When Are Phase 1 Clinical Trials Done?

The possible benefits of phase 1 trials has changed significantly

A Phase 1 clinical trial is the first phase of three or four phases of research studies to test a treatment on humans. The major goal of a clinical trial is to determine if a drug or procedure is safe for human use. Prior to phase 1 clinical trials, a drug must be studied extensively on disease cells in the laboratory and/or in laboratory animals. The role of phase 1 clinical trials in cancer, however, has changed tremendously in recent years, mostly due to the Human Genome Project (HGP). Completed in 2003, the HGP allowed scientists to discover the sequence of all genes found in humans, which allowed for medical advances in the diagnosis and treatment of many diseases, including cancer. Before the HGP, clinical trials for new experimental drugs were often a "last ditch" effort, with only a small chance that a person would benefit. Instead, participating in a phase 1 clinical trial may be an excellent (and only) option to extend life.

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In addition, since many drugs being tested in these trials have been carefully devised to interfere with specific targets in the progression and spread of cancer, for example, they tend to be less "risky" than in the past. At the current time, there are many people surviving cancer due to the existence of these experimental trials.

Keep in mind that the purpose of clinical trials is to find treatments that either work better or have fewer side effects than medications currently available. All medications used to treat cancer (or any condition) were once tested in a clinical trial. And during that trial period, the only people who were able to reap the benefits of these treatments were those who were enrolled in the clinical trial study group.

Definition and Purpose of Phase 1 Clinical Trials

Phase 1 clinical trials must be done to see if an experimental drug or treatment is safe. After treatment is tested in the lab or on animals (called preclinical testing), it enters a phase 1 clinical trial that involves testing on humans. It's important to note that preclinical testing is often extensive, and significant and positive results must be found in order to have a human trial approved.


Phase 1 clinical trials involve only a small number of people to determine if a drug or treatment is safe and to determine the best dose of a drug and how it should be given (whether orally or intravenously). A low dose of medication is usually used, and a group may be divided such that some people receive a higher dose and others, a lower dose of the drug.

Though the primary purpose of these trials is to evaluate treatment safety, they may also determine that a treatment appears to work favorably against cancer if enrolled subjects respond well to the drug (such as if cancer stabilizes or decreases in size).


Since phase 1 trials are the first studies to be tested on humans, and thus carry the greatest risks, people enrolled in the study are usually monitored very closely by the study investigators. For example, blood and urine samples may be collected regularly. In addition, these trials are often conducted at major cancer centers (such as the National Cancer Institute designated centers) that have oncologists who specialize in specific cancer types.

Other Phases of Clinical Trials

There are three phases of clinical trials that must be completed before a drug is approved by the Food and Drug Administration (FDA). If a treatment appears safe at the end of a phase 1 clinical trial, it may then move forward to a phase 2 clinical trial, a study done to see if a treatment is effective. If a drug or treatment is deemed safe in a phase 1 trial and effective in a phase 2 trial, it will then enter a phase 3 clinical trial. Phase 3 clinical trials have much larger study popualtions and are done to see if a treatment is not only safe and effective but works better or has fewer side effects than treatments currently available.

Phase 1 Clinical Trials Have Changed

Phase 1 clinical trials, and what you may expect if you are enrolled in one, have changed significantly in just the last few years.

With the advancement in precision medicine, which allows treatment to account for individual genetic differences, it's likely that phase 1 clinical trials will continue to offer more promise for individuals rather than simply studies performed to see if a drug is safe.

Targeted cancer therapy, which target specific cell abnormalities and differ from standard chemotherapy, can help make a difference for your cancer. After all, if you can inhibit a specific step that cancer must go through to divide (and thus grow and spread), there is a reasonable chance that cancer that has been shown to be dependent on that step will respond.

Targeted drugs are often more likely to hold cancer in check for some time, as well as immunotherapy drugs, may result in a durable long-term response.

An Example: Vitrakvi (Larotrectinib)

An example of a successful phase 1 clinical trial is that of the targeted therapy Vitrakvi (Larotrectinib), which was granted accelerated approval by the FDA in 2018. This medication works by inhibiting a step in the growth of cancers that have a particular genetic profile, rather than on any cancer (people with over 17 types of cancer were studied, including both adults and children).

In phase 1 clinical trials leading up to approval, the drug was given to people with advanced cancers who either had no other treatment options available or had progressed with those options. Of the study particpants, 75% responded to the drug, and many continued to respond when the study period ended after nine months. In comparison, if people were treated with chemotherapy (if that was even an option), the majority would have seen their cancer progress within six months. There were even a few people with metastatic or inoperative cancer who had tumor progression significant enough that curative surgery could then be performed.

Considering a Phase 1 Clinical Trial

There are a few reasons someone may consider participating in a phase 1 clinical trial. One is the hope of improving medicine that may help others with the same disease in the future. Another is the hope that a new drug or procedure that has not yet been tested on humans will offer a chance of survival when other treatments have failed. The only way advances in cancer treatment, and subsequent survival, are made, is via human participation in clinical trials. That said, clinical trials are not for everyone.

Risks and Benefits

It's important to consider all of the risks and benefits of clinical trials if you are considering participating in one of these studies. It's often helpful to write down both the pros and cons of the study on a sheet of paper so you can visibly weigh your options. There is not a right or wrong choice, only the choice that is best for you.

Other Options for Receiving Experimental Drugs

For the most part, the only way that you can use an experimental (investigational) drug is to take part in a clinical trial. That's not always the case, and some people may qualify for compassionate drug use or expanded access to drugs not yet approved by the FDA. If you do not qualify for a clinical trial but an investigational drug appears promising for your particular cancer, you may opt for compassionate drug use.

Bottom Line

Phase 1 clinical trials are the first medical studies in which a new or newly improved drug is tested in humans. While traditionally this has been anxiety-provoking and has led to jokes about being a "guinea pig", these initial studies can be looked at in different ways. From one side they may be risky. After all, the primary purpose of these trials is to determine if a drug is safe for people (and also to get an idea about the best dose to use).

Yet, from a different angle, the benefits may outweight the risks of a phase 1 clinical trial. Many phase 3 clinical trials compare drugs that have already been looked at. For cancer patients, the hope may be that a drug will improve survival if only for a few months. A new experimental drug (and possibly a new category of drugs) may help more than anything else currently available.

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Article Sources
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