Clinical Trial Glossary — Medical Terms in Plain English
Clinical trials use specialised medical language. This glossary explains every term in plain English so you can understand eligibility criteria, trial designs, and medical procedures.
A
A trial that can be modified while it is running, based on pre-planned rules and interim results.
Additional treatment given after surgery to reduce the chance of disease returning.
Any unwanted medical problem that happens during a clinical trial.
Agreement from a child or young teenager to participate in a trial.
B
Measurements taken at the start of a trial, before treatment begins.
How much of a drug actually reaches your bloodstream and is available to work.
A measurable substance in your body that helps determine treatment decisions.
An FDA designation for drugs showing substantial improvement over existing treatments.
C
Powerful drugs that kill rapidly dividing cells, including cancer cells.
A company hired to help run clinical trials on behalf of the sponsor.
A group of participants who share a common characteristic and are studied together.
Using two or more treatments together to attack disease from multiple angles.
A medical condition you have in addition to the one being studied.
Access to an experimental treatment for seriously ill patients with no other options.
All detectable signs of disease have disappeared after treatment.
A range of values that likely contains the true treatment effect.
A reason why a particular treatment should not be given to you.
The group that does not receive the new treatment, providing a baseline for comparison.
A trial where participants receive one treatment and then switch to the other.
D
An independent group that reviews trial data to protect participant safety.
A study where the dose is gradually increased to find the right amount.
A side effect severe enough to prevent the dose from being increased further.
Neither the participant nor the doctor knows which treatment is being given.
E
A 0-to-5 scale measuring your ability to function in daily life.
You meet all the requirements to join a specific trial.
The European Medicines Agency — the EU equivalent of the FDA.
FDA mechanism allowing unapproved treatments during public health emergencies.
The specific outcome a clinical trial is designed to measure.
You have passed screening and are officially a participant in the trial.
Conditions that prevent you from joining a trial, designed to protect your safety.
A pathway to use an unapproved drug outside of a clinical trial for serious conditions.
F
An FDA designation speeding up review for drugs treating serious conditions.
The US Food and Drug Administration — the agency that approves new drugs.
G
Analysing your DNA to identify gene mutations relevant to treatment.
International ethical and quality standards for conducting clinical trials.
H
The time it takes for the amount of drug in your body to decrease by half.
A number comparing the rate of an event between two treatment groups.
A person without any illness who participates in a trial to test drug safety.
I
Treatment that helps your immune system recognise and fight disease.
Requirements you must meet to join a trial.
Investigational New Drug application — the FDA filing required before human testing.
You do not meet one or more requirements for a specific trial.
The process of learning about a trial before agreeing to participate.
The ethics committee that oversees clinical research at hospitals and universities.
Analysis including every randomised participant, regardless of whether they completed treatment.
A planned review of trial data before the study is complete.
A study where participants receive a specific treatment and researchers measure the results.
A drug being tested in clinical trials that has not yet been approved.
Institutional Review Board — the independent committee that approves trial plans.
M
Ongoing treatment to keep disease from returning after initial therapy worked.
The highest dose of a drug that does not cause unacceptable side effects.
A lab-made protein designed to attach to a specific target on cells.
A trial that runs at multiple hospitals or clinics across different locations.
N
New Drug Application — the formal submission requesting FDA approval to sell a drug.
Treatment given before surgery to shrink a tumour.
O
A study that watches participants without changing their treatment.
Everyone knows which treatment each participant is receiving.
A medication developed to treat a rare disease affecting fewer than 200,000 people.
How long participants live after starting treatment, the most meaningful cancer endpoint.
P
A number showing how likely it is that trial results happened by chance.
Care focused on relieving symptoms and improving quality of life.
A trial where groups receive different treatments simultaneously without switching.
The disease has shrunk significantly but not completely disappeared.
Analysis including only participants who completed the trial exactly as planned.
A score measuring how well you can carry out daily activities.
The study of what a drug does to your body.
The study of how your body absorbs, distributes, and eliminates a drug.
An inactive treatment that looks identical to the real drug, used for comparison.
A trial that compares the new treatment against an inactive placebo.
The probability that a trial will detect a treatment effect if one truly exists.
The main outcome measure the trial is designed to evaluate.
The lead doctor responsible for the trial at a specific hospital or clinic.
Treatments you have already received before joining a trial.
Your disease is getting worse — a tumour is growing or spreading.
How long you live without your disease getting worse.
R
The process of randomly assigning participants to different treatment groups.
A computer randomly assigns participants to treatment groups, like flipping a coin.
A long-term study collecting health data from people with a specific condition.
Official authorization from the FDA or EMA allowing a drug to be sold to the public.
Signs and symptoms of disease have partially or completely disappeared.
The percentage of participants whose disease shrank meaningfully during treatment.
S
The number of participants needed to detect a meaningful treatment effect.
Medical tests to check whether you meet a trial's eligibility criteria.
Additional outcomes measured alongside the primary endpoint.
A medical event during a trial that is life-threatening or requires hospitalisation.
The participant does not know which treatment they are receiving, but the doctor does.
A trial that takes place at just one hospital or clinic.
The organisation that funds and oversees a clinical trial.
Your condition is neither getting better nor getting worse.
The currently accepted, best-available treatment for a condition.
Results that are unlikely to have occurred by chance alone.
Balancing key patient characteristics across treatment groups during randomization.
A stand-in measurement used when the real outcome takes too long to measure.
T
Drugs designed to attack specific molecules that cancer cells depend on.
One of the groups in a trial, each receiving a different treatment or dose.
W
Time when you must stop certain medications before a trial begins.
96 terms defined · Written for patients and caregivers