How long do clinical trial phases take?

Before a potential new therapy can be administered to patients, it must go through several clinical trial phases designed to test the drug or device for safety and effectiveness. For many new treatments, it will take approximately ten years for the therapy to progress from initial discovery to being approved. Clinical trials alone take six to seven years on average to complete.

Before the potential therapy enters the clinical trial stage, researchers begin by investigating ideas in the discovery phase, which typically takes three to six years. In most cases, a potential new treatment will first be tested in animals before it enters the first phase of clinical trials with human participants.

How long do clinical trial phases take?

Clinical trials progress through phases that test potential treatments in larger groups until they are deemed both safe and effective. The typical clinical trials timeline looks like this:

Phase 1: The first phase of clinical trials typically accepts between 20 and 100 people and lasts for several months. This phase is designed to measure safety by looking for any adverse side effects, but is not designed to evaluate the efficacy of the potential treatment. People who participate in Phase 1 trials are either healthy volunteers or people with the condition being studied, depending on the therapy being researched.

Phase 2: About 70% of potential new drugs will progress to Phase 2, which is designed to continue measuring safety and evaluating side effects while also measuring the effectiveness of the treatment. Trials in Phase 2 usually accept several hundred patients and last several months to two years.

Phase 3: Only 33% of drugs will progress to Phase 3, which tests the potential therapy on the largest number of people. Phase 3 measures both safety and efficacy in broader samples of the patient populations, and participant quotas are often in the thousands. The third phase of clinical trials typically lasts between one and four years. 

FDA Approval: Once Phase 3 has concluded, the company studying the drug can submit a New Drug Application (NDA) or a biologics license application (BLA) for the treatment to the Food and Drug Administration (FDA). The FDA will review all the information the researchers gathered during each stage of the trial to determine if the drug will be approved. 

Phase 4: Phase 4, also called “Post-Approval Research and Monitoring,” takes place after the new treatment is approved by the FDA. The company that researched the drug may want to continue monitoring patients in order to gain more insight into any long-term effects and how the drug or device compares to other treatment options.

Your time commitment to a clinical trial

If you’re considering participating in a research study, ask the study team about the schedule of the trial. Many trials are several years long, but some require only a few visits while others require more frequent check-ins. Trials will also often involve keeping an online or paper logbook between visits. It is important to consider the time commitment against the potential benefits to make sure the trial is a good fit.

If you do participate in a clinical trial, you will be able to leave at any time and for any reason, even before the trial is concluded. Some trials are also concluded early if researchers are not getting meaningful results.

Because it is so important that drugs are thoroughly evaluated before they are taken to market, the clinical trial process is long — but the length of the research is one of the reasons it is so important for people to take part. Nearly 80% of clinical trials are delayed due to a lack of volunteers. If you’re interested in participating in this meaningful process, use the tool below to find a clinical trial near you.