Clinical trials are a research method that doctors and scientists use to study the potential risks and benefits of an investigational therapy in treating diseases or conditions and to determine if the therapy is safe.1-3
The journey to approval for investigational therapies
Before a therapy can be approved it must first go through a series of clinical trials which are done in phases (also known as steps), starting with small groups and expanding as researchers learn more. If clinical trial data demonstrates sufficient safety and efficacy for a therapy’s intended use(s), FDA (or equivalent health authorities in other countries) approve the product for sale to patients.1
Steps of a typical clinical trial1,3
Phase 1: The first step in testing a new therapy in humans.
It helps doctors figure out if the therapy is safe and what amount can be given safely before moving on to larger studies.
Phase 2: Determines whether a new therapy works for people who have the condition it is meant to treat.
It includes more participants and focuses on how well the therapy works and its ongoing safety. Doctors evaluate whether it improves symptoms, slows disease, or provides other benefits.
Phase 3: The final and largest step before a therapy can be considered for approval. It typically includes hundreds of patients.
It compares the study therapy to the current standard of care. The goal is to see how well it works in a larger group and to make sure it is safe for most people.
Application for Approval: If a study shows that a therapy works well and is generally safe, the company sponsoring the study can apply for FDA approval in the United States.
The FDA reviews all of the data to determine whether the new therapy is safe and effective.
Approval: The FDA reviews all the data and agrees that the new therapy is safe and effective, and it will be approved for use.
Phase 4: Takes place to keep learning about the therapy’s safety and effectiveness in a larger, real-world population.
This is sometimes referred to as a post-marketing study, and it helps doctors and patients understand how the therapy performs outside of a clinical trial setting.
Participation in a clinical trial contributes to scientific, medical, and patient communities’ knowledge about a disease and allows for:2,3
- Access to a therapy that is still being studied and not yet widely available
- Additional and closer monitoring by research and medical teams according to a structured study plan
It is important to understand that the therapy being studied may or may not work as expected, and participation can involve additional visits, tests, or potential side effects. Your doctor can help you decide whether a clinical trial is the right option for you.
Taking part is a commitment: it requires attending multiple visits according to a pre-set schedule. At these visits, participants may undergo procedures, tests and assessments, all based on a specific study protocol and its schedule of events.
Every clinical trial has a set of requirements—called eligibility criteria—that decide who can join the study.2,3
These rules are there to:
- Protect patient safety
- Make sure results are reliable
- Match the right therapy to the right groups of patients
There are two main types of eligibility criteria:
- Inclusion criteria: things you must have to join (for example: a certain type of cancer or being within a certain age range)
- Exclusion criteria: things that would prevent you from joining (for example: another health condition, a history of taking certain medications or therapies)
All the requirements are fully described prior to enrollment in an informed consent document. Participants may not enroll in any clinical trial until informed consent is provided.
Your doctor will be able to let you know if there are any clinical trials that are enrolling patients with conditions like yours and if you meet the eligibility criteria.
References
- Clinical Trials Overview. World Health Organization. Accessed January 15 2026. https://www.who.int/health-topics/clinical-trials#tab=tab_1
- Learn About Studies. National Library of Medicine. Updated June 10, 2024. Accessed January 15 2026. https://clinicaltrials.gov/study-basics/learn-about-studies
- NIH Clinical Research Trials and You, The Basics. National Institutes of Health. Updated April 24, 2025. Accessed January 15 2026. https://www.nih.gov/health-information/nih-clinical-research-trials-you/basics



