Clinical trials can last anywhere from a few months to over two decades. The official timeline for a clinical trial can vary by phase, disease, and study design. Individuals interested in participating in a clinical trial should be aware of access to treatment, potential timeline commitment, and travel expenses.
Here’s an overview of how long clinical trials last.
Within the four phases of clinical trials, these periods can last from just a few months to over 20 years. Kardie Tobb, DO, MS, CPE, FASPC, FACC, FACOI, a cardiologist, clinical integration officer, and medical director for a women’s heart health clinic in North Carolina, has served as a primary investigator for clinical trials. According to Dr. Tobb, the timelines can vary. “It varies based on a trial phase, disease, and what outcome we’re measuring,” she explains. “Some of the cardiology trials go very long over time, years.”
Some of the typical ranges of clinical trials are as follows:
To help researchers answer their research questions, clinical trials are divided into several phases. As these phases progress, researchers gradually increase the number of participants to assess potential risks, side effects, and optimal dosage. These phases help researchers learn more information about the treatment and its effectiveness.
The U.S. Food and Drug Administration (FDA) requires a regulatory process, also called oversight, to ensure that these studies and trials comply with federal law in design, execution, and reporting. This includes ensuring the safety of human participants, maintaining data integrity, and verifying that the study adheres to good clinical practice (GCP).
Phase I trials typically focus on finding the ideal dose, determining side effects, and the body’s reaction. Researchers use a smaller participant group, ranging from about 20 to 100 people.
While other trials test a drug’s efficacy, this stage focuses on short-term safety, so it is limited to a smaller number of participants and a shorter time span.
About 70 percent of drugs will complete this level and move to the next phase.
While Phase II trials also focus on side effects, they assess a treatment’s effectiveness.
The participant number typically increases, reaching about 100 to 300 people with the specific disease or condition, and can last up to two years. The researchers are now working to determine how effective the treatment is for a specific condition or disease.
Participants are often split into randomized groups: one taking the new drug, another taking a standard treatment (control), and one taking a placebo. About 33 percent of drugs will progress from this phase to the next.
At Phase III, researchers have reached the stage of large-scale testing. This means hundreds to thousands of subjects with a specific disease or condition are involved in ongoing monitoring of the drug or treatment’s efficacy and safety. The large number of subjects helps researchers to discover any rare side effects.
The drug or treatment is also compared to the current standard level of care. This phase tends to take longer, ranging from one to four years, due to the need to find more participants, to continue long-term follow-up, and to implement more intensive study protocols.
The drug or treatment receives official approval from the FDA, and can continue into Phase IV, also known as post-marketing.
With the drug now on the market, researchers continue to monitor its efficacy and side effects, using data from thousands of subjects in the “real world.”
This phase can last years, decades, or even indefinitely as researchers continue to follow up with patients. This, however, does not mean all participants will be a part of the decades-long study. Typically, one participant’s involvement does not last the entire trial.
“Phase one, we’re thinking about safety in humans,” Dr. Tobb explains. “Phase two: Does it work? And how safe is it? Phase three: Does it really work? And how does it compare to our standard of care? And then phase four will be: How does it perform in the real world?”
Several factors can influence a clinical trial’s length:
Trials for chronic illnesses can last months to years as they require long-term monitoring. These trials are more about managing the condition rather than treating it. Acute illnesses can have shorter clinical trials, sometimes lasting only a few weeks.
A cancer clinical trial can last anywhere from 10 to 15 years, depending heavily on the type of disease, the treatment, and the number of patients needed. It can take longer to recruit study participants who have the disease. While infectious disease clinical trials can also take years, we know it’s possible to accelerate the process, as with the COVID-19 vaccines.
The length of a clinical trial can depend on the study design, which can range from observational studies, such as cross-sectional studies, to experimental studies, such as randomized controlled trials (RCTs).
A cross-sectional study analyzes data from a population at a specific time point.
In an RCT, participants are randomly assigned to a test group and a control group. (In a placebo-controlled trial, you include a placebo group.)
