Conducting a clinical trial requires moving through a series of defined stages: designing a protocol, securing ethical and regulatory approval, recruiting participants, collecting data, and reporting results. Each stage has specific requirements, and skipping or rushing any of them can derail the entire effort. Here’s how the process works from beginning to end.
Start With a Sound Protocol
The protocol is the blueprint for the entire trial. It defines the research question, the hypothesis, the study design, eligibility criteria for participants, the procedures and methods you’ll use, the endpoints you’ll measure, and the timeline and budget. A well-written protocol should be detailed enough that another investigator could replicate the study and reach comparable conclusions.
Several elements deserve particular attention. Your proposed number of participants needs scientific justification, typically through a statistical power calculation that shows you’ll enroll enough people to detect a meaningful difference. Your eligibility criteria (who can and can’t participate) need to be specific enough to reduce confounding variables but broad enough to make recruitment feasible. And your endpoints, the outcomes you’re measuring, need to be clearly defined before enrollment begins. Changing them mid-trial introduces bias and raises serious credibility problems.
Choose the Right Phase
Clinical trials are organized into four phases, each with a different purpose and scale.
- Phase I tests a drug or treatment in 20 to 80 people for the first time. The goal is to evaluate safety and identify side effects, not to prove the treatment works.
- Phase II expands to 100 to 300 participants. Here you’re looking at whether the treatment actually works while continuing to monitor safety.
- Phase III involves 1,000 to 3,000 participants. This phase confirms effectiveness, compares the treatment against existing options, and gathers the safety data needed for regulatory approval.
- Phase IV happens after a drug is already approved and on the market. Researchers track long-term safety, explore optimal use, and identify rare side effects that only appear in larger populations.
Each phase builds on the one before it. A treatment that causes dangerous side effects in Phase I won’t advance to Phase II. Most experimental treatments never make it through all four phases.
Secure Ethical Approval
Before enrolling a single participant, your study must be reviewed and approved by an Institutional Review Board (IRB) or ethics committee. The IRB’s job is to protect the rights and welfare of the people in your study. They review the full protocol, the informed consent documents, and investigator materials to make sure participants won’t be exposed to unreasonable risk and that they’ll understand what they’re agreeing to.
The informed consent process itself has eight required elements under federal regulations. Participants must be told that the study involves research, what procedures they’ll undergo and how long participation lasts, the foreseeable risks and potential benefits, any alternative treatments available, how their confidentiality will be protected, whether compensation or medical treatment is available if they’re injured, who to contact with questions, and that participation is entirely voluntary. They can withdraw at any time without penalty.
This isn’t just a form to sign. The consent process should be a genuine conversation where participants can ask questions and take time to decide. IRBs will reject consent forms that are written in dense legal or medical language that an average person can’t understand.
File the Regulatory Application
For trials involving unapproved drugs or new uses of approved drugs in the United States, you need to file an Investigational New Drug (IND) application with the FDA before the trial can begin. This requires three forms: FDA Form 1571, which details the study itself; FDA Form 1572, the investigator’s statement providing information about the researcher and study site; and FDA Form 3674, which certifies the trial is registered on ClinicalTrials.gov.
If you’re studying an unapproved drug, the IND application also requires a comprehensive package of supporting data: animal studies, pharmacokinetic analyses, toxicology data, and manufacturing information. If you’re using an already-approved drug in its existing packaging, the requirements are lighter. You’ll need the trade name, generic name, dosage form, strength, and lot number, but you generally won’t need to submit manufacturing files or toxicology data.
The FDA has 30 days to review an IND. If they don’t place a clinical hold during that window, you can proceed.
Recruit and Enroll Participants
Recruitment is where many trials stall. Scheduling conflicts, strict eligibility criteria, lack of awareness, and participant hesitation all create friction. Choosing the right recruitment strategy makes a significant difference.
In-person recruitment tends to be the most efficient and cost-effective approach. In one study tracking multiple recruitment methods, every participant recruited in person who passed screening completed the trial, a 100% completion rate. Personal referrals performed similarly well, with all 19 screened participants finishing the study. Flyers yielded a 95.7% completion rate, and social media reached the broadest audience with a 92.3% completion rate among those screened, though it required prescreening a much larger pool (102 people to eventually enroll 12). Community events had the lowest completion rate at 75%.
The takeaway: cast a wide net with digital outreach, but don’t underestimate the power of direct, in-person contact. Participants recruited through personal interaction tend to be more committed. Whatever strategy you use, plan for a meaningful gap between the number of people who express interest and the number who actually complete the study.
Set Up Data Collection and Management
Most modern trials use an Electronic Data Capture (EDC) system to collect and store data. When selecting an EDC platform, look for compliance with 21 CFR Part 11 regulations (the federal standard for electronic records), robust information security, disaster recovery features, a complete audit trail that logs every change to the data, and electronic signature capability.
Before data collection begins, you need a data management plan that specifies how data will be entered, validated, queried, and eventually locked. “Database lock” is the point after which no further changes can be made, and it follows a structured sequence of checks: confirming all expected case report forms have been entered, verifying the database matches the data dictionary, determining the status of every enrolled participant (completed, withdrawn, lost to follow-up), checking for formatting problems in data exports, and confirming all required site signatures are in place.
Many teams perform a “soft lock” first, restricting editing access while final quality checks are run, followed by a “hard lock” that permanently freezes the dataset for analysis. A quality assurance audit, often comparing a sample of original case report forms against the exported datasets, happens before the final lock to catch any remaining errors.
Monitor Quality Throughout the Trial
Quality control isn’t something you do at the end. It runs throughout the life of the trial through a series of monitoring visits.
Before enrollment begins, a site assessment visit evaluates whether the facility has the right equipment, staffing, training, and standard operating procedures to conduct the trial properly. This covers everything from the clinic to the lab, pharmacy, and data management operations.
During the trial, interim monitoring visits check that the study is being conducted correctly. Monitors review regulatory files, verify source documents against the database, assess pharmacy operations (including drug storage, temperature monitoring, and chain of custody), evaluate site management and quality management activities, and verify laboratory specimen handling and storage. These visits catch problems early, before they compromise the data.
At the end of the trial, a close-out visit confirms that all participants have either completed their study visits, withdrawn, or been transferred. The site wraps up remaining documentation and follows sponsor instructions for final archiving of study materials.
Report Results Publicly
Federal law requires that trial results be submitted to ClinicalTrials.gov within one year of the primary completion date. Sponsors or investigators can request an extension in certain circumstances, but the one-year deadline is the standard expectation. Study records must also be updated in a timely manner throughout the trial, not just at the end.
Registration and results reporting aren’t optional steps or nice-to-haves. They’re legal requirements tied to the IND certification you signed at the start. Beyond legal compliance, public reporting is what makes the broader research ecosystem work. Unpublished negative results lead other researchers to waste time and money repeating failed approaches, and they leave clinicians without the full picture when making treatment decisions.