How Are Cancer Drugs Discovered and Developed?

Approved by the Cancer.Net Editorial Board, 02/2021

Doctors and scientists are always looking for better ways to care for people with cancer. One way to do this is to create and study new drugs. They also look for new ways to use drugs that are already available.

Drugs go through a long development and approval process in the United States. Before any drug can be prescribed to a patient, researchers make sure the drug is safe and that it effectively treats cancer. This process often takes many years and significant resources. The actual amount of time it takes to go from a researcher's idea to the drug's development and approval varies.

There are 3 main steps in developing a new drug:

  • Preclinical research, when the drug is found and first tested

  • Clinical research, when the drug is tested in people

  • Post-clinical research, which takes place after the drug is approved and studies continue

Who develops new cancer drugs?

Medical research universities, government agencies like the National Cancer Institute (NCI), and pharmaceutical companies find and test new drugs. In drug research, the "sponsor" is the group that develops a drug. They do the initial research needed for the U.S. Food and Drug Administration (FDA) to approve the drug. The FDA does not develop or test drugs.

How are cancer drugs discovered?

The discovery of new cancer drugs can happen in different ways:

Accidental discovery. Sometimes, drugs are discovered by accident. For example, in the early 1940s, an explosion exposed sailors to poisonous mustard gas. Doctors found that these sailors had low white blood cell counts. They began treating Hodgkin lymphoma with a byproduct of mustard gas known as nitrogen mustard. The drug meclorethamine (Mustargen), for example, is nitrogen mustard. Hodgkin lymphoma is a cancer of the lymphatic system involving the white blood cells. Nitrogen mustards are still used as a cancer treatment today. Accidental discoveries like this are rare.

Testing plants, fungi, and animals. Some cancer treatments are found in nature. For example, paclitaxel (Taxol) treats several types of cancer. It was first found in the bark of the Pacific yew tree. And the cancer drug eribulin (Halaven) was developed from the sea sponge, a small ocean animal. The NCI has samples of thousands of plants, marine organisms, bacteria, and fungi. These are collected from around the world in the hopes of finding new cancer treatments.

Studying the biology of cancer cells. Researchers can find different ways to treat cancer by studying the biology of cancer cells. Most cancer researchers start by comparing the genes found in DNA and the growth patterns of cancer cells to healthy cells. By knowing how cancer cells grow, researchers can try to find drugs to stop that process. They can also make drugs that can target specific genes found in the cancer.

For example, researchers learned that about 20% of all breast cancers have an abnormal amount of a certain protein. It is called HER2 and controls the growth and spread of cancer cells. Multiple drugs have been developed over the years to treat HER2-positive breast cancer. Everyone with breast cancer has their tumor tested for the HER2 protein. This test shows if these drugs can treat the cancer. Learn more about the basics of targeted treatments.

Understanding the chemical structure of a drug target. Scientists can use computers to mimic how a potential drug will interact with its target. This is similar to fitting puzzle pieces together. Researchers can then make chemical compounds that interact with the specific drug target.

Creating drugs that are similar to existing drugs, called biosimilars. Biologic drugs are drugs that are made from living things like cells, tissues, or proteins. Biosimilars are drugs that are almost the same as an existing biologic drug that has already been approved by the FDA. The sponsors of a biosimilar must show that it is just as safe as the original drug, called the reference drug. In order to be approved, the biosimilar must have a similar structure and function to the reference drug and have no large differences. Biosimilars often cost less than similar drugs and they take less time to approve than a new drug. Learn more about biosimilars.

How are new cancer drugs tested during preclinical research?

After a new drug is discovered, researchers need to see if the new drug works. First, the drug is tested on human tumor cells in the lab. Researchers watch to see if the drug stops the growth of cancer cells. If the drug successfully treats the tumor cells in the lab, testing can move onto the next step.

Next, a drug is tested in animals to find out if it is still effective at treating cancer. Researchers test the drug in 2 or more animal species. This helps them learn how the body uses the new drug. They also learn what side effects the drug may cause and what dose of the drug to test in people.

