Conducting a clinical trial requires navigating a structured sequence of regulatory filings, safety reviews, and phased testing that typically spans several years from first application to final results. The process is governed primarily by the FDA in the United States, with parallel systems in other countries, and every step is designed to protect participants while generating reliable evidence about a treatment’s safety and effectiveness.
Start With Preclinical Work and an IND Application
Before any treatment can be tested in humans, you need preclinical data, usually from animal studies, showing the drug or intervention is reasonably safe to try in people. This data, along with manufacturing details and your proposed study plan, forms the core of an Investigational New Drug (IND) application submitted to the FDA. The IND has three required components: animal pharmacology and toxicology studies, manufacturing information proving you can produce consistent batches of the drug, and detailed clinical protocols with information about the investigators who will run the trial.
The IND exists because federal law prohibits shipping an unapproved drug across state lines. Since most trials involve multiple sites in different states, the IND serves as your legal exemption. Once you submit it, you must wait 30 calendar days before enrolling a single participant. During that window, the FDA reviews your application to confirm the study won’t expose people to unreasonable risk. If the agency doesn’t object within 30 days, you can proceed.
There are a few IND variations worth knowing about. An investigator IND is filed by a physician who both designs and personally oversees the study. An emergency use IND lets the FDA authorize an experimental drug when there isn’t time for a standard submission. A treatment IND covers drugs that show promise during testing for serious or life-threatening conditions, allowing limited use while final trials and FDA review continue.
Secure Ethics Approval Through an IRB
No clinical trial moves forward without approval from an Institutional Review Board. The IRB is an independent committee that evaluates whether your study design adequately protects participants. Federal regulations require the board to confirm two things: that risks to subjects are minimized, and that whatever risks remain are reasonable relative to the anticipated benefits of the research.
The IRB also reviews your informed consent documents. Federal law specifies exactly what these must contain. Every consent form needs a clear statement that the study is research, an explanation of its purpose and expected duration, a description of foreseeable risks and potential benefits, disclosure of alternative treatments, a confidentiality statement noting that the FDA may inspect records, and contact information for questions or injuries. Critically, the form must state that participation is voluntary and that a person can withdraw at any time without penalty or loss of benefits they’d otherwise receive. For studies involving more than minimal risk, you also need to explain whether compensation or medical treatment is available if someone is injured.
Understand the Four Phases of Testing
Clinical trials follow a phased structure, each with a different goal and scale.
Phase I is the first test in humans. It enrolls 20 to 100 participants, often healthy volunteers, and focuses on safety and dosage. Researchers are trying to identify side effects and determine a safe dose range. These trials typically last several months.
Phase II expands to up to several hundred people who have the disease or condition being studied. The focus shifts to whether the treatment actually works (efficacy) while continuing to track side effects. Phase II trials run anywhere from several months to two years.
Phase III is the large-scale test required before seeking FDA approval. These trials enroll 300 to 3,000 participants with the target condition and run for one to four years. The goal is to confirm efficacy across a larger population and monitor for adverse reactions that might not show up in smaller groups. Phase III trials for pharmaceuticals have been estimated to cost anywhere from $11.5 million to $52.9 million, with per-participant costs that can reach $16,000 to $24,000 depending on the complexity of the intervention and number of study visits.
Phase IV happens after a drug is already on the market. These post-marketing studies enroll several thousand participants and continue tracking safety and efficacy in real-world conditions over longer time periods.
Design the Protocol and Choose a Study Structure
Your protocol is the blueprint for the entire trial. It defines the research question, eligibility criteria for participants, the treatment and control groups, what outcomes you’ll measure, and how you’ll analyze the data. A well-designed protocol also specifies how participants will be randomized (assigned to groups), whether the study is blinded (meaning participants or researchers don’t know who receives the treatment versus a placebo), and what statistical methods will determine success or failure.
Randomized, double-blind, placebo-controlled trials are considered the gold standard because they minimize bias. But not every research question fits that mold. Some trials compare a new treatment to an existing standard of care rather than a placebo. Others use adaptive designs that allow modifications based on interim data. The right structure depends on the condition, the phase of testing, and what’s ethically appropriate.
Recruit and Retain Participants
Recruitment is one of the most persistent challenges in clinical research. Despite decades of effort, there is no strong evidence for which recruitment strategies consistently work best. Researchers have tested financial incentives, multimedia outreach programs, decision aids, follow-up reminders, and optimized trial information documents. Some improve enrollment modestly, but none have produced dramatic gains. Compounding the problem, most trials don’t formally document or publish their recruitment strategies, making it nearly impossible for future researchers to learn from what was tried.
What does help is designing recruitment around the patient population you’re targeting. Clear, jargon-free descriptions of what the trial involves, realistic expectations about time commitment, and strong relationships with referring clinicians all contribute. Retention matters just as much as initial enrollment. Participants who drop out reduce statistical power and can introduce bias, so building in regular communication and minimizing the burden of study visits pays off over the life of a trial.
Monitor Safety Throughout the Trial
Safety monitoring doesn’t stop after Phase I. For larger or higher-risk trials, an independent Data Safety Monitoring Board (DSMB) reviews accumulating data at regular intervals while the study is ongoing. A typical DSMB includes three to seven members: clinical experts in the disease being studied, at least one biostatistician, and investigators experienced in trial methodology.
The board reviews a wide range of data points: adverse events, interim efficacy results measured against pre-established statistical thresholds, data quality and completeness, individual site performance, protocol adherence, recruitment and retention rates, and any external developments in the scientific landscape that could affect participant safety or the ethics of continuing. Based on this review, a DSMB can recommend continuing the trial as planned, modifying the protocol, or stopping the trial early. Early termination happens for two main reasons: either serious safety concerns emerge, or the treatment has already met its efficacy goals so convincingly that continuing to give some participants a placebo would be unethical.
Register the Trial and Report Results
U.S. law requires most clinical trials to be registered on ClinicalTrials.gov. The Food and Drug Administration Amendments Act of 2007 and a 2016 final rule clarify which trials must be submitted, when registration and results must be posted, and what counts as compliance. Summary results are generally due within one year of the study’s primary completion date.
Non-compliance carries real consequences. If the FDA determines a responsible party has violated registration or reporting requirements, it issues a formal Notice of Noncompliance, which becomes part of the public study record on ClinicalTrials.gov. The FDA can also impose civil monetary penalties. These enforcement mechanisms exist to ensure that trial results, whether positive or negative, become part of the public scientific record rather than disappearing when outcomes are unfavorable.
Submit Your Findings for Regulatory Review
After completing Phase III, the next step is compiling all data from every phase into a New Drug Application (or Biologics License Application for biological products). This submission includes the full body of evidence on safety, efficacy, manufacturing, and labeling. The FDA then conducts its own review, which can take months to over a year depending on the product and review pathway.
Even after approval, your obligations continue. Phase IV studies, adverse event reporting, and ongoing manufacturing compliance are all part of the post-approval landscape. A clinical trial isn’t a single event but a years-long process where each phase builds on the last, and the regulatory framework is designed to make sure shortcuts at any stage don’t put patients at risk.