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What is an Experimental Drug?


Updated July 12, 2013

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Question: What is an Experimental Drug?

An experimental drug is a medication that has gone through intitial testing in the lab (and usually on animals) so that it may be given to humans, but has not yet received approval by the Food and Drug Administration (FDA.)

These drugs are also known as an “investigational drugs.” Since they have not yet been approved by the FDA, they can’t yet be legally marketed and sold. With a few exceptions, such as expanded access and special exceptions (compassionate use,) the most common method of using an experimental drug is to participate in a clinical trial using the medication.

It can be frightening at first if your doctor recommends a drug classified as “experimental,” but understanding what this means, and having a list of questions to ask, is very helpful.

Different Phases of Experimental Drugs

Not all experimental drugs have been studied to the same degree. Some are just beginning to be used in humans, and some have been used for a significant length of time and are nearing FDA approval.

Before a drug is tested on humans, it is usually tested on cancer cells in the lab, as well as in laboratory animals. The first studies done on humans are phase 1 trials. There are only a few people in these trials. The purpose of these earliest of trials is primarily to determine if an experimental drug is safe for humans, and to figure out what dose is most appropriate.

The next level of testing is phase 2 trials. These trials include more people, and are used to evaluate whether or not a drug is effective. Since a larger number of people are present in these studies, further information is also gained about safety. The last stage of research before FDA approval is phase 3 trials. While again testing safety, these trials are done to see if the new drug is more effective than treatments currently available.

Who Can Use Experimental Drugs?

By far the most common way to use an experimental drug is to enroll and participate in a clinical trial that is studying the drug. Occasionally experimental drugs are able to be obtained outside of clinical trials, but very specific criteria must be met in order to do so. To be eligible for use of an experimental drug outside of a clinical trial:
  • Standard treatment for your condition has to have failed.
  • You are otherwise ineligible to participate in clinical trials investigating the drug.
  • There must be no alternative treatments available.
  • The drug must have demonstrated some activity against your particular cancer in studies to date.
  • The benefits of using the drug must outweigh any anticipated risks of using the drug.

In addition:

  • There must be evidence that the drug will be of benefit to you.
  • The drug must be able to be given safely outside the protocol of a clinical trial.
  • There must be a sufficient supply of the drug available for those people who are part of ongoing clinical trials.

Pros and Cons of Experimental Drugs

  • An experimental drug may give you the opportunity to treat a cancer in which other treatments have failed.
  • The medication may have benefits that current treatments do not.
  • Researchers may obtain valuable information about the drug that could help others in the future.
  • Most people who are given an experimental drug as part of a clinical trial are followed closely by a medical team.
  • Drugs that are considered investigational are usually free of charge to people participating in a trial.


  • The drug could have negative effects (adverse reactions) that researchers have not yet discovered.
  • The drug may not help you specifically.
  • If the study is a placebo controlled trial, you may not know if you are receiving the experimental drug or a placebo (note: the researchers will let you know if this is a possibility.)
  • Using the drug may eliminate your chances of using another treatment or participating in another clinical trial.

Questions to Ask if You Are Considering an Experimental Drug

  • How might the drug benefit me?
  • What side effects may I expect?
  • Who pays for the drug and any related tests and follow-up?
  • If I decide to stop the drug, what will happen (both physically and in regard to taking part in the clinical trial?)
  • How long will I take the drug, and how long will the study take?
  • Will I need to be hospitalized, or will treatment be done as an outpatient?
  • How will I know if the treatment is working?
  • Who should I call if I have questions while taking the drug?
  • Is there anyone who has taken the drug that I can talk to?

Further Reading:


National Cancer Institute. Access to Investigational Drugs. Updated 08/04/09. http://www.cancer.gov/cancertopics/factsheet/Therapy/investigational-drug-access

National Cancer Institute. What Are Clinical Trials? Updated 11/02/12. http://www.cancer.gov/clinicaltrials/learningabout/what-are-clinical-trials

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