Another common option is a crossover trial, in which subjects are shifted between different treatment groups.
The specific disease or condition can affect how many participants you need for each phase of a clinical trial, thus affecting overall recruitment timelines.
Phase I subjects might be easier to source, as they are usually healthy participants. Phases II and III take longer because sourcing a higher number of participants can be difficult.
“When you’re doing a high blood pressure study, you could find 100 people in three months,” Dr. Tobb explains. “But if you’re doing something like a rare disease, it’s very hard to find those people.”
Diversity and representation are vital in clinical trials, especially for Black women. The more a population is represented in a study, the more researchers can ensure the safety and efficacy of their drug or treatment for all populations.
“The reflection of Black women’s realities is transitioned through other information,” Dr. Tobb says. “We want to be able to reflect our own realities in terms of how medications impact us because if we’re represented in research studies, doctors like myself can make decisions based on those studies.”
To ensure the rights and safety of human subjects, Institutional Review Boards (IRBs) must approve research for the trial to continue. These protective measures can extend the trial’s duration but are necessary for patient welfare.
“That means that multiple people from different backgrounds have looked at everything, including racial, ethnic background, geographic background, social, and economic background,” Dr. Tobb explains.
As for U.S. FDA regulations, trials must comply with and be registered at ClinicalTrials.gov, whose safety standards can be rigorous and time-consuming.
To ensure the safety of all participants, studies will continue to conduct regular check-ups on their subjects. This can last for five years for lower-risk products and up to 15 years for high-risk products. Follow-ups also include survival tracking, with measurements of Overall Survival (OS) and Progression-Free Survival (PFS).
Even if a clinical trial takes years, a participant’s involvement lasts much shorter.
Subjects can commit for as long as they desire to be involved, which could be weeks or months. They start with a screening period that lasts about one to two weeks.
Depending on the study, the following treatment period can last months to years.
Finally, there is a follow-up period, which can vary from a few weeks to a few years. However, a participant can always withdraw.
Clinical trials may end early for several key reasons.
If the treatment tested is highly effective, the study may end prematurely. Studies can also be terminated due to safety concerns, treatment efficacy concerns, or funding issues.
As a participant, you have the right to voluntary and informed consent, voluntary withdrawal, safety monitoring, and to be informed about the treatment’s impact on your care.
“Even signing an informed consent doesn’t bind you to stay in that study,” Dr. Tobb says. “Being a part of a clinical study is all voluntary. You always have the option to withdraw.”
As the trial subject, you should be informed of the trial’s length as you are committing your time. This includes travel considerations, impacts on your work and family, and any concerns about cost and insurance. Logistical barriers such as time constraints, insurance coverage, and transportation can affect the ability of underrepresented communities to participate in clinical trials.
If you are interested in participating in a clinical trial, you can visit ClinicalTrials.gov or BlackDoctor’s Clinical Trial Resource Center.
Before participating in a clinical trial, it is vital to speak with your doctor to ensure your safety throughout the process.
Clinical trial length can vary depending on multiple factors, including the type of disease, the type of drug or treatment, the type of study, the number of participants needed, and more.
Dr. Tobb encourages interested participants to read the consent forms. “Informed consent should be really spelled out on a sixth-grade level,” she says. “Read the information, and if you don’t understand, ask questions before you say yes.”
While participation may not be for the entire duration, cancer clinical trials can last anywhere from five years to over a decade, from Phase I to Phase IV.
Sourcing patients for clinical trials for rare diseases can be tedious, prolonging these trials. While these trials are often smaller and include fewer subjects, they can often face delays.
Yes, you can receive compensation for participating in a long clinical trial. The payment amount will vary depending on time, effort, and travel expenses. This could range from $200 to over $1,000.
The shortest clinical trials can last only a few days to a few weeks. Phase 0 trials, also known as exploratory trials, are often about that length. Trials can also end early due to unforeseen circumstances.
You can search for a timeline on ClinicalTrials.gov or BlackDoctor’s Clinical Trial Resource Center to see the length of the trial.
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