase III trials usually receive a dose of the new drug that has been found to be relatively safe and potentially effective during Phase I and/or II trials.

Phase III trials are performed to find out:

  • whether symptoms of the disease change with treatment with the experimental drug
  • whether the treatment delays the progression of the disease
  • how the treatment affects a patient’s quality of life
  • if the drug causes any adverse effects on the body

Are you thinking of participating in a Clinical Trial?

As with any important decision, you should take time to talk to your teating physician and discuss and think through the advantages and disadvantages of taking part in a clinical trial. You should never feel pressured into entering a study. It is your choice.

To make sure you are fully informed about participation, you should:

  • ask your treating physician if he/she may be able to connect you with someone who is currently enrolled or has been in a clinical trial and who is willing to share their experience
  • discuss your thoughts with friends and family
  • refer to other reliable sources of information, such as patient support (advocacy) groups
  • ask questions

Armed with the facts, you can decide whether or not to take part in medical research if you are eligible for a clinical trial, helping to shape your future and possibly future treatments for other patients living with serious diseases.


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