Clinical trials are the engine of medical innovation. Every approved treatment or therapy on the market today began its life in a lab and went through years of careful testing and analysis. But what does the process of enrolling in a clinical trial actually look like?
In this post, we break down the path from preclinical screenings to participation—and explain the different phases of clinical trials to elucidate how new therapies move from idea to impact.
Step 1: Preclinical Screenings – The First Line of Testing
Before any clinical trial begins, researchers perform preclinical studies to determine if a treatment is safe enough to test in people. These studies happen in laboratories and often use cell cultures and animal models.
The goals of preclinical screening are to:
- Understand how a drug or treatment works in the body
- Identify potential toxicities or side effects
- Explore dosing and delivery methods
Step 2: Recruitment and Eligibility
Once approval is granted, researchers begin recruiting participants. This isn’t as simple as just signing up—each trial has very specific inclusion and exclusion criteria that define who can participate.
These criteria might include:
- Age, gender, or lifestyle factors
- Stage or type of illness
- Medical history and current health status
Eligible participants typically go through a screening process, which may include lab work, medical evaluations, and interviews to ensure they are a good fit for the study.
Step 3: Informed Consent – Knowing Your Rights
Before joining a trial, participants are taken through an informed consent process. This step ensures that participants:
- Understand the purpose and procedures of the trial
- Are aware of possible risks and benefits
- Know they can withdraw at any time
This process is both ethical and legal—designed to protect participants and ensure their decision to join is completely voluntary.
Step 4: The Phases of Clinical Trials – How Testing Progresses
Not all clinical trials are the same. In fact, they are structured in phases that build upon one another to answer different research questions. Here’s how they break down:
Phase I – Is it safe?
- Participants: Small group (20–100 people)
- Goal: Assess safety, determine safe dosage ranges, and identify side effects
- Focus: Healthy volunteers or people with the condition being studied
This phase is often the first time a treatment is tested in humans. Researchers monitor participants very closely to understand how the body responds to the drug or intervention.
Phase II – Does it work?
- Participants: Larger group (100–300 people)
- Goal: Evaluate effectiveness and further assess safety
- Focus: People who have the condition the treatment is designed to treat
This phase begins to look at whether the treatment produces the desired effect. It also refines the dosing regimen and continues safety monitoring.
Phase III – Is it better than current treatments?
- Participants: Large group (300–3,000+ people)
- Goal: Confirm effectiveness, monitor side effects, compare with standard treatments
- Focus: Broad population that mirrors the target market
Phase III trials often span multiple locations and are randomized and blinded (neither participants nor researchers know who gets the treatment or placebo). Success here is typically the final step before the treatment is submitted for approval.
Phase IV – What happens after approval?
- Participants: Thousands of people in real-world settings
- Goal: Track long-term effectiveness and rare side effects
- Focus: Approved treatments already on the market
These post-marketing studies help regulators and healthcare providers understand how the treatment performs outside the clinical setting and among diverse patient groups.
Step 5: Enrollment and Participation
Once you’ve passed screening and given informed consent, you’re officially enrolled. Your participation might include:
- Regular visits to a clinic or hospital
- Medication or treatment administration
- Blood tests, imaging, or questionnaires
- Remote monitoring through apps or wearables
Throughout the trial, researchers will monitor your progress closely to ensure your safety and gather data that contributes to the study’s outcomes.
Step 6: Follow-Up and What Comes Next
After the trial ends, you may be asked to return for follow-up visits—especially if the study looks at long-term effects. Sometimes participants are invited to join extension studies, particularly if the treatment shows promise or additional data is needed.
Why Trial Enrollment Matters
Clinical trials are essential to advancing medicine. Without volunteers, there would be no new treatments, no breakthroughs, and no progress. By enrolling in a trial, participants not only gain access to potentially cutting-edge therapies—they also contribute to a future where healthcare is smarter, faster, and more effective.
