What Are The 4 Phases Of Clinical Trials?

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Clinical trials are designed to make sure that new treatments are better than existing ones. To do this, trials are structured by a framework that is made up of phases. Each phase has a different purpose, and a participant will usually only partake in one of the phases during a trial. But what are these phases, and what does each involve?

What Are Phases In Clinical Trials?

Clinical studies evaluate the effectiveness and efficacy of new drugs in real-time situations.

Early phase trials examine the safety and dosing of the candidate drugs
Later phase trials are more concerned with safety, tolerability and comparison with competitor drugs.

Biopharmaceutical companies and medical device manufacturers can take 6-7 years to complete all clinical trials for a new therapy. So, each trial phase can last from months to years, depending on the study design.

What Are The 4 Phases Of Clinical Trials?

The 4 clinical trial phases are known as I, II, III, and IV.

Phase I

Phase I is the very first stage of a trial. Researchers have tested a new therapy on people for the first time to establish a safe dosage range and identify and evaluate its side effects.
This phase is usually small and involves around 20-50 volunteers. These could either be healthy members of the public or patients with the disease that the therapy targets.
A trial can last several months, and their results are vital to the design of further trials. Once the new therapy is safe and well tolerated, it moves into phase II. The FDA reports that approximately 70% of drugs undergoing Phase I trials move to Phase II.

Phase II

This stage of the trial tests the new therapy against potential disease profiles. Phase II clinical trials may also provide more detailed information about the latest therapy’s safety and side effects.
Phase II clinical trials are usually bigger than Phase I and involve many more subjects, some working with up to several hundred people. In phase II trials, researchers sometimes randomise subjects to receive the new drug, a standard treatment, or a placebo. This helps improve the accuracy of the results by removing investigator bias.
It can last anywhere from months to 2 years, with about 33% of drugs moving onto the next phase – Phase III.

Phase III

By Phase III, the drug had proven safe, well tolerated, and effective against the target disease.
It’s usually quite large and can involve hundreds to several thousands of people. The number of subjects required is based on the need to demonstrate the new therapy’s statistical significance against existing standard therapies (if the drug competes with an existing treatment). These studies are often multinational.
In stage III, researchers can observe less common side effects due to the scale and range of participants. Often, researchers will identify uncommon side effects here that could have gone undetected in the preceding smaller trials.
Phase III trials involve randomization and can last for several years.

Phase IV

Phase IV trials happen once the new drug has been approved. These look for side effects not seen in earlier trials and provide further information on the therapy’s efficacy over a long period. They may also explore new indications or formulations of the newly approved drug and its cost-effectiveness.

Different Phases Of Clinical Trials

By navigating through the different phases of clinical trials researchers are effectively and safely developing new therapies to provide patients with better outcomes and treatments. Each phase in the trial design process is in place to improve patient care and safety, while advancing medical understanding.

For more information and support for clinical trial designs, contact Aixial Group. We are a Clinical Research Organisation with the knowledge and expertise needed to deliver efficient clinical trials.