In the United States, researchers must show the results from these tests to the FDA in order to begin clinical trials, which are research studies involving volunteers.

How are new cancer drugs tested during clinical research?

After the drug has been shown to be effective during the preclinical research, it needs to be tested in people through clinical trials.

Before new drugs can be tested in people, the sponsor must submit an Investigational New Drug (IND) application to the FDA. The IND provides information about past and future research plans. It includes the results from the preclinical studies done in the lab and in animals, the plans for clinical trials in people, and information about how the new drug is made.

The FDA will approve potential drugs for testing under certain conditions:

  • The research shows that the drug is likely to work and be safe.

  • The proposed clinical trials are designed correctly.

  • The drug can be made the same way every time.

Clinical trials are used to find out if a new drug is safe, effective, and better than standard treatments. Before FDA approval, clinical trials for a medication must go through 3 phases. Early phases of clinical trials focus on the drug's safety, its dosing, and how the body processes the drug. Later phases study how well the drug works. Each phase involves a larger number of people than the phase before it.

Clinical trials for a drug may eventually involve hundreds or thousands of people. They usually take years to complete. Sometimes, if a small clinical trial shows very promising results, the process can be sped up. Learn more about clinical trials.

When can new cancer drugs be used outside of a clinical trial?

If the clinical trials are successful, the drug sponsor submits a New Drug Application (NDA) to the FDA. The NDA requests approval so that the drug can be prescribed by doctors. This request includes:

  • Results from the preclinical research and clinical trials.

  • Details about how the drug will be made and labeled.

  • The drug's possible side effects and any interactions with food or other drugs.

The FDA may approve the drug if the evidence shows it is effective and safe for use. While no drug is completely safe or free from side effects, a drug will be approved if there are more benefits than risks.

How does the FDA approve biosimilars?

Biosimilars are drugs that are almost the same as a drug that has already been approved by the FDA. Certain minor differences between a biosimilar and its reference drug do not affect how well it works or how safe it is. Because of this, researchers may not need to do as many clinical trials to get FDA approval.

The approval process for biosimilars includes the same steps as the approval for any other drug by the FDA. First, researchers must present preclinical data showing that there are only minor differences between the biosimilar and the reference drug. This research should also show that these differences do not affect how well the biosimilar works or how safe it is.

After the preclinical research has been evaluated, the FDA will determine how much additional testing is required for the biosimilar. Some steps in the process can be waived based on how similar the biosimilar and reference drug are. The FDA can also require the biosimilar go through more clinical trials if there are any concerns.

What happens after a cancer drug is approved by the FDA?

When a new drug has received FDA approval, it can be prescribed by doctors.

The FDA may also require that the sponsor conduct more clinical trials. These are called phase IV clinical trials. Phase IV clinical trials look for more possible side effects or confirm that the treatment is beneficial. They may also study the drug in different doses, new combinations, or in different schedules. They may also study the drug's long-term effects.

Some drug makers may conduct their own phase IV clinical trials. They may do more research to get FDA approval to use the drug in a new way, such as as a treatment for another type of cancer.

The FDA also continues to monitor the safety of drugs currently on the market. This is called post-marketing monitoring. The sponsor of the drug is required to submit periodic safety updates to the FDA. They do this to make sure that drug makers report any new or serious side effects. The FDA may withdraw a drug from the market if new research shows it is not safe or effective.

Questions to ask the health care team

If you have questions about a new drug you've heard about or a drug you have been prescribed, be sure to talk with your cancer care team. Below are a list of questions to consider asking about a specific medication:

  • Has this new drug been approved for my type of cancer?

  • How effective is the drug in clinical trials?

  • What are the drug’s side effects?

  • Will my insurance cover this drug?

  • Are there other treatment options I should consider?

  • What clinical trials are open to me?

Related Resources

Drug Approval and Labeling

How Can I Get the Latest Cancer Drug?

What Are Biosimilars in Cancer Treatment?

Cancer.Net Podcast: Biosimilars and Cancer Care

Cancer.Net Video: What are Clinical Trials, with Richard Goldberg, MD

More Information

FDA: Drug Development and Approval Process