Medically Reviewed by Jenny Blair, MD

Clinical trials. Maybe you’ve heard about them but don’t have the clearest idea of what they are or what they involve. Or maybe you’re considering participating in one, but have questions before diving in.

Here you’ll find out the basic structure of a clinical trial, who participates in them, what people get out of them, and the kinds of questions you should ask about their results—especially if you’re planning to get involved.

Understanding the Terminology

When you see the word “clinical,” think “people.” Trials conducted with people are always called “clinical trials,” as opposed to “preclinical trials” or “animal studies,” which rely on work done with animals as substitutes for people.

The process of testing a drug in clinical trials usually follows a predictable path. First come those preclinical studies, which can reveal how a mammal processes a drug, whether or not the drug or intervention causes acute or dire unwanted effects, and some information about safety and dosing. If a candidate therapy clears the animal studies, it goes through a series of trial phases that usually break down like this:

Crohn's disease clinical trial research scientist reviewing treatment safety and efficacy

Phase 0/1

Purpose: This type of trial takes the drug or therapy to the first human step, examining how the human body reacts to it. It also helps establish an approximate dose or range of doses.
Participants: These early trials usually involve a relatively small number of people, under 100 or so, and a low dose of the drug. Sometimes, participants are healthy volunteers, and sometimes, they have the condition the therapy targets.
Time: This phase usually lasts a few months.

Phase 2

Purpose: This phase is the safety and early efficacy phase of testing.
Participants: Researchers will give some patients a low dose of the trial drug and escalate it in groups of patients until they see the effect they’re hoping to see or the side effects become unbearable. This approach can help investigators find the right balance between benefit and the cost in side-effects.
Time: A few months to a couple of years.

Phase 3

Purpose: To see if a therapy works in a larger patient population, to track adverse reactions, and to compare the therapy to other interventions, if they exist.
Participants: At this phase, the patient population is usually larger than in earlier phases, possibly numbering in the thousands.
Time: 1 to 4 years.

Phase 4

Purpose: Tracking of safety and efficacy over the long term after the drug has been approved by the US Food and Drug Administration.
Participants: Whoever is taking the drug.
Time: Variable.

You’ll notice that sometimes, clinical trials don’t last very long. Peter Higgins, director of the IBD Program at the University of Michigan, notes that it is important for patients to understand that all trials are relatively brief.

“Even if the medication works for you, the trial will stop,” he says. That said, trials that have reached phase 3 may have what is called an open-label extension, which allows for more data collection on safety and how well the drug works. Patients can enroll in these extension studies, if they are offered, after a phase 3 trial has ended.

IBD patients in a clinical trial in waiting room

Why Should You Participate?

It could benefit the IBD community

If you have inflammatory bowel disease (IBD) and you come across a recruitment announcement for a clinical trial, you may ask yourself, “Should I participate?” There are lots of good reasons to take part. If you are randomized to the study drug and it works for you, you’ll benefit, of course. However, you could be randomized to the placebo group, which receives a therapy that seems just like one being tested but without the active agent. Some patients may see being in the placebo group as pointless for them. But these trials that lead to therapies for people with IBD wouldn’t be possible without patients who are willing to risk being assigned to the placebo group.

Most people expect that in every clinical trial, both the investigators and participants will be unaware of who is receiving what treatment a technique called “blinding.” But IBD can be different because some interventions, such as diet, are hard to blind, says Adam Cifu, professor of medicine at the University of Chicago.

If you’re considering participating, you can look for a trial that takes a personal report about symptoms and converts it into something numerical. Cifu says that most of the good studies in IBD use disease activity scores based on patient reports, which yields numbers for data crunching.

You could help improve symptoms in yourself or others

Another consideration, says Cifu, is whether or not the trial is looking for an outcome that matters to you. “I think it’s important for people to think ‘what is it about my disease that bothers me’ and how likely this treatment is to help those symptoms,” he says. A trial should target results that patients care about. So a study that examines how a drug affects blood levels of inflammatory markers might be less useful for you than one that targets reducing the number of episodes of bloody diarrhea.

A Final Word About Clinical Trials

In addition to questions about what the trial drug is expected to do, other things you’ll want to find out include how long the trial will last, how many in-person visits it will require, and what the known risks of the intervention are. Before you begin participating in any trial, the people running it are required to inform you completely about all aspects of it so that you can give what is called “informed consent” to being involved. The researchers conducting the trial also must continue to keep you informed throughout the study.

A final important thing to understand is that your participation in a clinical trial is always voluntary, and you can leave the trial at any time for whatever reason—and give no reason at all.

Author Emily WillinghamEmily Willingham writes about health and medicine. Her work has appeared at Scientific American, Everyday Health, Sharecare and others. She is co-author with Tara Haelle of The Informed Parent: A Science-based Resource for Your Child’s First 4 Years.

Jenny Blair is a writer and journalist covering science, medicine, and the humanities. She earned her MD at Yale University, then completed a residency in emergency medicine at the University of Chicago. After several years in practice, she transitioned to working with words and ideas full-time. Jenny has contributed to Discover, New Scientist, Washington Spectator, and Medtech Insight, among other publications. She lives in New York City.

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