How Experimental Drugs Are Used in Clinical Trials

lab room with beakers used to study an experimental drug Photo©shironosov

Experimental or investigational drugs are medications that are not yet approved by the FDA, but are being studied to see if they are safe, the best doses to use, whether they work, and what side effects they may cause. In order to be treated with these drugs it's necessary to participate in a clinical trial, or to meet the criteria for compassionate use. Learn about the ways in which these drugs are used, the potential advantages as well as possible disadvantages associated with their use, and questions to consider and ask your doctor before taking one of these medications.


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

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. It may also reduce your fears to realize that there are many myths about clinical trials but every medication we have that has been approved was once studied as an experimental drug.

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. The different phases of clinical trials have different purposes and vary in the number of people who are treated.

Before a drug is tested on humans, it is usually tested on cancer cells or other tissue 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 a phase 3 trial. While again testing safety, these trials are done to see if the new drug is more effective than treatments currently available or if it is as effective but has fewer side effects than other available drugs.

Who Can Use Experimental Drugs?

Experimental drugs are often available only in a clinical trial, but for those outside of a clinical trial there may be other options.

Experimental Drugs in Clinical Trials

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. To enter a clinical trial you must fulfill a checklist of eligibility criteria outlined by the researchers. These criteria may include things such as gender, age, performance status, and more, and therefore not everyone who might benefit will be admitted to the trial.

Use of Experimental Drugs Outside of a Clinical Trial

Occasionally experimental drugs can be obtained outside of clinical trials, for example, via compassionate use or advanced access, but very specific criteria must be met in order to be eligible for use. These include:

  • 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

There are a number of advantages as well as disadvantages to using an experimental drug. Many people find it helpful to list these out on paper so that they can weigh their options carefully. Pros and cons include:


There are a number of reasons why an experimental drug may have advantages with respect to FDA approved options. Some of these include:

  • An experimental drug may give you the opportunity to effectively treat a cancer or other health condition for which effective treatments are not yet available, when other treatments have failed, or when currently approved treatments are thought to have more risks or side effects.
  • 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 often free of charge to people participating in a trial.


Since an experimental drug has not yet undergone sufficient testing on enough people to receive FDA approval, less may be known about its effectiveness and safety. Possible disadvantages include:

  • 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). With cancer clinical trials a placebo is used infrequently, and instead, newer medications are usually compared to older "standard of care" medications. What this means is that you will receive either the experimental drug or the currently prescribed best first choice drug for your cancer.
  • Using the drug may eliminate your chances of using another treatment or participating in another clinical trial.

Questions to Ask

If you are considering the use of an experimental drug, either in a clinical trial or via compassionate it's helpful to ask yourself and your doctor (or the researchers) several questions. In doing this it's very helpful to bring someone with you who can support you and ask questions you may not think to ask, and who can take notes during your consultation. Questions to ask might include:

  • How might the drug benefit me?
  • What side effects may I expect?
  • How does the drug work (in plain English rather than technical terms)?
  • 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?
  • What happens if the clinical trial ends but the medication is not yet approved? Will you be be able to continue taking the drug if it was effective?

Clinical Trials and Informed Consent

If you choose to use an experimental drug, your doctor will have you complete a consent form. These are similar to forms that people sign prior to surgery and indicate that you aware of the possible risks related to the drug.

A Word From Verywell

The option of using an experimental drug can create tremendous anxiety, even when there is a reasonable chance that it will be safe and effective. Phase 1 trials might make you hesitate even more, but understanding what happens before a drug is tested on humans can be helpful if you find yourself in this situation. Extensive research must be done and presented to a committee before any consideration is given to trying a drug in clinical trials on humans. In addition, many of the new drugs being studied have been carefully designed to target specific processes, such that there is a greater chance that it will be effective than clinical trials done in the past. Certainly, asking a lot of questions, and asking for further clarification regarding anything you that seems unclear, is essential as you weigh your options.

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