Understanding Clinical Trials: What Each Stage Means and Why Phase III Matters

Every therapy that reaches a patient’s hands has passed through a series of clinical trials, each designed to answer a progressively higher-stakes question. The process exists to protect patients, generate evidence, and give physicians confidence that a treatment does what it claims to do.

For anyone following the development of new therapies in cardiovascular medicine or any other field, understanding what each stage involves makes it easier to interpret headlines, evaluate progress and appreciate why some milestones matter more than others.

Phase I: Establishing Safety

Phase I trials are typically small, often involving a few dozen healthy volunteers or patients. The primary goal is to evaluate safety, tolerability, and dosing. Researchers are answering a foundational question: can this therapy be administered to humans without causing unacceptable harm?

Phase I studies also generate early pharmacokinetic data, helping researchers understand how the drug is absorbed, distributed, and eliminated by the body. A Phase I trial that demonstrates a therapy is safe and well tolerated at relevant dose levels provides the basis for moving forward.

Phase II: Testing for Signals of Activity

Phase II trials expand the study population and begin to explore whether the therapy has a measurable effect on the disease. These studies are often randomized and may be placebo-controlled, but they typically enroll a more limited number of patients than a Phase III trial.

The goal at this stage is to detect meaningful clinical signals. In cardiovascular medicine, for example, a Phase II trial might measure changes in cardiac imaging parameters, reductions in inflammatory markers, improvements in patient-reported symptoms, or reduction in disease burden. Not every endpoint will reach statistical significance in a Phase II study, and that is by design. These trials are often sized to detect signals and trends to inform the design of larger studies, rather than to deliver definitive proof of efficacy.

As an example, our Phase II MAvERIC study enrolled 27 patients with recurrent pericarditis and showed rapid, sustained reductions in pain and inflammation over six months of treatment with CardiolRx™. Those findings informed the design of our Phase III trial. Separately, our Phase II ARCHER trial in acute myocarditis produced the first clinical evidence that CardiolRx™ can improve cardiac structure, including a significant reduction in left ventricular mass, which provides sound rational for advancing clinical development in multiple conditions of the myocardium characterized by edema, fibrosis, and remodeling, including heart failure.

Phase III: Where Evidence Becomes Definitive

Phase III is the stage that separates promising therapies from proven ones. These trials are larger, longer, and held to the most rigorous standards in clinical research. They are almost always randomized, double-blind, and placebo-controlled, meaning neither the patient nor the treating physician knows who is receiving the therapy and who is receiving placebo.

The scale matters. Where a Phase II trial might enroll 25 to 100 patients, a Phase III trial will often enroll 100 or more. That larger population makes it possible to detect treatment effects with statistical confidence, to identify less common safety signals, and to evaluate whether a therapy works consistently across different patient subgroups.

The endpoints matter too. Phase III trials are typically designed around clinical outcomes that directly reflect what patients and physicians care about. In oncology, that might be overall survival. In cardiovascular medicine, it could be prevention of disease recurrence, reduction in hospitalizations, or sustained improvement in cardiac function.

Our pivotal Phase III MAVERIC trial in recurrent pericarditis illustrates this progression. The trial is enrolling approximately 110 patients across 25 sites in the United States, Canada, and Europe. The primary endpoint is freedom from a new episode of recurrent pericarditis. That endpoint was chosen because it reflects the outcome that matters most to patients living with this condition: whether the disease comes back.

Phase III results are what regulatory agencies evaluate when deciding whether to approve a therapy. A successful Phase III trial, in most cases, is the final piece of clinical evidence required to support a New Drug Application with the U.S. FDA.

Why Phase III Carries Particular Weight in Cardiovascular Medicine

Heart disease remains the leading cause of death globally, and many cardiovascular conditions involve complex biological processes including chronic inflammation and fibrosis. Clinical trials in this field must demonstrate that a therapy can produce durable, clinically meaningful improvement in how the heart functions and how patients feel over time.

For conditions like recurrent pericarditis, where patients may cycle through multiple lines of therapy as their disease recurs, the bar is especially clear: the treatment needs to prevent the next episode, not just manage the symptoms of the current one.

That is why Phase III trials in cardiovascular medicine tend to attract significant attention from clinicians, regulators, and investors. They are the stage at which a therapy must demonstrate it can meaningfully change the course of a relevant disease endpoint. There is very little ambiguity in a well-designed Phase III result.

Advances in our understanding of inflammatory mechanisms in heart disease are opening new avenues for therapeutic development. Targeting the inflammasome pathway, which plays a central role in conditions like pericarditis, myocarditis, and heart failure, has become a focus for multiple research programs.

As these programs progress through clinical development, Phase III trials will continue to serve as the definitive test of whether new science can translate into new care for patients.